Ultrasound‐Assessed Rotator Interval Vascularity Is Associated With the Immediate Response to Corticosteroid Injection Combined With Radial Extracorporeal Shock‐Wave Therapy in Adhesive Capsulitis: A Single‐Group Quasi‐Experimental Preliminary Study

BACKGROUND AND PURPOSE: Adhesive capsulitis is characterized by progressive pain and restricted shoulder mobility, with inflammatory changes frequently observed in the rotator interval (RI). This study aimed to evaluate whether ultrasound-assessed RI vascularity is associated with immediate changes in shoulder external rotation range of motion following combined corticosteroid injection and radial extracorporeal shock-wave therapy (r-ESWT) in adhesive capsulitis. METHODS: In this single-group quasi-experimental preliminary study, 20 patients with adhesive capsulitis received intra-articular corticosteroid injection followed by five r-ESWT sessions targeting the RI. RI vascularity was assessed using power Doppler ultrasonography (PD-US) and graded using a four-point scale (Grades 0-3). Passive external rotation (ER) was measured before and after each session, and the immediate ER change (ΔER) was calculated. A linear mixed-effects model was employed to identify factors associated with ΔER while accounting for repeated measures. RESULTS: Vascularity grade was significantly associated with ΔER (F = 11.42, p < 0.001). Compared with Grade 3, significantly smaller gains were observed in Grades 0 (estimate = -8.72, p = 0.014) and 1 (estimate = -8.91, p = 0.003), whereas Grade 2 exhibited a smaller improvement that did not reach statistical significance (estimate = -6.23, p = 0.051). No significant associations were observed for other examined covariates. DISCUSSION: Greater RI vascularity assessed using PD-US was associated with larger immediate ΔER following combined corticosteroid injection and r-ESWT in patients with adhesive capsulitis. These exploratory findings suggest that PD-US-based vascular assessment may provide clinically relevant information regarding stage-related biological activity and short-term physiological responsiveness and warrant further investigation in larger controlled studies.