ANATOMIC BASIS FOR SUBFASCIAL COMPRESSION OF THE SUPRASCAPULAR NERVE IN THE SUPRASPINOUS FOSSA

Abstract

Purpose of the study: Compression of the suprascapular nerve in the superior or inferior scapular incisures is a well-known syndrome compression syndrome triggered in the narrow osteofibrous tunnel. This study was undertaken after observing several cases of nerve compression in the supraspinatus fossa after neruolysis procedures. We wanted to better understand the relations with the supraspinatus fascia.

Material and methods: Thirty human cadaver shoulders were dissected. After exposing the supra and infraspina-tus fossae and section of the scapular spine, the supra and infraspintus tendons were sectioned and folded back medially to expose the suprascapular pedicle in the superior scapular incisure, the supraspinatus fossa, and the inferior scapular incisure. The presence of a fascia sheathing the nerve, of subfascial tissue, and of a transversal inferior (spinoglenoid) ligament was noted together with the histology of the observed structures.

Results: A supraspinatus fascia sheathing the nerve was observed in 29 dissections. This fascia was inserted on the superior border of the scapula and the superior scapular ligament and the floor of the supraspinatus fossa. Diffuse adipose deposits under the fascia was observed in 55.5% of the dissections, or located around the vasculonervous bundle in 44.5%. There was a fibrous buttonhole facing the lateral border of the spine in 28 shoulders with a thickened zone which constituted histologically the equivalent of an inferior transvers ligament in 26 shoulders. One subfascial lipoma was discovered.

Discussion: Sheathing with a supraspinatus fascia could explain suprascapular nerve compression in the supra-spinatus fossa where the nerve is exposed to compression against the bony base on which it runs between the superior and inferior incisures. These anatomic data suggest that suprascapular neurolysis should release the nerve over its entire length and not just at the superior or inferior scapular incisure.

Conclusion: The succession of the superior transverse ligament, the supraspinatus fascia, and the inferior transverse ligament constitutes an osteofibrous tunnel which should be considered as a potential source of a suprascapular tunnel syndrome at three levels.