Angular kinematics at minimum toe clearance in people with transtibial amputation using articulated and non-articulated prosthesis.

Subjects with unilateral transtibial amputation exhibit altered minimum toe clearance (MTC) depending on the ankle prosthesis used, possibly due to a limited prosthetic ankle angle. The aim of this study was to investigate the alterations in joints kinematics responsible for the changes in MTC when using an Articulating Hydraulic Ankle (AHA) compared to a Non Articulating Ankle (NAA) prosthesis. Twelve participants with unilateral transtibial amputation walked at self-selected speed on a 10 meter pathway. They used 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 vs. NAA = 17.4 ± 5.2 mm, P < 0.01) and variability (13.4 ± 9.6 mm vs. 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° vs. NAA = -2.9 ± 1.5°, P = 0.01) while the variability of the prosthetic MTC appears to be influenced by changes in prosthetic mass. The results of this study suggests that ankle dorsiflexion during swing and the mass of the prosthesis have a direct influence in mean MTC and its variability, respectively.