Functional Outcomes and Patient Satisfaction With a Four-Site Myoelectric Prosthesis System Following the Starfish Procedure: A Case Series

ABSTRACT Introduction Partial hand amputations significantly impair fine motor skills and daily functionality. Myoelectric prostheses are a functional solution but are limited by suboptimal signal transmission in the hand and a small number of sites for control. The starfish procedure enhances the interface between residual limb muscles and prosthetic sensors for improved control of prosthetic digits. Methods This prospective case series evaluated functional outcomes and patient satisfaction in individuals with partial hand amputation who had previously undergone the starfish procedure and were then fitted with a commercially available four-site myoelectric prosthesis. Assessments included the Southampton Hand Assessment Procedure (SHAP), clothespin relocation test (CRT), NASA Task Load Index, and a Digit Control Accuracy Test (DCAT), along with patient satisfaction surveys. Three patients, each with a four-finger amputation, were assessed with their original prosthesis at baseline and with the research prosthesis during follow-up sessions. Results The median follow-up time was 13 months. Following an initial adaptation phase with the research prosthesis, patients showed significant improvements in SHAP Index of Function, with a median increase of 22 points, and CRT times, with a median decrease of 1.8 seconds for down trials and 0.9 seconds for up trials, indicating enhanced hand function and dexterity compared to their original prosthesis. The NASA Task Load Index revealed a median workload decrease of −2, suggesting intuitive control with the research prosthesis, despite individual variations. The DCAT confirmed high success rates in intended movements, demonstrating a learning curve with increased proficiency over time and ability for individualized digit control over. Patient satisfaction was positive, supporting the clinical efficacy of the four-site prosthetic system. Discussion The integration of a four-site myoelectric prosthesis in patients who had undergone the starfish procedure allowed for independent digit control and demonstrated improved outcomes compared to their original prostheses. Independent digit control enables more precise object manipulation and naturalistic hand movements, potentially improving performance of activities requiring fine motor control such as typing, fastening buttons, and handling small objects. While the study faced limitations like small sample size and follow-up variability due to COVID-19 restrictions, the results indicate a clear benefit, advocating for further research into this prosthetic approach. Future studies should aim for a broader participant base, extended follow-up, and comparisons with no prosthesis and passive devices to solidify these findings. Conclusions Results from this preliminary investigation suggest that advanced myoelectric prostheses enabling individual digit control may enhance functionality and user experience in patients who have previously undergone the starfish procedure. The observed improvements in task performance and device interaction, while limited by the small cohort size and variable follow-up period, support expanding availability of these functionally enhancing technologies to appropriate candidates. Clinical Relevance The use of a four-site myoelectric prosthesis in patients who have undergone the starfish procedure shows significant potential for improving outcomes for individuals with partial hand amputation, justifying further research to fully understand its benefits compared to other treatment options.