Reliability of humeral head measurements performed using two- and three-dimensional computed tomography in patients with shoulder instability

PURPOSE: The aim of the study was to compare two measurement methods of humeral head defects in patients with shoulder instability. Intra- and inter-observer reliability of humeral head parameters were performed with the use of 2D and 3D computed tomography. METHODS: The study group was composed of one hundred humeral heads measured with the use of preoperative 2D and 3D computed tomography by three independent observers (two experienced and one inexperienced). All observers repeated measurements after 1 week. The intra-class correlation coefficient (ICC) and the minimal detectable change with 95% confidence (MDC(95)%) were used for statistical analysis of diagnostic agreement. RESULTS: For 3D inter-observer reliability, ICC values were “excellent” for all parameters and MDC(95)% values were “excellent” or “reasonable.” All intra-observer ICC and MDC(95)% values for 3D were “excellent” for experienced and inexperienced observers. For 2D-CT, ICC values were usually “good” or “moderate” with MDC(95)% values higher than 10 or 30%. CONCLUSIONS: Three-dimensional CT measurements are more reliable than 2D for humeral head and Hill-Sachs lesion assessment. This study showed that 2D measurements, even performed by experienced observers (orthopaedic surgeons), are burdened with errors. The 3D reconstruction decreased the risk of error by eliminating inaccuracy in setting the plane of the measurements.