Morphometry of the Scapular Notch and Its Clinical Implication in Suprascapular Nerve Entrapment

Background/Objectives: The aim of the present study was to evaluate the relationship between the type of scapular notch (SN), the morphometry of the SN, and the area of the suprascapular nerve (SSN). In addition to determining whether scapular notches other than Type VI, according to the classification of Rengachary, can generate a predisposition to SSN entrapment neuropathy. Methods: One hundred and sixty-nine dry scapulae were examined, the scapular notches were classified, according to the classification of Rengachary, and for each SN, the superior transverse diameter (STD), longitudinal diameter (LD), and area of the SN were determined. The SSN was dissected in five shoulders and its area was calculated. The data were analyzed in the statistical software SPSS. Results: The values for the STD, LD, and area of the SN showed significant differences between the types of scapular notches (p < 0.0001). Along the same lines, a considerable positive correlation (r = 0.79; p < 0.0001) was established between the area of the SN and the STD. Similarly, a very strong positive correlation (r = 0.87; p < 0.0001) was established between the area of the SN and the LD. This indicated that, as the STD and the LD increase, the area of the SN increases. Conclusions: Although different studies have reported an association between SN Type VI and the compression of the SSN by the formation of a bony hole that reduces the area of the notch, we have found that SN Type IV presented a smaller area among the types of notches and a smaller area than the SSN, which exposes the SSN to be closer to or in contact with the superior transverse ligament of the scapula, potentially subjecting the nerve to greater pressure and potentially resulting in SSN entrapment. This is evidence that should be considered in the clinical diagnosis of patients with entrapment neuropathy, since the type of SN and the area of the SSN can be determined by ultrasound, which contributes to a more accurate preoperative evaluation and diagnosis.