Angular Kinematics at Minimum Toe Clearance in People With Transtibial Amputation Using Articulated and Nonarticulated Prosthesis

Subjects with unilateral transtibial amputation exhibit altered minimum toe clearance (MTC) depending on the ankle prosthesis used. It has been suggested that a limited prosthetic ankle angle could be the cause of the change. The aim of this study was to investigate the alterations in kinematics in the joints responsible for the changes in MTC when using an articulating hydraulic ankle (AHA) prosthesis compared to a nonarticulating ankle (NAA) prosthesis. Twelve participants with unilateral transtibial amputation walked at their self-selected speed on a 10 m pathway. They used both the same AHA and NAA prosthetic models and the prosthetic characteristics were unchanged except for the ankle mechanisms and, consequently, its mass. Data from MTC and hip, knee, and ankle angles in the sagittal, frontal, and transversal plane at the time of MTC were statistically analyzed with a paired sample t-test. The AHA prosthesis showed significantly higher MTC mean (⁠$AHA=24.7 ± 9.6$ mm versus $NAA=17.4 ± 5.2$ mm, $P<0.01$⁠) and variability (⁠$13.4 ± 9.6$ mm versus $6.7 ± 4.2$ mm, $P=0.03$⁠) on the prosthetic limb than the NAA. A higher mean MTC could be explained by an increase in ankle angle dorsiflexion (⁠$AHA=−1.2 ± 2.6 deg$ versus $NAA=−2.9 ± 1.5 deg$⁠, $P=0.01$⁠), while the variability of the prosthetic MTC appears to be influenced by changes in prosthetic mass. The results of this study suggest that ankle dorsiflexion during swing and the mass of the prosthesis have a direct influence in mean MTC and its variability, respectively.