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

Background: Understanding the geometry of the coracoid and coracoacromial arch will improve surgical intervention in shoulder surgery. Methods: 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). Results: 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. Conclusions: This is the first time that the 3D MicroScribe digitizer has been used to evaluate the geometry of the coracoacromial arch and coracoid process.