[Sexual dimorphism of the scapula]

The relationship between acromion thickness and body habitus: practical implications in subacromial decompression procedures

To define the bone's amount that should be removed during an acromioplasty has always been a challenge. We aimed to verify the correlations between scapular dimensions and acromial thickness, assess the differences between the two genders, investigate the relationship between acromial type and thickness. We examined 500 dried scapulae, measuring the major axis of the scapular body and the acromial thickness; these were also catalogued according to gender. Acromial shape was classified according to Bigliani's method. Frequencies: Type I 38.9 %, Type II 39.4 %, Type III 21.7 %. The mean acromial thickness was 0.85 cm, and it resulted wider in men. There was a direct linear relationship between scapular dimensions and acromial thickness. The range of thickness of Type III acromion was significantly different from the others. We should be aware that gender, scapular dimensions and acromial shape should be evaluated preoperatively since they influence the acromial thickness.

Osseous anatomy of the scapula

Detailed anatomy and morphometry of the scapula were obtained to provide information for surgical procedures such as hardware fixation, drill hole placement, arthroscopic portal placement, and prosthetic positioning. Twenty-six measurements were made in 15 pairs of scapulas from cadavers. The average length of the scapulas from the superior to the inferior angle was 155 +/- 16 mm (mean +/- standard deviation). The thickness of the medial border 1 cm from the edge was 4 +/- 1 mm. The superior border was sharp and thin, and the suprascapular notch was present as a foramen in two scapulas. The distance from the base of the suprascapular notch to the superior rim of the glenoid was 32 +/- 3 mm. The length of the spine from the medial edge of the scapula to the lateral edge of the acromion was 134 +/- 12 mm. The anteroposterior width of the spine at 1 and 4 cm from the medial edge was 7 +/- 1 and 18 +/- 3 mm, respectively; the width at the lateral edge (spinoglenoid notch) was 46 +/- 6 mm. The acromion measured 48 +/- 5 mm x 22 +/- 4 mm and was 9 +/- 1 mm thick. The acromial shape was flat in 23%, curved in 63%, and hooked in 14% of scapulas. The distance from the glenoid to the acromion was 16 +/- 2 mm. The glenoid dimensions were 29 +/- 3 mm (anteroposterior) x 36 +/- 4 mm (superoinferior) and faced posterior by 8 +/- 4 degrees. Anteroposterior thickness of the head of the scapula 1 cm from the surface was 22 +/- 4 mm. The thickness of the coracoid was 11 +/- 1 mm. The average length of the coracoacromial ligament was 27 +/- 5 mm. Scapulas from male cadavers were significantly larger than scapulas from female cadavers in 19 measurements.