Biomechanical effects of adding an articulating toe joint to a passive foot prosthesis for incline and decline walking.

Walking on sloped surfaces is challenging for many lower limb prosthesis users, in part due to the limited ankle range of motion provided by typical prosthetic ankle-foot devices. Adding a toe joint could potentially benefit users by providing an additional degree of flexibility to adapt to sloped surfaces, but this remains untested. The objective of this study was to characterize the effect of a prosthesis with an articulating toe joint on the preferences and gait biomechanics of individuals with unilateral below-knee limb loss walking on slopes. Nine active prosthesis users walked on an instrumented treadmill at a +5° incline and -5° decline while wearing an experimental foot prosthesis in two configurations: a Flexible toe joint and a Locked-out toe joint. Three participants preferred the Flexible toe joint over the Locked-out toe joint for incline and decline walking. Eight of nine participants went on to participate in a biomechanical data collection. The Flexible toe joint decreased prosthesis Push-off work by 2 Joules during both incline (p = 0.008; g = -0.63) and decline (p = 0.008; g = -0.65) walking. During incline walking, prosthetic limb knee flexion at toe-off was 3° greater in the Flexible configuration compared to the Locked (p = 0.008; g = 0.42). Overall, these results indicate that adding a toe joint to a passive foot prosthesis has relatively small effects on joint kinematics and kinetics during sloped walking. This study is part of a larger body of work that also assessed the impact of a prosthetic toe joint for level and uneven terrain walking and stair ascent/descent. Collectively, toe joints do not appear to substantially or consistently alter lower limb mechanics for active unilateral below-knee prosthesis users. Our findings also demonstrate that user preference for passive prosthetic technology may be both subject-specific and task-specific. Future work could investigate the inter-individual preferences and potential benefits of a prosthetic toe joint for lower-mobility individuals.

Biomechanical effects of an articulating prosthetic toe joint during stair navigation for individuals with unilateral, below-knee limb loss.

Stair navigation is an essential and demanding form of locomotion. During stair ascent and descent, persons with lower limb loss exhibit gait characteristics which may increase their risk of falls and joint degeneration of the intact limb. To reduce deviations from typically-able-bodied gait and overloading of the intact limb for this population, one potential intervention involves modifying passive prosthetic feet by incorporating a flexible toe joint that simulates the biological metatarsophalangeal joint. In this study, we aimed to assess the user preferences and biomechanical effects of a flexible prosthetic toe joint during stair ascent and descent for persons with unilateral lower-limb loss. Nine participants with unilateral lower-limb loss were recruited (Male; Medicare Functional Classification Level: eight K4, one K3; age: 41 ± 11 years; mass: 95 ± 13 kg; height: 1.84 ± 0.05 m; mean ± SD). No significant changes in lower-limb joint mechanics were identified. Five of nine participants preferred the unmodified prosthesis with a standard carbon fiber keel for both stair ascent and descent. Varied user preferences and inconsistent changes in lower-limb joint parameters between participants highlight the importance of subject-specific analyses and individualized device prescription.

Unilateral transtibial prosthesis users load their intact limb more than their prosthetic limb during sit-to-stand, squatting, and lifting.

BACKGROUND: Lower limb prosthesis users exhibit high rates of joint pain and disease, such as osteoarthritis, in their intact limb. Overloading of their intact limb during daily activities may be a contributing factor. Limb loading biomechanics have been extensively studied during walking, but fewer investigations into limb loading during other functional movements exist. The purpose of this study was to characterize the lower limb loading of transtibial prosthesis users during three common daily tasks: sit-to-stand, squatting, and lifting. METHODS: Eight unilateral transtibial prosthesis users performed sit-to-stand (from three chair heights), squatting, and lifting a 10 kg box. Peak vertical ground reaction forces and peak knee flexion moments were computed for each limb (intact and prosthetic) to characterize limb loading and asymmetry. Ranges of motion of the intact and prosthetic ankles were also quantified. FINDINGS: Users had greater peak ground reaction forces and knee flexion moments in their intact limb for all tasks (p < 0.02). On average, the intact limb had 36-48% greater peak ground reaction forces and 168-343% greater peak knee flexion moments compared to the prosthetic limb. The prosthetic ankle provided <10° of ankle range of motion for all tasks, less than half the range of motion provided by the intact ankle. INTERPRETATION: Prosthesis users overloaded their intact limb during all tasks. This asymmetric loading may lead to an accumulation of damage to the intact limb joints, such as the knee, and may contribute to the development of osteoarthritis. Prosthetic design and rehabilitation interventions that promote more symmetric loading should be investigated for these tasks.

Unilateral below-knee prosthesis users walking on uneven terrain: The effect of adding a toe joint to a passive prosthesis.

Lower limb prosthesis users cite uneven terrain as a challenging surface to walk on. We sought to determine whether adding a Flexible toe joint to a prosthetic foot would be preferred by unilateral below-knee prosthesis users relative to a Locked (non-articulating) toe joint for walking on uneven terrain. We also quantified lower limb joint kinetics for the Locked and Flexible toe joint configurations. Five of our nine participants preferred the Flexible toe joint when walking on uneven terrain, yet from a biomechanical standpoint, the reason for this is unclear. All participants exhibited reductions in prosthetic limb net positive hip joint work when walking with a Flexible toe joint (11%; p < 0.05). For other parameters (e.g., prosthetic side knee joint moments) we observed high inter-subject variation, which adds to a growing body of literature highlighting the need for subject-specific data analyses in lower limb prosthetics research.

Adding a toe joint to a prosthesis: walking biomechanics, energetics, and preference of individuals with unilateral below-knee limb loss.

Toe joints play an important functional role in able-bodied walking; however, for prosthesis users, the effect of adding a toe joint to a passive prosthetic foot remains largely unknown. The current study explores the kinematics, kinetics, rate of oxygen consumption and user preference of nine individuals with below-knee limb loss. Participants walked on a passive prosthetic foot in two configurations: with a Flexible, articulating toe joint and with a Locked-out toe joint. During level treadmill gait, participants exhibited a decrease in Push-Off work when using the Flexible toe joint prosthesis versus the Locked toe joint prosthesis: 16% less from the prosthesis (p = 0.004) and 10% less at the center of mass level (p = 0.039). However, between configurations, participants exhibited little change in other gait kinematics or kinetics, and no apparent or consistent difference in the rate of oxygen consumption (p = 0.097). None of the traditional biomechanical or metabolic outcomes seemed to explain user preference. However, an unexpected and intriguing observation was that all participants who wore the prosthesis on their dominant limb preferred the Flexible toe joint, and every other participant preferred the Locked configuration. Although perhaps coincidental, such findings may suggest a potential link between user preference and limb dominance, offering an interesting avenue for future research.

Assessment of the compressive and tensile mechanical properties of materials used in the Jaipur Foot prosthesis.

BACKGROUND: Designed by Dr. Sethi, the Jaipur Foot prosthesis is ideally suited for amputees in developing countries as it utilizes locally sourced, biodegradable, inexpensive materials and is focused on affordability and functionality. To date, however, no data have been reported on the material properties of the foot components. OBJECTIVES: The goal of this work was to evaluate mechanical properties of the Jaipur Foot components to guide foot design and manufacturing and reduce weight. STUDY DESIGN: Experimental. METHODS: Mechanical testing was conducted on two types of woods (ardu and cheed), microcellular rubber, tire cord, cushion compound, tread compound, and skin-colored rubber. Each material was subjected to testing in either tension or compression based on its location and function in the foot. Samples were tested before and after vulcanization. Two-sample t-tests were used to assess statistical differences. RESULTS: Cheed compressed perpendicular to the grain had a significantly higher modulus of elasticity than ardu ( p < 0.05); however, cheed had a higher density. Vulcanization significantly increased the modulus of skin-colored rubber, cushion compound, and tread compound ( p < 0.05) and decreased the moduli of both microcellular rubber and tire cord ( p < 0.05). CONCLUSION: The material property results from this study provide information for computer modeling to assess material construction on overall foot mechanics for design optimization. Ardu wood was ideal based on the desire to reduce weight, and the tire cord properties serve well to hold the foot together. Clinical relevance With new knowledge on the material properties of the components of the Jaipur Foot, future design modifications and standardized fabrication can be realized, making the Jaipur Foot more available on a global scale.