Evaluation of function, performance, and preference as transfemoral amputees transition from mechanical to microprocessor control of the prosthetic knee

Objective: To evaluate differences in function, performance, and preference between mechanical and microprocessor prosthetic knee control technologies. Design: A-B-A-B reversal design. Setting: Home, community, and laboratory environments. Participants: Twenty-one unilateral, transfemoral amputees. Intervention: Mechanical control prosthetic knee versus microprocessor control prosthetic knee (Otto Bock C-Leg). Main Outcome Measures: Stair rating, hill rating and time, obstacle course time, divided attention task accuracy and time, Amputee Mobility Predictor score, step activity, Prosthesis Evaluation Questionnaire score, Medical Outcomes Study 36-Item Short-Form Health Survey score, self-reported frequency of stumbles and falls, and self-reported concentration required for ambulation. Results: Stair descent score, hill descent time, and hill sound-side step length showed significant (P <.01) improvement with the C-Leg. Users reported a significant (P <.05) decrease in frequency of stumbles and falls, frustration with falling, and difficulty in multitasking while using the microprocessor knee. Subject satisfaction with the C-Leg was significantly (P <.001) greater than the mechanical control prosthesis. Conclusions: The study population showed improved performance when negotiating stairs and hills, reduced frequency of stumbling and falling, and a preference for the microprocessor control C-Leg as compared with the mechanical control prosthetic knee.