Posterior Shoulder Pain: A Dynamic Study of the Spinoglenoid Ligament and Treatment With Arthroscopic Release of the Scapular Tunnel

Purpose: The purpose of this study was to determine the pressure exerted on the suprascapular nerve by compression of the spinoglenoid ligament during glenohumeral range of motion. In addition, a 2-portal technique was described to arthroscopically visualize and safely release the spinoglenoid ligament while visualizing the suprascapular nerve, artery, and vein. Methods: Ten cadaveric shoulders were used for visual observation of variation in the position and tension of the spinoglenoid ligament. In 15 additional shoulders, a transducer was used to sense the pressure changes and was recorded in voltage. Pressure changes created by the spinoglenoid ligament on the distal suprascapular nerve in the scapular tunnel during glenohumeral motion were recorded. Results: Internal rotation, rather than external rotation, in any position of the shoulder created a visual increase of tension in the spinoglenoid ligament. Increased pressure readings were noted with internal rotation and with 90° of abduction, full abduction, and full adduction of the shoulder. The suprascapular nerve occupying the space created by the spinoglenoid ligament experiences an increased pressure during glenohumeral range of motion and positions that mimic overhead throwing. The dynamic nature of the ligament with its insertion on the posterior capsule required a new minimally invasive technique for its release that can be safe and straightforward. Conclusions: The spinoglenoid ligament was affected by the position of the glenohumeral joint. These changes in pressure in combination with repetitive shoulder movement are likely components that cause repeated trauma or compression on the distal suprascapular nerve created by a scapular tunnel syndrome. The surgical technique provides a treatment option when conservative treatment fails in the patient with posterior shoulder pain. Clinical Relevance: The spinoglenoid ligament was affected by the position of the shoulder, with the most pressure noted with the arm in full adduction and internal rotation. This pressure can be treated with arthroscopic release.