Anatomical relations between anterior coracoscapular ligament and suprascapular neurovascular structures and a proposal for classification.

Abstract

Although suprascapular nerve entrapment is rare, the most common site of compression is the suprascapular notch. The anterior coracoscapular ligament (ACSL), which lies inferior to the superior transverse scapular ligament (STSL), may also be a cause of entrapment. We aimed to investigate the presence of ACSL and its relations to the suprascapular nerve and vessels. We dissected 50 shoulders of 26 cadavers. We excluded 2 shoulders due to previous shoulder surgery. We observed the course of the suprascapular nerve, artery, and vein(s), and examined whether they passed between STSL and ACSL or under ACSL. We classified the anatomical relations between neurovascular structures, STSL, and ACSL. In Type I, the suprascapular nerve passed between STSL and ACSL; in Type Iıa, the suprascapular nerve and a single suprascapular vein passed between STSL and ACSL; in Type Iıb, a suprascapular vein passed under ACSL and the suprascapular nerve passed between STSL and ACSL; in Type III, the suprascapular artery, vein, and nerve passed between STSL and ACSL. ACSL was present in 16 shoulders (32%). The suprascapular nerve passed between STSL and ACSL in all cases. We observed Type I, Type Iıa, Type Iıb, and Type III anatomical relations in 14%, 12%, 2%, and 4% of cases, respectively. Vascular structures that pass under STSL may cause suprascapular nerve entrapment. Presence of ACSL with vessel(s) passing under it and/or between it and STSL may increase the risk of nerve entrapment.