Analysis of Agreement Between Computed Tomography Measurements of Glenoid Bone Defects in Anterior Shoulder Instability With and Without Comparison With the Contralateral Shoulder

Background: Computed tomography (CT) is frequently used to diagnose glenoid bone defects in anterior shoulder instability. The\r\nassessment of glenoid defects on 2-dimensional (2D) and 3-dimensional (3D) CT scans has been reported with and without a comparative\r\nstudy of the contralateral shoulder; however, no previous studies have analyzed if these 4 methods agree.\r\nPurpose: To estimate agreement between CT assessments of glenoid defects by examination of the affected shoulder alone and\r\nby comparison with the contralateral side on both 2D and 3D CT scans.\r\nStudy Design: Cohort study (diagnosis); Level of evidence, 2.\r\nMethods: A total of 200 prospectively enlisted patients affected by unilateral anterior shoulder instability underwent CT of both\r\nshoulders. The area of the missing glenoid was calculated on 4 sets of CT scans (2D and 3D CT images with and without comparison\r\nwith the contralateral shoulder) by using the circle method. Agreement between the 4 measurements in quantifying the\r\nbone defect was estimated according to the Bland-Altman method. Agreement between the 4 measurements in assessing the\r\npresence and type of defect (fracture or erosion) was analyzed with k statistics.\r\nResults: Analysis of agreement between CT measurements in quantifying glenoid bone defects showed that the mean difference\r\nbetween the 4 measures was less than 1% of the area of the inferior glenoid in each pairwise comparison. Limits of agreement\r\nwere always below the established acceptable limit of 5%. The assessment of the presence and type of bone defect showed\r\nstrong to near-complete agreement between the 4 measurement methods.\r\nConclusion: CT assessments of glenoid bone defects with and without comparison with the contralateral shoulder showed very\r\ngood agreement in identifying the size, presence, and type of defect in patients with anterior shoulder instability on both 2D and\r\n3D CT scans.