A Proposal for Classification of the Superior Transverse Scapular Ligament: Variable Morphology and Its Potential Influence on Suprascapular Nerve Entrapment

Background: The suprascapular region is the most common site of suprascapular nerve entrapment. The aim of the present study was to determine the morphologic variation of the superior transverse scapular ligament (STSL) and measure the reduction in size of the suprascapular opening. Other structures that might be potentially significant during open and arthroscopic procedures in this region are also described.

Materials And Methods: The study used 86 randomized formalin-fixed human cadaveric shoulders. After dissection of the suprascapular region, the following measurements were defined and collected for every STSL: length, proximal width, distal width, and thickness at the proximal and distal ends. Measurements were also taken of the area of the suprascapular opening (aSSO) and the middle width of the suprascapular opening (mwSSO).

Results: Three types of STSL may be distinguished: a fan-shaped type (54.6%), a band-shaped type (41.9%), and a bifid type (3.5%). Statistically significant differences between the specimens with fan-shaped and band-shaped types of STSL were observed in aSSO and mwSSO of the suprascapular opening. Anterior coracoscapular ligaments (ACSL) were present in 44 of 86 shoulders. The aSSO and mwSSO were smaller in specimens with an ACSL than in those without; however, this difference was only significant in the band-shaped type of STSL.

Conclusion: Knowledge of the morphologic variations of STSL presented in this study is important for better understanding the possible anatomic conditions that can promote suprascapular nerve entrapment and should be taken into particular consideration during surgical and arthroscopic procedures around the suprascapular notch.