A biomechanical assessment of hydraulic ankle-foot devices with and without micro-processor control during slope ambulation in trans-femoral amputees

Abstract

Slope ambulation is a challenge for trans-femoral amputees due to a relative lack of knee function. The assessment of prosthetic ankles on slopes is required for supporting the design, optimisation, and selection of prostheses. This study assessed two hydraulic ankle-foot devices (one of the hydraulic ankles is controlled by a micro-processor that allows real-time adjustment in ankle resistance and range of motion) used by trans-femoral amputees in ascending and descending a 5-degree slope walking, against a rigid ankle-foot device. Five experienced and active unilateral trans-femoral amputees performed ascending and descending slope tests with their usual prosthetic knee and socket fitted with a rigid ankle-foot, a hydraulic ankle-foot without a micro-processor, and a hydraulic ankle-foot with a micro-processor optimised for ascending and descending slopes. Peak values in hip, knee and ankle joint angles and moments were collected and the normalcy Trend Symmetry Index of the prosthetic ankle moments (as an indication of bio-mimicry) were calculated and assessment. Particular benefits of the hydraulic ankle-foot devices were better bio-mimicry of ankle resistance moment, greater range of motion, and improved passive prosthetic knee stability according to the greater mid-stance external knee extensor moment (especially in descending slope) compared to the rigid design. The micro-processor controlled device demonstrated optimised ankle angle and moment patterns for ascending and descending slope respectively, and was found to potentially further improve the ankle moment bio-minicry and prosthetic knee stability compared to the hydraulic device without a micro-processor. However the difference between the micro-processor controlled device and the one without a micro-processor does not reach a statistically significant level.

Benefits of a microprocessor-controlled prosthetic foot for ascending and descending slopes

“…Our results indicate that the MPF-M acted like a “regular” prosthetic foot for descending a slope, probably to not interfere with the MPK’s yielding mode. One of the few studies that investigated TFA slope walking with a MPF could not find benefits in ramp walking, although changes in the prosthetic ankle characteristics were reported [ 10 ]. In that study, participants with TFA showed neither knee stance flexion for Up nor continuous knee flexion for Down on a 5° slope that would be managed with normal knee characteristics by able-bodied controls.…”

“…A similar effect on the ROM might be achieved with decreasing the stiffness of the springs of ESR feet, but that could also negatively affect the energy efficiency and the roll-over behavior of the feet on level ground [ 7 ]. Another concept is to actively control an integrated ankle joint by adapting hydraulic plantar- and dorsiflexion resistances to the terrain to control the ROM [ 8 – 10 ] and regulate shank rotation velocity [ 11 ]. Such an adaptation likely shifts the foot’s neutral point—the angular position at which the acting external plantar- and dorsiflexion moments cancel each other out [ 12 ].…”

Design and development of safe gait prosthetic knee joint in India

“…passive, damping, and powered. No power is needed in the passive prosthesis while damping need power for variable damping and powered prosthetic knees can perform positive knee work [ 1 2 3 5 6 7 8 9 10 ]…”

“…The prosthetic technology in recent years has grown by leap and bounds. The mostadvanced prosthesis incorporates advanced gadgets like microprocessors [ 1 2 3 4 5 6 7 8 9 10 11 ] which are available at exorbitant costs. India is a developing country and the Indian Government endeavors to provide the aids and appliances to the disabled at the minimum costs.…”

“…In recent years, worldwide, we have many kinds of knee joints developed providing control either with the use of hydraulic fluid mechanisms or pneumatic control mechanisms. [ 1 3 4 5 6 7 9 11 ] For the consumer, choice of knee joint and selection of knee joint is becoming problematic.…”