Abstract
People with a transtibial amputation using passive-elastic prostheses exhibit reduced prosthetic ankle power and push-off work compared to non-amputees and compensate by increasing their affected leg (AL) hip joint work and unaffected leg (UL) ankle, knee, and hip joint and leg work during level-ground walking. Use of a powered ankle-foot prosthesis normalizes step-to-step transition work during level-ground walking over a range of speeds for people with a transtibial amputation, but the effects on joint work during level-ground, uphill and downhill walking have not been assessed. We investigated how use of passive-elastic and powered ankle-foot prostheses affect leg joint biomechanics during level-ground and sloped walking. 10 people with a unilateral transtibial amputation walked at 1.25 m/s on a dual-belt force-measuring treadmill at 0°, ±3°, ±6°, and ±9° using their own passive-elastic and a powered prosthesis (BiOM T2, BionX Medical Technologies, Inc. Bedford, MA, USA) while we measured kinematic and kinetic data. We calculated AL and UL prosthetic, ankle, knee, hip, and individual leg positive, negative, and net work. Use of a powered compared to passive-elastic ankle-foot prosthesis resulted in greater AL prosthetic and individual leg net work on uphill and downhill slopes. Over a stride, AL prosthetic positive work was 23-30% greater (p<0.05) during walking on uphill slopes of +6°, and +9°, prosthetic net work was up to 10 times greater (more positive) (p≤0.005) on all uphill and downhill slopes and individual leg net work was 146% and 82% more positive (p<0.05) at uphill slopes of +6° and +9°, respectively, with use of the powered compared to passive-elastic prosthesis. Greater prosthetic positive and net work through use of a powered ankle-foot prosthesis during uphill and downhill walking improves mechanical work symmetry between the legs, which could decrease metabolic cost and improve functional mobility in people with a transtibial amputation.
Highlights
People with a transtibial amputation are prescribed a passive-elastic energy storage and return (ESAR) prosthesis that is made of carbon fiber and functions like a spring with no ability to generate power anew or to articulate
In partial support of our hypothesis, affected leg (AL) individual leg net work was more positive at uphill slopes of +6° and +9° with use of the BiOM compared to ESAR prosthesis; but we found no effect of prosthetic foot type on individual leg total positive work
Despite the differences in prosthetic ankle biomechanics between the tuning days and the final day of the protocol, we found a significant increase in AL prosthetic net work for all slopes and a significant increase in AL prosthetic positive work at uphill slopes of +6° and +9° with use of the BiOM compared to ESAR prosthesis
Summary
People with a transtibial amputation are prescribed a passive-elastic energy storage and return (ESAR) prosthesis that is made of carbon fiber and functions like a spring with no ability to generate power anew or to articulate. People with a transtibial amputation using an ESAR prosthesis exhibit slower preferred walking velocities (Herr and Grabowski, 2012; Russell Esposito et al, 2014), increased sagittal plane angular momentum (Pickle et al, 2016), and increased knee joint adduction moments in their UL (Grabowski and D’Andrea, 2013) compared to non-amputees. When walking on level ground using passive-elastic prostheses, people with a transtibial amputation exhibit an increase in knee flexion in their AL compared to their UL at heel-strike and activate their AL biceps femoris more than their UL biceps femoris, suggesting that greater work is absorbed at the knee (Isakov et al, 2000). Normative knee moments and powers could improve symmetry between legs and mechanical energy transfer across the AL knee joint of people with transtibial amputations
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