Article

Stair ascent kinematics and kinetics with a powered lower leg system following transtibial amputation

Center for the Intrepid, Department of Orthopaedics and Rehabilitation, Brooke Army Medical Center, Ft. Sam Houston, TX 78234, USA.
Gait & posture (Impact Factor: 2.58). 05/2012; 36(2):291-5. DOI: 10.1016/j.gaitpost.2012.03.013
Source: PubMed

ABSTRACT During stair ascent (STA) persons with transtibial amputation (TTA) typically adopt a hip strategy to compensate for the limited ankle motion and joint power that is characteristic of conventional energy storing and returning (ESR) prosthetic feet. The purpose of this investigation was to determine if providing ankle power via a powered prosthetic device (BiOM) normalized STA kinematics and kinetics. Eleven individuals with TTA participated in two STA gait analysis sessions: (1) using an ESR foot, and (2) using the BiOM. Eleven height and weight matched able-bodied controls (CONT) were also assessed. Lower extremity peak kinematic and kinetic values were calculated at a self-selected and controlled cadence (80 steps/min). Increased prosthetic limb peak ankle plantarflexion and push-up power were observed while using the BiOM as compared to ESR. Peak ankle power was not significantly different between BiOM and CONT indicating normalization of ankle power generation. However, peak ankle plantarflexion was significantly lower than CONT. Limb asymmetries including greater prosthetic limb hip flexion and power during stance, and decreased prosthetic limb knee power during stance were observed in the BiOM and ESR conditions. The results suggest that the BiOM successfully increased ankle motion and restored ankle power during STA. These differences did not, however, reduce the use of a hip strategy while ascending stairs. Additional device specific training may be necessary to utilize the full benefits of the device.

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Since this time major changes in the structure, the material and the functionality led to improved prosthetic restoration of physically disabled. The characteristics of the biological leg structure are imitated by technical components. Using carbon fiber for the design of prosthetic feet made it possible to benefit from the elastic recoil like in the Achilles tendon in stance phase. Dampers in prosthetic knee joints are able to mimic eccentric muscle work during the gait cycle. Clutch-like mechanisms are used to lock the knee during stance. Such a function is comparable to isometric muscle work. Semiactive knee joints allow changes in damping ratio to adapt the mechanical joint properties to the requirements. Using integrated force or inertial sensors, movement tasks can be identified. An adaptation of damping to different walking speeds and conditions, such as walking inclines, declines, or climbing stairs is possible. 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Furthrmore, a concept on the improvement of an optimized walking motor pattern was successfully tested. By smoothening the motor curve to the main characteristics (low-pass filter) it was possible to increase the mechanical work output, to improve the system efficiency, and to decrease the electrical energy consumption and the noise. To further improve the prosthetic performance, the push off timing and the causes for prosthesis noise should be analyzed. Weight reductions and psychoacoustic analysis can additionally help to improve on the amputees acceptance. In addition it must be evaluated how training can effect amputees gait patterns when using powered prostheses. To further reduce the power and the energy requirements, an improvement on the powered prosthesis efficiency is recommended. The efficiency can be further increased by using higher efficiency parts and improving the interaction of the prosthesis and the amputee. 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