Abstract
The diagnostic value of ultrasonography (US) for frozen shoulder (FS) is not well established. This study aimed to assess the diagnostic value of US measurement of inferior joint capsule (IJC) thickness and evaluate changes in the thickness of the IJC by US depending on arm position. A total of 71 patients with clinically diagnosed unilateral FS who underwent bilateral US measurement of the IJC were enrolled in this study. The US measurement of the IJC was performed with a linear transducer positioned around the anterior axillary line with the shoulder 40° abducted and with neutral rotation of the glenohumeral joint (neutral position). We also measured the IJC thickness in the externally rotated and internally rotated positions with the shoulder 40° abducted. In the neutral position, as well as in the internally rotated and externally rotated positions, the thickness of the IJC on US was significantly higher in the affected shoulder than that in the unaffected shoulder (all p < 0.001). On both the affected and unaffected sides, the US thickness of the IJC in the neutral position was significantly higher than that in the externally rotated position (p < 0.001), but lower than that in the internally rotated position (p < 0.001). Regarding IJC thickness in the neutral position, a 3.2-mm cutoff value yielded the highest diagnostic accuracy for FS, with a sensitivity and specificity of 73.2% and 77.5%, respectively. The area under the curve for IJC thickness was 0.824 (95% confidence interval, 0.76–0.89). US measurement of the IJC in the neutral position yielded good diagnostic accuracy for FS. Because IJC thickness is affected by arm rotation, it is important to measure the IJC thickness in a standardized posture to ensure diagnostic value.
Highlights
Frozen shoulder (FS) is a common shoulder disease characterized by pain and limited range of motion (ROM) [1]
This study assessed the diagnostic value of inferior joint capsule (IJC) thickness measured by US for the diagnosis of FS and evaluated the changes in the thickness of the IJC depending on arm position
Our results showed that a cutoff value of 3.2 mm for IJC thickness on US yielded a sensitivity and specificity of 73.2% and 77.5% for FS diagnosis
Summary
Frozen shoulder (FS) is a common shoulder disease characterized by pain and limited range of motion (ROM) [1]. FS is understood as a series of pathological processes in which the synovium of the glenohumeral joint is initially inflamed by unknown triggering factors and gradually replaced by fibrosis; the joint recovers naturally through an unknown mechanism [2,3,4,5,6]. It is not clear whether the lesion in FS spans the entire synovium of the glenohumeral joint or whether only specific areas are involved. Increased thickness of the IJC on MRI or ultrasonography (US) is suggestive of synovitis representing primary or secondary FS [7,13,14,15,16]
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