Effect of transtibial prosthesis alignment changes on out-of-plane socket reaction moments during walking in amputees

Alignment of lower limb prostheses is important for the gait of amputees. Observed deviations in a particular plane are corrected by altering the prosthetic alignment of the same plane. The assumption is that observed deviations are due to alignment errors within the same plane, but no research has confirmed this assumption. Therefore, the aim of this study was to investigate the out-of-plane effect of systematic alignment changes on socket reaction moments measured by an instrumented prosthesis alignment component in the sagittal and coronal planes in eleven amputees with transtibial prostheses. Each subject walked at self-selected walking speed following randomized controlled angular (±3° and ±6°) and translational (±5 mm and ±10 mm) alignment changes from the nominally aligned condition. The following socket reaction moment parameters were subsequently analyzed: 3 parameters (maximum moment, minimum moment, moment at 45% of stance phase) in the sagittal plane and 2 parameters (moment at 30% and 75% of stance phase) in the coronal plane. A statistical comparison was performed between the nominally aligned and mal-aligned conditions using a repeated measures of ANOVA followed by Scheffe's post-hoc tests. Significant differences were found between the nominally aligned (-0.077±0.078 Nm/kg) and 3° extension (-0.033±0.075 Nm/kg; P=0.0258) and 6° extension (-0.029±0.071 Nm/kg; P=0.0098) conditions in the coronal plane socket reaction moments measured at 30% of stance. Our analysis suggests that the alignment of the transtibial prosthesis should be performed in the sagittal plane first followed by the coronal plane.