Infraspinatus injection is a useful diagnostic and therapeutic procedure for myofascial pain.
After informed consent is obtained, the patient is placed in the sitting or prone position. The infraspinatus muscle is palpated from the infraspinous fossa of the scapula to the humerus. Trigger points are most often located below the spine of the scapulae. The injection sites are identified as points of maximal tenderness to deep palpation, reproducing the patient’s pain complaint. This may or may not result in referred pain. The patient is prepared in a standard aseptic fashion over an area large enough to allow palpation of landmarks, and sterile technique is used throughout the procedure. A 1½-in. (4-cm), 21- to 25-gauge needle is inserted at the point of maximal tenderness and advanced to the area of the trigger point. After negative aspiration, the trigger point area is injected with 4 mL of local anesthetic (Fig. 67-25).
FIGURE 67-25. Infraspinatus. Trigger points and referred pain patterns.
The referred pain pattern for the infraspinatus often involves the deltoid muscle, as well as the area over the lateral shoulder and proximal upper extremity. Pain also may be referred in the infrascapular region. The patient should be fully familiar with the stretching program for the infraspinatus muscle and be instructed in a home program. Failure to include a home stretching program usually results in short-term relief.
Significant complications are uncommon with infraspinatus trigger point injections.