Inferior glenohumeral joint capsule thickness in frozen shoulder via ultrasonography.

Background: The thickening of the inferior glenohumeral joint capsule (IGC) is a characteristic finding in frozen shoulders. However, the relationship between the thickness of the IGC measured using ultrasonography (US) and the range of motion (ROM) remains unclear. This study aimed to investigate a suitable IGC thickness measurement site that can reflect the ROM of frozen shoulders.

Methods: The participants were 29 patients with frozen shoulder and 20 healthy shoulders of 10 healthy adult. US measurements of the IGC were performed at 80° elevation in the scapular plane, with thickness was measured at 3 levels in both groups: just above the surgical neck, just above the anatomical neck, and at the parenchymal level. The relationship between thickness and ROM at the 3 levels was also assessed. The thickness of the IGC was evaluated using magnetic resonance imaging and US, as well as the validity of US evaluation.

Results: There was a positive correlation (r = 0.72) between magnetic resonance imaging-measured and US-measured IGC thickness. The IGC was thicker in the frozen shoulder group than in the control group at all 3 levels ( < .001). The thickness of the IGC at the parenchymal level showed a significant negative correlation with all ROMs: flexion (r = -0.63), abduction (r = -0.60), external rotation (r = -0.50), and internal rotation (r = -0.52).

Conclusion: The thickness of the IGC at the parenchymal level is negatively correlated with the ROM. The evaluation of the IGC in this study will be helpful in selecting treatment options for frozen shoulders.