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Accuracy of Injections for Shoulder Rotator Cuff Syndrome

Symptoms that suggest a rotator cuff tendinopathy include pain with arm motion overhead, pain at night, and a positive impingement sign (pain during a particular arc of shoulder motion). A common treatment for this problem is a steroid injection into the acromial bursa. The antiinflammatory properties of the steroid medication are designed to reduce swelling and thereby decrease the size of the bursa. An inflamed bursa can be painful but can also take up space in the shoulder causing impingement (pinching) of the rotator cuff tendons.

An orthopedic surgeon performs this as an outpatient procedure in his or her office. First, the skin is numbed with a topical spray. Then the surgeon inserts a long, thin needle into the bursa underneath the acromion bone. The bursa is a fluid-filled sac between the bone and soft tissues. The acromion is the end of the bone from the scapula (shoulder blade) that forms a shelf over the top of the shoulder joint.

This area under the acromion can be reached with the needle from one of three directions: anterior (front), lateral (side), or posterior (back). But the question is: which route is the most accurate? In this study, one orthopedic surgeon injected 75 shoulders using these three pathways.

There were three groups of patients and each group received one of the three types of injection. Patients were randomly assigned to the group they were in. The fluid injected included the steroid medication, a numbing agent, and a dye. The dye was part of the injection so that X-rays taken would show the accuracy of the injection (i.e., did the fluid actually end up inside the bursa?).

This surgeon found that injecting the shoulder from the front and side (anterior and lateral routes) gave better results than injecting from the back (posterior). This was especially true for women. It turns out that the posterior route was the least accurate when injecting the subacromial bursa in females.

One possible reason for this difference between men and women may be the downward-sloping angle of the acromion. Differences in accuracy of the route (anterior, lateral, or posterior) could possibly be because only one physician performed the injections. These results might be different if a group of physicians gave injections and results were compared.

For this particular surgeon who normally used the posterior approach, the results suggested the need to switch to either the anterior or lateral approach, especially for women. When patients fail to get pain relief from a steroid injection for rotator cuff syndrome, it may not be because the injection failed. It could be the injection never reached its intended destination if the surgeon failed to accurately inject the bursa. Pain relief with successful steroid injection is expected to occur within the first hour after injection. A second reason pain relief may not occur is an incorrect diagnosis (the problem may not be a rotator cuff tendinopathy).

The author summarizes by saying that in-office steroid injections for rotator cuff syndrome can be successful. Accuracy is assured when using ultrasound or fluoroscopy (a type of X-ray) but without these tools, the rate of success increases when injecting through the anterior or lateral approaches.

In this study, the success rate when injecting women was highest (91 per cent accurate) when using the lateral route. This was compared with 38 per cent for the posterior route. For men, it didn't seem to matter; accuracy was fairly equal no matter what direction the injection was delivered.

References: Richard A. Marder, MD, et al. Injection of the Subacromial Bursa in Patients with Rotator Cuff Syndrome. In The Journal of Bone and Joint Surgery. August 15, 2012. Vol. 94A. No. 16. Pp. 1442-1447.

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