Evaluation of the coracoid and coracoacromial arch geometry on Thiel-embalmed cadavers using the three-dimensional MicroScribe digitizer

Abstract

Understanding the geometry of the coracoid and coracoacromial arch will improve surgical intervention in shoulder surgery. Thirty pairs of scapulae from 20 female and 10 male deceased donors, average age of 82 years (range, 62-101 years), were scanned and measurements taken using the 3-dimensional (3D) MicroScribe digitizer (Immersion Corp, San Jose CA, USA) and Rhino software (McNeel North America, Seattle, WA, USA). The following mean angles were determined: coracoid slope, 44° ± 11°; coracoid deviation, 35° ± 6°; coracoid root to glenoid, 115° ± 14°; coracoid head to glenoid, 110° ± 11°; scapular spine angle, 35° ± 6°; and coracoacromial angle, 63° ± 9°. The following mean distances were also determined: coracoid height, 10 ± 3 mm; coracoacromial distance, 42 ± 7 mm; coracoacromial arch height, 20 ± 5 mm; and coracoid (anterior, 29 ± 6 mm; middle, 20 ± 4 mm; posterior tip, 18 ± 6 mm) to the glenoid fossa. The coracoid root-to-glenoid angle was significantly correlated with the coracoacromial angle. In addition, coracoid slope was significantly correlated with coracoid root-to-glenoid angle and also with coracoid deviation. Left shoulders had a significantly higher coracoid-to-glenoid angle (P < .029) than right shoulders. Women had a significantly higher coracoid root-to-glenoid angle than men (P < .042), and men had a significantly higher coracoid deviation (P < .011), anterior (P < .006) and posterior coracoid-to-glenoid distances (P < .03), and coracoacromial arch height (P < .07) than women. This is the first time that the 3D MicroScribe digitizer has been used to evaluate the geometry of the coracoacromial arch and coracoid process.