Virtual Poster Session

Welcome to the Virtual Poster Session, a new and powerful tool for networking and information exchange. Here you can share your work, search though the poster library, and start a dialogue with others in your field. Each uploaded poster that pertains to force measurement and testing can currently be used to apply for an academic travel scholarship; please see the Scholarships page for application details and deadlines.

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Submitted by Kyeongtak Song

One in three individuals who suffer a lateral ankle sprain (LAS) subsequently develop chronic ankle instability. However, our inability to properly treat acute LAS is not surprising given our limited understanding of post-LAS consequences. 12 patients (21.6±2.9yrs; 172.9±13.1cm; 79.1±21.4kg) with an acute LAS participated. All participants were evaluated for dorsiflexion range of motion (DFROM), time-to-boundary (TTB) in single limb balance (SLB), and self-reported function (SRF) at 1-week, 2-weeks, 4-weeks, 6-weeks, and 8-weeks post injury. Both the involved and uninvolved limbs were measured during the patients first test session. DFROM was assessed using the weight-bearing lunge test and all participants performed 3, 10s of single limb stance with eyes open on a force plate to measure their single limb balance. SRF was measured using the Foot and Ankle Ability Measure (FAAM) and FAAM-Sport (FAAM-S). Post injury time points were compared to a control condition using multivariate ANOVAs (α=0.05). Relative to the control condition, FAAM and FAAM-S were significantly lower at 1-week and 2-weeks post injury. The FAAM-S was also significantly lower score compare to control condition at 4-weeks post-injury. Both FAAM and FAAM-S were not significant different at 6-weeks post-injury. Post-injury TTB measures and DFROM were not significantly different from the control condition. Non-significant declines in DFROM and TTB were observed as in this sample of acute LAS and appear to present with unique recovery patterns. Different recovery patterns among the tested outcomes indicate the need for further research with a larger cohort and for a longer post-injury duration.

Submitted by Andrea Ancillao

Strength measurements are popular in the clinical practice to evaluate the health status of patients and quantify the outcome of training programs. Currently a common method to measure strength is based on Hand Held Dynamometers (HHD) which is operator-dependent. Some studies were conducted on repeatability of strength measurements but they were limited to the statistical analysis of repeated measurements of force. In this work, the authors developed a methodology to study the quality of knee flexion/extension strength measurements by measuring the effective HHD position and orientation with respect to the patient. HHD positioning attitude was measured by means of an Optoelectronic System for which a marker protocol was defined ad-hoc. The approach allowed to assess quality of measurements and operator’s ability by means of quantitative indices. The protocol permitted the evaluation of: angles of HHD application, angular range of motion of the knee and range of motion of the HHD. RMSE parameters allowed to quantify the inaccuracy associated to the selected indices. Results showed that the operator was not able to keep the subject’s limb completely still. The force exerted by the subject was higher in knee extension and the knee range of motion was higher than expected, however the operator had more difficulties in holding the HHD in knee flexion trials. This work showed that HHD positioning should be as accurate as possible, as it plays an important role for the strength evaluation. Moreover, the operator should be properly trained and should be strong enough to counteract the force of the subject.

Submitted by Christopher McCrum

Patients with unilateral peripheral vestibular disorder (UPVD) have diminished postural stability and therefore the aim of this study was to examine the contribution of multiple sensory systems to postural control in UPVD. Seventeen adults with UPVD and 17 healthy controls participated in this study. Centre of pressure (COP) trajectories were assessed using a force plate during six standing tasks: Forwards and backwards leaning, and standing with and without Achilles tendon vibration, each with eyes open and eyes closed. Postural stability was evaluated over 30s by means of: total COP excursion distance (COPPath) and the distances between the most anterior and posterior points of the COPPath and the anterior and posterior anatomical boundaries of the base of support (COPAmin and COPPmin). In addition, the corrected COPAmin and COPPmin was assessed by taking the corrected base of support boundaries into account using the anterior and posterior COP data from the leaning tasks. UPVD patients showed a tendency for smaller limits of stability during the leaning tasks in both directions. Subject group and task condition effects were found (P<0.05) for COPPath, (i.e. higher values for patients compared to controls). UPVD patients showed lower (P<0.05) COPPmin values compared to the control group for all conditions (more pronounced with the corrected COPPmin). Disturbance of the visual system alone lead to a distinct postural backward sway in both subject groups which became significantly more pronounced in combination with Achilles tendon vibration. The individual limits of stability should be considered in future research when conducting posturographic measurements.

Submitted by S. Jun Son

Background: Knee joint pain (KJP) independently alters motor function and gait mechanics, and these alterations may accelerate chronic knee joint disease. While TENS restores motor function deficits, it is unclear whether TENS restores compensatory gait mechanics. The purpose was to examine the effects of KJP on lower-extremity joint moments, and the effects of TENS on the aforementioned variables. We hypothesized that KJP will result in altered gait patterns, and TENS will help restore these mechanical alterations.
Methods: We randomly selected 15 subjects for the TENS group, after which subjects were matched for the placebo group. Subjects underwent 3 sessions (hypertonic, isotonic, control). A 20-gauge flexible catheter was inserted into the right infrapatellar fat pad, and an infusion pump infused a saline of 0.154 mL•min¯¹ for 50 min (total = 7.7 mL). A TENS protocol was set at a biphasic mode with 120 µs and 180 Hz for 20 min. To blind placebo treatment, subjects in the placebo group was told that an electrical stimulation had been set to sub-sensory level. High-speed video (240 Hz) and an instrumented treadmill (1200 Hz) were used for gait analysis. Functional analysis of variance were used to evaluate differences between groups over time for joint moments. The mean curve with 95% CIs is represented by polynomial functions, showing us the entire stance, rather than identifying discrete peak points. If 95% CIs did not cross zero, significant difference existed (P < 0.05).
Discussion: KJP independently increase internal knee varus moments, which were consistent with previous finding using patients with osteoarthritic knee pain. These compensatory gait patterns may be a result of a pain-avoidance motor deficits strategies. Since observed patterns can create altered mechanical and biological stress patterns on articular surface, it may increase the risk of degenerative knee disease. However, attempting to reduce perceived pain and increase neuron activation through TENS can help overcome deficits in knee and hip joint moments.

Submitted by Alexandros Christou

Victims of improvised explosive devices (IEDs) that have presented spinal injury in recent conflicts have been shown to have a high incidence of lumbar spine fractures. Previous studies have shown that the initial positioning of spinal bone-disc-bone complexes affects their biomechanical response when loaded quasi-statically; such a correlation, however, has not been explored at appropriate high loading rate scenarios that simulate injury. This study aims to investigate the response of lumbar spine cadaveric segments in different postures under axial impact conditions. Three T11-L1 bi-segments were dissected and tested destructively in a drop tower under flexed/neutral/extended postures. Strains were measured on the vertebral body and the spinous process of T12. Forces were measured cranially using a 6-axis load cell, and a high-speed camera was used to capture displacements and fracture. The impacted specimens were CT-scanned to identify the fracture pattern. Whilst axial force to failure was similar for flexed and extended postures, the non-axial forces and the bending moments, however, were dissimilar between postures. Although all specimens showed a burst fracture pattern, the extended posture failed more posteriorly. This suggests that axial force alone is not adequate to predict injury severity in the lumbar spine. This insight would not have been possible without the use of the 6-axis load cell. As metrics for spinal injury in surrogates take into account only the axial force, this programme of work may provide data for a better injury criterion and allow for a mechanistic understanding of the effects of posture on injury risk.

Submitted by Chun-Kai Huang

People with diabetes mellitus (DM) have been reported of increased ground reaction force (GRF) and plantar propulsion force (PPF) that will worsen the formation of plantar ulcer. The reliance of perception of self-motion has been previously addressed for maintaining stability during locomotion in DM. Therefore, we speculate that perception of self-motion will affect DM’s plantar force adjustment by decreasing GRF/PPF along with reducing of variability (CV). We recruited five DMs and three healthy controls to walk on an instrumented treadmill with their self-selected pace. All subjects went through three no self-motion and three self-motion walking trials (120s/trial). The self-motion was generated by presenting a virtual corridor that moved toward subjects with their matched velocity. Three-axis force data were recorded at 300 Hz. Two-factor ANOVA with repeated measures were conducted to examine the role of visual cue impacts GRF/PPF in DM and age-matched healthy. The visual cue and group factors show significant interaction on PPFPeak and PPFCV. The following comparisons showed significant visual effect on reducing: (1) PPFPeak in healthy controls; (2) PPFCV in DM patients. Generally, the decreased PPFPeak and PPFCV founded in this study were in line with previous study and can be explained as the optimization of neuromuscular locomotor system in the anteroposterior direction. Furthermore, visual perception of self-motion shows its effect on reducing PPFPeak during toe-off in healthy controls. Lastly, the significant decreased PPFCV of DM versus healthy stands for the reduced human movement variability observed in DM’s neuromuscular locomotor system when perception of self-motion is provided.

Submitted by Christopher McCrum

Unilateral peripheral vestibular disorder (UPVD) negatively affects upper and lower body motor performance, but postural control during quiet stance in UPVD patients has not been directly compared with dynamic stability control after an unexpected perturbation during locomotion. We analysed centre of pressure (COP) characteristics during static posturography in UPVD patients and healthy controls and compared this with performance of a trip recovery task. 17 UPVD patients and 17 healthy controls were unexpectedly tripped while walking on a treadmill. The margin of stability (MoS) was calculated at touchdown (TD) of the perturbed step and the first six recovery steps. Posturography was used to assess postural stability during 30 seconds of standing with eyes open and closed using a force plate. The trip reduced the MoS of the perturbed leg (p<0.05) with no significant differences in MoS between the groups. Controls returned to MoS baseline level in five steps and patients did not return within the six steps. UPVD patients showed a greater total COP sway path excursion (closed eyes only), anterior-posterior range of COP distance and a more posterior COP position in relation to the posterior boundary of the base of support. There were no significant correlations between COP sway path excursion and MoS values. We concluded that UPVD patients have a diminished ability to control and recover dynamic gait stability after an unexpected trip and lower static postural stability control compared to healthy matched controls, but that trip recovery and static postural control rely on different control mechanisms.

Submitted by Niamh Whelan

A popular method for measuring initial contact (foot-strike) during running is the force platform. It has been proposed that the foot contact events can be estimated using peak impact related accelerations of the leg using accelerometers. Various studies have been conducted to compare force platform and accelerometer methods in walking and running. The aim of this study was to develop a method for identifying peak impact accelerations in the anterior- posterior axis using the Delsys Trigno System during running and compare this with initial contact via force plates. Seven national and international sprinters completed runs across a force platform with an accelerometer fixed to their shin. The results showed the acceleration of the anterior-posterior axis approximated foot-strike within ±0.017 s of the foot-strike event detected by the force plate.

Listed In: Biomechanics, Gait
Submitted by Michelle Norris

The purpose of this study was to investigate how a newly proposed method of stride time calculation, utilising data filtered at 2 Hz, compared to previous methods. Tibial accelerometry data for 6 participants completing half marathon running training were collected. One run was selected for each participant at random, from which five consecutive running strides were ascertained. Four calculation methods were employed to derive each stride time and results were compared. No significant difference was found between methods (p=1.00). The absolute difference in stride time, when comparing the proposed method to previous methods, ranged from 0.000 seconds to 0.039 seconds. Filtered data could offer a simplified technique for stride time output during running gait analysis, particularly when applied during automated data processing for large data sets.

Submitted by Lauren Sosdian

Background: Gait abnormalities can influence surgical outcomes in people with severe knee osteoarthritis (OA) and thus a thorough understanding of gait abnormalities in these people prior to arthroplasty is important. Varus-valgus thrust is a characteristic linked to OA disease progression that has not yet been investigated in a cohort with severe knee OA awaiting knee arthroplasty. The aims of this study were to determine i) prevalence of varus and valgus thrust in a cohort with severe knee OA compared to an asymptomatic group, ii) whether the thrust magnitude differed between these groups iii) differences between varus and valgus thrusters within the OA cohort and iv) whether certain measures could predict thrust in the OA cohort.

Methods: 40 patients with severe knee OA scheduled for primary TKR and 40 asymptomatic participants were recruited. Three-dimensional gait analysis was performed on all participants, with the primary biomechanical measures of interest being: varus and valgus thrust, knee adduction angle, peak KAM, and KAM impulse. Additionally, static knee alignment and quadriceps strength were assessed in the subgroup with knee OA.

Findings: No difference was found in the prevalence of varus and valgus thrust between the severe OA and control groups (Pearson chi-square = 3.735, p value = 0.151). The OA varus thrust group had a significantly higher peak KAM (p=0.000), KAM impulse (p=0.001), static alignment (p=0.021), and lower quadriceps strength (p=0.041) than the valgus thrust group. Peak KAM and quadriceps strength were found to explain 34.9% of the variation in maximum thrust, such that an increase in KAM and a decrease in quadriceps strength were associated with an increase in maximum (varus) thrust.

Interpretation: Few differences between the severe OA and control groups were seen, however dichotomizing the groups into varus and valgus cohorts revealed a number of biomechanical differences. Patients with severe OA are often treated as a homogenous cohort; however, by classifying which individuals have a varus or valgus thrust, we have identified a subset of patients with poorer biomechanics who could potentially be at a higher risk of a worse outcome after surgery.