Intra-observer and interobserver reliability of the 'Pico' computed tomography method for quantification of glenoid bone defect in anterior shoulder instability

To evaluate the intra-observer and interobserver reliability of the 'Pico' computed tomography (CT) method of quantifying glenoid bone defects in anterior glenohumeral instability. Forty patients with unilateral anterior shoulder instability underwent CT scanning of both shoulders. Images were processed in multiplanar reconstruction (MPR) to provide an en face view of the glenoid. In accordance with the Pico method, a circle was drawn on the inferior part of the healthy glenoid and transferred to the injured glenoid. The surface of the missing part of the circle was measured, and the size of the glenoid bone defect was expressed as a percentage of the entire circle. Each measurement was performed three times by one observer and once by a second observer. Intra-observer and interobserver reliability were analyzed using intraclass correlation coefficients (ICCs), 95% confidence intervals (CIs), and standard errors of measurement (SEMs). Analysis of intra-observer reliability showed ICC values of 0.94 (95% CI = 0.89-0.96; SEM = 1.1%) for single measurement, and 0.98 (95% CI = 0.96-0.99; SEM = 1.0%) for average measurement. Analysis of interobserver reliability showed ICC values of 0.90 (95% CI = 0.82-0.95; SEM = 1.0%) for single measurement, and 0.95 (95% CI = 0.90-0.97; SEM = 1.0%) for average measurement. Measurement of glenoid bone defect in anterior shoulder instability can be assessed with the Pico method, based on en face images of the glenoid processed in MPR, with a very good intra-observer and interobserver reliability.