Comparison of transtibial amputee and non-amputee biomechanics during a common turning task

The biomechanics of amputee turning gait has been minimally studied, in spite of its integral relationship with the more complex gait required for household or community ambulation. This study compares the biomechanics of unilateral transtibial amputees and non-amputees completing a common turning task. Full body gait analysis was completed for subjects walking at comparable self-selected speeds around a 1m radius circular path. Peak internal and external rotation moments of the hip, knee and ankle, mediolateral ground reaction impulse (ML GRI), peak effective limb length, and stride length were compared across conditions (non-amputee, amputee prosthetic limb, amputee sound limb). Amputees showed decreased internal rotation moments at the prosthetic limb hip and knee compared to non-amputees, perhaps as a protective mechanism to minimize stress on the residual limb. There was also an increase in amputee sound limb hip external rotation moment in early stance compared to non-amputees, which may be a compensation for the decrease in prosthetic limb internal rotation moment during late stance of the prior step. ML GRI was decreased for the amputee inside limb compared to non-amputee, possibly to minimize the body's acceleration in the direction of the turn. Amputees also exhibited a shorter inside limb stride length compared to non-amputees. Both decreased ML GRI and stride length indicate a COM that is more centered over the base of support, which may minimize the risk of falling. Finally, a longer effective limb length was found for the amputee inside limb turning, possibly due to excessive trunk shift.