Comparison of Shoulder Ultrasonographic Assessments between Polymyalgia Rheumatica and Frozen Shoulder in Patients with Bilateral Shoulder Pain: A Comparative Retrospective Study

This study aimed to assess and compare the ultrasonographic (US) pathologic findings in patients with polymyalgia rheumatica (PMR) and bilateral frozen shoulder (FS). We included 19 patients with clinically diagnosed PMR and 19 patients with stage II bilateral FS. The US evaluation included the assessment of subacromial-subdeltoid (SASD) bursitis, long head of biceps (LHB) tenosynovitis, and posterior and inferior glenohumeral (GH) synovitis. Unilateral SASD bursitis was noted significantly more frequently in PMR patients than in bilateral FS patients (p = 0.001). There were no significant differences in the incidence of unilateral LHB tenosynovitis and posterior GH synovitis between PMR and bilateral FS patients (p = 0.108 and p = 0.304, respectively). Unilateral inferior GH synovitis was more common among bilateral FS patients than among PMR patients (p < 0.001). Bilateral SASD bursitis and LHB tenosynovitis were noted significantly more frequently in PMR patients than in bilateral FS patients (p < 0.001 and 0.049, respectively). Significant differences were not observed in the incidence of bilateral posterior GH synovitis between PMR and bilateral FS patients (p = 0.426). Bilateral inferior GH synovitis was more common among bilateral FS patients than among PMR patients (p = 0.044). The US evidence for bilateral inferior GH synovitis without bilateral SASD showed high specificity (94.7%) with sensitivity (78.9%) for the diagnosis of bilateral FS. SASD bursitis, representing periarticular synovial inflammation, was more common among the patients with PMR than among the patients with bilateral FS. Inferior GH synovitis without SASD bursitis suggests FS rather than PMR in patients with bilateral shoulder pain.