Quantitative evaluation of adhesion severity around subscapularis and its relationship with shoulder range of motion in frozen shoulder and rotator cuff disorder: an observational study using dynamic ultrasonography

Abstract

BackgroundThis study aimed to evaluate the severity of adhesion between muscles in the shoulder joint using dynamic ultrasonography and to confirm whether adhesions cause range of motion (ROM) restrictions. MethodsTwenty-four shoulders from fifteen frozen shoulder (FS) patients and Twenty-four shoulders from eighteen rotator cuff disorder (RCD) patients were enrolled. We obtained ultrasound video sequences of the subscapularis and deltoid muscles during shoulder external rotation. The mean stretching velocities of the deltoid (VDelt) and subscapularis (VSSC) were subsequently analyzed using a PC. If adhesions occurred between both muscles, the deltoid was stretched more vigorously, and we calculated VDelt/VSSC as adhesion severity. The coracohumeral ligament (CHL) thickness was measured using the same images. Shoulder ROM was measured by using a universal goniometer. ResultsThe intraclass correlation coefficients (1.1) and (2.1) of the adhesion severity measurements were 0.85 and 0.91, respectively. Multiple linear regression analysis revealed that the adhesion severity is a significant predictor for external rotation ROM in the RCD group (R2 = 0.44, F = 10.1, p < 0.01, t = -2.9), while CHL thickness predicts ROM in the FS group (R2 = 0.28, F = 5.5, p = 0.01, t = -3.0). ConclusionThe proposed method is reliable. Muscle adhesion causes ROM restriction of the shoulder joint. The primary cause of shoulder ROM restriction differed between the diagnostic groups.