Abstract
Introduction
Subacromial corticosteroid injection is widely used in the treatment of Subacromial Impingement Syndrome (SIS). There is increasing interest in using ultrasound (US) to improve the accurate placement of injections. This study investigated whether the accuracy of placement of US-guided subacromial corticosteroid injections influences patients' outcome of pain and function.
Method
Secondary analysis of data from a 2−2 factorial randomised controlled trial investigating exercise and corticosteroid injection for pain and function in SIS. US-guided injections were delivered according to a pre-defined protocol. Video images were reviewed to categorise accuracy of injection into the subacromial bursa into 3 accuracy groups using pre-defined criteria: 1) not in the subacromial bursa; 2) probably in the subacromial bursa; and 3) definitely in the subacromial bursa. The primary outcome measure was the self-reported Shoulder Pain and Disability Index (SPADI) total score, compared at 6 weeks and 6 months. Secondary outcomes included SPADI pain and function subscales and participant global rating of overall change from baseline. A mixed effects model was used to compare accuracy groups' outcomes at 6 weeks and 6 months, adjusted for baseline covariates.
Results
US-guided injection accuracy data were available for 114 participants; with 22 participants in group 1, 21 in group 2 and 71 in group 3. There were no significant differences in mean SPADI scores among the three injection accuracy groups at 6 weeks (group 2 vs. 1: 8.22 (95% CI −4.01, 20.50); group 3 vs. 1: −0.57 (−10.27, 9.13)) and 6 months (group 2 vs. 1: 12.38 (−5.34, 30.10); group 3 vs. 1: 3.10 (−11.04, 17.23)). Similarly, no differences between accuracy groups were seen in SPADI pain, SPADI function or participant global rating of change.
Conclusion
The accuracy of US-guided subacromial corticosteroid injection in SIS does not influence clinical response to the injection, questioning the need for guided injections. Larger, adequately powered studies are required to explore this further.
