Excellent side-to-side symmetry in glenoid size and shape

In quantifying glenoid bone loss and as a means to determine initial glenoid size, the abnormal glenoid is often compared with the contralateral normal glenoid. The assumption is that good symmetry exists between both glenoid surfaces with regard to size and shape. The purpose of this study is to critically analyze the structural symmetry of both glenoids in an objective and quantitative manner to ascertain the degree of symmetry present.

The study cohort comprised 60 subjects (35 males and 25 females) with no shoulder pathology or injury. Each glenoid surface was extracted from the whole scapular model constructed from CT data using a 3D curvature-based incremental watershed algorithm. Glenoid morphometric analysiswas carried out based on the 2D contour of the glenoid projected on the principal plane.

There was no side-to-side difference in glenoid length (p =0.53), width (p =0.42), area (p =0.36), or circumference (p =0.73). All glenoid dimensions were larger in males than females (p <0.05). Point-wise curvature analysis showed no significant shape difference between both glenoids (all p >0.1). Regression analysis revealed a positive correlation (R²=0.3-0.5) between increasing age and increasing glenoid size.

In normal subjects, both glenoids are highly symmetric in shape and size. This study provides objective and quantitative justification for using the normal counterlateral glenoid as a reference standard for initial glenoid shape in patients with unilateral glenoid bone loss.