Ossification of the suprascapular ligament: A risk factor for suprascapular nerve compression?

Introduction: Entrapment of the suprascapular nerve at the suprascapular notch may be due to an ossified suprascapular ligament. The present study was conducted in order to investigate the incidence of this anomaly and to analyze the resultant bony foramen (foramen scapula) for gross nerve compression. Materials and Methods: We evaluated 104 human scapulae from 52 adult skeletons for the presence of complete ossification of the suprascapular ligament. When an ossified suprascapular ligament was identified, the diameter of the resultant foramen was measured. Also, the suprascapular regions of 50 adult cadavers (100 sides) were dissected. When an ossified suprascapular ligament was identified, the spinati musculature was evaluated for gross atrophy and the diameters of the resultant foramen scapulae and the suprascapular nerve were measured. Immunohistochemical analysis of the nerve was also performed. Results: For dry scapular specimens, 5.7% were found to have an ossified suprascapular ligament. The mean diameter of these resultant foramina was 2.6 mm. For cadavers, an ossified suprascapular ligament was identified in 5% of sides. Sections of the suprascapular nerve at the foramen scapulae ranged from 2 to 2.8 mm in diameter. In all cadaveric samples, the suprascapular nerve was grossly compressed (~10-20%) at this site. All nerves demonstrated histologic signs of neural degeneration distal to the site of compression. The presence of these foramina in male cadavers and on right sides was statistically significant. Conclusions: Based on our study, even in the absence of symptoms, gross compression of the suprascapular nerve exists in cases of an ossified suprascapular ligament. Asymptomatic patients with an ossified suprascapular ligament may warrant additional testing such as electromyography.