Biomechanics and Motion Analysis

Microprocessor Controlled Knee Prosthesis

Principal Investigator: Kenton R. Kaufman, Ph.D.
Project Coordinator: Denny Padgett — padgett.denny@mayo.edu

Figure 24: (Left) Mauch SNS knee component*
Figure 25: (right) Otto Bock C-leg knee component*
*Photos used with permission by Otto Bock

At the present there are two distinct types of knee components for transfemoral amputees: mechanical mechanisms and microprocessor controls. Microprocessor controlled knee joints have appeared on the market in the past decade. These sophisticated and expensive prosthetic components need to be analyzed objectively in order to verify the claims of their manufacturers and the views of prosthetists and transfemoral amputees currently using this advanced technology. Therefore, the purpose of this study is to quantify the gait and balance characteristics of active transfemoral amputees using a microprocessor controlled knee joint.

Figure 26: C-leg user knee moment

This pilot study employs a crossover design in which the knee component is changed. Each subject is tested using a mechanical knee prosthesis (Figure 24, Mauch SNS or CaTech) and retested eight weeks after receiving a microprocessor controlled knee joint (Figure 25, Otto Bock C-leg). Objective data consisting of gait, balance, energy consumption, and activity level measurements were obtained.

Figure 27: (top) Balance composite score
Figure 28: (bottom) PEQ Scores

Subjects demonstrated improved gait and balance characteristics after receiving the microprocessor controlled prosthetic knee joint. The knee moment demonstrated a significant shift from an external extension moment toward a more normal flexion moment during midstance (Figure 26). The subjects achieved greater gait symmetry. There was a significant improvement in the balance composite score (Figure 27). Two of the three subjects tested so far experienced a decrease in energy consumption. As a result of the reduced energy required for ambulation, the subjects increased their activity level. The subjects' subjective evaluation, as measured by the PEQ, showed improved satisfaction with a significant reduction in frustration and a significant improvement in well being (Figure 28).