Journal of biomechanics最新文献

The offloading effectiveness of custom-made footwear for people with diabetes is assessed using plantar pressure measurements. While such pressure data is multidimensional, it is mostly analyzed using a scalar - maximum peak plantar pressure (PMax). We aimed to investigate the associations between multiple peak plantar pressure parameters for footwear assessment and determine whether this assessment depends on the chosen parameter. In-shoe plantar pressure was measured in 77 participants with diabetes, peripheral neuropathy, and a recent ulcer or amputation history, while walking in their own custom-made footwear. Six peak plantar pressure parameters were extracted, both scalar (i.e. Pmax, time integral and gradient) and multidimensional (i.e. time curve, map and time map). Footwear was ranked from highest to lowest outcome for each parameter and associations with Pmax were compared using Spearman's rank correlation coefficient. A footwear comparison within subjects using Fleiss' Kappa analysis determined the agreement between parameters using two pairs of footwear of each participant. The rank correlation coefficient was moderate to strong between PMax and the other scalar parameters (ρ = 0.46-0.70), and negligible to weak between PMax and the multidimensional parameters (ρ = 0.03-0.25). Percentage agreement between parameters for the within-subject footwear comparison was poor (47.5 %, κ = 0.0652). We conclude that the association and agreement between in-shoe peak pressure parameters is low and the assessment of offloading effectiveness depends on the chosen parameter. This is the first step in unlocking the potential of a multidimensional approach in plantar pressure analysis, possibly changing how we evaluate footwear offloading effectiveness.

A CT-based method for objectively assessing fracture severity was previously developed and validated to address poor reliability in existing subjective fracture classification systems. The method involved quantifying the energy involved in creating a fracture. However, clinical utility of the method was hindered by reliance upon an intact contralateral CT and lengthy analysis time (8-10 h). Significant methodological improvements detailed here enable the assessment of fracture severity in any joints and bones, while obviating the need for an intact contralateral CT scan. Analysis time was reduced to <2 h per case. Fracture energies computed using the new methods showed strong agreement (R² = 0.95, p < 0.001) with prior results in analyzing twenty tibial pilon fractures. New metrics, articular fracture edge length and subchondral energy, were developed to better describe joint injuries by incorporating knowledge of preferential chondrocyte death along fracture edges. Based on two-year radiographic grading for these pilon fractures, fracture energy, articular fracture edge length, and subchondral energy were all significantly different (p < 0.01) between cases that did or did not develop post-traumatic osteoarthritis. These developments enable measurement of fracture severity in larger populations and in more clinically relevant timeframes with articular fractures involving a variety of joints and bones. This generalized assessment method offers opportunity to change the way severity is considered in fracture treatment algorithms. Studies involving larger cohorts are anticipated to yield insights into the impact of fracture severity on PTOA risk and serve as a foundation for evaluating new treatment strategies.

Improper socket fitting in lower-limb prostheses can lead to significant complications, including pain, skin lesions, and pressure ulcers. Current suspension and socket design practices rely predominantly on visual inspection of the residual limb and patient feedback. Monitoring stress distribution at the residual limb/socket interface offers a more objective approach. Finite Element Analysis (FEA) enables to estimate interface pressure distribution prior to manufacture to provide the orthoprosthetist with quantitative data during socket rectification and interface prosthetic components selection. However, although numerous FEA models are available, few have undergone rigorous validation against experimental pressure data. Indeed, limitations of commercial pressure sensors typically include cumbersomeness or imprecision, thereby hindering systematic measurements within the socket. In this study, we introduce a low-cost, accurate pressure sensing system integrated into 3D-printed sockets for FEA validation. The system is implemented on a roll-over simulator that uses a mock limb to mimic the interaction between a transtibial residual limb and socket during the unipodal stance phase. A FEA of the simulator was then conducted, and predicted interface pressures were compared to experimental measurements at seven discrete locations. The model demonstrated a high degree of sensitivity to the geometry of the mock limb; however, with an accurate shape description, it was able to predict pressure with an average absolute error of 12 kPa. This work advances the validation of residual limb FEA for estimating residual limb/socket interface pressures. It highlights the potential of FEA for designing data-driven sockets and ultimately improve the comfort of prosthesis users.

This study used musculoskeletal modelling to explore the relationship between cycling conditions (power output and cadence) and muscle activation and metabolic power. We hypothesized that the cadence that minimized the simulated average active muscle volume would be higher than the cadence that minimized the simulated metabolic power. We validated the simulation by comparing the predicted muscle activation and fascicle velocities with experimental electromyography and ultrasound images. We found strong correlations for averaged muscle activations and moderate to good correlations for fascicle dynamics. These correlations tended to weaken when analyzed at the individual participant level. Our study revealed a curvilinear relationship between the average active muscle volume and cadence, with the minimum active volume being aligned to the self-selected cadence. The simulated metabolic power was consistent with previous results and was minimized at lower cadences than that which minimized active muscle volume across power outputs. Although there are some limitations to the musculoskeletal modelling approach, the findings suggest that minimizing active muscle volume may be a more important factor than minimizing metabolic power for self-selected cycling cadence preferences. Further research is warranted to explore the potential of an active muscle volume-based objective function for control schemes across a wider range of cycling conditions.

Deficient trip recovery kinematics have been implicated in many trip-induced falls. Three key requisites for successful trip recovery include limiting trunk flexion, maintaining adequate hip height to enable repeated stepping, and completing recovery steps to extend the base of support. The purpose of this study was to evaluate sternum drop as a new measure of trip recovery performance. Sternum drop may be a more robust than other measures of trip recovery performance because, unlike other common trip recovery measures, it is sensitive to two of the three trip recovery requisites. Thirty community-dwelling older adults were exposed to two laboratory-induced trips while walking on a walkway. Sternum drop was determined using two separate methods: from optoelectronic motion capture and an inertial measurement unit. For comparison sternum drop, trunk angle and hip height, both at touchdown of the first recovery step, were also determined. Sternum drop from optoelectronic motion capture exhibited strong correlation with trunk angle at touchdown (repeated-measures correlation coefficient (r_rm) = 0.94; p < 0.001), strong correlation with hip height at touchdown (r_rm = -0.90; p < 0.001), and strong correlation with sternum drop from IMU (r_rm = 0.95; p < 0.001). In addition, sternum drop from optoelectronic motion capture (p < 0.001) and sternum drop from inertial measurement unit (p = 0.001) differed between falls and recoveries, with the former exhibiting the largest effect size (partial eta² = 0.36) between falls and recoveries. These results support sternum drop as a valid kinematic measure of trip recovery performance.

Portal hypertension (PH) is the initial and main consequence of liver cirrhosis. Hepatic venous pressure gradient (HVPG) measurement has been widely used to estimate portal pressure gradient (PPG) and detect portal hypertension. However, some clinical studies have found poor correlation between HVPG and PPG, which may lead to the misdiagnosis of portal hypertension. In this study, we provided a method to evaluate patients' PPG based on clinically measured HVPG with computational fluid dynamics (CFD). Twenty-five patients who underwent HVPG measurement were recruit for analysis. Results show that HVPG significantly correlates with PPG (R = 0.7499, P < 0.0001), with an accuracy to distinguish clinically significant portal hypertension (CSPH) as high as 92 %. However, PH severity classification was underestimated for 36 % patients, especially for patients with hepatic venous collateral formation and presinusoidal portal vein occlusion. It is concluded that HVPG is a relatively reliable diagnostic method for PH when PPG cannot be directly measured. For patients who have clinical symptoms of PH but their HVPG are within a normal range, numerical evaluation of PPG with CFD is an excellent way for their diagnosis.

Medical image-based diagnostic techniques have become increasingly common in the clinic. Estimating fractional flow reserve in coronary stenoses from medical image data is among the most prominent examples. The modeling techniques used in these clinical tools require rigorous experimental validation yet there is currently no standardized, public toolset to help assess model credibility. In this study, we present a generic coronary artery lumen geometry which will form the basis for a future publicly available validation database. We characterize the geometry using proximal and distal diameters along with the mean curvature, total curvature, total torsion, and tortuosity index. The coronary lumen geometry balances anatomic fidelity and simplicity with integration into a future experimental mock circulatory loop in mind. The lumen geometry, along with the data produced by our future work, will be made available for public use in FDA's Office of Science and Engineering Laboratories Regulatory Science Tool Catalog.

Analysis of the power produced by the foot and ankle during locomotion can provide insights into their function. Foot power is often quantified by applying the unified deformable (UD) power model to the hindfoot while ankle power is quantified by performing three or six degree-of-freedom joint power calculations. These measurements are possible with optical motion capture. Biplanar videoradiography (BVR) provides new opportunities for quantifying foot and ankle power as it provides highly accurate measurements of the individual foot bones that are not possible with optical motion capture. In this paper, we apply the UD power model to the talus to quantify foot power. This novel application of the UD power model also allows us to quantify talocrural joint power. We compared this new method of calculating foot and ankle power with the methods possible with optical motion capture. We found similar trends between the two methods, suggesting that applying the UD power model to the talus can quantify foot and talocrural power. Key differences between the two methods included the magnitude of power and work, as well as the timing of the power curves. These findings support the idea that the foot can actively produce power during propulsion and that the timing of arch and ankle mechanics, and their synchronization, is important for propulsion across locomotor modes.

Runners who experience insufficient recovery time after training demands may have increased injury risk. Training and exercises can induce fatigue and altered movement patterns, which may best be assessed by examining the dynamics of the movement structure during a sports-related task. This crossover experimental study investigated the immediate and prolonged effects of exercise at different intensities on lower-limb joints and coordinative patterns during a 60-second single-leg squat task in 30 healthy runners. Joints (ankle, knee, hip) and coordination (ankle-knee, knee-hip continuous relative phase) angles were assessed between measurement times (pre, post, post24h, post48h) and protocols (moderate- and high-intensity run, control). A Statistical Parametric Mapping (SPM) one-way repeated measures ANOVA analyzed the joints and coordination time-normalized curves. Additionally, the entropy (i.e., regularity) of the entire time series was assessed by a two-way ANOVA. Lower ankle-knee coordination entropy was observed immediately after running protocols (moderate-intensity, -17.6 %, p = 0.003, η²_p = 0.21; high-intensity, -18.6 %, p = 0.001, η²_p = 0.22) and was also observed individually on the ankle and knee at post48h (p < 0.001, η²_p = 0.10). . No time or protocol effects were observed for SPM analysis. Runners demonstrated more regular (lower entropy) ankle-knee coordination after running protocols, which is related to a less adaptative pattern. In addition, increased regularity was observed on ankle and knee joint angles 48 h after protocols, suggesting an ongoing recovery process. The analysis of time-normalized kinematics was not sensitive to detect the effect of running on movement. Therefore, evaluating the coordination regularity during a single-leg test helped track the effect of exercise and fatigue, even without maximal effort.

Anterior cruciate ligament (ACL) reinjury rates among athletes remain very high despite screening protocols designed to assess readiness for return to sport. To better identify biomechanical risk factors for ACL injury, combining neurocognitive challenges and high-impact tasks would more closely resemble sporting demands. We investigated the influence of secondary cognitive tasks on landing mechanics during bilateral drop vertical jumps (DVJs) among athletes following ACL reconstruction and whether sex affected these results. We also assessed whether adding secondary cognitive tasks to DVJs influenced loading asymmetries. Forty individuals (20 males) performed three DVJ conditions: (1) without secondary cognitive tasks (DVJ), (2) with secondary cognitive tasks targeting fast decision-making and inhibitory control of the motor action (DVJmot), and (3) with secondary cognitive tasks targeting fast decision-making, inhibitory control, attention, and short-term memory (DVJcogmot). We collected movement mechanics time-series data during the first 100 ms of landing using a motion capture system and force plates and compared outcomes between the three DVJs using functional t-tests. Secondary cognitive tasks altered trunk, hip, knee, and ankle landing mechanics (adjusted p-values < 0.05), representing more upright and stiffer landings. Loading asymmetries were increased by unloading the injured limb (adjusted p-values < 0.05). We found no differences between DVJmot and DVJcogmot or between males and females. Adding secondary cognitive tasks to DVJs better identifies landing mechanics associated with an increased ACL injury risk and inadequate rehabilitation. Future research should focus on optimizing the challenge point of the cognitive and motor tasks and how to best integrate them in RTS testing.