Variable osseous anatomy of costal surface of scapula and its implications in relation to snapping scapula syndrome

Variation in normal anatomy of costal surface of scapula may disrupt smooth scapulothoracic movements and may cause snapping scapula. The aim of this study was to assess variable anatomy of costal surface of scapula and its role in etiopathogenesis of snapping scapula syndrome. Superomedial angle, depth of costal surface, forward angulation of root of coracoid process and thickness of superior and inferior angles of 92 dry intact adult scapulae of unknown sex were studied. Superomedial angle ranged from 124A degrees to 162A degrees (144.34A degrees A A +/- A 9.09A degrees). The forward angulation of root of coracoid process ranged from 120A degrees to 160A degrees (141.60A degrees A A +/- A 6.53A degrees). Depth of costal surface at the level of root of spine varied widely between 10.5 and 26.7 mm (16.73 +/- A 3.367 mm). Thickness of superior and inferior angles measured 3.34 +/- A 0.87 and 6.71 +/- A 1.18 mm, respectively. Forwardly bent rhinoceros-horn-like projection at the lateral border of scapula was seen in 2.17% of specimens. Variation in anatomy of costal surface of scapula observed in this study may be clinically significant with respect to snapping scapula syndrome.