Comparison of 3-Dimensional Computed Tomography-Based Measurement of Glenoid Bone Loss With Arthroscopic Defect Size Estimation in Patients With Anterior Shoulder Instability.

<bold>Purpose: </bold>The purpose of this study was to compare four 3-dimensional (3D) computed tomography (CT) methods of measuring glenoid bone loss with the arthroscopic estimation of glenoid bone loss.<bold>Methods: </bold>Twenty patients with recurrent anterior shoulder instability underwent bilateral shoulder CT scans and were found to have glenoid bone loss. Arthroscopic estimation of glenoid bone loss was performed in all patients. Three-dimensional CT reconstruction was performed on the CT scans of each patient. The glenoid bone loss of each patient was measured using the surface area, Pico, ratio, and anteroposterior distance-from-bare area methods. The mean percent loss calculated with each method was compared with arthroscopy to determine the reliability of arthroscopy in the measurement of glenoid bone loss.<bold>Results: </bold>The mean percent bone loss calculated with arthroscopic estimation, surface area, Pico, ratio, and anteroposterior distance-from-bare area methods was 18.13% ± 11.81%, 12.15% ± 8.50% (P = .005), 12.77% ± 8.17% (P = .002), 9.50% ± 8.74% (P < .001), and 12.44% ± 10.68% (P = .001), respectively. Repeated-measures analysis of variance showed that the 3D CT methods and arthroscopy were significantly different (F4,76 = 13.168, P = .02). The estimate using arthroscopy is 55% greater than the average of the 3D CT methods.<bold>Conclusions: </bold>Our findings suggest that arthroscopy significantly overestimates glenoid bone loss compared with CT and call into question its validity as a method of measurement. A more internally consistent and accurate method for the measurement of glenoid bone loss is necessary to appropriately diagnose and treat shoulder instability.<bold>Level Of Evidence: </bold>Level IV, case series. [ABSTRACT FROM AUTHOR]