The agreement and repeatability of computer-based wear measurement of total hip arthroplasties

We assessed the agreement and repeatability of a software package for wear measurement in 19 total hip arthroplasties followed up for 4 to 8 years. Three observers with different levels of expertise (a hip surgeon [O1], a fellow [O2], and a medical student who is a research assistant of the laboratory in which the software was developed [O3]) determined the 2-dimensional wear and wear direction with the Hip Suite software (University of Chicago, Chicago, Ill). For intraobserver and interobserver comparisons, we used intraclass correlation coefficient (ICC) and repeatability. The intraobserver ICC for wear and wear direction was 0.83 and 0.78 for O1, 0.54 and 0.48 for O2, and 0.81 and 0.89 for 03. The interobserver ICCs were 0.43 (range, 0.07-0.87) for wear and 0.8 (range, 0.71-0.86) for wear direction. Computerized wear measurements have substantial intraobserver and interobserver variability, especially when performed by surgeons without extensive experience in the use of the software, a finding which questions its precision and validity.