Accuracy of measurement of Hill-Sachs lesions with computed tomography

Background Bone defects play a role in recurrent instability. There is no universal method to quantify humeral head defects. The purpose of this study is to assess the accuracy of 2-dimensional computed tomography (CT) scan measurements of Hill-Sachs lesions. Materials and methods Six Hill-Sachs defects were created in anatomically shaped bone substitutes. The samples were scanned with a 3-dimensional laser scanner. Maximum width and depth were measured and used as the true measurement. The samples underwent routine CT scanning, and 5 physicians measured maximum width and depth on each plane independently. The intraclass correlation coefficient (ICC) was used to assess agreement. Percent error and paired t test were used for statistical analysis ( P < .05 denoted significance). Results The ICC between observers was 0.879 (95% confidence interval, 0.780-0.946) and 0.721 (95% confidence interval, 0.543-0.865) for the depth and width measurement, respectively. The ICC was good between individual observers and the true measurement (range, 0.765-0.956). Individual observers were more accurate in depth rather than width measurements. The mean overall percent error of the depth and width measurements for the 6 defects was calculated: coronal, 19.2% ± 13.6%; sagittal, 11.8% ± 8.2%; and axial, 13.6% ± 8.4%. Conclusions The depth of Hill-Sachs lesions can be reliably assessed using CT scan. Observers consistently underestimated width in all imaging planes. Overall, sagittal- and axial-plane measurements are more accurate for evaluation of these defects than the coronal plane. Future studies using 3-dimensional CT may be helpful to further quantitatively assess the size of the Hill-Sachs lesion, including width and volume.