A reliable and inclusive method for assessing failure-causing mechanical wear in prosthetic feet

Wear assessment of prosthetic feet is critical for monitoring device performance and replacement, especially in rural or resource constrained areas where clinical follow-ups can be infrequent. Standardised, reliable methods for wear evaluation are limited. This study investigates the inter-observer reliability of a method for quantifying patterns and relative magnitudes of plantar surface wear of prosthetic feet and presents preliminary results for intra-observer error. Sixty-two plantar images of used SACH feet from Sri Lanka were scored by four independent groups a published method for quantifying prosthetic foot wear. A 20x10 grid was applied to each image, and wear was scored from 0-9 per cell based on visual indicators. Interobserver agreement was assessed on full (48 feet, 4 raters) and reduced (62 feet, 3 raters) datasets. Intraobserver reliability was tested by 2 raters re-scoring five images after 5 + days. Kendall's W evaluated agreement, and a modified scoring method was developed and evaluated. Interobserver agreement ranged from fair to excellent and was higher in the reduced dataset. Intraobserver agreement appears high, especially in central, less-worn areas of the foot. The modified method showed reduced intraobserver variability but lower interobserver agreement, largely due to increased ties affecting Kendall's W, not increased disagreement. The original and modified methods for wear qualification demonstrate high reliability, supporting their use as a low-cost, field-appropriate tool for monitoring prosthetic foot wear to enhance the evaluation and design of prosthetic feet, particularly in resource-limited settings. While the full method provides higher resolution data, the reduced method is more broadly applicable to different foot types. Clinically, this method offers a reliable, scalable approach to assessing prosthetic foot wear, potentially supporting community-based monitoring. Further testing and methodological alterations to encompass additional foot designs are required for clinical use.