Suprascapular Nerve Entrapment Caused by Protrusion of an Intraosseous Ganglion of the Glenoid into the Spinoglenoid Notch: A Rare Cause of Posterior Shoulder Pain

Abstract

We describe a case of suprascapular nerve entrapment caused by protrusion of an intraosseous ganglion of the glenoid into the spinoglenoid notch. A 47-year-old man with left shoulder pain developed an intraosseous cyst in the left glenoid, which came into contact with the suprascapular nerve. The area at which the patient experienced spontaneous shoulder pain was innervated by the suprascapular nerve, and 1% xylocaine injection into the spinoglenoid notch under ultrasonographic guidance relieved the pain. Therefore, we concluded that the protrusion of an intraosseous cyst of the glenoid into the spinoglenoid notch was a cause of the pain, and performed curettage. Consequently, the shoulder pain was resolved promptly without suprascapular nerve complications, and the cyst was histologically diagnosed as an intraosseous ganglion. This case demonstrated that the intraosseous ganglion of the glenoid was a benign lesion but could be a cause of suprascapular nerve entrapment syndrome. Curettage is a useful treatment option for a ganglion inside bone and very close to the suprascapular nerve.

Figure 1

(a) Clinical photograph before the surgery shows a dotted circle at the left shoulder that indicates the area at which the patient complained of pain. The area includes the supra- and infraspinatus muscles and the suprascapular nerve. (b) Radiograph of the left shoulder shows a radiolucent cystic lesion in the superior glenoid.

Figure 2

(a) Magnetic resonance (MR) T2-weighted axial image of the left shoulder shows a high intensity area at the glenoid. (b) MR T2-weighted sagittal image of the left shoulder shows that the intraosseous lesion is linked to the spinoglenoid notch. (c, d) Computed tomography (CT) axial and 3-dimensional CT images of the left shoulder show a bone cystic lesion of the glenoid with cortical bone destruction linked to the spinoglenoid notch.

Figure 3

(a) Surgery for the intraosseous ganglion is performed in the right lateral position. A 10 cm skin incision is made at the posterior glenohumeral joint. (b) Intraoperative photograph of the posterior shoulder shows the suprascapular nerve after splitting the infraspinatus (yellow arrow). (c) Intraoperative photograph shows a mucinous cyst wall after shifting the suprascapular nerve laterally. (d) Intraoperative photograph shows the bone cavity of the glenoid after curettage of the cyst (yellow arrowheads).

Figure 4

(a, b) Microscopic section of the cyst wall shows that the wall contained connective tissue, including collagen fibers and a few fibroblasts, and that the inner layer of connective tissue had myxoid change. The yellow arrow indicates the myxoid area, and the yellow arrowheads show connective tissue, including collagen fibers and a few fibroblasts (hematoxylin and eosin staining; A: ×12.5 magnification, B: ×50 magnification).