A robust technique for optimal fitting of roll-over shapes of human locomotor systems

The roll-over shape (ROS) effectively characterizes the lower limb\u27s ability to roll forward during the single-limb support phase of human walking. ROS is modelled as an optimally fitted circular arc to the center of pressure (CoP) data transformed in the shank/leg-based local coordinate system. The commonly used method for optimal fitting of ROS is complex to implement and eliminates inherent individual variability in the ROS parameters during walking. We propose and validate a novel computerized method for optimal fitting of roll-over shapes of the lower limb during walking. Gait data of a healthy individual from Winter\u27s book was used to generate ankle-foot and knee-ankle-foot roll-over shapes using the proposed method. The goodness of fit and form of both the roll-over shapes were validated with the literature. To test the robustness of the proposed technique, small random perturbations were introduced to the transformed CoP data and the effect of these small changes in the data on the ROS parameters was studied. The ROS parameters such as radius, arc length, subtended arc angle, and horizontal and vertical shift in the arc center did not change substantially with small changes in the CoP data. The proposed method is computationally efficient, and easy to implement for optimal fitting and characterization of ROS

Considerations for Implementation of an Ankle-Foot Orthosis to Improve Mobility in Peripheral Artery Disease

Objective To explore the perceptions of wearing an ankle-foot orthosis (AFO) in patients with peripheral artery disease (PAD) who did and did not adopt the AFO intervention. This follows a clinical trial of the effectiveness of an AFO in improving walking distances for patients with PAD-related claudication. Design A randomized crossover trial of standard of care and an AFO for 3 months. Semistructured interviews were conducted 1.5 months into the AFO intervention to understand acceptability, demand, implementation, and practicality. Data were analyzed using a summative content analysis approach. Setting Vascular surgery clinic and biomechanics research laboratory. Participants Patients (N=15; male, 100%; age, 71.9±.6.7y; body mass index [calculated as weight in kilograms divided by height in meters squared], 29.0±.5.5; ankle brachial index: AFO intervention withdrawal, 0.543; AFO intervention completion, 0.740) with claudication completed the study, and 6 withdrew prior to intervention completion. Interventions A certified orthotist fit participants with an AFO that was worn for 3 months. Main Outcome Measures Qualitative analysis of the semistructured interviews. Results Key differences were reported between AFO intervention completion and AFO intervention withdrawal. Six of 14 of AFO intervention completion participants described their initial reactions to the AFO as negative vs 3 of 6 AFO intervention withdrawal participants. Only 5 of 15 AFO intervention completion participants reported minimal use of the AFO compared with 5 of 6 AFO intervention withdrawal participants. The AFO intervention withdrawal group reported higher levels of physical discomfort with the use of the AFO (4/6 vs 7/15) and preexisting health issues becoming a barrier to the use of the AFO (3/6 vs 5/15). Positive aspects reported included ease in standing and walking for AFO intervention withdrawal (4/6) and AFO intervention completion groups (13/15) as well as walking straighter and longer with less pain for AFO intervention withdrawal (3/6) and AFO intervention completion groups (9/15). Conclusions Patients withdrawing prior to completion of AFO intervention tended to have more negative perceptions, more comorbidities, and more physical discomfort than those completing the intervention. Both groups reported positive aspects of the AFO. Implementation studies are needed to address barriers to AFO adoption

Roll-over characteristics in patients with peripheral artery disease during pain-free and painful overground walking

Human lower limbs demonstrate rocker like qualities during the stance phase of walking that facilitate the forward progression of the body. These rockers are quantified using equivalent roll-over shapes (ROS) which are invariant to walking speed, carrying additional weight and wearing different types of footwear. The aim of this work was to investigate the roll-over characteristics in patients with peripheral artery disease (PAD) during pain-free and painful overground walking. Gait data of ten patients with PAD walking overground at self-selected walking speed was collected using eight-camera motion capture system and a force plate embedded in the ground. Walking prior to the onset of pain was collected, followed by walking after claudication onset. The center-of-pressure data was transformed into the shank-based coordinate system to generate ROS, which was then fit to circular arcs using a MATLAB based optimization algorithm. Paired t-tests were used to determine the significant differences between the two walking conditions (p=0.05). Statistical analysis showed that the mean roll-over radius (p=0.819) and mean arc length (p=0.626) parameters were not significantly different between the pain-free and pain walking conditions. Our results indicate that the ROS is preserved even during claudication pain in patients with PAD. These findings corroborate with the general invariance model of ROS during different walking conditions in healthy individuals and thus, signify the use of ROS as a design goal for the assistive devices (orthosis/ exoskeleton) that are under development to assist patients with PAD