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. Layman's Abstract Prosthetic knees with computer-controlled systems help users walk more safely and confidently; however, they are expensive and not commonly used in low- and middle-income countries such as South Africa. Medical aids and other private funders sometimes cover the cost based on justifications that explain why the prosthesis is prescribed and how it can improve the user's function. Currently prosthetists have little evidence to support these justifications. This study assesses South African users’ function and experiences with one such knee, the Rheo XC knee. Sixteen participants tried the Rheo XC knee for two weeks. Before they started the trial period, they completed questions on their function and a timed walk test while using their own non-microprocessor knees (e.g. mechanical or hydraulic joints). After the two-week trial of the Rheo XC knee, they repeated the same tests to determine if their function or walking speed improved. Nine (56.3%) participants had an above knee amputation, six (37.5%) had a through knee amputation and one (6.3%) had bilateral amputations (below and above the knee). Baseline and follow-up data were paired for each participant and analyzed with a statistical test. Interviews were conducted with six selected participants to learn about their experiences using the Rheo XC knee. Participants walked on average 7.5 s faster with the Rheo XC knee than with their usual knee. They also had higher function scores for all activities except running, which remained the same. Although participants liked the Rheo XC knee, its length and weight posed challenges for certain individuals. The findings of this study may help justify funding for the Rheo XC knee in South Africa. However, it is recommended that the Rheo XC knee be prescribed only after a trial period has been completed to ensure it is an appropriate choice for the specific user. The test period used in the study was short, and further research over longer duration is recommended. Article PDF Link: https://jps.library.utoronto.ca/index.php/cpoj/article/view/45286/33986 How To Cite: Visagie S, Theron B. South African users’ function and experience with a magnetorheological microprocessor knee: A mixed methods study. Canadian Prosthetics & Orthotics Journal. 2025; Volume 8, Issue 1, No. 5. Https://doi.org/10.33137/cpoj.v8i1.45286 Corresponding Author: Surona Visagie, PhDAffiliation: University of Stellenbosch, Division of Disability and Rehabilitation Studies, Faculty of Medicine and Health Sciences, South Africa.E-Mail: suronav@sun.ac.zaORCID ID: https://orcid.org/0000-0003-4575-479X

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