Obstacle crossing in lower limb amputees

Objective To study limitations in function and adjustment strategies in lower limb amputees during obstacle crossing. Design Observational cohort study. Subjects Transfemoral and transtibial amputees and able-bodied control subjects. Methods In a motion analysis laboratory unimpeded and obstacle crossing runs were performed. The subjects stepped over an obstacle of 0.1 m height and thickness and 1 m width. Outcome measures were gait velocity, hip, knee and ankle joint angles and leading limb preference. Results Whereas able-bodied and transtibial subjects demonstrated an increase in knee flexion during obstacle crossing compared to unimpeded walking, in transfemoral amputees the opposite was seen, namely a decrease in knee flexion. The lack of knee strategy in transfemoral amputees was compensated by circumduction at the hip on the prosthetic side and plantar flexion of the non-affected ankle. Transtibial amputees preferred to cross the obstacle with the prosthetic limb first, while transfemoral amputees preferred the non-affected limb. Conclusion The different leading limb strategy in transfemoral and transtibial amputees could be explained by the restricted flexion and propulsion properties of the prosthetic knee. Training of obstacle crossing tasks during rehabilitation and improvement of prosthetic design may contribute to safe obstacle crossing.