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

Background: 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.

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

Methodology: 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.

Findings: 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.

Conclusion: 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.