Test-Retest Reliability of Sole Morphology Measurements Using a Novel Single-Image-Based Pin-Array Impression Reconstruction Method

Background: Assessment of the sole morphology provides a clinically useful measure of the foot condition, but existing methods are mostly limited to two-dimensional or non-weight-bearing conditions. The current study aimed to assess the reliability of a novel method called Single-Image-Based Pin-Array Impression Reconstruction Method (SIBPAIR) implemented on a commercial foot assessment system, and the intra-rater, inter-rater and inter-session reliability of the SIBPAIR-based protocol for three-dimensional sole morphological measurements. Methods: The reliability of the SIBPAIR method, and the intra-rater, inter-rater, and inter-session reliability of the SIBPAIR-based protocol in measuring morphological parameters of the sole were assessed by repeated measurements of fifteen young healthy adults by two male physical therapists, in terms of intra-class correlation coefficients (ICC) and standard error of measurement (SEM). Results and Conclusions: The SIBPAIR method was found to have very high reliability with very small SEM values, and the SIBPAIR-based protocol also showed very high intra-rater, inter-rater, and inter-session reliability with small SEM. These results indicate that accurate and reliable measurements could be obtained by following the protocol regardless of the rater’s experience or time of measurement. This will be useful for foot assessment and subsequent applications, such as design and manufacture of customized orthoses or shoes.