Diagnostic Injections About the Shoulder

Edward McFarland, MD; Johnathan Bernard, MD, MPH; Eric Dein, MD; Alex Johnson, MD

Disclosures

J Am Acad Orthop Surg. 2017;25(12):799-807. 

In This Article

The Acromioclavicular Joint

Presentation and Evaluation

Compared with rotator cuff disease, abnormalities of the acromioclavicular (AC) joint are diagnosed more predictably with physical examination because of the accessibility of the joint to palpation. In addition, physical examinations for AC joint pain are more accurate than those for rotator cuff disease. The AC joint often causes radiation of pain into the trapezius muscle and should be palpated in every patient with shoulder pain, especially those with trapezius pain. The cross-body adduction stress test, arm extension test, and active compression test also can be used to identify the AC joint as the origin of pain.[21]

Few studies have evaluated the diagnostic value of AC joint injections. Strobel et al[22] used magnetic resonance arthrography to understand features of the AC joint that predict pain relief from injections performed under fluoroscopic guidance. In 50 patients with symptomatic AC joints, 22% had substantial pain relief (>70% relief) at 15 minutes; at the same time point, 52% had some pain relief (<70% relief), and 25% of patients had no improvement in pain.

Technique Summary

Unlike injecting the subacromial space, where local anesthetic is thought to flow easily, injecting the AC joint is more challenging for several reasons (Figure 3). First, it is a small joint with a fibrous capsule. Second, the joint is oriented obliquely so the needle may not penetrate it. Third, a small meniscus occupies the joint space between the distal clavicle and the acromial articulation. As a result, the ability to accurately inject the AC joint has ranged from 39% to 67%, depending on the modality used to verify the location of the injected fluid[17,23–28] (Table 2).

Figure 3.

Illustration of an anterior view of the shoulder, showing injection of the acromioclavicular joint. (Copyright Louis Okafor, MD, Baltimore, MD.)

In a meta-analysis of three studies, Aly et al[20] found that ultrasonography-guided AC joint injections were more accurate than blind injections (94% versus 68%, respectively). However, Sabeti-Aschraf et al[29] questioned the need for perfect intra-articular placement. In a study of 106 peri-articular or intra-articular shoulder injections in 101 patients treated at seven centers, the authors found no statistically significant difference in pain scores between the two groups, with the exception of pain during the cross-body adduction test at 3 weeks (P < 0.016).

Before the AC joint is injected, the location of pain relative to the joint should be verified. Often, the patient will point directly to the AC joint when asked to localize the pain with one finger. The joint can be examined by palpating the clavicular shaft and slowly palpating laterally until a soft spot is felt, indicating that the AC joint is found. When the location is verified, it can be marked with a pen.

When the AC joint is injected, injecting the subcutaneous tissues on the way to the joint capsule will decrease the pain. Because the AC joint is small, a limited amount of anesthetic can be directly injected into it. Injection of the periosteum along the joint line from the front of the AC joint to the back may allow more anesthetic to penetrate the joint. Care should be taken not to inject through the AC joint into the subacromial space (Figure 4).

Figure 4.

Photograph of the sagittal view of the shoulder showing an injection of the acromioclavicular joint.

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