The effect of prosthesis alignment on the symmetry of gait in subjects with unilateral transtibial amputation.

A high degree of gait symmetry is characteristic of healthy gait. The aim of this study is to examine the symmetry of various gait parameters in subjects with unilateral trans-tibial amputation over a range of acceptable anteroposterior translational and tilt alignments, and further to examine if a consistent alignment of highest symmetry can be found. Acceptable alignments were determined by bench, static and dynamic testing on level and non-level surfaces. A total of 15 kinetic and kinematic parameters were then measured in the seven subjects participating in this study. Results indicate that some parameters show consistently higher symmetries, particularly the vertical ground reaction force parameters and the stance duration, step length and time to full knee flexion during the swing phase. Symmetries in other parameters such as knee flexion at loading response, acceleration impulse, and peak anteroposterior propulsive force seem to have little relevance in determining whether the gait pattern for that prosthetic alignment is acceptable or not. While analysis of the symmetry of more relevant gait parameters may assist the prosthetist in consistently and objectively identifying a most symmetrical alignment within the acceptable range, further clinical study is required before any conclusions can be drawn regarding evaluation of symmetry as a tool in defining any optimum alignment.