Backgrounds and aims: Irritable bowel syndrome (IBS) is one of the most common functional gastrointestinal (GI) disorders. IBS is associated with visceral hypersensitivity (1). The pathogenesis is poorly understood due to the functional nature of the disorder. Hence, it is important to understand the GI mechanical function and to determine the contraction threshold and contractile capability based on biomechanical analysis. The aim of the present study was to investigate stress and strain thresholds to evoke contraction and maximum contraction stress and strain in ileum and colon using the neonatal maternal deprivation (NMD) rat model (2). 

Materials and methods: Forty-two neonate Wistar rats were used. After delivery (day 1), 25 pups were selected for the NMD group and 17 pups for the Control group. Maternal deprivation was done using the methods reported by Barreau et al (2). Mechanical testing was done on intestinal segments in an organ bath containing Krebs solution when the rats reached 12 weeks of age.  The distal ileum and middle colon were distended with pressures from 0-10 cmH₂O and from 0-20 cmH₂O, respectively. The pressure and outer diameter were recorded. Circumferential stress and strain were computed using the zero-stress state as reference. The pressure, stress and strain at contraction threshold and maximum contraction force were determined. ANOVA was used for statistical analysis. 

Results: At the end of experiment, the body weight was smaller in NMD rats than in Control rats (P< 0.01). The passive stress-strain curve shifted to the left in the ileum of NMD rats. The same was not the case in the colon segments. The contraction threshold of pressure, stress and strain was significantly smaller in the ileum and colon of NMD rats (P<0.05). The maximum contraction pressure, stress and strain did not differ between NMD rats and Control rats (P>0.05). 

Conclusions and perspectives: The pressure, stress, and strain to evoke contraction of ileum and colon are smaller in isolated segments of NMD IBS rats. This indicates hypersensitivity of the involved receptors and intrinsic neural circuits to mechanical stimulation in the IBS intestine. Further studies on the relation between the intestinal biomechanical properties, hypersensitivity and afferent signaling in the IBS animal models are warranted. 

Key words: Ileum, Colon, IBS, Stress-strain, Contraction threshold, Maximal contraction, Rats 

1: Simrén M, et al. Visceral hypersensitivity is associated with GI symptom severity in functional GI disorders: consistent findings from five different patient cohorts. Gut. 2017 [Epub ahead of print].

Purpose
Ligament balancing has a tremendous impact on total knee arthroplasty (TKA) outcome. When performing a TKA, the depth of the tibial cut affects both the flexion and extension gap. The aim of this study is to assess the biomechanical consequences of a tibial cut on knee joint stability, according to the thickness of the tibial cut. Our hypothesis was that increasing depth of tibial resection would be associated with increasing valgus laxity throughout range of movement.

Methods
A cadaveric study was undertaken, with eleven knees included for analysis. The biomechanical effects of increasing tibial resection were studied, with bone cuts made at 6mm, 10mm, 14mm, 18mm and 24mm from the lateral tibial articular surface. A computer navigation system was used to perform the tibial resection and to measure the valgus laxity under a torque of 10 Nm. Measurements were taken in four knee positions: 0° or extension, 30°, 60° and 90° of flexion. Statistical analysis was performed using a nonparametric Spearman’s ranking correlation matrix at the different stages: in extension, at 30°, 60° and 90° of knee flexion. Significance was set at p<0.05.

Results
There was a statistically significant correlation between knee valgus laxity and the thickness of the tibial cut in knee flexion positions: 30° (p<0.0001), 60° (p<0.001) and 90° (p<0.0001). At knee extension position, no significant correlation was found between the valgus laxity and the thickness of the tibial cut. We noticed a valgus laxity greater than 5° at 90° of knee flexion after a tibial bone cut of 14mm.

Conclusion
Increased tibial resection depth is associated with greater valgus laxity when tested in positions from 30° to 90° of flexion. We propose that this is due to defunctioning of the medial ligament complex (MCL), especially the deep layer of the MCL, resulting from tibial resection. When a tibial bone cut of 14mm or greater is necessary, it is recommended to consider the use of a constrained knee prosthesis.

Keywords: Tibial bone cut - Total knee arthroplasty- Medial collateral ligament – Knee stability

Backgrounds and aims: Diabetes induced intestinal morphological and biomechanical remodeling may play an important role in diabetic GI complications (1).  However, the molecular pathways involved the colon remodeling are not well understood. The aim of the study is to investigate the role of advanced glycation end products (AGEs), TGF-β1, brain derived neurotrophic factor (BDNF) and their receptors of RAGE, TGF-β1 receptor and tropomyosin receptor kinase B (TrkB) on diabetes-induced colon remodeling. 

Materials and methods: Diabetes was induced by a single tail vein injection 40mg/kg of streptozotocin. Colonic morphometric and biomechanical parameters were obtained in diabetic and normal rats from our previous publication (2). The expressions of AGE, RAGE, TGF- β1, TGF- β1 receptor, BDNF and TrkB were immunohistochemically detected in different layers of the colon from the same animals as reported in the previous publication (2). Linear regression analysis was carried out to determine the association between the expressions of these proteins with remodeling parameters. ANOVA was used for statistical analysis. 

Results: The expression of all proteins was stronger in the muscle layer than other layers where AGE, RAGE, TGF-β1 and TGF- β1 receptor expressions were increased whereas BDNF and TrkB were decreased in the diabetic colon (P<0.05, P<0.01). The glucose level was associated with most morphometric and biomechanical parameters and with the expression of all proteins studied in the individual colonic wall layers. AGE, RAGE and TGF-β1 receptor expressions were positively correlated whereas the BDNF expression was negatively correlated with most of the morphometric and biomechanical parameters (P<0.05, P<0.01, P<0.001). AGE, TGF- β1 and BDNF in the layers strongly correlated with their receptors RAGE, TGF- β1 receptor and TrkB, respectively. 

Conclusions and perspectives: STZ-induced diabetes up-regulated the expression of AGE, RAGE, TGF- β1 and TGF- β1 receptor and down-regulated the expression of BDNF and TrkB in different colon layers of rats mainly due to hyperglycemia. Our results suggest that AGE, RAGE, TGF- β1 and TGF- β1 receptor are likely promotors whereas BDNF and TrkB are inhibiting factors for diabetes-induced colon remodeling.  In the future, it is necessary to investigate the detailed molecular pathway of the abnormal expressions of these proteins in diabetes and their association with diabetes-induced colon remodeling. 

Key words: AGE, TGF- β1, Neurotrophic factors, Colon, Biomechanical remodeling, Diabetes 

1: Zhao J, Nakaguchi T, Gregersen H. Biomechanical and histomorphometric colon remodelling in STZ-induced diabetic rats. Dig Dis Sci. 2009; 54(8): 1636-1642.

Introduction

Most studies investigating the effect of wearing high heels on the spine have not provided adequate empirical evidence. As a result, the underlying association between increased lumbar lordosis and lower back pain remains unclear [1]. There is also debate about whether wearing high heels can lead to an increase in lumbar lordosis [2]. Therefore, the purpose of this study was to assess the effects of wearing high heels on lower limb kinematics using the Oxford foot model, while evaluating the sagittal profile of the spinal curvature angle.

Methods

 Fifteen healthy women aged 20-25 years were measured while waking barefoot versus wearing high heels at speeds of 2.5km/h and 5km/h. The motion of the lower limb and spine was captured by a Vicon system (Oxford Foot Model) and the DIERS Formatric 3D device, respectively. Differences in all parameters were compared using one-way analyses of variance (ANOVA). For the same speed, results were compared between the two conditions of barefoot and high-heels; for the same state, results were compared between slow and fast walking speed. For all analysis the significance level was set at 0. 05.

Results

In the case of walking at 2.5km/h, the ROM of the ankle, knee hallux, forefoot, and hind foot increased significantly when wearing high heels, with an observably higher lordosis angle (Fig1 a). In the case of walking at 5km/h, compared with the barefoot condition, the ROM of the hallux, the forefoot, the hind foot, the ankle and the knee was significantly higher when walking wearing high heels (p<0.001) (Fig1 b). Walking with high heels also showed a remarkable increase in lordosis angle (Fig1 c). The angle of the hallux and forefoot showed a significant increase between slow and fast walking speed with high heeled shoes (Fig1 d).

Discussion

Wearing high heels increased the lordosis associated with maintaining stability and balance during walking. On the other hand, no statistical significance was found in kyphotic measures. In the meantime, the flexed range of the hallux and forefoot significantly increased when wearing high heels as walking speed increased. This dataset on the high heel kinematics observed during the walking gait cycle can provide an important basis for explanation on low back pain, knee osteoarthritis and forefoot deformity in relation to using and wearing high heels.

Acknowledgements

This study sponsored by National Natural Science Foundation of China (81772423).

References

1. Weitkunat, F. M., et al., (2016). J Eur Spine, 25(11) p3658

2. Dai, M., et al., (2015). J Eur Spine, 24(6) p1247

Introduction
Locking plate is widely used during medial opening wedge high tibial osteotomy as it provides satisfactory mechanical stability. However, several factors may affect the stability after medial opening wedge high tibial osteotomy(MOWHTO) using locking plate. We aim to determine the effect of screw-length on the stability after medial opening wedge high tibial osteotomy.

Methods
We randomly allocated 40 tibiae from fresh-frozen cadavers into 3 groups. MOWHTO was performed using locking plate (TomoFix®). Three groups received different surgeries in relation to the length of the proximal screws. Group A was fixated bicortically, while group B and C were fixated using shorter screws: 90% and 55% of drilled tunnel length, respectively. We defined the Group B as standard group. There was no difference in the demographics, tibial plateau size and tunnel length between these groups. Operated tibiae were tested under axial compressive load using material testing machine. The medial gap change under axial load of 100, 200, 300, 400, 500, 600N and ultimate failure load were measured.

Results & Discusson
The medial gap change showed an increasing tendency as the screw length was getting shorter, but the difference was not significant between group A (bicortical fiaxation), B (90% length-screws) and C (55% length-screws). The difference of ultimate failure load was also not significant between these three groups. Unicortical fixation in proximal screw holes of a locking plate was not inferior to the bicortical fixation regarding axial stability in MOWHTO, although too short proximal screw should be avoided.

Table 1 medial gap change according to axial load

Table 2 Ultimate failure load

Reference

(1) Amendola A et. al., (2010) Int. Orthop., 34(2) pp.155

(2) Han J.H. et. al. (2017) Knee Surg Sports Traumatol Arthrosc., 25(3) pp.808

(3) Smith T.O. et. al., Knee, 18(6) pp.361

Introduction

Parachuting was full of danger in landing phase [1]. Backpack carriages of paratroopers included necessities and could increase injury [2]. During parachuting landing, ground reaction force and joint displacement could be increased by backpack weight [3]. However, there had been few papers about effects on lower-extremity by backpack load in half-squat landing.

Methods

16 male volunteers (21.4±2.1y, 177.3±4.3cm, 66.9±5.1kg), without no musculoskeletal, were recruited. Reflective markers were pasted on the skin of volunteers to track the three-dimension displacement of body. Each volunteer, carrying a backpack (weight: 0kg, 5kg and 10kg), jumped from a platform (height: 40cm, 80cm and 120cm) and landed by using the half-squat landing posture. Their right feet landed ona force plate.

Results

Vertical ground reaction force (GRF) and flexion ground reaction moment (GRM) were increased by jumping height and backpack weight, while the time from the point when feet contacted ground to the peak vertical ground reaction force (TPvGRF) was decreased by jumping height. Flexion joint angle displacement (JAD), axial maximum joint force(MJF) and flexion maximum joint moment(MJM) of hip, knee and ankle were enlarged by jumping height and backpack weight, expect for flexion JAD and flexion MJM of knee and flexion JAD of hip. Maximum joint velocity(MJV) of hip, knee and ankle was increased by jumping height, but not affected by backpack weight. Axial MJF decreased from ankle to hip while MJM increased.

Discussion&Conclusions

With the increase of jumping height, GRF and GRM were increased according to the theorem of impulse. The joints needed to keep balance as soon as possible and the energy dissipation of joints was increased. Backpack weight added load so joints needed more displacement to absorb impact energy. However, the jumping heights were not changed so MJV was maintained. The impact energy was absorbed by the ankle, knee and hip sequentially. It could be resulted that ankle was more possible to be injured. This work could contribute to estimate injuries and to design parachuting backpack weight and protective equipment.

Acknowledgements

The work was supported by the Defense Industrial Technology Development Program [No. JCKY2016601B009] and the National Natural Science Foundation of China [No.11421202].

References:
1.Guo W J, et al., (2013). Applied Mechanics and Materials. 423 p1778-1781.
2.Wang H, et al.,  (2013). Research Quarterly for Exercise & Sport. 84(3) p305.
3.Feng W S, et al., (1987). Journal of the Fourth Military Medical University. 8(6) p392-396. (in Chinese)

Introduction
A previous retrieval study analyzed the backside wear of short term implanted liners and in-vitro tested liners with similar working life and showed similar results among both groups, with no significant backside wear due to micro-motion [1]. The purposes of the current study were to evaluate the backside wear of 0.1% vitamin E blended polyethylene liners, whose locking mechanism is based on a press-fit cone in combination with a rough titanium conical inner surface on the fixation area, under a 20 million cycles wear simulation; to analyze which wear modes can be expected and if this type of wear increases with time.

Methods
In vitro wear simulation was performed on a 6+2 (reference) stations hip simulator, with kinematic and load patterns according to ISO14242-1:2012(E), for 20 million cycles (mc). Acetabular shells (Plasmafit^® Poly Cup, Aesculap AG, Germany) made out of Ti6Al4V alloy were used in combination with highly cross-linked (80 kGy), vitamin E (0.1%) blended and EO sterilized polyethylene liners (Plasmafit^® Poly Insert, Aesculap AG, Germany) and 36 mm modular heads made out of zirconia toughened alumina ceramic (BIOLOX^® delta, Aesculap AG, Germany). The polyethylene liners were removed from the acetabular shells every 5 mc and an optical analysis of their backside surface was performed using a digital microscope at 50x magnification. A semi-quantitative method [1] was used in order to assess the damage on the backside of the liners. The backside surface was divided in 7 different sections and for each section, a score between 0 and 3 was given for each of seven damage modes (deformation, pitting, embedded particles, scratching, burnishing, abrasion and delamination). Each component was given a total damage score given by the sum of the scores from all its sections (maximal score 147).

Results
The total average backside wear was the smallest after 5 mc, increased after 10 mc, but showed no further increase after 15 and 20 mc (Fig.1). The reference liners (subjected only to axial load) showed similar wear scores and modes as the liners under walking simulation. Small scratches produced during insertion and removal were clearly seen at the rim (fixation) area and no considerable abrasion due to movement was observed. The machining marks on the convex surface were always visible. The most common wear modes observed were scratching, abrasion, burnishing, and embedded particles.

Discussion
These results determined that there was little to no micro-motion between the liner and the shell through the entire wear simulation. Moreover, it was demonstrated that most of the backside wear produced on the liners occurred during their insertion and removal rather than during their working life.

References
[1] Puente Reyna et al., (2016). BioMed Research International, Article ID 8687131

Introduction

Roentgen stereophotogrammetric analysis (RSA) accurately measures the early migration of implants in total joint arthroplasty and presents the gold standard to assess implant fixation in vivo [1]. The continuous development of RSA, from marker- to model-based approach not only reduces the costs, but also makes the application scope of RSA wider [2]. Accuracy of model-based RSA is comparable to the gold standard maker-based RSA [3, 4]. However, accuracy is less for superior-inferior axis of hip stems [4]. To the authors’ knowledge less data exist according intra- and interrater-reliability of available RSA methods. Therefore, the purpose of this study is to carry out a retrospective analysis of clinical RSA for total hip arthroplasty to assess intra- and interrater-reliability of two different RSA approaches.

Methods

A total of n=18 stems (Lubinus, Link, Hamburg, Germany) and n=11 cups (Phoenix, Peter Brehm GmbH, Weisendorf, Germany) components were included with a minimum follow-up period up to two years. All RSA radiographic image pairs were analyzed by model-based RSA using elementary geometrical shape models (EGS) and marker-based RSA method with MBRSA 4.1 (Medis Specials, Leiden, Netherlands). Analyses was repeated n=3 times by three different observers. Barnhart's [5] method was used to calculate intragroup and intergroup differences, represented by mean square difference (MSD).

Results

Overall, the results show that both marker-based and model-based RSA using EGS have low intragroup difference in the measurement of translational migration along all the three (Xt, Yt, Zt) axis and rotational migration around anterior-posterior (Zr) axis (stem <0.028 mm², cup <0.119 mm²). For rotations around cranial-caudal axis, MSD of the stem component for model-based RSA using EGS indicate an increasing intragroup difference of 0.994 mm², which is much smaller in marker-based RSA (0.242 mm²) (Fig. 1A). For the cup component, marker-based RSA shows the largest intragroup difference for rotations around the medial-lateral axis (0.337 mm²), followed by model-based RSA using EGS (0.176 mm²) (Fig. 1B).

Discussion

Migration detection for stem components for rotations around cranial-caudal axis indicates a higher intrarater difference for model-based RSA using EGS compared to marker-based RSA, which is possibly related to the limitation of its working principle using pose-estimation technique [4]. In migration detection of cups for rotations around medial-lateral axis, the highest variability is observable for marker-based RSA. Within a next step the interrater reliability analysis should be completed and give further information according reliability of RSA approaches.

References:

1. Valstar, E.R., et al., (2005). Acta Orthop, 76(4) p563

2. Kaptein, B.L., et al., (2003). J Biomech, 36(6) p873

3. Hurschler, C., et al., (2009). J Arthroplasty, 24(4) p594

4. Seehaus, F., et al., (2009). J Biomech Eng, 131(4) p041004

5. Barnhart, H.X., et al., (2007). J Biopharm Stat, 17(4) p697

Introduce
Roentgen Stereophotogrammetric Analysis (RSA) represents the gold standard to assess in-vivo migration of implants of total joint arthroplasty using rigid body kinematics, bone markers, surface models of implants and “stereo” images acquired over time of the investigated joints [1]. The technical jargon STEREO from stereophotogrammetry refers to a pair of radiographic images obtained by firing Roentgen tubes simultaneously in order to prevent artefacts due to patient motion [2]. However, to our knowledge, there is no information regarding the influence of acquired RSA images by means of asynchronized RSA. The aim of this study is to quantify the effect of patient motion on measurement accuracy within an asynchronous RSA set-up and non-simultaneous image acquisition.

Methods
Radiographs were taken within a special uniplanar set-up using a movable X-ray tube (Multitom Rax, Siemens Healthcare GmbH, Forchheim, Germany) to perform RSA examinations. A tibial component of total knee arthroplasty (BPK-S Peter Brehm, Weisendorf, Germany) and five bone markers represent a phantom model to enable migration measurements. Measurement protocol: A reference and a follow-up pairs of radiographs with no simulated patient motion were taken, afterwards these patient motions were mimicked between both radiographs by moving the phantom along medio-lateral axis sequentially in steps of 1, 2, 3, 4, 5, and 10 mm. The protocol was repeated three times. Radiographs were analyzed using RSA software MBRSA 4.1 (MedisSpecials, Leiden, Netherlands). Migration, crossing line distance (CLD) of five bone markers and difference of the model contour from the software were compared with each motion about the possibility of matching.

Results
The level of model-based RSA was possibly inferior to 4 mm for simulated migration, whereas marker-based RSA was generally not higher than 2 mm. With increasing the simulated patient motion, the calculated migration value increased for each axis. The results for CLD of the five bone-markers (Fig. 1A) and difference of the model contour (Fig. 1B) revealed that the results regarding the up-to-2 mm groups were higher than the groups of reference, 0, and 1 mm.

Discussion
Model-based RSA tends to be more robust according to possible artefacts resulting from patient motion. Measurements with simulated patient motion can be perceived, when the phantom motion in model-based RSA is up to 4 mm possibly, and classical marker-based RSA only up to 2 mm possibly. Furthermore, the influence of inevitable patient micro-motion during the interval of asynchronous X-ray exposures caused by breathing or arterial pulsations on accuracy has to be systematically characterized for the future RSA experiments.

Acknowledgements
The authors gratefully acknowledge the experiments’ funding from Siemens Healthcare GmbH, Forchheim, Germany.

Reference
1. Valstar, E., et al., (2006). Clin Orthop Rel Res, 448 p2
2. Valstar, E, (2001). ISBN 90-9014397-1, p22

Introduction

Kinesio Taping (KT) was commonly used in injury prevention and rehabilitation. It was shown to increase muscle activity, including muscle peak torque ^[1] and functional performance ^[2]. However, there was little study about effects of its use on time-related muscle fatigue. In this study, muscle fatigue was quantified during isometric contraction of biceps at different time points (0, 2, 4, 6, 8, 10h) with different taping methods. Then effects of KT on fatigue was analyzed in view of biomechanics.

Methods

Ten subjects were randomly divided into four groups including KT-contraction, KT-stretch, placebo-tape and no-tape (control group). KT was applied to biceps starting at its origin to the location of muscle insertion under 10% prestrain in KT-contraction group, and it was contrast for KT-stretch group. KT was taped on biceps without prestrain in placebo-tape group. There was no tape in control group. Each group was carried out 30s isometric contraction of biceps and the interval was 2 hours. Medium frequency of sEMG during the first 10s (MF_10s) was regarded as the initial fatigue indicator, and its rate of change from the first 10s to last 10s (ΔMF%) represented the development of muscle fatigue.

Results

The value of ΔMF% in placebo-tape group was always higher than that in no-tape group during 10 hours of taping. Compared with placebo-tape group, ΔMF% in KT-stretch group decreased gradually and it was dramatically lower than that in placebo-tape group after 4 taping hours. KT-contraction group showed higher MF_10s and ΔMF% compared with placebo-tape group.

Discussions

To analyze the effects of KT on fatigue in view of biomechanics, forces under different taping conditions were simplified. There was no external force on the skin in control group. In placebo-tape group, there was traction force in skin normal direction because of binding stuff. Compared with placebo-tape group, KT-stretch group existed shear force in the direction of muscle stretching additionally, while KT-contraction group existed shear force in the direction of muscle shortening additionally.

Traction force in skin normal direction didn’t change initial muscle fatigue, but it caused a slight increase in fatigue development during 10 hours of taping. Shear force in the direction of muscle stretching relieved muscle fatigue significantly, which might result in the lowest level of muscle fatigue at 8h. Shear force in the direction of muscle shortening caused more initial muscle fatigue and exacerbated fatigue damage, which might result in a state of extreme fatigue at 8h.

Acknowledgements

The study was supported by National Natural Science Foundation of China Grant (No. 11572029,11421202) and the Defense Industrial Technology Development Program (JCKY2016601B009).

References

1.     Hsu, Y. H., et al., (2009). J Electromyogr Kines, 19(6), p1092.

2.     Jaraczewska, E., et al., (2006). Top Stroke Rehabil, 13(3), p31.

Introduction

Custom-fit orthotics have proven to relieve pain, prevent injury, and reduce foot fatigue (Nigg, Nurse, and Stefanyshyn 1999). However, producing them is usually a time consuming and expensive process. We present a scalable software solution that produces 3D-printed biomechanically enhanced custom-fit insoles in minutes.

Methods

We present a solution that allows the production of custom-fit insoles in minutes. The proposed technique uses images of people's feet to retrieve all the necessary information to produce custom-fit orthotics.

Users download an app that allows them to capture four pictures of their feet: a top view image and a side view image for each foot. For the top view images, users include a standard object as a reference to estimate, among other parameters, the length and width of each foot. For the side view images, we obtain a 100-point contour of the bottom of each foot. This contour follows the unique shape of each arch and compensates in areas where extra support is needed (e.g. flat feet).

All these points can be obtained manually, by selecting them from the customer's images. However, to automate the process, we have trained deep learning algorithms (LeCun, Bengio, and Hinton 2015) using thousands of images that were previously labelled by biomechanics engineers. The resulting deep learning models are able to emulate the manual process and identify the points for new sets of images.

The resulting points are mapped into 3D structures that are unique to each foot (see Fig.1). These structures are 3D-printed to produce the custom insoles. The insoles are made of nylon, which offers both flexibility and arch support. A top layer made of polyurethane is added for cushioning.

Fig.1. Mapped points.

Results

We ran a study with 39 participants (20 female, 19 male). Each participant went through a running session wearing factory inserts in their shoes and a second session wearing our custom-fit insoles inside their shoes. There  were the following average reductions when using our insoles: 13% in the peak angle eversion angle, 17% in the peak angle inversion moment, 23% in the angular impulse, and 40% in the peak internal tibial rotation.

Discussion

We have introduced a software system that builds custom-fit orthotics. The system uses images of people's feet to identify, among other parameters, the unique arch curve of each foot. There is evidence of the biomechanics benefits of wearing our insoles when compared to wearing the mass-produced factory inserts.

References

LeCun, Yann, Yoshua Bengio, and Geoffrey Hinton. 2015. “Deep Learning.” Nature 521 (7553):436–44.

Nigg, Benno M., Matthew A. Nurse, and Darren J. Stefanyshyn. 1999. “Shoe Inserts and Orthotics for Sport and Physical Activities.” Medicine & Science in Sports & Exercise 31 (Supplement):S421–28.

BACKGROUND & AIM: Validation techniques for motor unit identification and discharge rates have been emerging. McManus et al. (2017) used discharge times identified by dEMG Analysis software (version 1.1, Delsys, Inc., Boston, MA) to spike trigger average (STA) the surface electromyographic signal.  The comparison between the STA-extracted motor unit potential (MUP) templates and those obtained by dEMG had high correlations for isometric contractions at 20-30% of maximal voluntary contraction (MVC) force. The aim of this study was to further validate the STA technique for the tibialis anterior (TA) during isometric dorsiflexion at 60% MVC. Superposition and misidentification of MUPs is likely to be greater at 60% MVC compared to 20-30% MVC. The variance ratio (VR) was used as a criterion to facilitate the validation methodology through STA-extracted template comparison.

METHODS: Forty subjects completed 3 isometric dorsiflexion MVCs, followed by 3 trapezoidal contractions to 60% MVC on 4 separate test days. Subjects were equipped with a 5-pin electrode (dEMG System, Delsys, Inc., Boston, MA), which was placed on the TA and resulted in 4 channels of recorded activity. Using a 25 ms epoch containing each MUP, the signal-to-noise ratio (SNR) and VR were calculated. The VR quantifies the similarity of the STA-extracted MUP waveforms by comparing firing instances on a point-by-point basis. The measure ranges from 0 to 1, where 0 represents waveforms overlaying perfectly. Various levels of VR were used as validation threshold criterion.

RESULTS: A significant negative correlation was observed between VR and SNR (r = -0.52, p<0.05). When the VR of 0.50 was used in each channel, only 9 MUP trains (MUPTs) could be extracted across all trials. An increased VR tolerance level of 0.73 then resulted in a total of 278 MUPTs. Regardless of VR threshold level, a large number of MUPTs were left unidentified. By using single-channel validation techniques, a VR of 0.75 would yield a minimum of 2 MUPTs per subject for any contraction. Increasing the VR to 0.85 could yield at least 5 MUPTs per subject for any test session; however, this is dependent on the source of signal variation.

CONCLUSIONS: The VR can facilitate the identification of MUPTs by supplementing analysis criteria with greater detail on the variability in the signal.

Introduction

During intensive aerobic exercise such as marching, running or cycling, O₂ consumption and pulmonary ventilation both rise dramatically in order to enable muscle contractions. There is an increase in the work required by the respiratory muscles and the limb locomotor muscles. The blood flow to these muscles increases as well in order to maintain a high metabolic level of the muscles. Trained subjects occasionally ceases the aerobic activity only when the discomfort that follows lack of oxygen would be intolerable. Reaching this fatigue condition might already cause organ damage, muscular damage and damage to different tissues of the body. The objective of this study was to develop new indices for prediction of human fatigue during training based on noninvasive techniques.

Methods

The transcutaneous oxygen tension (tcPO₂), Laser Doppler Flowmetry (LDF), electromyography (EMG) of the leg and calf muscles, heart rate and oxygen consumption (VO₂) were measured during a maximum oxygen uptake test from 14 healthy volunteers. The volunteers were divided into 2 groups: untrained group (n=7) vs. trained (n=7) group according to their maximal VO₂ (VO_2max). The protocol includes a treadmill run of 9 kmh, the treadmill incline was increased every 2 minutes by 2% until reaching maximum capacity. For each volunteer physiological variables were evaluated along with the Root-Mean-Square (RMS) and the Mean-Power-Frequency (MPF) values of the EMG signals. Concurrently, the changes in the tcPO₂ values during the running from the baseline value (dtcPO₂) and the LDF signal (cutaneous flux of the red blood cells) during 5 minutes pre-run and during the recovery period were assessed.

Results

The group of trained subjects reach AT after longer period and higher track incline. The tcPO₂ values decreased gradually while no significant changes were observed in the MPF and EMG_RMSn during the running (Fig 1). The decrease in the tcPO₂ values was found prior to the time reaching AT. The LDF values increased significantly during the run and returned to the baseline values at the end of the recovery period.

Fig 1. An example of EMG_RMS_n and dtcPO₂ during the running

Discussion

Mechanical properties such as stiffness or damping can influence the characteristics of a sport surface and thus be more or less appropriate for the performed movement. Today pluralities of surface testing devices are in use and many of them are covered by different standards (ASTM, DIN, EN). The devices use different mass and spring parameters, different drop heights and sensor locations for data collection during the testing procedure, which makes it difficult to compare published results obtained with different equipment. Aim of the study was the development of a universal model to simulate the artificial athlete berlin (AA) and the Vienna Surface Tester (VST) and the comparison of the results based upon conversion factors.

The model is based on a coupled mass-spring-damper arrangement and allows the simulation of the force-time-curve as well as the determination of all derived parameters. The surface was specified as a nonlinear spring (k2) parallel with a viscous damper (b2). The AA consists of a falling mass (m1=20 kg) and a reference spring (k1=2MNm^-1 and m2=3kg), which is placed on the ground. The influence of friction loss was considered by a further viscous damper (b1). The initial condition was set by an impact velocity (v1=1.04ms^-1) of the falling mass. Furthermore, the VST consists of a dropping ball (m1=6.15kg). In contrast to the AA, the spring (k1) and damper (b1) as well as the mass of the spring (m2) are set to zero. Since the maximum force is proportional to the contact area, the classical contact mechanics were considered. SimulinkV8.6 (The MathWorks, Inc., USA) was used to set up the model as an electrical network by the use of the electromechanical force-current analogy. To evaluate the force reduction between the testing devices and the simulation model, three different rubber floors were used, two of them soft with a thickness of 19mm (G3) and 55mm (G2) and one hard floor (G1).

The different methods (simulation and measurements) provide comparable results. They differ from 3.73% (G1), 7.32% (G2) and 10.71% (G3); with the maximum always occur between AA and simulation.

The model allows a theoretical comparison of surface testing devices with close results to the measurements. The differences in the setup of the devices can be adapted fast within the model. In advance, the influence of stiffness- and damping-behaviour of the surface can be simulated by the change of the relevant parameters. Therefore, the method of simulation may simplify the preselection of a suitable surface. The differences to simulation may be an effect of the non-linear behaviour of the surface.

Aim: Tertiary crowding is a common finding in adult patients. These are often accompanied by fenestrations, attachment loss or gingival recessions. Orthodontic treatment may be considered to prevent progression. The aim of this finite element (FE) simulation was to investigate the biomechanical behaviour of the mandibular incisors in the presence of a local gingival recession in combination with a tertiary crowding.

Material and Methods: Based on 3D data sets of the lower jaw (Viewpoint Data-Labs, UK), a finite element model of a fully dentition, with surrounding tooth support apparatus (PDL) was generated. In the FE program system Marc, a recession of approx. 4 mm was modelled with tertiary crowding of incisors. Various force-torque situations were applied. Using material parameters from previous studies (tooth: E = 20 GPa, bone: E = 2 GPa, both homogeneous and isotropic and PDL: bilinearly elastic, different material behaviour), the centres of resistance (CR) and the initial tooth movements were calculated. The results were compared with those of a morphologically healthy  model.

Results: The orovestibular CR of central lower front tooth is shifted by about 1 mm (about 10%) to coronal in the presented model with crowding and without recession defect compared to a lower jaw model with downright anterior teeth. In the crowding model with recession defect, the CR is again at the same height as in the healthy model, meaning it has again shifted apically by about 10%.

Due to the apical shift of the CR at the incisors with gingival recessions, the strains in the apical area of ​​the PDL increased clearly. In case of unfavourable forces or torques, this can lead to periodontal overloads.

Figure 1: Model of a mandibular with gingival Recession with crowded teeth.

Introduction

Facial asymmetry is one of the most common types of jaw deformities. The prevalence of facial asymmetry varied from 8.7% to 23.3% [1]. The signs and symptoms of temporomandibular joint (TMJ) dysfunction are commonly found in patients with facial asymmetry. Bilateral sagittal split ramus osteotomy (BSSRO) is a representative surgery for the correction of facial asymmetry. The morphology of TMJs in patients with facial asymmetry was proven to be improved after the BSSRO [2]. However, the biomechanical effects of BSSRO on TMJs are unclear. The purpose of this study was to compare the differences in the stress distributions in the TMJs between the asymptomatic subjects and facial asymmetry patients, pre-operatively and post-operatively.

Methods

Ten patients (Pre-operation and Post-operation groups, 24.6±4.8 years) diagnosed with facial asymmetry and ten asymptomatic subjects (Control group, 26.8±4.9 years) took part in this study. Three-dimensional (3D) finite element models of the mandible, disc, maxilla and teeth were reconstructed with 3D image software. Contact elements were used to simulate the interaction of the disc-condyle, disc-temporal bone and upper-lower dentition.The same muscle forces and boundary conditions corresponding to the unilateral occlusions were applied on the models of the Pre-operation, Post-operation and Control groups. The stresses in each group were assessed by Student t-test and the level of significance was 0.05.

Results

The stresses of TMJ in the Pre-operation group were significantly higher than those in the Control group, especially on the non-occlusal side of TMJ. At six months after BSSRO, the contact stress, maximum and minimum principal stress and von Mises stress in Post-operation group were significantly smaller than those in the Pre-operation group. Meanwhile, there was no significant difference for the stresses of TMJ between the Post-operation and Control groups (Figure 1). The results suggested that BSSRO could significantly reduce the stresses of TMJ, and it may alleviate or eliminate the symptom of joint pain, joint sounds and bone resorption.

Figure 1. The von Mises stress (MPa) of TMJ in the asymptomatic subjects and facial asymmetry patients under the non-deviated side occlusion. A, anterior; P, posterior; M, medial; L, lateral; T, top; B, bottom.

Discussion

The BSSRO could decrease the excessive stresses of TMJ in the preoperative patients. The stress distributions of TMJ in postoperative patients were consistent with those in the asymptomatic subjects. Therefore, BSSRO could significantly improve the biomechanical environment of TMJ for patients with facial asymmetry, and it may alleviate or eliminate the TMD symptoms to some extent.

Acknowledgements

This study was supported by the National Natural Science Foundation of China under Grant Number 31670963 and 11202143.

References

1. Bishara et al., (1994). Angle Orthod 64(2):89-98.

2. Ueki et al., (2012). J Craniomaxillofac Surg 40(8):821-827.

Introduction

Prolonged wheelchair propulsion has been a risk factor for upper extremity injuries in wheelchair users, especially in a demanded environment such as steep inclines, turning or under heavy load conditions [1].  Knowledge of the biomechanics of wheelchair propulsion is crucial for improving mechanical efficiency and for the evaluation of different propulsion strategies.  Ergometers offer a platform for biomechanical measurements during prolonged repetitive dynamic activities but propulsions on an ergometer and on the ground have been shown to be different.  Therefore, the current study aimed to develop a wheelchair ergometer to minimize the differences.

Methods

A new wheelchair ergometer was designed and built by integrating a propulsion platform with a magnetic resistance module installed on each of the two rollers on each side of the platform.  The torques applied by the upper extremities were transferred to the field coil of the magnetic resistance module, the current of which was measured and controlled.  A feedforward-feedback control technique was used to control the resistance modules to enable the ergometer to offer simulated heavy load propulsion while moving straight forward or turning. The new wheelchair ergometer was tested in a gait laboratory and the motions of the upper extremities and loadings on the wheels measured and compared to those during over-ground propulsion.

Results and Discussion

A magnetic resistance type wheelchair ergometer integrating a propulsion system, sensors, feedforward-feedback control system and motion analysis module has been developed.  Feedforward control method successfully predicted the rotating periodic movement and feedback control was for tracking.  The motions of the upper extremities and loadings on the wheels measured using the ergometer were shown to be comparable to those measured during over-ground wheelchair propulsion.  The current results suggest that the new ergometer can provide a training platform for conditions including propulsion forward or turning to the right or left.  It also enables the measurements of the biomechanical variables of wheelchair propulsion for improving mechanical efficiency and for the evaluation of different propulsion strategies.  The knowledge will be helpful for future propulsion wheelchair design, and rehabilitation and exercise of physical disabilities.

Acknowledgements

The authors gratefully acknowledge the financial support from the Ministry of Science and Technology, Taiwan (MOST 105-2221-E-131-023-) and truly thank T.K. Wei, Y.H. Chiang, K.Y. Huang, U Fang, J.H. Hu, W.L Tseng, H.R. Huang and C.R. Lin in the early manufacture stage.

References

1. Boninger ML, et al. (1999). Arch Phys Med Rehabil. 80, 910-915.

(a)    (b)

Fig. 1 (a) A wheelchair on the magnetic resistance type wheelchair ergometer.  (b) The magnetic resistance type wheelchair ergometer with its propulsion system, sensors, feedforward- feedback control system and motion analysis module integrated provides a training conditions including propulsion forward or turning to the right or left.

Introduction:

Many people with mobility impairments, have difficulties to use joystick operated electric wheelchairs. To alleviate such difficulties, alternative methods to steer and maneuver an electric wheelchair using vocal, visual or brain signals are now becoming available. While promising, to date, these systems still need to be evaluated thoroughly in terms of performances because they induce mental workload and fatigue. The aim of this study is to compare navigation trajectories and the issued commands between the traditional joystick and vision based wheelchair navigation task involving a door crossing to assess the performances of the latter.

Methods

Fifteen able bodied subjects were recruited for this study. The subjects had to accomplish a navigation task consisting in door crossing with two different door standard widths (73 and 93 cm). Six different initial positions were proposed with two varying distances (1 and 2m from the door) and three lateral positions (left, middle and right). Three trials were executed for each combination of door widths, distances, lateral positions and interfaces (joystick or visual) resulting in 72 trials per subject. The electric wheelchair was equipped with retroreflective markers, the movements of which was recorded with an optoelectronic system. The visual commands were detected using an eye tracking device and a laptop, then they were transformed in adequate voltages to command the wheelchair motors through a custom made electronic card. Apart from classical, forward, backward, stop, left and right commands the interface integrated right forward and left forward commands. Indeed, after initial testing, and unlike most of the available systems, their integration rendered the navigation much more natural. The performance outcomes are the success ratio, the ratio of distances between joystick and visual command. Also, the percentage of left and right forward commands was assessed to validate the choice of these commands.

Results

The success rate with the visual command is high (84.29%) even though the clearance between wheelchair and door is only 7.5cm for narrow door condition (73cm). The path optimally ratio is 0.97 and the subject adopt very similar trajectories between joystick and visual command. The results highlight the important utilization of the left forward and right forward commands (22% of all issued commands) that may explain the similarity between the trajectories of both systems.

Conclusion

Introduction:

Traditional marker based motion capture systems are considered the gold standard in kinematic motion analysis. Recently technological advances in computing and a demand for reduced data collection and processing time have prompted the development of markerless motion capture systems.

This study aims to compare data collected using a markerless and a marker based 3D motion capture system using a within-subject and between session design and using both systems concurrently.

Methods:

Eleven male Elite Academy soccer players (n=11) of age (19.2 years), height (182.4 cm),  weight (79.5 kg) completed  five repetitions of the following movement tests performed in the same order and following explicit instruction :
thoracic rotation, overhead Squat, right leg lunge, right leg 20 second balance and squat jump. Movements were captured simultaneously using both marker-based and markerless 3D systems.

The marker based system comprised of 8 infra red cameras capturing at 100 Hz (Miqus, Qualysis Medical Ltd., Sweden) using Qualysis track manager (QTM, Version 2.16, Qualysis Medical Ltd., Sweden) software for data acquisition and Visual 3D™ (version 6.01.16 system, C-Motion Inc. USA) for model building and processing.

Simultaneously the same movements were filmed with an 8 camera marker-less motion capture system at 50 Hz (Captury Live, version 1.0.16, The Captury™, Germany) using a custom skeletal tracking model (version 1.0, DARI, USA). Data was processed using the DARI Vault processor (version 407, DARI, USA). A low pass fourth order butterworth filter was applied to each dataset at 7Hz.

Results:

Direct comparison of each trial will be completed for repetability similarity or difference over the 5 trials. Kinematic and kinetic data will be analysed for all tests: x,y,z cardan sequence, peak angle range of  motion, mean +/-SD,  for all variables trunk, pelvis, hip, knee in the frontal, saggital and transverse planes. Time series data analysis between both systems will be completed to compare both systems.

Statistical Analysis; To be completed Jan 2018
Levels of agreement within and between subject for each system (within subject analysis of variance WSCV) assessing lower limb kinematics will be analysed. Standard Error of mean values and confidence intervals, p value and mean difference for each variable will be used to compare the systems.

Discussion: Completed once data analysed.

References:

Comparison of lower limb and trunk kinematics between markerless and marker-based motion capture systems.  Perrott et al : Gait & Posture 2017: Vol: 52 pg 57-61

Markerless motion capture can provide reliable 3D gait kinematics in the sagittal and frontal plane. Sandau et al Medical Engineering & Physics 2014 : Vol: 36; (9).

Accuracy and repeatability of joint angles measured using a single camera markerless motion capture system. Schmitz et al, Journal of Biomechanics 2017: Vol 47

Introduction:

Lingual orthodontic systems (i.e. brackets placed on the inside of the tooth) have become popular due to their aesthetic advantages over conventional ones; however, much remains to be elucidated in terms of their biomechanics. The goal of this pilot research was to investigate initial expansion forces generated during anterior and posterior arch expansion procedures using mushroom-shaped lingual archwires.

Methods:

An in vitro Orthodontic SIMulator (OSIM) incorporating anatomically-shaped simulated teeth was utilized to create tooth misalignments and measure resulting expansion forces (Fig. 1a) [1]. The experiments consisted of two parts: 1. anterior arch expansion in a dentition with anterior crowding; 2. posterior arch expansion. As Study 1 simulated anterior crowding whereby the canines are displaced out of the archform, the canines were not incorporated. Round 0.016” mushroom-shaped Nickel-Titanium archwires (G&H Orthodontics) were ligated into lingual brackets (Dentsply GAC). In one case, archwire stops were positioned just anterior to first-premolar brackets in the passive position. For the other, Nickel-Titanium open coil springs (G&H Orthodontics) were inserted such that they passively contacted brackets on the lateral incisors and first premolars. All incisors were then displaced inward 2mm using attached digital micrometers (M-227.50, Physik Instrumente GmbH and Co. KG), and forces were measured using a six-axis load cell (Nano17, ATI Industrial Automation). All tests in Study 1 were conducted at 37°C. In Study 2, 0.0175”X0.0175” Beta-Titanium archwires (G&H Orthodontics) were bent to a widened archform by an experienced clinician.  To simulate a crowded dentition, all teeth were included and the following inward movements were implemented as guided by values from the literature [2]: Canines=0.35mm, First-Premolars=2.15mm, Second-Premolars=1.80mm, Molars=0.90mm. Again, forces were measured in the crowded position.

Results:

Figure 1b and 1c present the resulting buccal-lingual (towards-away from the cheek) forces in Study 1 and Study 2, respectively. A positive value indicates an expansive force in the buccal direction, and negative indicates an inward lingual-directed force.

Discussion:

These preliminary results elucidate the magnitude of expansion forces generated during different modes of arch expansion using a lingual mushroom-shaped archwire. For the amount of crowding tested, forces above the expected clinical threshold of 0.2N to generate tooth movement were measured. While only the initial forces were measured, the presence of lingual-directed forces suggest some teeth would move in the opposite direction before moving outward - known as round-tripping. Future work will examine the full three-dimensional force/moment state, include additional types of archwires (e.g. straight lingual archwires), and increase sample size allowing for statistically relevant comparisons between treatments in each Study.

Acknowledgements:

G&H Orthodontics for donation of archwires.

References:

[1]Owen B. et al, 2017. Eur J Orthod. 39:665-672.

Introduction

            Torsional stiffness (TS), the tendency of an object to resist twisting, has been studied in footwear. Most studies have explored the links between torsional stiffness and injury susceptibility, as well as gait [1,2,3]. However, there is a lack of standardization between the definition and measurement methods of TS.  Some studies have quantified the torque at specific angles of longitudinal angular displacement (twist) between the forefoot and heel [2,4], while others have characterized the torque throughout a range of twist [1].  While the latter method may be more comprehensive, it requires an instrumented torsional load cell, which may not be feasible for many field or clinical studies.  However, it is unknown whether TS is sufficiently linear to support torque measurement at one angular displacement, or whether TS differs between inversion and eversion. Therefore, the purposes of this study are (1) to identify whether standard-issue Army boots demonstrate a linear relationship between TS and angular displacement, and (2) to see if there are any differences between the boots’ eversion and inversion stiffness properties.  Army boots are of interest due to their potential to act as personal protective equipment during combat, and the desire to characterize their material properties.   

Methods

The right side only of six pairs of boots (varying sizes and brands) were each tested using an Instron multi-axis measurement system fit with a custom jig. The system captured torque (T) and angular displacement ( throughout +/- 15 degrees of forefoot eversion and inversion while the heel was held stable.  The total length of each boot (L) was also recorded to  calculate torsional stiffness: . Each trials data sets for were graphed with respect to . A linear trendline was used to identify the R² values and slopes for each trial.

Results and Discussion

            All boots had similar R² values ranging from 0.982 – 0.999.  Despite the differing sizes and brands, TS values were very similar between boots, and there was very little variation between eversion and inversion values (Figure 1).

Conclusion

Boot TS appears to be linear over many angular displacement values.  Therefore, one displacement angle and its corresponding torque may be sufficient to characterize the boot’s TS. This suggests that portable devices can characterize footwear using measurements at one angular displacement.  The similarity of TS between the eversion and inversion directions should be explored further with a larger sample size and with additional footwear types.  

References

1. Buckland, MA, et al. Pediatric Physical Therapy, 26, 411-417, 2014.
2. Graf, ES, et al. Footwear Science, 4:3, 199-206, 2012.
3. Hillstrom, HJ, et al. JAPMA. 103(4), 297-305, 2013.
4. Zifchock, R et al. Footwear Science, 2017.

Introduction

Deep vein thrombosis (DVT) and pulmonary embolism (PE) are estimated to affect 1 in 1000 people in the US annually [1]. Inferior vena cava (IVC) filter placement is often performed when patients cannot undergo anticoagulation therapies for DVT/PE. IVC filters are used to capture thromboemboli traveling through the IVC to prevent PE. Many factors can affect the trapping efficiency of an IVC filter, including filter orientation with respect to the IVC axis, IVC orientation in relationship to gravity, and ratio of clot to fluid density [2]. To study these factors, researchers at the FDA recently designed a generic IVC filter for research purposes. The objective of this study is to characterize the embolus trapping efficiency of the generic IVC filter and to generate data that can be used to validate computational simulations of the device.

Methods

The generic IVC filter is made of nitinol and consists of 16 identical struts equally spaced in a conical fashion around the hub. The filter was placed in the infrarenal region of an optically accessible anatomical model of the IVC that was fabricated using inkjet 3D printing [3]. The blood analog fluid was a 40% glycerin/ 60% water by weight. Nylon spheres (ρ=1.142 g/cm³) of diameters 3 mm, 4.5 mm, and 6 mm (n=5 each) were injected into either the left or right iliac entrances for each trial. The mean flow rate was 6.26 +/- 0.10 LPM to simulate physiological exercise flow conditions [4]. Long entrance tubes were connected to the iliac veins of the IVC model to ensure fully developed flow. The infrarenal Reynolds number is approximately 900.

Results

The trapping efficiency of the generic IVC filter for the 3 mm diameter spheres was 40% from the left iliac (2 of 5 captured) and 0% from the right iliac (0 of 5 captured). The trapping efficiencies for the 4.5 mm and 6 mm spheres were 100% for both veins.

Discussion

In this study the embolus trapping efficiency of the FDA generic IVC filter was characterized. The trapping efficiency has thus far been shown to depend on embolus size and the iliac vein from which the embolus originates. Future work will consider characterizing the performance at other flow rates and using deformable bovine blood clots.

Acknowledgements

This study was funded by the U.S. FDA Center for Devices and Radiological Health (CDRH) Critical Path program.

References

1. Venous Thromboembolism: Data and Statistics. CDC. 2015
2. Aycock KI et al., (2017). Biomech Model Mechanobiol. 16(6):1957-69.
3. Aycock KI et al., (2017). Experiments in Fluids. 58:154.
4. Cheng CP et al., (2003). Am J Physiol. 284(4): H1161-67.

Introduction The purpose of this study was to establish a reference database of cartilage mechanical properties and cartilage thickness of normal human knee articular surfaces.

Methods 33 articular surfaces from donors reported as asymptomatic for osteoarthritis aged between 17-64 years were obtained from an accredited tissue bank (RTI Surgical, USA). Samples were subjected to exclusion criteria to eliminate regions of degenerated cartilage (Fig.1A) in order to create a normal reference database. The samples were also macroscopically assessed through the International Cartilage Repair Society (ICRS) grading system (Mainil-Varlet et al., 2003) by an orthopedist. Mechanical properties and cartilage thickness were extracted from an automated indentation and thickness mapping performed in the distal femurs, femoral condyles, patellas and tibial plateaus. Both techniques were carried out using a multiaxial mechanical system (Mach-1 v500css, Biomomentum Inc., Canada) accessorized with a multiple-axis load cell (load range of 70N), a spherical indenter of 6.35mm diameter, a needle probe and a camera-registration system (Mapping Toolbox). A position grid was created to automatically guide the tester at each position to indent the cartilage perpendicularly at its surface (indentation amplitude of 150µm and indentation speed of 150µm/s) while measuring the resulting load. Subsequently, cartilage thickness was measured automatically with an adapted version of the needle technique (Jurvelin et al., 1995). Load-displacement curves (with appropriate thickness) were analyzed using an elastic model in indentation (Hayes et al., 1972) to extract the instantaneous modulus at each position.

Results A total of 3008 positions were measured and all positions with an ICRS grade>0 indicating degeneration were discarded, which corresponded to a total of 1076 positions. Our final reference database contained 1932 measurement positions for cartilage thickness and instantaneous modulus. Both parameters were calculated by interpolating between points at which cartilage was considered normal (Fig.1B). The standard error (SE) of both measurements was considered as an overall accuracy for the reference database. The instantaneous modulus (mean±SE) was respectively 5.5±0.7, 7.0±1.0, 4.7±0.9 and 4.6±1.0MPa for the distal femur, femoral condyles, patella and tibial plateau. The cartilage thickness (mean±SE) was respectively 2.2±0.1, 2.11±0.0, 2.7±0.3 and 2.3±0.2mm for the same articular surfaces. We found that reference values of normal articular cartilage depend on the articular surface type and location on the surface and that cartilage thickness topography was consistent with literature values (Cohen et al., 1999). 

Discussion This study provides a comprehensive reference database of normal human cartilage mechanical properties and thickness of knee articular surfaces. This database will serve as a reference to enhance our ability to diagnose cartilage changes and degeneration and to measure the effects of a treatment.

Introduction

Mechanical stress generated by joint movement are of major importance for maintaining the integrity of the joint. Reduced mechanical stress by joint immobilization leads to contractures; and this is a common complication and is characterized by limitations in the passive range of motion (ROM) of affected joints. Stretching, the intervention of applying mechanical stress to joint tissues, is the most widely accepted means to treat contractures. However, the clinically worthwhile of stretching is insufficient to heal completely, and therefore novel alternative therapeutic approaches are required. Carbon dioxide (CO₂) therapy can be applied to treat a variety of disorders such as trauma, fracture, and sarcoma, although its effect on contractures remains unclear. Our objective was to determine whether the benefit would occur in immobilization-induced contractures.

Methods

This study was approved by the Institutional Animal Care and Use Committee of Kobe University. Twenty-eight 10-week-old male Wistar rats were randomized into 3 groups: control without interventions, knee joint immobilization (IM), and knee joint immobilization treated with CO₂ therapy (CO₂). In the IM and CO₂ groups, the animals’ knee joints were externally fixed in full flexed position. At 2 or 4 weeks after immobilization, the fixation device was removed so that the knee joints could move freely and the intervention was started. The remobilized hindlimb was exposed CO₂ gas for 20 min once daily for 2 weeks. After that, the degree of knee flexion contractures (total contracture) was assessed by measuring the ROM. Myotomy of the knee flexors was then performed, and the ROM was measured again. The degree of myogenic contracture and arthrogenic contracture were calculated from the ROM values before and after the myotomy.

Results

Knee flexion contractures developed in the rats after immobilization for 2 or 4 weeks. At 2 weeks, myogenic contracture in the CO₂ group showed significant improvement compared with IM group, although no significant differences in total contracture were found among groups. At 4 weeks, total and arthrogenic contractures in the CO₂ group were significantly smaller than those in the IM group.

Discussion

The causes of joint contractures are classified into 2 components: myogenic (muscle, tendon, and fascia) and arthrogenic (bone, cartilage, synovial membrane, capsule and ligaments). With short-term immobilization (≤ 2 weeks), contractures are mainly responsible for myogenic components and fully recover after remobilization. Conversely, arthrogenic contracture develops during prolonged period (≥ 4 weeks) and does not improve spontaneously after remobilization. Our findings showed that CO₂ therapy improved both total and arthrogenic contracture after immobilization for 4 weeks and provided evidence that this therapy without applying mechanical stress may be effective for the treatment of immobilization-induced contractures.

Acknowledgements

The spinal fusion is the gold standard to treat low back pain. Fusions can induce the degeneration of the adjacent levels and an alternative suggested is posterior stabilisation devices. The BDyn is a dynamic device (S14 Implants, Pessac), designed to maintain the intersegmental range of motion and reduce the intradiscal pressure. The partial three-dimensional movement is allowed by a mobile titanium rod that can move between two elastomer components: polycarbonate urethane (PCU) and silicone (Sil).  The aim of this study was the development and validation of the BDyn Finite Element (FE) model.

Materials and Methods

Two mechanical tests were performed: (i) a compression test to obtain the constitutive laws of the elastomer components; (ii) Dynamic Mechanic Analysis (DMA) at several frequencies.  The DMA experimental setup (1) was implemented on the BDyn FE model (Abaqus CAE/Implicit, Dassault Systèmes, Providence, USA) and the resulting displacements of the experimental and computational studies were compared. 

A material optimization subroutine was performed in Abaqus and the stress-strain curves of the compression test were used to evaluate the best-fit hyperelastic formulations assigned to the FE model. The BDyn components were meshed accordingly to a mesh convergence study and hexahedral elements of different sizes were used. A dynamic FEA was performed, applying a sinusoidal load to the upper surface of the BDyn at six frequencies (1, 3, 5, 10, 15, 20 Hz) and fully constraining the lower surface. The resulting displacements were compared with the experimental data obtained from the DMA.

Table 1. Material properties.

Component	Material formulation	Coefficients	Density [g/cm3]
Titanium	Linear elastic	E=105 GPa,ν=0.3	4.43
PCU	Mooney-Rivlin	C10=1, C01=0.603, D=0	1.19
Sil	Second order polynomial	C10=3, C01=1, C11=1,        C02=0, C20=2, D1=D2=0	1.10

Results

The material evaluation of the elastomer components was performed and the coefficients and constitutive laws are stated in Table 1. A validation of the BDyn device against experimental data has been performed, for the frequency ranging between 5 and 20 Hz. In that range, the differences, evaluated as percentage error peak to peak (Figure 1) between the experimental and computational displacements, ranged from 0.2% to 8% during the compression phase (Sil) and between 2% and 7.9% in the tension phase (PCU).

Figure 1. BDyn device and material properties.

Discussion

The hyperelastic material properties have been evaluated and the model predictions compared with expermental test. The results were accurate in the range of frequencies between 5 and 20 Hz, which included the physiological range of vibrations. This validated FE model, will be used in further studies to understand the effect of the device on the lumbar segment.

References

1. Lawless BM et al, Viscoelastic properties of a spinal posterior dynamic stabilisation device. J Mech Behav Biomed Mater. 2016.

Introduction

Knee injuries present as one of the most common sites amongst rowers [1,2]. Feedback given by coaches within the sport is generally subjective and it is difficult for athletes to make changes that could prevent injury. 3D motion capture systems are able to provide real-time objective feedback but are constrained to indoor usage due to the many cameras, wires and bulky sensors. The objective of this study was to manufacture and characterise a flexible strain sensor that can be used to measure knee flexion within the rowing stroke. The sensor is made from an elastic band matrix and a conductive filler, enabling an objective and unobtrusive measurement of kinematics throughout the rowing stroke.

Method

The strain sensors were fabricated from an elastic band matrix with dimensions 110mm x 11mm x 1mm. The conductive filler consisted of a carbon nanotube dispersion in water (concentration 5mg.mL^-1). A solvent exchange process allowed the dispersion to enter the elastic band pores. A PVA coating was used to protect users from touching the nanomaterials.

An Instron 5866 was used to test the mechanical and electrical properties of the sensor under cyclic loading. The sensor was cycle between 0-15% strain over a number of different cycles (1, 100, 200, 500 and 1000) across varying speeds (50mm.min^-1, 100mm.min^-1 and 350mm.min^-1). This was to recreate varying stroke rates and session lengths within rowing. An external circuit was used to measure to the voltage response, with electrodes attached to the surface of the sensor. The sampling rate for the Instron and circuit was 100Hz.

Results

The sensor exhibited low loads across all speeds, with a maximum of 6.53N being recorded at 350mm.min^-1 and 6.29N at 350mm.min^-1. During cycling, the average voltage range was 2.02V. Over 100 cycles at 350mm.min^-1, maximum voltage values were noted as 2.10V and 2.05V for two tests, and ranges as 2.05V and 2.00V.  Load ranges for the same tests were 7.51N and 6.96N respectively.

Discussion

Repeatability was displayed by the flexible strain sensors as there was little variation between the load and voltage ranges and peaks under the same cycling conditions. The same sensor was able to be used under all the different cycling conditions showing no sign of fatigue. This suggests durability and long-term use of the sensor and when needing to be replaced, the fabrication method is low-cost and also repeatable. Higher loads were experienced by the sensor at 350mm.min^-1 compared to 100mm.min^-1.

Acknowledgements

Professor Alison McGregor, Dr. Peter Sherrel, Mr Matthew Hopkins - Imperial College London

References

1. Thornton, J.S., et al., (2016). Sports Med, 47(4), p650
2. Hickey, G. J., et al., (1997). The American College of Sports Medicine, 29(12) p1570

Introduction

A multi-segmental trunk behavior appears to play an important role during explosive dynamic movements [1]. In three-dimensional movement analyses, the trunk has often been simplified to a single or small number of linked-rigid body segments to reduce the complexity of its flexible multi-segmental structure [2]. However, this simplification could underestimate the mechanical outputs caused by multi-segmental trunk behavior [3]. This study aimed to quantitatively examine the kinetic contribution of the trunk, when the trunk was modeled with different number of linked-rigid body segments.

Methods

Ten male subjects performed maximal-effort countermovement jumps (CMJ), while three-dimensional whole-body kinematic data and ground reaction forces were obtained using a three-dimensional motion capture system and two force platforms. The trunk was modeled with a single or three linked rigid-body segments (M1, M3 models) [2]. The M1 model included the feet, shanks, thighs and one trunk segment linked with the ankle, knee, and hip joints. The M3 model further separated the trunk into three segments: the lower trunk, middle trunk, and upper trunk linked with lower and upper trunk joints (Fig.1-a). Newton–Euler equations were used to calculate the joint forces and moments. The total joint work was then calculated to examine the difference in the trunk kinetics between these models. Paired t-tests were performed to examine the difference in the joint work for each joint and total joint work between the M1 and M3 models. The significance level was set at p<0.05.

Results and Discussion

The total joint work in M3 was significantly larger than in M1 (Fig1-b), which suggests that the joint work in the trunk would be underestimated when the trunk was modeled with a single-rigid body segment. For M3, the percent contribution of the lower trunk and upper trunk joint to the total joint work were 2.7 and 11.1 %, respectively. This indicates that approximately 14% of the total joint work could be produced in the trunk during CMJ, when the trunk was modeled with three rigid-body segments. These findings imply that the number of rigid body segments to model the trunk would significantly affect resultant trunk kinetics, and thereby the number of segment should be considered when analyzing the kinetic contribution of the trunk during dynamic movements.

References

[1] Sado, N., et al., (2017). Sports Biomech., 16(2), p258.

[2] Pablo, d, L., (1996). J. Biomech., 29(9), p1223.

[3] Kudo, S., et al., (2017). J. Biomech., 59, p116

Introduction: In this retrospective study, a cluster analysis was conducted on the balance and vestibular diagnostic database of the Swiss Concussion Center (SCC). The first goal of the study was to evaluate what clustering tool might be most appropriate to use for extracting subgroups from the concussive population. The second goal was to identify what features were most discriminating between the subgroups.

Methods: For the cluster analyses learning (Self-Organizing Map, SOM-toolbox for MATLAB 5¹, SOM) and non-learning (Kmeans) tools were compared by calculating the overlap between the methods. Diagnostic data from the balance and vestibular battery were extracted from patient files, as well as sex, age, sport type, time since injury and symptoms reported by patient. All information except from the symptoms was used for cluster analyses. The desired number of clusters was estimated with the cluster evaluation function within the machine learning toolbox of MATLAB using Calinski-Harabasz criterion. Stability of the clustering tool was tested by repeating the clustering procedure 3 times and calculating the highest number of patients clustered differently, if this was above 10 the result was seen as unstable. The subgroups formed were compared with Mann-Whitney-U, chi-square and Fisher-exact tests, eta square was used to calculate effect size. Significance was set at 0.0006, after the Bonferroni correction.

Results: In total 96 patients (81.3% male, age: 26.1±9.0) suspected of suffering from a concussion or a post-concussion syndrome were included. Cluster evaluation indicated to divide the data into two groups, agreement between the methods was 76%. While results from the SOM were stable, the results from the Kmeans were not. When comparing subgroups, the biggest difference was found in caloric scores for maximal speed of the slow phase (mSPV), where group 1 scored 30.7% lower than group two. Group 1 also scored significantly lower on postural stability and higher on dynamic visual acuity (DVA) outcomes and tended to report headache, visual and balance problems more frequently while group 2 reported more anterograde amnesia (>10% difference). 

Discussion: Only the SOM gave a stable outcome, therefore it might be a more appropriate method for extracting subgroups from the concussive population when the number of patients is low. The SOM divided the data into one group with clear vestibular problems and another with no clear vestibular or balance pathology. Especially mSVP values showed to diver between the groups. The next step will be to compare the subgroups with clinical diagnoses and therapy outcomes.

Acknowledgements: The authors like to thank the clinicians of the Swiss Concussion Centre for their collaboration.

References:

1.         Vesanto J, Alhoniemi E. Clustering of the self-organizing map. IEEE Trans Neural Netw 2000;11:586-600.

During mastication, food is broken down by the balanced mechanical action between several juxtaposed dental tissues. Thus the necessary mastication forces are achieved while avoiding damage to the tissues. One important component is a thin and compliant soft tissue, the periodontal ligament (PDL) that helps channelling the mastication forces from the tooth into the surrounding jaw bone. As a result, each tooth moves substantially in its anchor-site during a typical chewing stroke. In a series of experiments [1]we studied the reaction of three-rooted teeth to a single chewing event by finite element (FE) modelling. To consider its nonlinear behaviour the PDL was modelled as a hyperelastic material. The in silico results are validated by our own in vitro experiments. We examine the displacement response of the complete tooth-PDL-bone complex to increasing chewing loads. The varying thickness of the PDL was shown to be an important factor leading to significantly different tooth reaction movements, PDL strain and bone stress. When reproducing the varying geometry of the PDL observed in vivo, FE simulations reveal subtle but significant tooth motion that leads to an even distribution of the stresses in the jaw bone, and to lower strains in the PDL. Furthermore, the results of our in silico experiments are in agreement with recent studies [2,3] on different animal models. To conclude, our work helps to gain a better understanding of the role of the variable PDL geometry in the tooth-PDL-bone complex during mastication.

Ever since the invention of the wheelchair, many improvements in terms of technological and functional features have been escorted for the patients. Nevertheless, the amount of evolutions suggestively decreased over the last decade. Manual wheelchairs (MWCs), today appear to be obsolete, cumbersome, and stigmatizing while the daily use remains far from ergonomic. Indeed, most of the wheelchairs are designed on a static seat basis. These seats associated with hand-rim propulsion, leading to micro-traumas to the wrist and shoulder joints and affecting the patient’s daily life even more difficult. Various researches have recommended alternate propulsion mechanisms of higher energetic efficiency.

The main aim of this study is to propose a new concept of MWC focused on novel kinematics, including a lifting system which is fully synchronized with the whole structure (seat, headrest, backrest, armrests). Operation simply consists in actuating a lever at the seat level in order to switch from seated to lifted position. Contrary to the classical MWCs, the guiding wheels are placed at the rear, while large driving wheels are positioned at the front. This design mostly aims at making the obstacles easier to manage.

Maneuverability of the propulsion system has always last as a major ergonomic concern. Three main categories of manual propulsion systems can be distinguished from the literature: 1) the classical hand-rim propulsion, 2) the hand-cycling and 3) the lever propulsion. Each manual propulsion displays both advantages and inconveniences. Some are unsuitable for standing propulsion while others are very bulky, noisy and require thorough maintenance. By contrast a good mechanical efficiency (about 15%) is provided. The lever propulsion system proves more efficiency than the conventional propulsion, which hardly ever exceed 10%. Moreover, the lever propulsion can be easily adapted for vertical mobility and results in fewer and lower traumas for the upper limbs.

The musculoskeletal numerical analysis performed in this study compared performance of the movement on a conventional hand-rim propulsion mechanism to the lever propulsion mechanism. Results confirmed that the use of the lever was less traumatic in the sense that effort is distributed on a greater number of muscular groups. More precisely, physical exertion was distributed on the deltoid, triceps, brachial and flexor muscles. The major pectoral, great dorsal and trapezium muscles also remained permanently involved in the movement. This not only allows the prevention of secondary disabilities that can be observed among users today, but rather provides increased mobility for people with low physical endurance - the elderly or quadriplegic subjects mostly. The new wheelchair prototype will finally be presented to manufacturers for optimization purposes.

Introduction

The primary measure of performance of a medical guidewire is its torque response, i.e. the rotation of the guidewire tip in response to rotations applied by the surgeon. Mechanical performance of guidewires is dominated by the behaviour of the metal core which are typically stainless steel or cobalt chrome alloys. Phenomena such as lag, whereby the tip rotation is less than the user input rotation, and whip, whereby this lag is suddenly recovered via the release of elastic energy, are undesirable. This work seeks to elucidate the relationship between these phenomena and material properties. The stress states for combined bending and torsion in plastic materials have previously been studied [1,2] however, the interaction between the stress state, material properties, and guidewire performance has not been studied.

Methods

The guide wire, radius r, is modelled using three-dimensional continuum finite elements with an elastic, perfectly plastic material definition using J₂ flow theory. Subsequent models introduce material hardening with tangent modulus E_t. The curved path is represented by rigid surfaces with frictionless contact. The initially straight wire is inserted into the curved path, which imposes a curvature 1/R and then a rotation about the long axis of the wire is applied at A (Fig 1.a).

Results

Simulations show that decreasing the yield strain ε_y to a value less than the maximum strain in the wire ε_m=r/R=0.05 elicits the lag phenomena (Fig 1.b) whereby the rotation at B is less than the rotation at A. Similarly, for ε_y≥ε_m there is no reaction moment for the applied rotation at A; as material is stretched during rotation, a corresponding volume of material on the opposite side of the wire is unloaded (Fig 1.c). Plastic yielding removes this symmetry and thus work is required to rotate the wire for ε_y<ε_m. Introducing hardening and a straight section of wire captures the phenomena of whipping (Fig 1.d); lag is observed for ~5π followed by a sudden change in behaviour where the changes in input angle are now observed at B.

Discussion

The lag and whip phenomena observed in clinical and bench-top testing of guidewires are captured here and are strongly linked to the plastic behaviour of the guidewire material. Lag is caused by dissipation of energy in plastic yielding and the whip phenomenon is the sudden release of torsional elastic energy; adding the straight section increases the available elastic energy to be released.

Acknowledgements

This research is supported by Science Foundation Ireland and is co-funded under the European Regional Development Fund under Grant Number 13/RC/2073

References

1. Hill, R., and M.P.L. Siebel, (1953) JMPS,1(3) p207

2. Christopherson, D.G., (1940) Aeronaut J,44(353) p425

Introduction:

The ear canal is an air filled tubular structure with a three-dimensionally curved irregular geometry. The ear canal matures in length and volume with age [1]. Further, there are variations in the shape of the canal between individuals. This variation in the canal shape and dimensions will affect the acoustic properties of the ear.

Methods:

High Resolution Computed Tomography (HRCT) scans of the temporal bone was used for three-dimensional (3D) model reconstruction of the ear canal. Two volunteers CT data was used in the study (2 and 21 year-old male). For uniformity, left ear canal of each patient was 3D reconstructed by manual segmentation approach in MIMICS® v17.0. Reconstructed 3D model was meshed and finite element analysis (FEA) was carried out using ABAQUS® v6.14. The number of elements in the FEA mesh was 15,093 and 39,225 for 2 and 21 year subjects respectively. The meshing was carried with acoustic quadratic element for the air in ear canal while the tympanic membrane was meshed with quadratic membrane element. FEA was carried out using a steady-state dynamic analysis. A localized finer meshing was also performed along the ear canal opening and the tympanic membrane with a maximum element size set to 2 mm. To reflect an actual ear canal closely, the canal was made partly of cartilage and partly of bone. The material properties on the boundary was assigned accordingly. An acoustic pressure of 94 dB with the frequency varying from 100 Hz to 10 kHz was applied at the entrance of the air-filled ear canal.

Results:

For the simulated steady state inlet acoustic pressure at the entrance of the ear canal, the acoustic pressure at the tympanic membrane was studied at different frequencies. The peak pressure at tympanic membrane was observed at 4751 Hz for 2 year old male and 3765 Hz for 21 year old male. The measured ECV was 0.38 mL and 0.91 mL for 2 and 21 year old male respectively.

Discussion:

A difference in the peak frequency at the tympanic membrane was observed. The peak acoustic pressure response occurred at a lower frequency of 3765 Hz for 21-year-old and 4751 Hz for 2-year-old, thereby confirming that a change in ECV as well as the length of the ear canal affects the acoustic response. The difference in ECV between 21 and 2 year old is 0.53 mL. From the 3D reconstructed model it is seen that the shape of the canals are different and the angle at which tympanic membrane is present also differs. These difference create a backward shift of the peak pressure response in adult model when compared with the child model.

References:

1. Pracy, Robert. "Developmental anatomy." (1930).

Introduction

The decision of returning to play after anterior cruciate ligament (ACL) injury is often based on a series of objective and subjective standards but the relationship between these diverse measures remains ambiguous. The purposes of this study were to quantify these relationships and determine if scores in the deficient (ACLd) state were correlated to, and capable of predicting a patient’s functional score in the reconstructed (ACLr) state.

Methods

Twenty participants (13 male; 27.7 ± 5.9 years) with an ACL injury completed jump lunge and side cut movements prior to and 10 months post-reconstruction. Their self-reported questionnaire (Tegner, Lysholm, IKDC, KOOS, and KNEES) scores were related to objective measures of functional ability (peak knee flexion, peak knee extensor moment, knee joint stiffness, knee joint center excursion (KJCE), and knee joint center boundary (KJCB). Stiffness was the change in knee sagittal moment over the change in knee sagittal angle, KJCE was the Euclidean distance traveled by the KJC, and the KJCB was the Euclidean distance between KJC of three within-participant trials and summed for each time-step. Spearman and Pearson correlations were used to determine relationships between variables while linear and ordinal regressions were used to identify ACLd score’s predictive ability of an ACLr score.

Results

Relationships between objective and subjective measures were task and ACL status dependent with KJCE and stiffness most commonly being related to subjective scores. The greatest correlation observed was between knee stiffness and Tegner in the ACLr group during the side cut (r = 0.69, p = 0.002). Peak knee flexion angle (r = 0.66 - 0.83, adj. R² = 0.4 – 0.66) was the best objective predictor between ACLd and ACLr states (Figure 1) while KOOS-ADL had the strongest correlations (r = 0.70 – 0.77) and Tegner had the greatest predictive power (Odds Ratio: 1.46 -1.86) between states in both tasks.

Discussion

The current results suggest that using these more dynamic functional measures led to stronger correlations than what have been observed for non-weight bearing clinical laxity and other functional performance measures (1). Predictive results demonstrated that given the task, some scores in the ACLd state are in fact effective at predicting the performance of the same patients once they have received their elected operations. These findings can therefore provide information and encourage an evidence-supported discussion between the clinician and patient when determining the appropriate course of treatment.

References

1. Snyder-Mackler L, et al. Am J Sports Med; 25(2):191–5.

Figure 1. Pearson correlation coefficients (r) for the objective functional ability measures and Spearman correlation coefficients for the subjective functional ability measures. Results display the relationship between the ACLd and ACLr state for the jump lunge and side cut tasks. Darker shade represents p value ≤ 0.05.

Introduction

It has been widely accepted that movement is inherently variable. Vertical jumping is a discrete skill requiring effective coordination of the lower and upper limbs for optimal movement, within which variations in movement strategies have been observed [1]. Considering the variant and invariant characteristics of movements, between and within individuals, can be valuable in understanding strategies individuals use to achieve the same movement outcome. Principal component analysis (PCA) is a technique that reduces multidimensional data to key features of a movement and highlight variations in the structure of a movement between individuals [2]. This analysis can be valuable within biomechanical research to understand the structure of movements. Therefore, the aim of this study is to determine the main characteristics of vertical jumping and how these are represented between and within individuals.

Methods

Thirty eight physically trained males (n=24) and females (n=14) took part in this research. Prior to commencing testing participants completed a warm up. Following this 18 reflective markers were placed on the right lower limb. Participants then completed five maximal effort countermovement jumps with hands on the hips. A motion capture system (Vicon V5, Oxford, UK) was used to obtain kinematic data (500Hz) while two force plates (Kistler 9287BA, Kistler Instruments Ltd, UK) recorded ground reaction forces (1000Hz). Data was processed using freely available software (Freebody) and a standard inverse dynamics analysis was performed to obtain internal kinetic data. Each participant’s data was normalised to allow comparison between repetitions. A PCA was performed on lower limb joint moment data for five repetitions of the countermovement jump.

Results

The PCA results from eight representative participants indicate for most participants one principal component is required to explain over 90% of the variance in a countermovement jump. Only three participants required two principal components to explain over 90% of the variance. Figure 1 displays the first principal component from hip joint moment data across the eight representative participants.


Figure 1. First principal component for hip moment data from eight representative participants. 

Discussion

Initial results suggest the first principal component can be used to explain the majority of explained variance in vertical jumping. This poster will present a comparison of PCA results between individuals to establish if this finding is consistent among individuals from various training backgrounds.

References

1. Vanezis A., et al., (2005). Ergonomics, 48(11) 1594-603
2. Daffertshofer  A., et al., (2004). Clin Biomech, 19(4) 415-428

Introduction
Anterior cruciate ligament (ACL) injuries are common and occur primarily in athletes involved in sports with pivoting movements. Further, females have ~3-8 times higher injury incidence rate compared to males. The ACL is an important structure in controlling knee joint stability and a rupture leads to negative consequences for knee function and stability. Knee laxity, i.e. anterior tibial translation in relation to femur, increases after an ACL rupture. To be able to return-to-sport a goal of rehabilitation is to reach high functional level and a stable knee. When evaluating knee laxity after an ACL injury reliable methods are needed as well as reference values. The aims of the study were to; 1) examine test-retest reliability and agreement of knee laxity 2) evaluate knee laxity in elite athletes and controls without knee injuries 3) compare knee laxity in ACL-injured persons compared to athletes and controls.

Methods
So far 43 females (age 23±4 years) have been included in this ongoing study comprising three groups; 15 ACL-injured treated with ACL-reconstruction (ACLR) (3.7±3.3years), 14 athletes and 14 controls. Of the 43, 19 have been tested twice within 7-30 days (17.5±6.6 days) for test-test reliability of knee laxity for both legs using a KT1000 arthrometer. All tests were performed by the same test leader. Three repetitions and three loads (15, 20, 30 lb) were tested but so far only 30 lb was analysed. Test-retest reliability and agreement were analysed with intraclass correlation coefficients (ICC_3,1) and with typical error (TE) and minimal differences (MD), respectively[1]. Paired t-tests and ANOVAs were used for legs and group comparisons (p<0.5).

Results
Preliminary results indicate excellent test-retest reliability (ICC_3,1 0.78 for dominant leg and 0.86 for non-dominant leg) with TEs and MDs of 0.9 and 0.8 mm and 2.6 and 2.1 mm respectively. The injured legs of ACLR had larger knee laxity values compared to non-injured leg (p<0.001) as well as compared to athletes (p<0.001) and controls (p=0.009). No paired leg differences were seen for athletes or controls. Athletes had however lower knee laxity values compared to controls (p<0.001 regardless of leg) and to non-injured legs of ACLR (p=0.001).

Discussion 
The results suggest that knee laxity can be reliably estimated using the KT1000 and that elite athletes have more stable knees compared to controls and non-injured legs of ACLR. Further, despite ACL-reconstruction the knee has larger anterior tibial translation several years post-surgery which needs to be considered in relation to return-to-sports. Laxity should also be related to more advanced biomechanical measures of dynamic knee stability during functional tests.

Acknowledgements
Funding support

References
1. Hopkins, W.G., Measures of reliability in sports medicine and science. Sports medicine NZ;2000;30(1):p.1-15

The human body contemplates two distinct ages called “The Chronological Age” and The Biological Age”. The Chronological age manifests the time a human  has  been  alive  that  is  the period  in  years,  days  and  minutes  from  the moment someone is born. On the other hand, the Biological age is the true manifestation of how the body is developing or breaking down compared to the average. Invariably, the biological age refers to how old the person seems in terms of functionality or physiology. As a matter of fact, while all of us age chronologically at a same rate but our bodies run on a separate biological clock, which means the bodies of two people at the chronological age of 50 years, could have significantly different biological ages. Therefore, a person's biological age could be a better measure for determining his health than the chronological age. The prevalence of age related diseases such as Alzheimer, Osteoporosis, and Dementia are strongly found to be related to biological age. The ability to accurately distinguish a person's biological age could not only determine the onset of Dementia and Alzheimer at an early stage but could also considerably increase the success rate of organ transplant by matching the biological age of the patient with that of the donor. Human development is the process of growing to maturity. In biological terms, this entails growth from a one-celled zygote to an adult human being.

Maturation of different systems tends to proceed independent of chronological age, therefore chronological age is not a good indicator of biological maturity.  Nevertheless,  the  growth and maturity status of an individual or sample of individuals is routinely placed in the context of chronological age.

So, the objective of this paper is to find out the effect of biological maturity on physical, physiological and biochemical parameters in adolescents.

Keywords: Biological Age, Chronological Age, Early Maturer, Late Maturer.

Introduction
A mechanical stability of nine minimally invasive fixation techniques for treatment of transforaminal fractures of sacral bone is studied both experimentally and computationally. The investigated techniques are based on application of transiliac internal fixators [1], iliosacral screws [2], sacral bars [3], transiliac plates [4] or their combinations.

Methods
The experimental study is performed using orthopaedic models [5] rather than cadaveric pelves in order to maintain consistency and repeatability of the tests. This provides a solid base of unambiguous data for validation of computational models being developed. Each fixation technique is experimentally tested using a new pelvic model and the tests are performed for both intact pelvis and fractured pelvis with the fixation applied. Stability of each fixation is evaluated according to the stiffness of the treated pelvic structure and to the relative displacements of both parts of the fractured bone under loading. A multi-camera digital image correlation (DIC) system is applied in order to resolve deformations at dorsal surface of the sacral bone. Displacements of the sacral base under loading are monitored by an extensometer.

The computational models of the pelvic structure treated with fixators are based on CT scans and implemented using the finite element method. Since the validation data are based on orthopaedic models made of solid foam, the computational models utilise homogenous isotropic material model for bone tissue. Its material parameters are set according to the in-house performed experimental analysis of the applied solid foam.

Results
Decrease in pelvic structure stiffness after the fracture and the consequent surgical treatment is in a range from 9% to 33% based on the fixation technique applied. For comparison, when the fracture is not treated the drop in the pelvic structure stiffness is about 58%. A dislocation of the fractured bone parts without treatment (in terms of displacements [mm]) under 500 N loading can be observed in Fig. 1, which compares results of the computational model and of the DIC analysis.

Fig. 1: Comparison of computational (a) and experimental (b) data for unilateral transforaminal fracture without treatment.

Discussion
Based on a set of well correlated experimental and computational data (which is hard to find in the published literature) fixation techniques using two iliosacral screws or two sacral bars positioned in craniocaudal direction provide the best results in terms of mechanical stability. Nevertheless, potential clinical risks must be considered.

Acknowledgements
This publication was supported by the project LO1506 of the Czech Ministry of Education, Youth and Sports.

References
1. Dienstknecht, T., et al., (2011). Int. Orthop. 35(12) p1863.
2. Giráldez-Sánchez, M.A., et al., (2015). Injury 46(2) p327.
3. Gorczyca J.T., et al., (1996). Injury 27(8) p561.
4. Suzuki, T., et al., (2009). Injury 40(4) p405.
5. http://www.sawbones.com/products/product.aspx?231

Introduction

Body symmetry is a key component of normal movement and represents an essential part of clinical examination. To this end, limb symmetry indices have been reported however with a focus on strength (Lanshammar and Ribom 2011). To date lower limb symmetry for balance, across a range of tasks has yet to be established. 

Methods

Seventeen adults (27.6+/-5.7 years) were recruited from the student body. Volunteers had no prior injury. Balance was measured using two devices: an instrumented wobbleboard (SMARTwobble, THETAmetrix, UK) and a sacral mounted accelerometer (Balance Sensor, THETAmetrix, UK). The wobbleboard quantifies its tilt angle at 15Hz providing percentage time spent in tilt angle bandings (thirds) (Williams and Bentman 2014). The balance sensor quantifies postural sway through tilt-corrected linear accelerations of the sacrum (Williams et al. 2016). Participants completed single-leg stance with eyes-open and closed, single-leg squat on both the dominant and non-dominant limb, with the balance sensor and with the wobbleboard. In addition participants completed forward, lateral and medial hop landing where sacral acceleration were measured for 1 second following landing. Dominant and non-dominant limb balance were compared using Wilcoxon signed rank pairwise comparisons and percentage differences between limbs was calculated.

Results

There were no significant differences between the dominant and non-dominant limb for any balance task. The limb symmetry for balance varied from 3.4-4.5% for wobbleboard tasks, 1.8-8.6% for single-leg stance and squat tasks and 0.9-12.1% for hop landing tasks.  

Discussion

This study set out to quantify the lower limb symmetry index for balance across a range of tasks. These values serve as critical knowledge to guide clinical decision making. Clinicians should use these values as targets for the rehabilitation of individuals with unilateral limb injury or pathology. Moreover such values may serves as a guide for screening programmes where impairments in symmetry maybe identified. This is also the first study to use accelerometery to measure balance associated with hop landing and such a method maybe usable for high level clinical balance measurement. 

References

Lanshammar K, Ribom EL. Difference in muscle strength in dominant and non-dominant leg females aged 20-39 years – a population based study. Physical Therapy in Sport. 2011.12:76-9.

Williams JM, Bentman S. An investigation into the reliability and variability of wobble board performance in a healthy population using the SMARTwobble instrumented wobble board. Physical Therapy in Sport. 2014.15:143-7.

Williams JM, Dorey C, Clark, S, Clark C. The within-day and between-day reliability of using sacral acceleration to quantify balance performance. Physical Therapy in Sport. 2016. 17:45-50.

Purpose: After an anterior cruciate ligament(ACL) tear, reconstruction surgery(ACLR) is performed with aims to restore mechanics of the limb. Neuromuscular mechanics of the lower extremities(LE) can be affected asymmetrically due to alterations in weight bearing and integrity of the reconstructed ACL. The ACL is comprised of inert tissue, which has lower adaptability under tension. With altered LE mechanics after ACLR, mistranslated force distribution between joints can increase risk for secondary tears while running, jump-landing or cutting. The purpose of this study was to analyze walking, jogging and sprinting using 2-Dimesional(2D) motion analysis to assess LE limb asymmetries in individuals with ACLR.

Methods: 6 ACLR(4 females, 2 males, age 20.5±1.6yrs, 2.6±1.4yrs post-surgery) & 6 BMI-matched controls(CON) participated. Participants walked(WALK) for 2 minutes, jogged(JOG) for 2 minutes and sprinted(MAX) for 30s at self-selected speeds on a treadmill. Apple iPads were used to record 2D joint kinematics in the sagittal plane. Maximum joint angular displacements(AngDisp: max flexion to extension) at the hip, knee and ankle were analyzed via Kinovea^©. AngDisp were compared between groups using Kruskal-Wallis H Test. ACLR limbs were compared to dominant limbs(Dom) and healthy ACL limbs(UnI) were compared to non-dominant limbs(NDom). Limb symmetry indices(LSI) were calculated(Involved/Healthy*100) for participants.¹ Differences in LSI were compared between ACLR and MC groups.

References:
1. Lynch, A.D., et al. (2015). Br J Sports Med, 49(5) p335
2. Capin, J.J., et al. (2017). Clin Orthop Relat Res. 475(10) p2531
3. Wiggins A.J., et al. (2016). Am J Sports Med. 44(7) p1861

Introduction

Few studies report on the geometry of the costovertebral joint and how it is affected by scoliotic deformity. Preliminary studies in our lab show the ribs of AIS subjects to be bilaterally morphologically symmetric, while the orientation of the ribs relative to the vertebrae differ bilaterally and are distinct from skeletally normal subjects. How this mal-rotation of the ribs in AIS affects the geometry of the costovertebral joint is unknown.

Methods

Retrospective chest CT scans were collected from 6 AIS subjects (5F/1M, mean age: 14.09±1.62 years, primary curves between T5 and L1, mean Cobb angle: 60±17.7 degrees and 6 age and sex-matched skeletally normal subjects (6F, mean age: 13.89±1.55 years) selected from a cohort of 100 normative scans using linear programming. Using MIMICS (Materialise Inc., Belgum), the vertebrae and ribs of each subject were digitally reconstructed in 3D, and manually segmented to isolate rib-vertebra units (a thoracic vertebra and its associated rib pair) from T1 to T10. To insure comparability of measurements within and between AIS and normal subjects, each rib-vertebra unit was rotated such that the endplates of the vertebral body lay in the transverse plane with the sagittal plane bisecting the vertebral body. The position of the rib head was recorded along the lateral, superior-inferior, and anterior-posterior directions relative to the centroid of the vertebral body. Measurements were collected bilaterally for all subjects and separated into right and left measurements for normal subjects and into convex and concave measurements for AIS subjects. Permutation tests with 10,000 replications were used to examine bilateral symmetry in both normal and AIS subjects and to evaluate differences between right and convex and left and concave measurements between normal and AIS subjects.

Results

No bilateral asymmetry was found in either the AIS or normal subjects; however, significant differences (p ≤ 0.0008) between normal and AIS subjects were found for right/convex lateral rib head distances at T3, T4, and T6, and for left/concave lateral rib head distances at T2 and T5.

Discussion

Differences between skeletally normal and AIS lateral rib head positions suggest a lateral subluxation of the rib heads in AIS. Such a dislocation may affect thorax morphology and impair pulmonary function.

Acknowledgments

Scoliosis Research Society

Introduction

Surgical treatments for adolescent idiopathic scoliosis (AIS) are typically successful in correcting spine curvature, but not the associated rib hump which is a common source of dissatisfaction for patients. It is assumed that this prominence results from malformation of the ribs; however, there is a lack of agreement in the literature regarding the extent of rib deformity in scoliosis.

Methods

Retrospective chest CT scans were collected from 6 AIS subjects (5F/1M, mean age: 14.09±1.62 years, primary curves between T5 and L1, mean Cobb angle: 60±17.7 degrees) and 6 age and sex-matched skeletally normal subjects (6F, mean age: 13.89±1.55 years) selected from a cohort of 100 normative scans using linear programming [6]. Using MIMICS (Materialise Inc., Belgum), the vertebrae and ribs of each subject were digitally reconstructed in 3D, and manually segmented to isolate rib-vertebra units (a thoracic vertebra and its associated rib pair) from T1 to T10. To insure comparability of measurements within and between AIS and normal subjects, each rib-vertebra unit was rotated such that the endplates of the vertebral body lay in the transverse plane with the sagittal plane bisecting the vertebral body. Bilateral rib centerlines consisting of 30 points per rib were generated from each oriented rib-vertebra unit and used to measure frontal, lateral, and axial rib angles, width-to-depth ratios, and apparent curvature at 10% intervals along the length of each rib. Permutation tests with 10,000 replications were used to examine bilateral symmetry in both skeletally normal and AIS subjects and to evaluate differences between right and convex and left and concave measurements between skeletally normal and AIS subjects.

Results

No significant bilateral differences were found for any rib morphology measures in the skeletally normal and AIS subjects. Significant differences (p ≤ 0.0008) between convex and concave sides were found for frontal angles at T4 and T5 in AIS subjects. Significant differences (p ≤ 0.0008) between skeletally normal and AIS subjects were also found for right/convex frontal angles from T4 to T6, for right/convex axial angles at T7 and T8.

Discussion

Previously, it has been assumed that rib cage deformity in scoliosis is the consequence of rib malformation. As a result, rib resections are commonly performed to reduce rib hump and improve cosmesis following a scoliosis surgery. However, the current study found significant bilateral differences in rib orientation but not geometry which suggests that the rib hump in scoliosis may be due to positional asymmetry of the rib pairs rather than deformity of the structures. These findings suggest that future treatments for scoliotic rib cage deformity should consider rib de-rotation.

Acknowledgments

Scoliosis Research Society

Introduction

Loosening of the acetabular cup accounts for more than 50% of revisions and is strictly related to the primary stability¹.  The assessment of micromotions and migrations of acetabular reconstructions is an unsolved problem.  The aim of the present work is to measure the displacements at the cup/bone interface, and the strain map of the cranial region of the acetabulum during load, through the use of the Digital Image Correlation (DIC).

Methods

A commercial DIC system (Dantec) was used to measure relative displacement between cup and bone.  To acquire 3D data, two 5Mpixels cameras were used. Hemipelvises in polyurethane were used to optimize the black-on-white pattern for the correlation and the setup for imaging and analysis.  Hemipelvises in composite material were used to measure the maps of displacement and strain under load.  The hemipelvises were implanted with primary press-fit acetabular cups (Plasmafit, Aesculap).  A standardized protocol was used to reproducibly implant the specimens, and to align them consistently². The hemipelvises were oriented in a way that simulates a peak load during walking³. The implanted specimen was loaded through the cup.  A single ramp (0-2BW) was applied.  The relative motion was measured by tracking patches in the cup and in the surrounding bone.  The full-field distributions of principal strains were extracted.

Results

The system was able to correlate the specimen throughout the test; maps of displacement and strain were successfully computed.  The relative motion at the cup/bone interface grew non-linearly from 120μm at 1BW (about 100μm along the direction of load) to 270μm at 2BW (about 210μm along the direction of load).  The largest strains were measured at the cranial/posterior region, close to the acetabulum, and grew linearly with load.  The maximum principal strains were in the order of 3000μξ at 1BW and 6000μξ at 2BW.  The minimum principal strains were in the order of -2000μξ at 1BW and -4000μξ at 2BW. 

Discussion

This study demonstrated, for the first time, the feasibility of using DIC to measure at the same time the relative displacements at the cup/bone interface, and the full-field distribution of strain of the surrounding bone. The regions that withstood the highest strains are comparable with other in silico studies in the literature. The next step will consist in applying a cyclic load up to 2-3BW, in order to assess the primary stability in vitro with the DIC.

Acknowledgements

Aesculap AG for funding this study.

References

1. Leif Haveli et al. (2009). The Nordic Arthroplasty Register Association. Acta Orthopaedica, 80(4):393-401.
2. F. Morosato, F. Traina, L. Cristofolini (2017). Standardization of hemipelvis alignment for in vitro biomechanical testing, J.Orthopaedic Research.
3. G. Bergmann et al. (2001). Hip contact forces and gait patterns from routine activities, J. Biomechanics.

Introduction

Kinesiotaping® (KT®) uses an elastic tape to provide a constant shear force to the skin over which it is applied. It has being widely used for rehabilitation, prevention and performance enhancement purposes. According to the creator (1), KT improves muscles and joints function, circulation of blood and lymph, and it seems to improve proprioception by stimulating cutaneous mechanoreceptors (2). Purpose of this study is to evaluate if KT application on ankle joint may improve dynamic balance in semi-professional football players.

Methods

15 semi-professional football players (age: 25.6 ± 5.1 yrs, BMI: 23.2 ± 1.7 kg/m2) from the same team (A.C. Fucecchio), without lower limbs pain and injuries in the last 6 months were recruited. Each participant was tested in three different conditions: without KT, with tape and with placebo tape. Placebo tape and KT were placed by the same-trained physical therapist. KT was applied according to Kase (1) recommendations. Condition test order was randomized and 15 minutes rest was allowed between each testing condition. Both static and dynamic balance tasks were performed for the dominant limb three times. During static task, subjects were asked to stand as still as possible for 10s, with the dominant leg on force platform. During dynamic task, subjects performed a maximal vertical jump and, after landing on force platform with the dominant leg, remained for 30s. Force platform was used to evaluate centre of pressure (CoP) motion. For the static task, sway area (95% confidence ellipse) was taken. For dynamic task maximum jump height, anterior-posterior (AP) and medio-lateral (ML) CoP time to stabilization (TTS) and maximal excursions were evaluated. TTS was calculated for both directions as the time taken for the AP and ML COP trajectories to arrive within reference values measured in the static task. A threshold was calculated as the mean plus three times the standard deviation of the ML or AP trajectory acquired for the static task. Analysis by ANOVA for repeated measures (3 conditions) was used to assess the overall effect of different condition on data.

Results

For the static test, no significant differences were found among testing conditions for the sway area. Similar results were found for the dynamic test, as no significant differences were found among testing condition for all variables measured (Fig. 1).

Discussion

The application of KT tape does not appear to improve static balance and dynamic balance after maximal vertical jump in healthy trained semi-professional football players. Further studies are need to evaluate possible improvements in different subjects groups and different tasks.    

Acknowledgements

None.

References

1. Kase, K., et al., (1996). Kinesio Taping Association, 6(10), p117.
2. Nakajima, M. A., et al., (2013). Int J Sports Phys Ther. 8(4): p393.

Ultra-high-molecular-weight-polyethylene (UHMWPE) is the most used material in hip joint replacement. Unfortunately, its oxidative degradation can decreases its mechanical properties with debris production and eventual osteolysis and implant loosening. Some efforts were done to improve the mechanical and molecular characteristic of the UHMWPE in highly cross-linked polyethylenes with different design. It is believed that wear of UHMWPE is to take place via plastic deformation of the polymer, with molecular alignment in the direction of motion that results in the formation of fine. Vitamin E was introduced to solve the oxidation and wear problems of the UHMWPE. The purpose of this work was to investigate the wear performance of vitamin E-stabilised ultra-high-molecular-weight-polyethylene in comparison with those so-called standard and cross-linked polyethylene. We tested four different batches of polyethylenes (standard polyethylene, standard polyethylene doped with vitamin E, cross-linking polyethylene irradiated with 50KG, cross-linking polyethylene irradiated with 75KG), in a hip joint simulator for five millions cycles. Bovine calf serum was used as lubricant. The cross-linking polyethylene irradiated with 75KG configuration maintained a lower mass loss than the other configurations during the whole test (P = 0.032).

Introduction

In clinical and sportive contexts, the symmetrical patterns seem to be necessary and commonly aims to measure abnormal movement patterns. Also analysis of reliability and measurements errors from the raters, biomechanical instruments and physical performance tests, are essential for establishment of protocols in training and rehabilitation programs.

Methods

Twenty asymptomatic athletes’ participants performed physical tests in two distinct phases (pre and post) with 5 min of rest period during lumbar spinal manipulative therapy (SMT) between phases.  
In one single session of data collection, participants were invited to carry out 1 trial of static position, three trials of squat and three trials countermovement jump (CMJ), during pre-phase and repeated the same amount of time spent and sequence during post phase.
Data was collected with motion capture system using opto-electronic cameras and  force platforms to measure the kinetic and kinematic symmetry from both indexes. Through SPSS software (version 24: IBM, IL) and Microsoft Office Excel (version 3: Microsoft Software’s, U.S), the relative and absolute statistical reliability were evaluated considering 95% of confidence intervals.

Results

The symmetry parameters were quantified using the intra-class correlation coefficient (ICC) and standard error of measurements (SEM). The minimal detectible changes (MDC) were also computed from the standard error.
Kinetic Symmetry, presented an excellent relative reliability for static position (ICC=0.92). Good relative reliability was also noted during the squat (ICC=0.77) and Countermovement Jump (ICC=0.71).
Kinematic symmetry, presented moderated relative reliability (ICC=0.61) for squat. Good to excellent relative reliability were noted in static trials (ICC=0.78) and countermovement jump (ICC=0.93).
The  SEM and MDC presented lowers and acceptables values in both indexes. 

Figure 1- The blue box, red line and red cross signal indicating variability of percentage values from both symmetry indexes, in all participants.

Discussion

The intra-rater, intra-session, test-retest reliability, agreement and minimal detectible changes of physical performance tests, presented excellent relative reliability and acceptable absolute reliability values, confirming statistically the reproducibility and accuracy of kinetic (local) and kinematic (global) symmetry measured outcomes. Relative to pre to post lumbar SMT, statistical significance differences were found only in static position, namely in local kinetic symmetry in asymptomatic athletes participants.

Acknowledgments

Thank to CAPES, Brazil, for funds supporting Bruno Alvarenga.

References

Robinson, R., Herzog, W., & Nigg, B. (1987). Use of force platform variables to quantify the effects of chiropractic manipulation on gait symmetry. Journal of Manipulative and Physiological Therapeutics, 10(4), 172–176.

Atkinson, G., & Nevill, A. (1998). Statistical Methods for Assessing Measurement Error (Reliability) in Variables Relevant to Sports Medicine. Sports Medicine, 26(4), 217–   238.

Cabral, S., Fernandes, R., Selbie, W. S., Moniz-Pereira, V., & Veloso, A. P. (2017). Inter- session agreement and reliability of the Global Gait Asymmetry index in healthy adults. Gait and Posture, 51, 20–24.

Introduction
Sibilant fricatives such as /s/ and /sh/ are generated by turbulent flow passing through the constriction formed by raising the tip of tongue in the oral cavity [1]. The sound production mechanism of the sibilant have been investigated using both simplified and realistic configuration models of the vocal tract [2]-[5]. However, there are few quantitative data to link the essential acoustic mechanism and the actual flow phenomena. In this study, in order to understand the aeroacoustic mechanism to produce the sibilants, the relationship between the flow and sound acoustic in the vocal tract were investigated by computational analysis and experimental measurements using both the simplified and realistic models.

Methods
A realistic configuration model of the vocal tract used for the computational analysis was constructed from the CT images of a Japanese subject producing sibilant /s/. The simplified model of a straight duct with different rectangular cross-sections was designed based on the dimensions of the realistic model. To calculate both the flow and acoustic fields in the models, a large eddy simulation of a compressible airflow was conducted. The experimental models were also produced using a 3D printer [4][5] and the measurements were carried out for the far-field sound generated by the models as well as the airflow velocity at the several specific points in the models.

Results and Discussion
It was confirmed by the experiments that both the simplified and realistic models produce acoustically the sibilant /s/ at a far-field under a physiological flow conditions [4][5].  The flow fluctuation was observed in the space at the back of upper teeth and the front of lower teeth.  The computational analysis revealed the detail of flow patterns and acoustics in the vocal tract models. Figure 1 shows the instantaneous velocity distribution at the mid-sagittal plane in the models. The flow patterns obtained by the simplified model were well corresponded to those of the realistic model and those results are consistent with the experimental observation. It was also found that the acoustic characteristics of sibilant /s/ were reproduced by the computer simulation using both the simplified and the realistic models.

Figure 1 Instantaneous flow velocity at the mid-sagittal plane; (a) realistic model,  (b) simplified model.

Acknowledgements
This work was supported by MEXT as a Priority Issue II using post-K computer (hp170265).

References
[1] Stevens KN. 1971. J Acoust Soc Am 50, 1180-1192.
[2] Howe MS. and McGowan RS. 2005, Proc R Soc A 461, 1005-1028.
[3] Shadle CH. 1985. PhD thesis, Massachusetts Institute of Technology, Cambridge, MA.
[4] Nozaki K, Yoshinaga T, Wada S. 2014. J Dent Res 93, 207–211.
[5] Yoshinaga T, Nozaki K. Wada, S, 2017. J Acous Soc Am 141, EL314-EL318.

Introduction: Acetabular orientation has profound impacts on the biomechanical function of the hip. Deviations from normal are indicative of multiple disease states, including dysplasia and femoroacetabular impingement^1,2. Knowledge of acetabular orientation, described as anteversion and inclination, is required for hip reconstructive surgery. To aid assessment of acetabular orientation, a semi-automated feature recognition algorithm was developed³. This program provided acetabular version and inclination angles, requiring user specfied locations of pelvis bony landmarks as inputs. Our aim was to remove the dependence of user input by fully automating this algorithm, with the end goal of creating a full suite of femur and pelvis analytical software.

Methods: 3D models of 200 pelvises (200 patients, mean age 41±14.5 yrs; 82:118 male:female) were obtained from CT scans segmented in Mimics (Materialse, Leuven Belgium). Feature extraction was performed in Matlab (MathWorks, Natick MA) on the resulting stereolithography (.stl) files containing surface and vertex data for each pelvis. The algorithm began by detecting the anterior pelvis plane (APP)⁴ defined by three points: the left and right anterior superior iliac spines and the centroid of the left and right pubic tubercles. This was accomplished by creating a convex hull of the pelvis which always contained a plane connecting the three of these points, allowing consistent identification. The program then detected an approximate location of the acetabula by measuring anterior deviation at each point of the anterior pelvis. The selection of the acetabula was further refined by computing radii of curvature across the entire pelvis, knowing the acetabular rim to be a region of high curvature. A graph was then created using the vertices and edges of the identified rim and a curve traced along the regions of highest curvature, resulting in a single curve spanning the entire acetabular rim. A plane was fit to the curve, with the normal vector representing the orientation of the acetabulum (Figure 1).

Results: The difference between version and inclination measures calculated by the proposed automated algorithm and the established semi-automated algorithm had a mean of -0.17° with a standard deviation of 1.20. 95% of measurements made by the automatic algorithm lay between -0.17±2.36° of validated results.

Discussion: The proposed automatic algorithm yielded nearly identical results to the previously-created semi-automatic algorithm. Minor variation occurred within the manual point selection required to initialize the semi-automated algorithm. This form of variance was corrected in the proposed automated algorithm, as the rim selection was based on pre-defined rules instead of user discretion. This algorithm allows for accurate and rapid measurement of acetabular orientation.

References:
1) Merle: JBJS 172:2013. 2) Hirata: Int Orth 38:2014. 3). Higgins: JBJS 96:2014. 4) Tannast: Clin Orthop Relat Res 436:2005.

Introduction

Lung growth and maturation are complex processes of lung development which involve structural components primarily controlled by physical factors. The alveolar distension in size and number promotes pulmonary growth with age [1]. This maturation is characterized by morphometric changes in size, shape, width, and length of lungs, heart and vascular structures till adulthood [2, 3]. This study focuses on characterizing the age- and sex-related changes in the geometric features of the lungs from chest radiographs using automated image processing techniques.

Methods

Retrospectively obtained digital chest radiographs of 90 normal pediatric subjects (39 males and 51 females; ages 1-19 years) were obtained from the Children’s Hospital of Philadelphia, USA. The chest X-ray lung fields were contrast enhanced by Contrast limited Adaptive histogram equalization and segmented using Adaptive K-means clustering followed by morphological operations to generate binary masks. For each subject, geometry-based signatures such as area, major axis length, minor axis length, and orientation were extracted from the left and right lung masks, respectively. For all measures, differences associated with age and sex, along with bilateral symmetry were compared within and between groups using polynomial regression analysis and, Wilcoxon Sign-Rank and Mann-Whitney-U statistical tests.

Results

Figure 1 shows a representative image of the segmented lung masks, and coefficients of the regression equations for each measure. From Figure 1(b), in case of the right lung, the major axis length significantly increases (p<0.05) at a rate of 6.792 mm/year and 10.539 mm/year, for female and male subjects, respectively. This emphasizes rapid growth rate for male subjects as compared to females. Also, the adjusted R-square values were found to be 0.350 and 0.794, respectively indicating significant differences in fitted model coefficients age- and sex-wise between lungs. Statistically significant differences (p<0.05) were observed in the bilateral symmetry of lungs for both sexes using Wilcoxon sign-rank tests. No significant inter-sex lung differences were found for features applied using Mann-Whitney tests except for Minor axis length which showed significant variations (p<0.05) in lung width between sexes.

Discussion

The results entail an accurate analysis of the growth rate patterns in lungs associated with age-, and, within and between groups. Thus, it provides clinical significance in comparing normative pulmonary geometry with an abnormal one. Hence, the work seems to be robust in the detection of lung field geometry with age and between sexes using shape measures for the normal pediatric subjects.

Acknowledgments

Drexel University – School of Biomedical Engineering and Health Sciences, and Children’s Hospital of Philadelphia.

References

1. DiFiore, J. W., et al., (1994). Semin Pediatr Surg, 3(4) p221

2. Grivas, T. B., et al., (1991). J Anat, 178 p21

3. Candemir, S., et al., (2015). Proc SPIE, 9418 p94180Q

Introduction

Individualization of medical treat is one of the hot points of today’s medicine. A computer simulation of orthopedic rehabilitation planning for a patient (born in 1947) with implant placement onto the edentulous mandible was carried out.

Methods

In order to optimize the distribution of functional stresses in the bone tissue around the implants, as well as in prosthetic structures, several implantation schemes were considered: with 2, 4 and 6 implants. Implant computer models were created according to the data given in the accompanying documentation, as well as from the results of direct measurements. To personalize the diagnostic data, mandible cone-beam computerized tomography was done with the dental tomograph Galileos (Sirona). Image processing, including segmentation, creation of a three-dimensional triangulated surface model and a tetrahedral grid, was carried out in the MIMICS program (Fig. 1). The model obtained was supplemented with implants

Fig. 1: Determination of the x-ray density of the mandible

models and passed on to the finite-element complex ANSYS, where numerical simulation was carried out.

Titanium and zirconium dioxide implants 10-11 mm long and 3.5 mm in diameter were taken. For removable dentures schemes were studied on a beam with a semi labile fixation and with rigid locking fastening to the beam, fixed dentures were provided with small cantilevers.

Different loading schemes were considered, corresponding to central (nibble) and one-sided (chewing) occlusion. Central occlusion was modeled by applying vertical or oblique loads to two central implants. There were cases of complete (adhesion on the implant-bone interface) and incomplete (sliding or friction on the interface) osseointegration.

Results

Areas of stress concentration in the bone in all cases arose at the thread tops and carvings, and especially in the vicinity of the implant neck (platform). Micromotions (relative displacement of corresponding points on the implant-bone interface) in the case of complete osseointegration were absent, while for incomplete osseointegration (primary stability) the maximum micromotions appeared on the first (apex) thread.

Conclusions

1. The material of implants and dentures (titanium or zirconium dioxide) has little effect on the stress-strain state of bone tissue.

2. Increased osseointegration (modeled by increasing friction from full slip to full adhesion) leads to a decrease in the concentration of both stresses and displacements.

3. Oblique loads are more dangerous than vertical ones, loading in the lateral part of the artificial dentition is more dangerous than in the frontal compartment.

4. Comparison of different implantation schemes shows that:

• an increase in the number of implants somewhat smoothes the concentration of both stresses and displacements in bone tissues;

• for prosthetics on an edentulous mandible, fixed dentures on a larger number of implants are biomechanically preferable compared to a removable denture.

Acknowledgements

RFBR №17-08-01579 and RFBR №17-08-01312.

Introduction

One of the key factors in the success of dental implantation is osseointegration. Excessive micromobility on the implant-bone (I-B) interface (IF) at loading violates the osseointegration. A natural question arises: is it possible to minimize micromobility by controlling the structural characteristics of the implant, in particular, of the threads?

Methods

In this paper, the emphasis was on immediate loading (primary stability), when osseointegration has not yet occurred and there is no complete adhesion at the I-B IF. The bone was modeled by a half-space, the implant – by a cylinder flush with the half-space surface, the slip condition was set on the implant-bone interface, typical values were taken for the load, geometrical and mechanical characteristics of the bone and implant. Calculations were conducted in ANSYS.

Results

The change in the thread profile was modeled by the variation in the slope angle of the profile sides with a successive transition from the triangular through the trapezoidal and square threads to the dovetail thread. With this, the implant subsidence (global mobility) varied little (a fraction of a percent). At the same time, the maximums of local displacements (relative displacements of the implant and bone corresponding points) – and they are that affect osseointegration – could vary at times (with a general tendency to fall) with this change in the profile of the thread (Fig. 1). Apparently, this is due to the increase in the engagement and,

Fig. 1: Evolution of the displacements pattern at the interface of a dental implant and bone versus thread profile under vertical loading

consequently, in constraint of movements on the faces of the thread. Minima of maximum local displacements were obtained for the square and dovetail profiles. Their values ​​were microns, which corresponds to the results of other authors. In this case, the displacements values ​​grew monotonically from the last turn to the first (apex) one and the maximum was invariably observed at the apex thread turn.

Since the dovetail profile may be problematic in manufacturing the effect of the thread depth and pitch was studied on the square profile. It turned out that an increase in the thread depth from 0.1 to 0.4 mm (as well as reducing the thread pitch from 2.0 to 0.4 mm) led to a decrease in the implant sediment by 3-6% and to a significant (multiple) monotonic fall in the displacements on the IF.

Conclusions

With the same occlusal load values and observed macromobility of the implant the thread characteristics can change micromobility on the implant-bone interface by times.

Minimal local displacements were obtained for the square and dovetail profiles.

Maximum of local displacements was observed at the apex thread turn.

Acknowledgements

RFBR №17-08-01579 and RFBR №17-08-01312.

Introduction. Immediate or delayed loading after implantation in tooth replacement is remained challenging. Previous clinical works stated that the survival rate of the immediately-loaded replacement is comparable with the delayed-loaded. However, the main obstacle against the IL is relied on the primary stability of the implant which is closely dependent on the macro and microstructure of the implant at the bone-implant interface. Numerical simulations along the experimental studies have shown that surface roughness of the implant can moderate the harsh stress values at the interface which is induced by daily chewing loads. The aim of the present study is to numerically investigate the role of surface roughness on stress distribution through the interface in immediately-loaded implant models.

Methods. Finite element analysis was used to calculate the stress distribution at the bone-implant interface. To this end, a precise model of the implant with detailed geometrical aspects was used to be implanted in a jaw bone model derived from the CT-scan data. Three surface conditions of polished, sandblasted, plasma-sprayed were considered as three different surface friction coefficients. Respectively, the coefficients of 0.4, 0.68 and 1.0 were assigned to the models. A force vector (200 N vertical, 20 N lateral) was applied to the occlusal surface of the crown. Having checked the network independence, the finite element model consisted of 367,452 elements.

Results. Simulations uttered that the surface roughness in terms of friction coefficients in the finite element analysis affect the stress distribution at the interface. Roughness influenced stress level in trabecular and cortical part reversely.

Discussion. In this study, an accurate, high resolution, digital replica model of the cortical and underlying alveolar bone structure was generated. An increase in the roughness of the implant surfaces leads to an increase the maximum stresses at the cortical bone interface, while the trabecular bone received lower maximum stresses. The present analysis of immediately loaded implants unveiled that an increase in friction of the implant surface results in higher stress levels at the cortical bone and in lower stress levels at the trabecular bone interface.

Introduction

MRI imaging data allows for nuanced categorization of intervertebral disc degeneration. Pfirrmann et al. [1], for instance, defines five grades of disc degeneration depending on image attributes such as the signal intensity and homogeneity of the nucleus, discriminability of annulus and nucleus or disc height.

While easy to understand and apparently intuitive, applying Pfirrmann’s scheme in practice in a consistent, unbiased manner has proven to be difficult. This limited reproducibility interferes with the requirements of studies that rely on consistent grading, such as longitudinal studies. We therefore developed a system that automatically and reproducibly classifies MRI images of discs.

Material & Methods

At the core of our system is a deep convolutional neural network (CNN), consisting of eight convolutional layers and two fully connected classification layers. We trained the CNN to map gray-value images of the disc to one of 13 possible degrees of degeneration (1.0, 1.3, 1.7, …, 5.0).

To create the training set, we evaluated the lumbar discs of 1238 T₂-weighted MRI data sets, resulting in 6182 training samples, which we quadrupled to 24,728 via augmentation. 90 % of this data was used for supervised learning, while the remaining 10 % constituted the validation set for estimating the prediction error.

Results

In more than 97 % of the validation set cases the CNN exactly agrees with the human evaluator and in 99.9 % the CNN’s grading deviates no more than one Pfirrmann level. The mean prediction error is 0.14 (RMSE) or 0.03 (mean absolute error) grades, respectively. The ground truth and the CNN’s grading are highly correlated with Kendall’s τ = 0.97 and Pearson’s r = 0.98. Expressed in terms of interrater reliability (human evaluator vs. artificial neural network) this corresponds to an unweighted Cohen’s κ = 0.96 (0.97 with linearly weighted errors).

Discussion

Our system demonstrates excellent consistency with its human “teacher”, surpassing even the intrarater agreement of 88 % of the human evaluator. Considering the modest interrater reliability of the Pfirrmann grading scheme with an agreement somewhere between 45 – 85 % according to [1,2] (76 % according to our own investigation) and κ ranging between 0.49 and 0.81 [1,3–5], our system already achieves superior reproducibility compared to human evaluators.

Pfirrmann grades 1 and 5 are highly underrepresented in our training data set, leading to a low sensitivity for these degeneration grades. To improve the prediction quality further we are currently adding more training data covering these classes to complement the existing training set.

References

[1] Pfirrmann et al., Spine. 26, 1873–1878 (2001)

[2] Urrutia et al., Eur Spine J. 25, 2728–2733 (2016)

[3] Arana et al., Radiology. 254, 809–817 (2010)

[4] Pfirrmann et al., Radiology. 230, 583–588 (2004)

[5] Carrino et al., Radiology. 250, 161–170 (2009)

Ultrasonic-based characterization of soft tissue is an emerging technology with great potential as a clinical diagnostic tool. There is evidence that abnormalities in the structural architecture of soft tissues are linked to a broad range of pathologies including tumours, liver fibrosis, preterm birth... Existing ultrasonic techniques are restricted to linear theories and to map first-order tissue parameters. Further advances in this technology require the development of new mathematical and physical models that represent more faithfully the reality.
The present work derives a general non-linear formulation of wave propagation using generalized coordinates on a material characterized by Hamilton’s strain energy function.  Afterwards, this general formulation is adapted to simulate the propagation of torsional waves on nonlinear elastic materials to explain the properties of soft tissue when is measured under this conditions. The resultant system of equations is solved under a finite differences framework and probabilistic inverse problem to explore how this model improves the understanding of soft tissues [1-3].

To simplify the mathematical development, covariant and contravariant coordinates were used. Compatibility equations and Hamilton strain energy potential are introduced in the motion equations Next, simplifications due to the symmetries, boundary conditions and dimensional analysis are performed in the previous system of equations. Due to the complexity of nonlinear terms FDTD methodology is used to obtain the solution. As a last step Probabilistic Inverse Problem is applied to decide the plausibility of the different models considered in this work to explain experimental measurements.

Overall, different models were analyzed with different values of the linear/nonlinear parameters using different frequencies in the excitation signal. The methodology of PIP is applied to decide the most plausibility model between linear elastic, linear viscoelastic, nonlinear elastic and nonlinear viscoelastic. The response of the system varying the linear/non-linear parameters of the strain energy is obtained via FDTD simulation showing significant variations among the different models. (Fig.1A-C) compares two linear and non-linear responses of the system with different excitation frequencies.


Fig.1: Displacement at the control node for a frequency of (A) 1500 Hz, (B) 2000 Hz and (C) 3000 Hz.

Nonlinear torsional wave propagation on generalized coordinates approach implies a new paradigm to model the nonlinear biomechanical behavior of soft tissue improving the plausibility versus previous elastic or viscoelastic predictions.  

This research was supported by the Ministry of Education DPI2017-83859-R, DPI2014-51870-R, DPI2010-17065 and UNGR15-CE-3664, Ministry of Health DTS15/00093 and PI16/00339, PI-0107-2017, PIN-0030-2017 and Junta de Andalucía P11-CTS-8089 projects.

1. Hamilton, M.F., et al., (2004). J Acoust Soc Am, 116(1) p41.
2. Destrade, M., et al., (2010). J Acoust Soc Am, 127(4) p2103.
3. Callejas, A., et al., (2017) Sensors, 17(9), p2078.

Systems to assess operational casualties are used to model in-theater injuries for penetrating and other threats across military environments. The goal of this study was to update the virtual human models that serve as the foundation of these systems. This was achieved by: 1) Recruiting participants representative of the modern U.S. military anthropometry, 2) Collecting multi-modality imaging and external anthropometry data in set postures, and 3) Developing CAD for manikins in 4 military relevant postures: standing, seated, kneeling firing, and prone firing.

Recruitment Methods: A set of 6 boundary manikins for each gender were determined through principal components analysis and provided by the sponsor. After obtaining IRB approval, participants were recruited based on 36 anthropometric measurements, 6 of which were key measures that required a match to the target within 10 percentile deviation or less. Subjects most closely matching the target sizes were enrolled as full participants (12 individuals), near matches were enrolled as partial participants (61 individuals). 484 individuals were screened, 73 were enrolled in the study.

Imaging Methods: Slice thickness is given after each modality. Full participants were scanned using 3T MRI (0.8-2mm), CT (0.625mm) and upright MRI (1.5mm). Four external surface scans were collected with a Faro Freestyle scanner (3D point accuracy ≤1mm). Digital landmarks were obtained by palpation. Custom imaging protocols were used to acquire data in all body regions. Partial participants received scans of the thoracoabdominal cavity, where anatomical variation is greatest. Custom supports were designed for each posture providing consistent and repeatable support during external scanning.

CAD Development: The study details the development methods of the full body CAD model for the Large Female in all 4 postures (Fig.1). All image data and segmentation was reviewed by a collaborating radiologist (CML). The seated model is at 90 degrees for the hips, knees and ankles. The last two postures are based on rifle marksmanship standard practice. The digitized landmarks were used to reconstruct the skeleton position, and scans were used to verify joint and organ placement. All body structures visible in the scans were segmented and surfaced, while body structures not reproducible from scans, due to contrast or resolution deficiency, were reconstructed using sources from the literature.

CAD Development Results: The Large Female model was completed in all 4 postures with differences between participant anthropometry and CAD within 5%. All 4 models contain the same set of 742 anatomical features broken out by tissue type (skin, 196 bone, 29 brain, 63 thoracoabdominal organ, 284 vessels, 66 nerves).

Introduction :
The acoustic source of the human phonation is generated due to the interaction between the laryngeal airflow and the two vocal folds that are excited to periodical oscillations. The investigation of this process is very challenging because of the highly restricted accessibility of the human larynx. As a consequence, clinical diagnostic techniques are still restrained to endoscopic visualization and sound analysis. For a better understanding of the physical process of sound generation, the development of a realistic shaped synthetic larynx model which imitates the human physiology is highly desired. Such models will offer the possibility to investigate the entire phonatory process with a high degree of reproducibility in contrast to ex vivo larynx models using cadaver larynges.

Methods :
To investigate the process of the sound generation for normal phonation as well as certain cases of voice disorders, a new synthetic larynx model is developed. It basically consists of two parts:

• The synthetic larynx which is composed of a flexible cylinder representing the thyroid cartilage and two vocal fold models as displayed in figure 1. The entire model is made of silicone rubber. Due to its elasticity, the design enables to posture the vocal folds by reproducing the three basic motions of the human larynx physiology, the abduction, adduction and elongation. The shape of the vocal folds is transferred from anatomical data known as the M5 model introduced by Scherer et al. (2001). Based on that, two prototypes of the model were fabricated, one with 1-layered and one with 3-layered vocal folds.
• The synthetic vocal tract model is based on magnetic resonance imaging (MRI) of professional singers.

 The focus of this work lies on the synthetic larynx segment. In order to validate the basic function of the synthetic larynx models, the vocal fold oscillation was visualized by a digital high-speed camera. Simultaneously, the volume flow rate was detected.

Subsequently, the high-speed footage was analyzed by the in-house software Glottis Analysis Tools (GAT), (Figure, 1) that provides the time dependent glottal area waveform function.

Results :
The model reproduces periodic oscillations of the vocal folds. Thereby, the oscillation pattern exhibits a symmetrical motion between left and right vocal fold.The oscillation frequency ranges between 100 and 130 Hz and the mean oscillation onset flow rate was detected between 30 and 50 l/min depending on vocal fold posturing and pre-stress.
Conclusion:
The two synthetic larynx models reproduce the basic physiology of the phonation process. The oscillation frequency and onset flow rates lie in the physiological range. The next step is to integrate the synthetic vocal tract model.
Acknowledgement :
The work was supported by the Else Kröner-Fresenius Stiftung under grant agreement no. 2016 A78.

Introduction
Bariatric surgery is the most effective intervention for severe obesity, which is one of the most serious health problem. Laparoscopic adjustable gastric banding is one of the principal techniques. Nonetheless, major complications are frequent and weight-loss is not always successful. Non-optimal intervention design and general anaesthesia are the principal cause of this situation. A novel approach is required, integrating bioengineering and medical competences, aiming to engineering design the procedure, to improve efficacy and to reduce the need for anaesthesia.

Materials and Methods
The methods of biomechanics were exploited to provide computational tools that allow properly identifying the optimal post-surgical configuration of the stomach, aiming at both reducing the stomach capacity and making earlier the feeling of satiety [1].
A computational model of the stomach was developed starting from the analysis of data from histo-morphometric investigations and mechanical tests [2]. Computational analyses were performed to evaluate stomach functionality in the post-surgical conformation. In detail, gastric banding was analyzed, considering the influence of band position and pre-tension.
Bariatric surgery is mainly developed by laparoscopic approach, which requires general anesthesia. The anesthesiology risk in obese patient is relevant. Endoscopic techniques are less invasive and sedation requirement is minor, but efforts are mandatory to define a reliable approach. The computational model of the stomach was applied to investigate an endoscopic approach to gastric banding, with particular regard to the design of clips for endoscopic band fixation.

Results
With regard to gastric banding, computational methods allowed investigating the stomach pressure-volume behavior and the mechanical stimulation of gastric receptors depending on surgical parameters. Both laparoscopic and endoscopic approaches were analyzed. With reference to endoscopic techniques, the major efforts pertained to design reliable surgical clips, considering both the endoscopic applicability and the capability to support band traction. Different clips conformations were investigated, as anchors, spiders, screws and spirals.

Discussion
Preliminary outcomes were reported from activities that are under development in the research field of stomach mechanics and bariatric surgery. The results pointed out the potentiality of computational methods for the investigation of stomach functionality and the planning of bariatric surgery procedures and techniques.

References
[1] EL Carniel et al., A biomechanical approach to the analysis of methods and procedures of bariatric surgery, J Biomech, 56: 32-41, 2017.
[2] J Zhao et al., Stomach stress and strain depend on location, direction and the layered structure, J Biomech, 41:3441-3447, 2008.

Introduction: Biomechanical deficits proximal to the knee can generate deleterious forces across the knee joint in anterior cruciate ligament reconstructed (ACLR) athletes, which increases the risk of second knee injury.¹ The efficacy of a neuromuscular training (NMT) program to improve hip biomechanical deficits in ACL reconstructed (ACLR) athletes is currently unknown.² Therefore, the purpose of this investigation was to quantify the effects of a NMT training program on hip biomechanics in an ACLR cohort. The comparative effects of NMT on hip biomechanics between the ACLR cohort and an uninjured, control group were also analyzed. The primary hypothesis tested was that the measured hip biomechanics associated with increased risk of second ACL injury would be significantly reduced in ACLR athletes after participation in a NMT program. A secondary hypothesis tested was that following training hip biomechanics in the ACLR cohort would not differ from a control cohort who also completed the same training program.

Methods: Eighteen ACLR and ten control athletes were recruited and completed a 12 session NMT program.³ Both groups of athletes participated in a biomechanics testing session prior to and after completion of the NMT program to evaluate hip biomechanics during a drop vertical jump. The analysis of the effect of NMT focused on hip biomechanical variables at initial contact because injuries typically occur within the first 30-50 milliseconds of landing. The presented hip biomechanical variables all occur at initial contact. To understand the effect of NMT within this ACLR cohort, a repeated measures analysis of variance (ANOVA) was conducted to assess discrete hip kinematic and kinetic variables. Secondly, to compare groups after training, a two-way ANOVA was conducted to understand differences of the same hip biomechanical variables. Post-hoc t-tests were utilized to determine differences when a significant interaction was found. The alpha level was set to 0.05 a priori.

Results: After participation in the NMT program ACLR athletes demonstrated significantly greater hip external rotation moment, lower hip flexion moment, and greater hip flexion angle (p<0.05). Post-training comparison between the ACLR and control group revealed significant differences in hip abduction moment and vertical ground reaction force (vGRF) (p<0.05). No significant differences were found were found for hip flexion moment and hip external rotation moment between the ACLR and control groups.

Discussion: Hip biomechanics and neuromuscular measures of ACL injury risk demonstrate significant improvements after completion of a NMT program in ACLR athletes. In addition, comparison of post-training hip biomechanics between ACLR athletes and controls demonstrate recovery of hip biomechanical control. 

1. Paterno et al., AJSM, 2010
2. Hewett et al., AJSM, 2012
3. Di Stasi et al., JOSPT, 2013

Anterior cruciate ligament tears (ACL) are associated with impairments in quadriceps strength and gait (1). The rate of torque development (RTD) is believed to be important for performing functional tasks. To date, RTD has not been evaluated in an ACL-injured population.  Additionally, the relationship of RTD to function such as the knee flexion angle during gait has yet to be defined. Therefore the purpose of this study was to evaluate differences in RTD between the injured and non-injured limb as well as to a control group. We also sought to evaluate the relationship between RTD and peak knee flexion angle during the stance phase of gait.

Methods: Twelve subjects (6 ACL, 6 control) completed the study and were matched for age (23±7.2, 22.6± 1.2 yrs old), mass (79±12.2, 69.3±8.1 Kg), and sex (4M/2F per group).  Subjects in the ACL-injured group were 36±21.2 days from injury. Isometric knee extension strength was assessed on a Biodex isokinetic dynamometer. Custom code determined the mean slope of the torque-time curve between 20 and 80% between the onset of the trial and peak torque and was normalized to the subjects mass in Newton’s.  Subjects in the ACL-injured group completed an instrumented gait analysis walking at 1.0±0.27 m\s using standard marker and data collection procedures (2). Data was post processed in visual 3D and with custom code. T-tests were used to assess differences and the relationship between knee flexion angle and RTD was determined between all subjects using a Pearson correlation.

Results: We found a significant reduction in RTD between the injured and non-injured side (0.41±0.19, 0.65±0.14 Nm/s/N, p=0.01) and when compared to the control group (1.04±0.26 Nm/s/N p=0.001). Additionally, the ACL-injured group walked with greater knee flexion on the involved side (-18.92±3.13, -14.5±2.4 p=0.01). There was a strong relationship between RTD and knee flexion angle (r=0.82 p=0.01, Figure 1).

Discussion: There were significant impairments in RTD in the ACL-injured leg which was associated with greater knee flexion (figure 1). The knee flexion angle in the injured subjects is larger than what has been previously reported (1). Subjects in the current study were more acutely injured than those reported in other studies (1). RTD is believed to be affected by both a reduction in descending neural input and alterations within intrinsic factors in the muscle (2). Additional subjects will further clarify these observations and determine if these relationships are maintained over time. 

Acknowledgements:  NIH\NIAMS AR071398-01A1

References:

1. Slater, LV., et al., (2017) JAT 52(9) p847
2. Kline, PW., et al., (2015) AJSM 43(10) p2553