Predictive value of subacromial motion metrics for the effectiveness of ultrasound-guided dual-target injection: a longitudinal follow-up cohort trial

Objective: Subacromial impingement syndrome (SIS) frequently causes shoulder pain. This study aimed to (1) assess the predictive utility of quantitative dynamic subacromial ultrasound for ultrasound-guided dual-target injections and (2) compare the long-term efficacy of dual-target injections with standard subdeltoid-subacromial injections in SIS patients. Methods: Patients with SIS received 40 mg of triamcinolone acetonide via ultrasound-guided dual-target injections (subdeltoid-subacromial bursa and long head of the biceps brachii tendon). Clinical assessments and static/dynamic ultrasound were performed at baseline and 4 weeks post-procedure. Minimal vertical acromiohumeral distance (mVAHD) was measured by tracing the humeral greater tuberosity against the acromion. A historical cohort receiving standard subdeltoid-subacromial corticosteroid injections was used for comparison. Results: Of 90 patients receiving dual-target injections, 70 (77.7%) achieved early treatment success. An enlarged minimal mVAHD was associated with success, except during the abduction phase in the full-can posture. Among these 70 patients, 25 (35.7%) had shoulder pain recurrence requiring repeat injections, linked to a decreased mVAHD across all phases and postures. Compared to 90 patients in a historical cohort receiving standard subdeltoid-subacromial injections, the dual-target group had a significantly longer mean time to pain recurrence (309.1 ± 130.1 days vs. 267.5 ± 184.2 days, p = 0.03). Conclusion: Dynamic ultrasound metrics, including mVAHD, predict early success and pain recurrence following dual-target injections in SIS. Dual-target injections offer a longer duration of effectiveness compared to standard subdeltoid-subacromial injections. Future research should explore the predictive value of mVAHD with deep learning algorithms and evaluate the approach in adhesive capsulitis. Trial registration: ClinicalTrials.gov (NCT04219527). Registered on 27 December 2019, https://clinicaltrials.gov/study/NCT04219527. Critical relevance statement: Dynamic ultrasound metrics predict early success and pain recurrence following dual-target injections in SIS, offering a longer duration of effectiveness compared to standard subdeltoid-subacromial injections. Key Points: Dynamic ultrasound metrics predict injection success and pain recurrence in impingement. Dual-target injections offer a longer duration of effectiveness than standard injections. Future research should assess deep learning’s predictive value in adhesive capsulitis.