Individuals with unilateral transtibial amputation exhibit reduced accuracy and precision during a targeted stepping task.
Accurate foot placement is important for dynamic balance during activities of daily living. Disruption of sensory information and prosthetic componentry characteristics may result in increased locomotor task difficulty for individuals with lower limb amputation. This study investigated the accuracy and precision of prosthetic and intact foot placement during a targeted stepping task in individuals with unilateral transtibial amputation (IUTAs; N = 8, 47 ± 13 yrs), compared to the preferred foot of control participant's (N = 8, 33 ± 15 yrs). Participants walked along a 10-metre walkway, placing their foot into a rectangular floor-based target with dimensions normalised to a percentage of participant's foot length and width; 'standard' = 150% x 150%, 'wide' = 150% x 200%, 'long' = 200% x 150%. Foot placement accuracy (relative distance between foot and target centre), precision (between-trial variability), and foot-reach kinematics were determined for each limb and target, using three-dimensional motion capture. A significant foot-by-target interaction revealed less mediolateral foot placement accuracy for IUTAs in the wide target, which was significantly less accurate for the intact (28 ± 12 mm) compared to prosthetic foot (16 ± 14 mm). Intact peak foot velocity (4.6 ± 0.8 m.s-1) was greater than the prosthetic foot (4.5 ± 0.8 m.s-1) for all targets. Controls were more accurate and precise than IUTAs, regardless of target size. Less accurate and precise intact foot placement in IUTAs, coupled with a faster moving intact limb, is likely due to several factors including reduced proprioceptive feedback and active control during prosthetic limb single stance. This could affect activities of daily living where foot placement is critical, such as negotiating cluttered travel paths or obstacles whilst maintaining balance.