Magnetic resonance imaging evaluation of normal glenoid length and width: an anatomic study.

PURPOSE The purpose of this study was to evaluate the measured dimensions of the normal glenoid on sagittal magnetic resonance (MR) imaging to determine whether a fixed ratio of glenoid length and width can be determined. METHODS MR images of 90 glenoids in 84 patients were analyzed. The mean age was 54.8 years, with 44 male and 40 female patients. Glenoid length and width at the widest dimension were measured and recorded by 3 independent examiners. The ratio of length to width and the ratio of the length of the superior pole at the widest point to the total length were calculated. Intraclass correlation coefficients, Spearman and Pearson correlations, regression analysis with cross validation, and coefficients of variation were calculated. RESULTS The mean glenoid length was 37.5 ± 3.8 mm, whereas the mean width was 24.4 ± 2.9 mm. The mean ratio of length to width was 1.55 ± 0.1, whereas the mean ratio of the distance from the superior pole to the widest point to the total glenoid length was 0.64 ± 0.03. The calculated ratios were less variable than the absolute length and width. Cross validation of length for width showed a 95% prediction band width of 4.48 mm, with an average absolute error of prediction of 1.46 mm, and was equally specific when separated by gender. The width was equal to 0.65 times the length. CONCLUSIONS Measurement of glenoid length and width using MR imaging results in a consistent ratio of length to width independent of patient age and gender, where the width was equal to 0.65 times the length at a point two-thirds along the inferosuperior axis. LEVEL OF EVIDENCE Level IV, case series.