Assessment of transfemoral amputees using a passive microprocessor-controlled knee versus an active powered microprocessor-controlled knee for level walking

Abstract

Background: In transfemoral (TF) amputees, the forward propulsion of the prosthetic leg in swing has to be mainly carried out by hip muscles. With hip strength being the strongest predictor to ambulation ability, an active powered knee joint could have a positive influence, lowering hip loading and contributing to ambulation mobility. To assess this, gait of four TF amputees was measured for level walking, first while using a passive microprocessor-controlled prosthetic knee (P-MPK), subsequently while using an active powered microprocessor-controlled prosthetic knee (A-MPK). Furthermore, to assess long-term effects of the use of an A-MPK, a 4-weeks follow-up case study was performed.

Methods: The kinetics and kinematics of the gait of four TF amputees were assessed while walking with subsequently the P-MPK and the A-MPK. For one amputee, a follow-up study was performed: he used the A-MPK for 4 weeks, his gait was measured weekly.

Results: The range of motion of the knee was higher on both the prosthetic and the sound leg in the A-MPK compared to the P-MPK. Maximum hip torque (HT) during early stance increased for the prosthetic leg and decreased for the sound leg with the A-MPK compared to the P-MPK. During late stance, the maximum HT decreased for the prosthetic leg. The difference between prosthetic and sound leg for HT disappeared when using the A-MPK. Also, an increase in stance phase duration was observed. The follow-up study showed an increase in confidence with the A-MPK over time.

Conclusions: Results suggested that, partially due to an induced knee flexion during stance, HT can be diminished when walking with the A-MPK compared to the P-MPK. The single case follow-up study showed positive trends indicating that an adaptation time is beneficial for the A-MPK.

Keywords: Active prosthesis; Artificial limbs; Knee; Patient satisfaction; Prosthesis; Rehabilitation; Transfemoral amputee.

Figures

Fig. 1

Results of the stance phase duration for four patients walking with the P-AMPK and the A-AMPK (s)

Fig. 2

Results of the asymmetry factor of stance phase duration for four patients walking with the P-AMPK and the A-AMPK (m/s). A positive ASF indicates a longer stance phase duration of the SL compared to PL

Fig. 3

Results of the walking speed for four patients walking with the P-AMPK and the A-AMPK (m/s)

Fig. 4

Results of the knee range during loading response for four patients walking with the P-AMPK and the A-AMPK (°)

Fig. 5

Results of the maximum hip torque during early stance for four patients walking with the P-AMPK and the A-AMPK (Nm/kg)

Fig. 6

Results of the maximum hip torque during late stance for four patients walking with the P-AMPK and the A-AMPK (Nm/kg)

Fig. 7

Results of the questionnaire: satisfaction of one patient walking with the A-MPK for four subsequent trials with a time interval of 1 week. The middle of the diagram represents 0 for low satisfaction, the outer border 10, for high satisfaction