Injection of the subacromial bursa in patients with rotator cuff syndrome: a prospective, randomized study comparing the effectiveness of different routes.

Background: Rotator cuff syndrome is often treated with subacromial injection of corticosteroid and local anesthetic. It has not been established if the common injection routes of the bursa are equally accurate.

Methods: We conducted a prospective clinical trial involving seventy-five shoulders in seventy-five patients who were randomly assigned to receive a subacromial injection through an anterior, lateral, or posterior route with respect to the acromion. An experienced physician performed the injections, which contained radiopaque contrast medium, corticosteroid, and local anesthetic. After the injection, a musculoskeletal radiologist, blinded to the injection route, interpreted all of the radiographs.

Results: The rate of accuracy varied with the route of injection, with a rate of 56% for the posterior route, 84% for the anterior route, and 92% for the lateral route (p = 0.006; chi-square test). The accuracy of injection through the posterior route was significantly lower than that through either the anterior or the lateral route (p < 0.05 for both comparisons; Poisson regression). In addition, the accuracy of injection was significantly lower in females than in males (p < 0.006; chi-square test). Among males, no differences between the routes were noted (with accuracy rates of 89% for the posterior route, 92% for the anterior route, and 93% for the lateral route). Among females, however, the accuracy of injection was lower for the posterior route than for either the anterior or the lateral route (with accuracy rates of 38% for the posterior route, 77% for the anterior route, and 91% for the lateral route) (p < 0.05).

Conclusions: The anterior and lateral routes of subacromial bursal injection were more accurate than the posterior route. The accuracy of subacromial bursal injection was significantly different between males and females, mainly because of a lower accuracy of bursal injection with use of the posterior route in females. The present study suggests that the posterior route is the least accurate method for injection of the subacromial bursa in females.