866 A Lateral Approach Is More Likely to Be Successful Than A Posterior Approach for An Injection to Reach the Subacromial Space

Abstract

Background Subacromial injections are common for diagnosis and therapy of shoulder impingement secondary to subacromial bursitis. We evaluated the likelihood of a successful subacromial injection from both the posterior and lateral injection sites. Method We reviewed 100 MRI scans of the shoulder and recorded measurements in both the sagittal (representative of posterior injection) and coronal (representative of lateral injection) orientations. We compared these to the lengths of standard needles. Multiple measurements were taken: Results Measuring along the angle of the acromion demonstrated shorter mean distances from the lateral injection site. The distance from skin to mid-point of the acromion) provided mean values of 51.4mm for posterior and 40.1mm for lateral. A standard 40mm (green) needle would reach the midpoint of the acromion in 58% of lateral measurements and 23% from posterior. Conclusions Injections are more likely to enter the subacromial space from a lateral rather than a posterior entry point.