Evaluation of glenohumeral adduction restriction in frozen shoulder as a predictor of intra-articular lesion severity: a comparison study of the freezing and frozen phases.

Background: Glenohumeral adduction restriction (AR), which is found in rotator cuff tears, is also observed in frozen shoulder (FS). AR was examined using an adduction test and treated through adduction manipulation. We aimed to compare the incidence and severity of AR and investigate clinical characteristics and outcomes of the freezing and frozen phases. Methods: Two hundred sixteen patients with FS were enrolled in this study; consequently, 120 were classified into the freezing phase (mean age 58 years, 37 men) and 56 into the frozen phase (mean age 55.4 years, 29 men). Using the adduction test, the patients in 2 phases were divided into 2 groups, with and without AR. The glenohumeral adduction angle (GAA) was measured radiographically. Treatments in the freezing phase were physiotherapy and/or adduction manipulation and joint manipulation and physiotherapy for the frozen phase. We recorded the visual analog scale of pain severity, EuroQol-visual analog scale, flexion, abduction, external rotation (ER), internal rotation, and American Shoulder and Elbow Surgeons and Constant scores at the baseline and at the 1-, 3-, 6-, 12-, and 24-month follow-ups. Results: Seventy-five of 120 patients in the freezing phase were divided into group 1 without AR and 45 into group 2 with AR. Eight of 56 patients in the frozen phase were classified into group 3 without AR and 48 into group 4 with AR. AR was identified in 37.5% of patients in the freezing phase and 85.7% in the frozen phase. The mean GAA decreased from the freezing (-3.0°) to the frozen phases (-18.3°). GAA was positively correlated with ER. The treatment duration in group 1 (5.2 M) was shorter than in group 2 (7.4 M), and the percentage of transition to joint manipulation in group 1 (5.3%) was lower than in group 2 (17.8%). Complete rupture of intra-articular soft tissues was observed in group 4 but not in group 3 with magnetic resonance imaging. Clinical items, except for ER in the freezing phase (group 1 vs. 2) and frozen phase (group 3 vs. 4), were not significantly different from those at the initial visit to the 24-month follow-up appointment. Conclusion: The incidence and severity of AR increase from the freezing phase to the frozen phase. AR correlating with ER reflects the progression of intra-articular lesions, which prolongs the treatment duration and increases the joint manipulation rate in the freezing phase. Negative AR in the frozen phase suggests mild intra-articular pathologies.