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: todd19

This study presents a new technique for acquiring ground reaction forces from novel, nanocomposite piezo-responsive foam (NCPF) sensors. A shoe was fitted with four NCPF sensors located at the heel, arch, ball, and toe positions. Running data was collected simultaneously from both the shoe sensors and from a force-sensing treadmill. A portion (30 randomly selected stance phases) of the treadmill data was used to develop a predictive stochastic model of GRF based on the sensor inputs. The stochastic model was then used to predict GRF for the remaining shoe sensor data, which was then benchmarked against the treadmill data. The results indicated that this model was able to predict forces in the x-axis (anterior-posterior) with 2.38% error, forces in the y-axis (medial-lateral) with 6.01% error, and forces in the z-axis (vertical) with 2.43% error. These novel sensors hold potential to dramatically improve both the ease and expense associated with GRF data, as well as allow unprecedented ability to measure GRF during real world applications outside of the laboratory.


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: 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: ulmans22

Multi-segmented foot and ankle (FandA) models provide more information regarding intrinsic foot motion compared to rigid-body models due to additional markers on bony landmarks of the foot. Marker placement sensitivity is a concern, especially in patients with bony abnormalities, because kinematics vary with marker placement deviations. PURPOSE: Assess kinematic changes due to marker placement error using the TSRHC multi-segmented FandA model. METHODS: Our participant was an 18yo female lacking any prior orthopedic conditions. The Plug-in-Gait model was used with the TSRHC model. An experienced clinician executed all marker placements, systematically moving each marker approximately 2.5mm within two planes. Three dynamic trials were collected for each condition, and static trials were used to calculate exact distances markers moved. Six force plates (AMTI) were utilized to confirm a consistent walking pattern. Graphs analyzed included: 1)PIG–ankle dorsiflexion, foot rotation, foot progression angle, 2)TSRHC–hindfoot, forefoot, FF-tibia. For each condition, the peaks of affected kinematic graphs were compared to assess correlations. Intra-trial error was determined by the maximum difference across walking trials. CONCLUSION: The hindfoot was most sensitive to transverse plane marker placement errors. Markers on metatarsals periodically rose vertically when moved laterally due to foot curvature causing errors in the sagittal plane as well. The forefoot also had transverse plane errors when metatarsal markers were moved. This case study illustrates the importance of proper marker placement training when utilizing a multi-segmented foot model. A thorough understanding of a utilized model is imperative, including how sensitive the model is to marker placement.


Name: claesamy

Nucleotomy is a surgical procedure following herniation and also simulates the reduced nucleus pulpousus (NP) pressure that occurs with disc degeneration. Internal disc strains are an important factor in disc function, yet it is unclear how internal strains are affected by nucleotomy. Grade II L3-L4 human cadaveric discs (n=6) were analyzed intact and after a partial nucleotomy that removed 30-50% of the NP through a left posterolateral incision (incision) while the contralateral side remained intact (uninjured). Two cycles of stress-relaxation testing were performed for reference (50N) and loaded (0.70MPa) configurations. After each 8hour equilibration period, the reference and loaded discs were imaged separately in a 7T MRI scanner (0.3mm isotropic resolution). The reference and loaded images were registered to calculate internal strain within the annulus fibrosus (AF) lamellae and discs were averaged to create anatomical templates. Circumferential, radial, and axial strains for each disc were transformed to the average templates, effectively normalizing the strains. Five circumferential regions were defined within the mid-third of the templates. Nucleotomy altered disc strains on both the incision and uninjured sides from the intact state. Strain fields were inhomogeneous through the five regions. Mean circumferential strain was unaffected by nucleotomy on the uninjured side, but decreased with incision, showing hoop strains through the AF were disrupted. Mean compressive axial strains were higher after nucleotomy, effectively reducing AF stiffness, and mean radial strains were unaltered after partial nucleotomy. These findings are important to address etiology and progression of degeneration, and to develop and evaluate therapeutic interventions.


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: ADiffendaffer

Peripheral arterial disease (PAD) is a vascular disease characterized by atherosclerotic blockages restricting blood flow to the lower extremities causing pain and discomfort with physical activity. Several studies have previously found decrements in ambulation associated with PAD, such as decreased joint moments and powers before and after the onset of claudication pain [1]. With decreases in moments and powers, the joint work may also be decremented as well. Thus, the purpose of this study was to investigate the positive and negative work at the ankle, knee and hip of PAD patients in a pain-free condition and compare them to gait-velocity matched controls.

Five patients with PAD and five healthy older controls were consented for participation. Subjects walked along a 10-meter walkway at their own self-selected speed while kinematics and kinetics were recorded. Each subject rested one minute between trials to mitigate fatigue and prevent ischemic pain. The positive and negative joint work for the PAD patients’ affected limb and the right limb of each control were analyzed and compared through independent t-tests (α=0.05).

Five PAD patients (66.6 + 6.2 years; 178.2 + 9.3 cm; 102.6 + 18.5 kg; 1.16 + 0.07 m/s) and five controls (69 + 4.6 years; 174.5 + 1.6 cm; 79.4 + 8.14 kg; 1.30 + 0.09 m/s) were used for analysis.

From this study it was found that patients with PAD exhibit a 26% reduction in positive ankle joint work during stance phase than their healthy counterparts (p=0.012).


Listed In: Biomechanics
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: gasparepro

Introduction and Objectives: It has previously been reported that deterioration in contractile strength and tendon
stiffness in the elderly is associated with altered motor task execution and reduced performance while walking [1,2], and
that resistance training improves muscle function, resulting in more effective and safer gait characteristics in the older
population [3]. In particular, triceps surae (TS) muscle-tendon unit (MTU) properties seem to be an important determinant
for walk-to-run transition speed [4], emphasizing the relevant role intrinsic MTU properties play in gait performance. The
objective of this empirical study was to examine the hypothesis that maximal walking velocity is related to TS MTU
mechanical and morphological properties and their enhanced capacities would improve gait velocity in the elderly.
Methods: Thirty four older female adults (66±7 yrs.) took part in the study. Nineteen of them were recruited for the
experimental group, who underwent a 14-week TS MTU physical exercise intervention which has been previously
established to increase muscle strength and tendon stiffness [5]. The remaining 15 subjects formed the control group (no
physical exercise intervention). The experimental group performed three times per week five sets of four repetitive (3·s
loading, 3·s relaxation) isometric plantar flexion contractions in order to induce high cyclic strain magnitudes on the TS
tendon and aponeurosis. Maximal walking velocity, defined as walking with a double support phase, was determined by
using two force plates (60 x 40 cm, 1080 Hz; Kistler, Winterthur, CH) and a motion capture system (Vicon Motion
Systems, Oxford, UK) with 12 infrared cameras operating at a frequency of 120 Hz. TS MTU properties were assessed
using simultaneous dynamometry and ultrasonography (Esaote MyLab Five; Esaote Biomedica, Genoa, IT).
Results: A significant correlation was found between the TS MTU mechanical and morphological properties and maximal
gait velocity (0.40 < r < 0.64; P < 0.05; n = 34). The experimental group showed higher TS contractile strength, tendon
stiffness, and higher gastrocnemius medialis muscle thickness post- compared to pre-intervention (P < 0.05). However,
calculated maximal gait velocity did not differ between pre and post-intervention measurements (2.39 ± 0.41 vs. 2.44 ±
0.45 m·s-1). Control subjects showed no statistically significant differences in maximal gait velocity or TS MTU mechanical
and morphological properties.
Conclusion: This empirical study confirms previous forward simulation models [4] proposing that intrinsic TS MTU
properties are significant determinants of gait performance. However, older adults may not be capable of fully utilizing
improvements of the MTU capacities while walking at maximal velocities following a 14 week physical exercise
intervention. Therefore, the benefits of a long term physical exercise intervention (1.5 years) will be discussed.


Listed In: Biomechanics, Gait, Other
Name: jessef32

While the popularity of triathlon is increasing, the underlying biomechanics of the various bicycling positions and saddle types are not yet understood.

PURPOSE: To determine how bicycle rider position and saddle type (road vs. triathlon) affect the bicycle-rider interface forces (BRIFs) at a standardized power and cadence. METHODS: A stationary cycling ergometer was modified to include force transducers at the saddle, bottom bracket, and stem. Anatomical measurements were made in order to fine-tune rider fit on the ergometer. 9 subjects completed riding trials in all combinations of road position, road saddle, triathlon position, and triathlon saddle. Riding trials were 6 minutes, at a standardized power output of 2 Watts per kilogram (W/kg) and 90 Revolutions per Minute (RPM). RESULTS: Analysis was broken into three categories: Road Saddle, Road Position (RR) vs. Triathlon Saddle, Road Position (TR), Road Saddle, Triathlon Position (RT) vs. Triathlon Saddle, Triathlon Position (TT), and Road Saddle, Road Position vs. Triathlon Saddle, Triathlon Position. Surprisingly, there were no significant differences in saddle vertical forces between either body positions or saddle type. However, there were significant differences at the handlebar; 8.4% more body weight supported at the handlebar in the triathlon position compared to the road position while using a triathlon saddle. CONCLUSION: Across cycling positions, there is a significant change in saddle and stem vertical forces. However, within a cycling position, saddle type does not change the amount of vertical force seen at the saddle.