Original article
The Accuracy of Subacromial Injections: A Prospective Randomized Magnetic Resonance Imaging Study

https://doi.org/10.1016/j.arthro.2005.12.019Get rights and content

Purpose: To assess the accuracy of shoulder infiltrations in the subacromial bursa (SAB) by a posterior or an anteromedial approach. Magnetic resonance imaging (MRI) and clinical outcome were used for evaluation. Type of Study: A prospective randomized study. Methods: Thirty-three patients (22 women, 11 men; average age, 46 years; range, 25 to 64 years) with clinical signs of subacromial impingement were infiltrated with a mixture of bupivacaine, methylprednisolone, and gadolinium-DTPA directly followed by MRI to determine the actual site of injection. The SAB was randomly infiltrated posteriorly (n = 17) or anteromedially (n = 16). Injection confidence of the surgeon and body-mass index of the patient were recorded. Follow-up consisted of the Constant Score, Simple Shoulder Test, and visual analog scale score for pain taken within 24 hours and 6 weeks after infiltration. Results: Thirteen injections (76%) were in the SAB with a posterior approach and 10 (69%) with an anteromedial approach. Many surrounding structures were hit as well, especially the rotator cuff. A positive correlation between the injection confidence of the orthopaedic surgeon and the MRI was found in 66%. Only injection of the SAB alone resulted in a significant decrease of the pain (P = .004) and an increase in the functional scores. Injection in the bursa and rotator cuff muscle showed a significant increase in pain (P = .032) but no change in clinical scores. The body mass index had no influence on the scores. Conclusions: Injections in the SAB are inaccurate, despite the confident feeling of the clinician. The finding that many different structures can be infiltrated with 1 injection can create both false-positive and -negative results. Level of Evidence: Level II.

Section snippets

Methods

Thirty-three patients with subacromial pain were included in the study. There where 11 men and 22 women with an average age of 46 years (range, 25 to 64 years). Subacromial impingement was diagnosed when patients complained of nontraumatic shoulder pain localized to the deltoid region with an inability to lie on the affected side. Furthermore, pain provocation was present when movements of abduction, retroversion, or internal rotation in the glenohumeral joint against resistance were performed.

Results

There was no lack of consensus between the 2 radiologists. No shoulder had evidence of a full-thickness rotator cuff rupture on the MRI. No differences were found among groups, including gender, age, Simple Shoulder, Constant, and VAS scores. The average BMI was 26 (minimum, 18; maximum, 33) for the posterior injected group and 27 (minimum, 20; maximum, 44) for the anteromedial injected group (Table 1).

The injection confidence of the orthopaedic surgeon was high. With the posteromedial

Discussion

Injections with a local anesthetic around the shoulder are widely used in the diagnostic process of shoulder pain. Neer’s impingement test describes the reaction of the patient after infiltration of the subacromial bursa and is used in the decision-making if an acromioplasty is considered.2, 3 Searching for factors influencing the result after subacromial decompression, Patel et al.10 associated a positive impingement test with a satisfactory result after acromioplasty. However, Kirkley et al.11

Conclusions

We conclude that injections given in the subacromial bursa for diagnostic or therapeutic use, without any radiological support, are inaccurate, despite the confident feeling of the clinician. In this study, the accuracy was only 66%. The many different structures hit with 1 injection can create both false-positive and -negative results. This makes the diagnostic use of local injections in the subacromial bursa a poor tool.

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