Coracoid process anatomy: implications in radiographic imaging and surgery

The coracoid process forms an important part of scapular-glenoid construct and is involved in many surgical procedures on the glenohumeral joint. The unique three-dimensional orientation of each coracoid pillar makes radiographic imaging difficult. Congenital variations and minimal traumatic/iatrogenic changes in this orientation can predispose to subcoracoid impingement. We performed a quantitative and statistical analysis of the osseous anatomy of the coracoid process in 101 scapulae; the purpose was to determine the anatomical variations and gender-specific differences in the length, breadth, thickness, vertical and horizontal projections, and triplane angulations of each individual coracoid pillar. All parameters were measured in reference to the glenoid plane to ensure surgical and radiological applicability. The mean dimensions of the inferior coracoid pillar were 31.1 x 16.6 x 9.9 mm and that of the superior coracoid pillar were 41.7 x 14.2 x 8.4 mm (medial)/6.6 mm (lateral). The mean maximal harvestable coracoid length measured 19.0 mm. The mean angular orientation of the inferior coracoid pillar, with reference to the glenoid, measured 51.2 degrees (axial), 126.1 degrees (sagittal), and 134.6 degrees (coronal), and that of the superior coracoid pillar measured 146.1 degrees (axial) with an interpillar angulation of 84.9 degrees (axial). A statistically significant gender difference (P < 0.05) was found in the lengths, breadths, and projections of each coracoid pillar. We used data from this study to devise two new radiographic views (for imaging individual coracoid pillars), to calculate dimensions and orientation of internal fixation/prosthetic hardware during surgery, and conceptualize a geometric model to explain the role of measured parameters in coracoid impingement syndrome.