Biomechanical analysis of stair ambulation in lower limb amputees

Lower extremity amputees have to cope with many activities in everyday life that are substantially more difficult than walking on level ground, and such demands require a high degree of functionality from their prosthetic components. The present study is a biomechanical evaluation (kinematics, kinetics and EMG) of stair ascent and descent in a group of eight transtibial amputees (mean (standard deviation): age 51(14) years, height 176(7) cm, mass 88(19) kg); a group of 12 transfemoral amputees (age 37(8) years, height 182(7) cm, mass 83(7) kg) fitted with the electronically controlled C-LEG knee joint system; and a group of 12 able bodied persons (age 30(10) years, height 174(12) cm, mass 69(12) kg). During stair descent the transfemoral amputees presented a strong reduction of the prosthetic ankle moments (0.11 Nm/kg) compared to transtibial amputees (0.93 Nm/kg) and control subjects (1.26 Nm/kg). Loading of the prosthetic knee joint in the transfemoral amputees more closely resembles the loading seen in the control population when compared to transtibial amputees (mean maximum flexion moment: controls 1.31 Nm/kg, transfemoral amputees 1.00 Nm/kg, transtibial amputees 0.50 Nm/kg). Overload of the contralateral limb is more prominent in the transfemoral amputee than in the transtibial amputee. During stair ascent, the transtibial amputee presents a significant reduction of the knee flexion moment compared to the controls (mean maximum flexion moment: transtibial amputees 0.28 Nm/kg, controls 1.31 Nm/kg). These differences correlate with a change in the muscle activity of the knee extensor and hamstring muscles. The results also show adaptations in motor strategies during stair negotiation, for those with the partial loss of a lower limb due to the functional limits of current prosthetic components. The present data may contribute to a further enhancement of the efficiency of prosthetic feet and knee joints.