Increase in range of motion after intra-articular injection of triamcinolone acetonide for the treatment of frozen shoulder is related to body mass index

OBJECTIVES: The aim of this study was to evaluate the clinical effect of glenohumeral injection with triamcinolone acetonide for frozen shoulder and to identify the factors related to extent of range of motion (ROM) recovery. PATIENTS AND METHODS: Between July 2015 and May 2020, a total of 305 patients with primary frozen shoulder (147 males, 158 females; mean age: 55.8±4.3 years; range, 52 to 73 years) who underwent intra-articular glenohumeral injection of triamcinolone acetonide were retrospectively analyzed. The primary outcome measure was the range of changes in each aspect of ROM at six weeks after injection. The relationship between improvement and unresponsiveness to intra-articular injection for the treatment of frozen shoulder with various factors were evaluated. The analyzed factors were as follows: age, sex, body mass index (BMI), initial ROM before injection, symptom duration, hand dominance, smoking history, and the existence of underlying disease including diabetes mellitus, hypertension, coronary disease, thyroid disease, and hypercholesterolemia. RESULTS: There were significant improvements in all aspects of ROM at six weeks after injection. The forward flexion (r=-0.346, p<0.001) and external rotation (r=-0.204, p=0.040) showed a negative correlation with BMI. Multivariate analysis revealed that BMI was the sole factor related to recovery of forward flexion (p=0.032) and external rotation (p=0.007) at six weeks post-injection. CONCLUSION: Intra-articular injection of triamcinolone acetonide is an effective method for improving ROM in patients with frozen shoulder. Increased BMI showed adverse effects on ROM recovery.