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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Name: paigelin7

While normalization of gait is a primary goal of early rehabilitation, between limb asymmetries in knee extensor moment can persist 6-24 months later and previous literature assessing gait interventions is limited. The purpose of this study was to assess the influence of subject-specific cadence gait training program on knee loading mechanics following ACLr. Nine individuals completed an 8-week cadence training program (20min, 3x/week; Table1) and nine sex- and surgery-matched individuals served as controls. All eighteen participants received standard physical therapy and were tested at 1 and 3 months post-op. Kinematic and kinetic data were collected during walking at a self-selected speed. Repeated measures ANOVAs were used for comparisons; significance α≤0.05. Main effects of limb and time were observed: knee ROM (kROM;p<0.001;p=0.044;Fig.1) and knee extensor moment (kEXT;p=0.003;p=0.002) in the cadence and control groups, respectively. No main effects of group for kROM (p=0.136) or kEXT (p=0.229) were found. A trend toward a significant group x time x limb interaction was observed in kEXT (p=0.092), but not kROM (p=0.412). Post-hoc analyses of kEXT (Fig.2) revealed a significant time x limb interaction for the cadence group (p=0.053) but not the control group (p=0.884). In the cadence group, the time x limb interaction was driven by a 131% increase in kEXT in the surgical limb versus a 42% increase in the non-surgical limb between T1 and T2. Consistent with previous findings, these pilot data show promising results as the cadence intervention resulted in improvements in sagittal plane knee loading compared to controls.


Name: catelli

Dual-mobility (DM) bearing implants reduce the incidence of dislocation following total hip arthroplasty (THA) also it increases hip stability and range of motion (ROM). However, it is unclear whether the improved ROM will lead to better mechanical symmetry. Ground reaction forces (GRF) analysis would help to understand joint compensatory effects and symmetry in THA patients. The purpose was to compare GRF symmetry between the operated and non-operated limbs in THA patients, of either DM or conventional-cup (CC) implant, during standing and sitting tasks. Twenty-four patients and 10 control participants (5M/5F; 62±10 years; 26±4 kg/m2) were recruited and underwent motion analysis before and nine months after THA. Patients were randomly assigned to either a DM (8M/4F; 63±5 years; 28±3 kg/m2) or CC (9M/3F; 62±5 years; 28±5 kg/m2) cementless replacement. Participants performed five sit-to-stand and stand-to-sit trials, with a bench adjusted to their knee heights and each foot on an individual force plate, with motion capture and GRF data been collected. Control group demonstrated standing (0.4±1.6%) and sitting (1.2±1.6%) symmetry. During sit-to-stand, DM group reduced its SI from pre- (5.5±1.6%) to post-op (1.2±1.9%, p=0.09), while the CC group showed a significant improvement (from 8.7±2.1% to 1.5±1.4%, p=0.02). For stand-to-sit, DM group reduced its SI (from 3.3±2.2% to 0.5±1.7%) while the CC group again had a significant improvement (from 8.2±2.1% to 1.2±1.1%, p=0.02). Larger improvements in symmetry were noticed for both groups during trunk flexion when standing; and for CC group during trunk extension when sitting. After surgery, patients with either implant reached SI inside the margin of 1.5 standard deviation from the CTRL (p>0.05). Statistical significance on paired condition was only observed on CC group due to its high pre-op score; however, both surgical groups showed an improved symmetry after THA.


Name: bthakkar

INTRODUCTION
Running-related injuries are most often single-sided and are partially attributed to lower limb movement and loading asymmetries. For example, runners with tibial stress fractures demonstrate asymmetry in loading rate. Running is a dynamic athletic event in which runners often engage in both inclined and declined running with the goal of improving conditioning. Symmetry Angle (SA) is a commonly used, robust measure of determining symmetry. The purpose of this study was to compare peak vertical ground reaction force (VGRF) symmetry using the SA during uphill, level and downhill running on an instrumented treadmill.
METHODS
Eleven healthy adults volunteered to participate in this study and running at 2.7 m/s at grades of 0°, 5.74° incline and 5.74° decline were analyzed. SA was computed using the peak VGRF values from both the limbs.
RESULTS AND DISCUSSION
No statistically significant differences in SA were observed between the three running conditions. (p=0.61) The unexpected uniformity in vertical GRF across uphill, level, and downhill running is consistent with the absence of changes in the peak magnitudes of the GRF observed previously. This suggests that neither moderate uphill or downhill running result in increases in peak GRF that may be considered injurious.
CONCLUSIONS
This was the first study that looked at kinetic symmetry using peak GRF in healthy recreational runners during the three running conditions. This study suggested that uphill and downhill running does not contribute to potential differences in interlimb symmetry and could be considered as a safe alternative to level running on a treadmill.


Listed In: Biomechanics, Gait
Name: danialkia

As a treatment for end-stage elbow joint arthritis, total elbow replacement (TER) results in joint motions similar to the intact joint; however, bearing wear, excessive deformations and/or early fracture may necessitate early revision of failed implant components.
A finite element model of a TER assembly was developed based on measurements from a Coonrad-Morrey implant (Zimmer, Inc., Warsaw, IN) using nonlinear elasto-plastic UHMWPE material properties and a frictional penalty contact formulation. The loading scenario applied to the model includes a flexion-extension motion, a joint force reaction with variable magnitude and direction and a time varying varus-valgus (VV) moment with a maximum magnitude of 13 N.m, simulating a chair-rise scenario as an extreme loading condition. Model results were compared directly with corresponding experimental data. Experimental wear tests were performed on the abovementioned implants using a VIVO (AMTI, Watertown, MA) six degree-of-freedom (6-DOF) joint motion simulator apparatus. The worn TER bushings were scanned after the test using micro computed tomography (μCT) imaging techniques, and reconstructed as 3D models.
Contact pressure distributions on the humeral and ulnar bushings correlate with the sites of damage as represented by the μCT data and gross observation of clinical retrievals. The results demonstrate UHMWPE bushing damage due to different loading protocols. Numerical results demonstrate strong agreement with experimental data based on the location of deformation and creep on bushings and exhibit promising capabilities for predicting the damage and failure mechanisms of TER implants.


Name: 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
Name: afalaki

Over the past years, we have developed a test for postural stability based on the theory of synergies stabilizing salient performance variables. In this study, effects of Parkinson's disease (PD) and dopamine-replacement therapy on multi-muscle synergies stabilizing the center of pressure (COP) coordinate were explored between: (1) a cohort of 11 patients without clinically identifiable postural problems (Hoehn-Yahr stage II) and 11 age-matched controls, and (2) a cohort of 10 patients tested off- and on-medication, with and without postural problems (stage II and III, n = 5 per stage). Participants stood on a force platform and performed cyclical body sway at 0.5 Hz along the anterior-posterior direction. Electromyographic signals from 13 leg and trunk muscles were used to compute: (1) the amount of inter-cycle variance that did not affect (VUCM) and affected (VORT) COP coordinate, and (2) the magnitude of the cycle-to-cycle motion that did not change (motor equivalent: ME) and changed (non-motor equivalent: nME) the COP coordinate. We hypothesized that both methods would produce indices sensitive to PD and dopaminergic medications. Compared to controls, patients showed significantly smaller inter-cycle VUCM and ME components suggesting a less flexible, and hence less stable, behavior. Moreover, inter-cycle variance within/orthogonal to the UCM correlated with ME/nME displacements. Results suggest clinical utility of variance and motor equivalence analyses of postural instability in early stages of PD and quantifying the effects of dopamine-replacement drugs. The analysis of motor equivalence is particularly attractive because it requires only a handful of trials (observations).


Listed In: Neuroscience
Name: mevan6

Asymmetries in discrete measures following anterior cruciate ligament reconstruction (ACL-R) during landing have been reported to be risk factors for secondary ACL injuries. Our purpose was to examine the impact of functional brace wear on kinematic and kinetic inter-limb movement symmetry during landing in ACL-R patients. 20 adolescent athletes (15.8 ± 1.2 years) (7 male, 13 female) 6 months following ACL reconstruction performed 5 trials of a stop-jump task in both a braced (B) and non-braced (NB) condition, with the first landing being analyzed. A custom fit functional knee brace (DJO, Vista, CA) was worn on the ACL reconstructed limb (AL) during the B trials. Mean curves were created for each limb (AL and unaffected limb (UL)) for the vertical (vGRF) and anterior-posterior ground reaction forces (apGRF) and frontal and sagittal knee angles and moments. Coefficients of multiple determination (CMD) between the AL and UL curves were compared between B and NB conditions with students’ t-tests (p≤0.05). No significant differences existed for movement and loading symmetry between B and NB conditions among all subjects. Secondary analysis revealed significant differences in apGRF (p=0.014), vGRF (p=0.011) and sagittal knee angles (p=0.003) in subjects with improved sagittal knee angle symmetry in the B condition. The data show that brace wear improves loading symmetry in adolescent patients that also exhibit improved sagittal knee angle symmetry while braced 6 months following ACL-R. Identifying factors that affect inter-limb movement and loading response to brace wear could assist in determining each patient’s need for a brace.


Name: kbsmale

Since OpenSim uses motion capture data as input while solving inverse kinematic (IK), it is subjected to soft tissue artifact (STA) as the commonly used surface markers do not correctly represent the underlying rigid bones. The purpose of this study was to determine the effect of applying bone pin (BP) marker defined ranges of knee motion in OpenSim IK solutions. Participants completed successful jump lunges where they were asked to stand on their non-test limb and jump forward onto a force plate (AMTI OR 6-7-OP), land on their test limb and maintain balance for two seconds. Data were processed through OpenSim with generic knee joint constraints as well as constraints derived from BP kinematic data.

BP constrained results yielded a significantly more flexed, adducted and externally rotated knee. Significant differences were also observed for anterior/ posterior and distraction/ compression translations throughout the entire jump lunge while medial/lateral translations were only significant pre and 50 ms post contact. After contact, BP constraints produced a significantly greater flexor, abductor, and external rotator moment. With respect to translation forces, the BP solutions produced smaller posterior shear and greater medial shear and compressive forces at the knee joint.

Generic models available in the OpenSim repository contain knee joint ranges that are not physiologically realistic. Therefore, caution should be expressed when using the results from musculoskeletal modelling as STA and optimizations can introduce error in both the kinematics and kinetic solutions. This error is amplified during ballistic and high impact tasks such as jump landing.


Name: robin.healy

Accelerometers have become extremely popular in the measurement of stride frequency as well as other related stride variables with current sensors capable of recording both accelerations and electromyography. The purpose of this preliminary investigation was to assess the estimation of stride frequency during running using a single tri-axial accelerometer compared to a commonly used infrared device the OptojumpTM system. Five healthy participants wore a Delsys Trigno tri-axial accelerometer attached to the right anterior shin and participants repeatedly ran at a submaximal pace through a four metre section of OptojumpTM. Stride frequency was calculated as stride time divided by one. For the OptojumpTM, stride time was the sum of contact and flight times from two consecutive steps. For the accelerometer, stride time was calculated as the time between two consecutive foot contacts on the right side. Foot contact was identified by local maxima in the Y (medial-lateral) acceleration trace. Estimates of stride frequency were compared using paired samples t- tests, intraclass correlation coefficients (ICCs) and Bland and Altman 95% limits of agreement (LOA) with significance set at p < 0.05. The mean difference between estimates was 0.01 Hz (95% LOA: -0.05-0.07 Hz) with single and average ICCs for stride frequency of 0.93 and 0.96 respectively. The results suggest that an accelerometer attached to the shin can accurately estimate stride frequency in running. Discrepancies in stride frequencies can be partially explained by differences in device sampling rates i.e. 137.15 Hz versus 1,000 Hz


Name: chigh

Previous research has shown the utility of vibrotactile feedback to improve postural sway characteristics in persons with vestibular deficits. Tactile feedback given through vibration has been used more as a modality of training but immediate effects on postural control among older adults have not been investigated.
PURPOSE: To compare the immediate effects of tactile vibration on postural sway in healthy older adults in challenging stance and sensory conditions. METHODS: 10 healthy older adults (76.4 ± 6.8years), performed five standing balance conditions on a AMTI forceplate for 30s each: feet together on firm surface eyes open (C1), eyes closed (C2); feet together on foam surface eyes open (C3), eyes closed (C4), and tandem stance on firm surface eyes open (C5). Participants did 2 trials of each condition both with and without vibrotactile feedback. The feedback was given using a waist belt with sensors that were activated when participants swayed in a particular direction as detected by an Xbox Kinect camera (Sensory Kinetics system; Engineering Acoustics, Casselberry, FL). Center of pressure sway area was compared within each condition using a paired samples t-test to estimate the effect of vibration. RESULTS: See Table 1. Since only 5 subjects could complete C4 data was not included in statistical analysis. CONCLUSION: Tactile vibration did not acutely effect postural sway in challenging stance conditions in healthy older adults. Long term effects of tactile vibration on postural sway in challenging stance conditions need to be investigated.


Listed In: Physical Therapy