Evaluation of three-dimensional glenoid structure using MRI

The tilting angle and the shape of the glenoid cavity are considered to rel ate closely to shoulder stability. They are also important when planning ar throplasty and developing new designs. This study examines the glenoid cavi ty using 3-dimensional MRI. Forty volunteers (20 men, 20 women; average age 21.4; range 18-35 y) were enrolled in the study. The tilting angles of the glenoid bone were measured in 5 consecutive axial planes perpendicular to the glenoidal long axis. Cross sections were divided into 3 types (concave, flat, convex) according to the shape on each plane. The average tilting angles for the 5 planes from the bottom to the top were 3.3 +/- 4.1, 1.4 +/- 3.8, - 0.6 +/- 1.9, - 1.4 +/- 3.3, and - 6.2 +/- 3.3 degrees anteriorly, indicating that the 3-dimensional bony structure of the glenoid was twisted anteriorly to posteriorly. Images on the bottom plane consisted of 82.5% concave type, 15% flat type and 2.5% convex type, while only 3 cases (7.5%) showed concave at the top plane. The shape of the gleno id cavity is thought to be conducive to glenohumeral motion and stability.