South African users' function and experience with a magnetorheological microprocessor knee: A mixed methods study

Microprocessor knees (MPKs) support safe and confident prosthetic walking. Their cost often prohibits prescription in low- and middle-income settings like South Africa. Funding of high-end prosthetic products in South Africa is dependent on justifications that explain why the component is prescribed, and how it can improve the user`s function. There is little local evidence to support these justifications.

To explore and describe South African users' function and experience with the Rheo XC microprocessor knee (MPK).

An explanatory sequential mixed methods design was used. A pre-test, post-test study was followed by a descriptive qualitative study to explore and explain the observed outcomes. In the pre-test phase, baseline data were collected while participants used their regular non-microprocessor knees (e.g., mechanical or hydraulic joints). Post-test data were collected after a two-week trial with the Rheo XC knee joint. Data were collected from 16 consecutively sampled participants, using a self-developed functional level scale and the L-Test. Nine (56.3%) participants had a transfemoral amputation, six (37.5%) had a knee disarticulation and one (6.3%) had bilateral amputations (transtibial and transfemoral). Baseline and follow-up data were paired for each participant and analyzed with the Wilcoxon Signed-Rank test. The descriptive qualitative study explored six purposively sampled participants' experiences of the trial knee through semi-structured interviews. Inductive thematic analysis was done.

The time to complete the L-Test decreased on average 7.5 s between baseline (35.4 s) and post-test (27.9 s) data. L-Test Wilcoxon Singed-rank findings showed a significant increase in walking speed (p < 0.001). Mean functional level scores increased by an average of 12.7 points (p < 0.001) with improvements observed across all activities except running, for which scores remained unchanged. Two themes emerged from the qualitative data. Theme 1: Acceptance of the MPK showed enthusiasm for the MPK. However, Theme 2: Real-world limitations of the MPK cautioned that the MPK is not suitable for everybody.

This study provides context specific scientific evidence that may support funding decisions for MPKs in South Africa. However, it is not suitable for everyone, and a trial period to assess appropriateness is advised before prescription. The test period in this study was short, and further research over longer durations is recommended.