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: tiffytiru

INTRODUCTION: Patellofemoral pain (PFP) is a common condition seen in orthopedic practice, accounting for approximately 25-40% of all knee injuries [1]. A commonly cited hypothesis as to the cause of PFP is elevated patellofemoral joint (PFJ) stress [2] secondary to abnormal PFJ structure. Previous studies have shown that persons with PFP exhibit altered patella position [3], abnormal femoral morphology [4], and decreased patella cartilage thickness [5] when compared to healthy individuals. However, the influence of the abnormal morphology on PFJ stress is unknown.
METHODS: Nineteen subjects (10 PFP and 9 pain-free controls) were recruited for this study. Each subject completed 2 phases of data collection: magnetic resonance imaging (MRI) assessment and biomechanical testing. The measurement of morphological variables (patella height (Insall-Salvati ratio or ISR), lateral trochlear inclination angle (LTI), and patella cartilage thickness). For the biomechanical testing, kinematic, kinetic, and electromyographic were obtained.
RESULTS AND DISCUSSION: Pearson correlation coefficients revealed that only patella height (r=0.48, p=0.018) and patella cartilage thickness (r=-0.58, p=0.005) were significantly correlated with peak hydrostatic pressure (Table 1). Results of the stepwise regression analysis revealed that patella cartilage thickness was the single best predictor of peak hydrostatic pressure, followed by patella height. Together, these 2 variables explained 50% of the variance in peak PFJ stress.
The results of the current study support the premise that PFJ stress is associated with PFJ morphology. Patella height was the best predictor of PFJ stress with greater degrees of patella height being correlated with greater stress. This is logical given that a higher positioned patella articulates with the more shallow portion of the trochlear groove, thus decreasing PFJ contact area [6]. The finding that patella cartilage thickness was negatively correlated with PFJ stress is in agreement with the results of Li et al. [7], who demonstrated that a reduction of cartilage thickness causes increase cartilage stress. Furthermore, our findings revealed that 50% of the variance in PFJ stress could be explained by morphological factors.
CONCLUSIONS: Identifying the underlying factors that contribute to elevated PFJ stress is an important step in developing effective interventions for persons with PFP. Although abnormal structure may not be correctable through conservative measures, it is important to recognize abnormal structure may play a role in contributing to pain and pathology.


Name: meadowkd

Disc function is mechanical, and measures of disc mechanical function are important to address spine function, degenerative disc disease, and low back pain. In vivo measures of disc mechanical function are needed, however the current standard in disc imaging is to acquire a single static image and classify the disc’s appearance using qualitative integer scales for degree of degeneration. Current grading standards are acknowledged as insufficient to identify symptomatic discs for treatment. In addition, static T2 weighted MRI cannot provide mechanical function information – mechanics must be measured as the change following a load or deformation perturbation. Because the disc experiences significant compression and height loss throughout the day, and because flexion-extension postures are often associated with low back pain, these physiological mechanical perturbations have potential to be used to quantify disc mechanics in vivo. The objective of this study was to use MRI-based methods to quantify in vivo disc function by measuring changes in disc geometry and T2 relaxation time with diurnal changes and with controllable posture. Quantification of in vivo disc mechanics by using diurnal loading or prescribed posture changes has potential to improve our ability to identify, evaluate, and treat degenerative disc disease. Symptomatic discs may have aberrant mechanics; if so, in vivo measurements of mechanical function may, with continued development, facilitate diagnosis of pathological discs.


Name: mcdonaac

The shoulder complex affords multiple opportunities for kinematic and muscular variability during repetitive work, which could change physical exposure and risk at work. The purpose of this study was to examine kinematic and muscular adaptations during continued performance of submaximal, repetitive work following a fatiguing protocol.

Participants (n=12) completed a sequence of three protocols: (1) 20 pre-fatigue work cycles, (2) anterior deltoid fatigue protocol, (3) 60 post-fatigue work cycles. Each work cycle was 60 seconds and consisted of 4 tasks. Reaction forces and moments were recorded with a 6DOF force sensor (MC3-500, AMTI, Watertown, MA, USA) during the work tasks. The fatigue protocol consisted of static and dynamic efforts targeting the anterior deltoid. Fatigue was quantified through changes in strength, RPE and EMG frequency and amplitude. Activity of 14 muscles of the upper extremity and torso were measured with surface electrodes and kinematics were tracked with a passive motion capture system, 30 reflective markers and a scapular tracker.
Immediately following the fatigue protocol, there were significant signs of muscle fatigue and reduced physical capacity. These changes were accompanied by significant muscular and kinematic adaptations in the work tasks during the post-fatigue work cycles (p<.05). Although these adaptations allowed for recovery in some muscles, fatigue persisted and developed in other muscles by the end of the post-fatigue work cycles, despite subjective ratings of perceived exertions returning to pre-fatigue levels. If people are unable to perceive negative behavioral changes during repetitive work, they may be at greater risk of developing workplace injuries.


Listed In: Biomechanics
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: fmaguire

The established pathway of cognitive decline identifies Mild Cognitive Impairment (MCI) as a common pre-dementia syndrome. As MCI can represent the endpoint of cognitive decline or a transient state, more predictive diagnostic tools are required. A new pre-dementia syndrome, Motoric Cognitive Risk (MCR) syndrome, has been proposed. It is defined by slow gait and cognitive complaints but absence of dementia and mobility disability. MCR aims to improve on the predictive power of MCI, this study aims to explore it’s claim.

Associations have been uncovered between differing cognitive domains and specific characteristics of gait. Leveraging the gait-cognitive function relationship is a novel approach to potentially highlighting those experiencing cognitive decline. However, the diagnostic tool of MCR is a new construct and currently imperfect, its efficacy not fully validated and sensitivity for dementia prediction relatively unknown. Reliable data on prevalence and risk factors help contribute to this validation process.

In this presentation prevalence data for a multi-country aging study and a nationally representative community dwelling aging study will be presented. The variables available in both datasets which will be of interest in this study include; Gait Speed, Global Cognition (Mini-Mental State Exam (MMSE) score), Presence of Cognitive Complaints, Age, Body Mass Index (BMI), Dementia diagnosis (reported or imputed) and Waist Circumference. This study will inform the following research project, which will aim to assess whether specific gait components or combinations alone are better than the MCR construct in their association to cognitive decline.


Listed In: Gait, Neuroscience
Name: danialkia

Knowledge of ligamentous contributions to joint stability is essential to restore normal joint range of motion and functionality through reconstruction procedures. Although, there has been numerous studies on the pathomechanics of the elbow joint, there have been very few rigorous and systematic attempts to characterize the roles of soft tissues during clinically relevant motions.
Five fresh frozen cadaveric elbows from three male subjects were used for this study. In-vitro simulations were performed using a VIVO six degree-of-freedom (6-DOF) joint motion simulator (AMTI, Watertown, MA) capable of virtually simulating the effects of soft tissue constraints (virtual ligaments). This study introduces a unique, hybrid experimental-computational technique for measuring and simulating the biomechanical contributions of ligaments to elbow joint kinematics and stability. In vitro testing of cadaveric joints is enhanced by the incorporation of fully parametric virtual ligaments, which are used in place of the native joint stabilizers to characterize the contribution of elbow ligaments during simple flexion-extension motions using the principle of superposition.
our results demonstrate the importance of AMCL and RCL structures as primary stabilizers under valgus and varus loading respectively. Virtual ligaments demonstrate the ability to restore the VV stability of the joint in the absence of any soft tissues attached to the osseous structures. This demonstrates the effectiveness of “virtual” ligaments for in vitro testing of elbow joint biomechanics, with applications in pre-clinical assessment of elbow 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: deluccaj27

Residual stresses are known to exist in human intervertebral discs but have not been incorporated in finite element models. A multigeneration model was applied to the annulus fibrosus of the intervertebral disc to simulate residual stresses arising from growth and remodeling. The intervertebral disc shape and compressive creep were used to verify that the multigeneration approach generates realistic values of residual stress. The model was then validated by comparing its 6 degree-of-freedom mechanical response to experimental data. Human intervertebral discs were tested in a custom-built hexapod in all 6 degrees-of-freedom (lateral shear, anterior-posterior shear, torsion, bending, flexion, and compression). Incorporating residual stresses resulted in a finite element model which can predict 4 degrees-of-freedom while excluding residual stresses produces a finite element model that can only predict 2 degrees-of-freedom.


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: gtierne

Rugby is intrinsically an impact sport which results in concussions being a frequent injury within the game. Repeated concussion is linked to early-onset dementia and depression, and the rules for limiting repeated concussion are an ongoing controversy. Therefore a greater understanding of the dynamics of head impacts in rugby and the mechanism of concussion is required. Accordingly, this study focuses on assessing the use of Model Based Image Matching (MBIM) and multi-camera view video for measuring six degree of freedom head kinematics during an impact event in rugby union. The matching is performed on video evidence using 3-D animation software Poser 4. The surroundings are built in the virtual environment based on the real dimensions of the sport field. A skeleton model is then used to fit the player’s anthropometry for each video frame thus allowing player kinematics to be measured. The results from this initial study suggest that the MBIM method can be applied to head impact cases in rugby union. The head kinematics results from this case are similar to those reported in literature. The MBIM method should be applied to a number of head impact cases to establish thresholds for concussion injuries in rugby. The data gained from the MBIM method can allow for more reliable kinematic data to be inputted into finite element analysis and rigid body simulations of concussion impacts. This can allow multi-axis force measurements to be measured within the brain and neck. This can ultimately lead to an improvement in concussion injury prevention and management.