Influence of coronal and sagittal prosthetic foot alignment on socket reaction moments in transtibial prostheses during walking.

BACKGROUND

The socket reaction moment (SRM) has been reported to change because of alignment changes in transtibial prosthetic sockets. However, the influence of prosthetic foot alignment on SRM remains unclear.

RESEARCH QUESTION

Are SRMs predictable from alignment changes of prosthetic feet?

METHODS

Ten users of transtibial prostheses participated in this study. Under five alignment conditions (3 ° plantarflexion and dorsiflexion, 6 ° inversion and eversion, and baseline alignment), temporal-spatial parameters and sagittal and coronal SRMs were measured during walking. Cadence, walking speed, step time, single support time, and step length were compared. The maximum/minimum SRM, % stance (timing) of the maximum/minimum SRM, Zero-cross, and SRMs at 5 %, 20 %, and 75 % stance were extracted and compared. Repeated measures analysis of variance or Friedman tests, and linear regression analyses were conducted for statistical analyses (i.e., alignment conditions as independent variables and SRM parameters as dependent variables).

RESULTS

The SRMs at 5%, 20 %, and 75 % stance showed significant differences under coronal angular changes. The minimum SRM, % stance of the minimum/maximum SRM, and Zero-cross showed significant differences under sagittal alignment changes. In linear regression analysis, the minimum SRM, % stance of the minimum/maximum SRM, SRM at 20 % stance, and Zero-cross were significant dependent variables in the sagittal plane. The maximum/minimum SRM, SRM at 20 % and 75 % stance, and % stance of the minimum SRM were significant dependent variables in the coronal plane.

SIGNIFICANCE

The results indicated that the changes in prosthetic feet angles may predict the magnitude of SRM (maximum/minimum SRM, SRM at 20 % and 75 % stance) in the coronal plane, and the timing of SRM (Zero-cross, % stance of the maximum/minimum SRM) in the sagittal plane. These findings suggest that the SRM may be useful for evaluating foot alignment in transtibial prostheses.