Surona Visagie, Benje Theron

SOUTH AFRICAN USERS’ FUNCTION AND EXPERIENCE WITH A MAGNETORHEOLOGICAL MICROPROCESSOR KNEE: A MIXED METHODS STUDY

Introduction

South african users’ function and experience with a magnetorheological microprocessor knee: a mixed methods study. Explore South African amputees' function and experience with the Rheo XC microprocessor knee. This mixed-methods study justifies funding, showing improved walking and function, but notes limitations.

Abstract

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

Review

This study by Visagie and Theron provides valuable context-specific insights into the function and experience of South African users with the Rheo XC microprocessor knee (MPK). Addressing a critical gap in evidence, the research responds to the challenge of justifying the prescription and funding of high-cost prosthetic technologies in low- and middle-income settings like South Africa. The authors highlight the current lack of local data to support decisions that could significantly improve the quality of life for amputees. By exploring both objective functional improvements and subjective user experiences, the study aims to furnish the necessary scientific evidence for informed funding decisions and clinical practice, underscoring its relevance for healthcare policy and patient access in the region. Employing an explanatory sequential mixed-methods design, the study first conducted a pre-test, post-test quantitative analysis on 16 participants, comparing their baseline function with a non-microprocessor knee to their function after a two-week trial with the Rheo XC. Key quantitative findings demonstrated significant improvements: participants’ L-Test completion time decreased by an average of 7.5 seconds (p < 0.001), indicating increased walking speed, and mean functional level scores rose by an average of 12.7 points (p < 0.001) across most activities. This quantitative data was complemented by a descriptive qualitative study involving semi-structured interviews with six purposively sampled participants. The qualitative analysis yielded two critical themes: "Acceptance of the MPK," reflecting general enthusiasm, and "Real-world limitations of the MPK," which cautioned that the device might not be universally suitable. This mixed-methods approach effectively captures both the measurable benefits and the nuanced, lived experiences of users. While the study successfully provides foundational evidence for the Rheo XC MPK in South Africa, it also openly acknowledges several limitations and offers important recommendations. The most significant limitation noted is the short two-week trial period, which may not fully capture long-term adaptations, issues, or sustained benefits. Consequently, the authors rightly recommend further research over longer durations to comprehensively assess the MPK's long-term utility and impact. Furthermore, the qualitative findings highlight that the MPK is "not suitable for everybody," leading to the pragmatic recommendation that a trial period is essential to assess individual appropriateness before prescription. Overall, this research contributes important, context-specific data that can inform funding decisions and clinical guidelines for MPKs in South Africa, albeit with a crucial emphasis on individualized assessment and the need for more extensive longitudinal studies.

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