Evaluation of glenoid bone defects in anterior shoulder instability: determination of the center of the glenoid inferior portion

Abstract

Objective To explore the feasibility and application of determining the center of the inferior portion of the glenoid on a standard anteroposterior view of the normal glenoid. Methods Seventy shoulders of 35 mature adults were measured in this study. A 64-slice CT 3D reconstruction was performed for each glenoid. A standard anteroposterior view and the scale of glenoid were made at a 3D workstation by one radiologist, and then transferred to software AutoCAD as 2D images. The 2D images were analyzed with AutoCAD respectively by 3 radiologists. The line was drawn between the most anterior and the most inferior points of the glenoid bony rim. On the same image, another line was drawn between the most posterior and the most inferior points of the glenoid bony rim. Two perpendicular bisectors of the 2 lines were drawn. The cross point of the 2 perpendicular bisectors was regarded as the circle center of the inferior part of the glenoid. The distances from the circle center to the anteroinferior and the posteroinferoir rims of the glenoid and the most posterior point were measured. Measurements were expressed as the mean ± standard deviation. Several related samples Friedman rank sum test was used to compare the measurements (the distance from the circle center to the most posterior point) by the 3 radiologists. Paired t tests were used to compare the differences between the left and right glenoids. Results The mean distance from the circle center to the most posterior point was ( 14. 1 ± 1.6) mm, the anteroinferior rim was ( 14. 0 ± 1.7) mm, and the posteroinferoir rim was ( 14. 1 ±1.6) mm. No significant differences were found ( P>0. 05) between measurements by the 3 radiologists. No significant differences were found ( P>0. 05) between the measurements of the both-side glenoids. Conclusions The method of determining the center of the inferior portion of the glenoid based on the most anterior,posterior and inferior points of the glenoid on a standard 3D anteroinferior view of the normal glenoid is easy,practical and highly repeatable. The radius of the left glenoid is comparable to the radius of the right side in normal shoulders. This method can be used to quantify a glenoid bone defect precisely. Key words: Shoulder joint; Joint instability; Imaging, three-dimensional; Glenoid; Bone defects