Unilateral Transtibial Amputees’ Step Accuracy Impaired

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A study, published online in the Journal of Biomechanics, found less accurate and precise intact foot placement among people with unilateral transtibial amputations. The study concluded that the lack of precision, coupled with a faster moving intact limb, is likely due to 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 paths or obstacles.

Eight participants with unilateral transtibial amputations (47 ± 13 years of age) and eight control group participants without amputations (33 ± 15 years of age) walked on a 10-meter walkway, placing their foot into a rectangular floor-based target with dimensions normalized to a percentage of the participant's foot length and width (standard = 150 percent x 150 percent; wide = 150 percent x 200 percent; long = 200 percent x 150 percent).

Foot placement accuracy (relative distance between foot and target center), 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 the participants with amputations in the wide target, which was significantly less accurate for the intact compared to prosthetic foot (28 ± 12mm versus 16 ± 14mm). Intact peak foot velocity (4.6 ± 0.8m/s-1) was greater than the prosthetic foot (4.5 ± 0.8m/s-1) for all targets.

Control participant's steps were more accurate and precise than the participants with amputations, regardless of target size.