Variability and Distribution of Minimum Toe Clearance in Individuals with Unilateral Transtibial Amputation

Abstract

Introduction: Maintenance of consistently adequate minimum toe clearance (MTC) is a critical factor in gait safety. Three separate strategies to achieve this have been identified previously; these are as follows: 1) increase average toe clearance; 2) reduce toe clearance variability; and 3) alter toe clearance distribution. Individuals with a unilateral transtibial amputation (UTA) have reduced average toe clearance on the prosthetic limb compared with the able-bodied. In addition, they lack speed-related modulation of toe clearance on the prosthetic limb. This study determines the effects of walking speed on the MTC variability and distribution of individuals with amputation. Methods: Ten able-bodied and 10 unilateral transtibial participants walked at slow, customary, and fast speeds. Variability and distribution of MTC were determined and compared between intact and prosthetic limbs and the able-bodied. Results: Minimum toe clearance variability was highest on the intact limb and lowest in the able-bodied, and differences between all limbs were significant (P ≤ 0.011). Variability was highest at the “fast” walking speed and lowest at the “customary” walking speed (P = 0.045). Skewness of MTC distribution was highest for the able-bodied and lowest for the intact limb of persons with amputation. Conclusions: Individuals with a UTA have increased MTC variability compared with the able-bodied across all walking speeds. In addition, as a response to altered walking speed, they have similar directional changes to toe clearance variability as the able-bodied but are unable to alter the skewness of distribution in the same manner. This, combined with their lack of speed-related increases to average prosthetic-limb toe clearance, suggests that individuals with a UTA may be at higher risk of trips when walking at speeds other than their customary walking speed, especially when walking more quickly.