Immediate effects of a new microprocessor-controlled prosthetic knee joint: a comparative biomechanical evaluation.

OBJECTIVE To investigate the immediate biomechanical effects after transition to a new microprocessor-controlled prosthetic knee joint. DESIGN Intervention cross-over study with repeated measures. Only prosthetic knee joints were changed. SETTING Motion analysis laboratory. PARTICIPANTS Men (N=11; mean age ± SD, 36.7±10.2y; Medicare functional classification level, 3-4) with unilateral transfemoral amputation. INTERVENTIONS Two microprocessor-controlled prosthetic knee joints: C-Leg and a new prosthetic knee joint, Genium. MAIN OUTCOME MEASURES Static prosthetic alignment, time-distance parameters, kinematic and kinetic parameters, and center of pressure. RESULTS After a half-day training and an additional half-day accommodation, improved biomechanical outcomes were demonstrated by the Genium: lower ground reaction forces at weight acceptance during level walking at various velocities, increased swing phase flexion angles during walking on a ramp, and level walking with small steps. Maximum knee flexion angle during swing phase at various velocities was nearly equal for Genium. Step-over-step stair ascent with the Genium knee was more physiologic as demonstrated by a more equal load distribution between the prosthetic and contralateral sides and a more natural gait pattern. When descending stairs and ramps, knee flexion moments with the Genium tended to increase. During quiet stance on a decline, subjects using Genium accepted higher loading of the prosthetic side knee joint, thus reducing same side hip joint loading as well as postural sway. CONCLUSIONS In comparision to the C-Leg, the Genium demonstrated immediate biomechanical advantages during various daily ambulatory activities, which may lead to an increase in range and diversity of activity of people with above-knee amputations. Results showed that use of the Genium facilitated more natural gait biomechanics and load distribution throughout the affected and sound musculoskeletal structure. This was observed during quiet stance on a decline, walking on level ground, and walking up and down ramps and stairs.