Ultrasonic Identification of Polymyalgia Rheumatica and Frozen Shoulder

Abstract

Objective/Background: Polymyalgia rheumatica (PMR) shoulder involvement and frozen shoulder (FS) are two diseases with similar clinical features. In this study, the shoulder joint ultrasound of patients with PMR and FS was analysed to explore the differential diagnosis of the two ultrasound imaging problems. Methods: PMR patients diagnosed from July 2020 to April 2022 were reviewed, and a 1:1 case‒control study was conducted with FS patients diagnosed simultaneously according to their age±3 years. Results: The eligible samples were finally screened from 169 PMR patients and matched 1:1 from 367 FS patients according to their age ±3 years. Finally, 23 groups of patients were included, and a total of 92 shoulder joints were analysed. There were 34 females (73.91%) and 12 males (26.09%), with a mean age at inclusion of 70 [63.25, 75] years. There were significant differences in sex (P=0.017), erythrocyte sedimentation rate (p < 0.001) and C-reactive protein (p < 0.001) between the two groups. Ultrasonographic characteristics showed that the incidence of subacromial-subdeltoid (SASD) bursitis (P =0.009) in PMR patients was significantly increased. Glenohumeral (GH) synovitis was more common in FS patients (P=0.013). Axillary pouch thickness had a certain advantage in the diagnosis of FS, but not PMR, with an area under the AUC of 0.827 (P < 0.001). The cut-off value was 2.85 mm, the diagnostic sensitivity was 82.61%, and the diagnostic specificity was 78.26%. Conclusions: There were some differential differences in the ultrasound features of PMR and FS. These results may provide valuable clues for the differential diagnosis.