Recovery After Arthroscopic Subacromial Decompression: Prognostic Value of the Subacromial Injection Test

Purpose: To evaluate the use of a steroid/local anesthetic subacromial injection as a prognostic tool for patient recovery following arthroscopic subacromial decompression (ASD). Type of Study: Prospective cohort study. Methods: A local anesthetic/steroid subacromial injection was administered to all patients with a clinical diagnosis of subacromial impingement syndrome. In the event of a negative result to the injection test, the diagnosis was confirmed by computed tomographic arthrography or magnetic resonance imaging. All patients underwent standard ASD. The outcome was assessed using the Constant score, performed preoperatively, at 3 weeks, 3 months, and at discharge. The eventual functional outcome was correlated with the results of the injection test and the operative findings. Results: There were 101 patients (53 male, 48 female), with a mean age of 52 years (range, 21 to 77 years) in the study. Patients were followed-up for a mean of 14 months (range, 3 to 24 months). All patients had an impingement lesion noted at arthroscopy. The mean preoperative Constant score for the entire group was 48 points (range, 20-67) with a postoperative mean of 81 (range, 46-98). Sixteen patients had a negative preoperative injection test. The mean improvement in this group was 21 points (47 rising to 68) compared with 35 points (48 to 83) in the positive group (P < .05, Mann-Whitney U test). The groups were otherwise similar for age, gender, and operative findings. Conclusions: The steroid/local anesthetic injection test is a useful tool both diagnostically and prognostically in patients with subacromial impingement syndrome. In patients with a confirmed diagnosis but a negative test there is still a significant improvement in the postoperative Constant score, but this is of a lesser degree than in those with a positive result to local anesthetic injection. Level of Evidence: Level III, Diagnostic Study of Nonconsecutive Patients.