Contrast-enhanced Magnetic Resonance Imaging Revealing the Joint Capsule Pathology of a Refractory Frozen Shoulder

Abstract

Background: Frozen shoulder (FS) is clinically diagnosed on the basis of patients’ medical history and physical examination. Its confirmation is based on joint capsule and coracohumeral ligament thickening, subcoracoid fat obliteration, and joint capsule contrast enhancement on magnetic resonance imaging (MRI). We performed bilateral contrast-enhanced MRI (CE-MRI) in FS patients to compare the outcomes with those of their unaffected contralateral counterparts. Methods: Ten patients (3 men, 7 women, median age: 54.5 years) with unilateral FS, requiring arthroscopic capsular release after failed conservative treatment, were included. The median forward elevation, abduction, external rotation, and internal rotation of the 10 patients were 100°, 60°, 7.5°, and the buttock, respectively. The median visual analog scale score was 5.3, and American Shoulder and Elbow Surgeons (ASES) score was 42. Bilateral CE-MRI was simultaneously performed on the day before surgery, and MRI findings were compared between FS and contralateral healthy shoulders (controls). Results: Significant axillary pouch enhancement and rotator interval were observed in all FS, but not in the unaffected comparable sides (p=0.002, respectively). The thickness of the axillary pouch (FS: 4.8 mm, C: 4.4 mm, p=0.58), coracohumeral ligament (FS: 3.9 mm, C: 4.1 mm, p=0.33), and subcoracoid fat obliteration (p=1.00) were not significantly different between FS and controls. Conclusion: CE-MRI aids in the clinical diagnosis of FS. However, axillary pouch joint capsule and coracohumeral ligament thickening or subcoracoid fat obliteration differences were not characteristic findings when contralateral shoulders were compared.