The lateral or posterior approach can be used to inject the subacromial bursa; the lateral approach shown here is safer to perform, since injection into the rotator cuff tendons is nearly impossible with this technique. The patient is to be sitting up, with the hands placed in the lap. The patient is asked to relax the shoulder and neck muscles. Traction applied to the flexed elbow may be necessary to open the subacromial space. The lateral edge of the acromion is located and its midpoint marked. The point of entry is 1 to 1.5 inches (about 2.5 to 4 cm) below the marked midpoint. The angle of entry should parallel the patient's own acromial angle (averaging 50 to 65 degrees). The depth will vary according to the patient's weight and muscle development (1.5 inches [about 4 cm] in an asthenic patient and up to 3.5 inches [about 9 cm] in an obese patient over 30 percent ideal body weight). Ethyl chloride is sprayed on the skin. Local anesthetic is placed in the deltoid muscle (1 mL) and the deep deltoid fascia (0.5 mL). The needle is advanced through the subcutaneous tissue and the deltoid muscle until the subtle resistance of the deep deltoid fascia is encountered. If firm or hard tissue resistance is encountered (deltoid tendon or periosteum, often painful), then the needle is withdrawn 0.5 inch (about 1.5 cm) and the angle is redirected 5 to 10 degrees either up or down. A "giving way" or "popping" sensation is often appreciated when the subacromial bursa is entered. Following 1 to 2 mL of anesthesia and leaving the needle in position, the patient strength is tested again. If pain is reduced by 50 percent and the strength of abduction and external rotation are 75 to 80 percent of the unaffected side, then 1 mL of depo-medrol (80 mg/mL) is injected. Note, never inject under moderate to high pressure. If high injection pressure is encountered, first try rotating the syringe 180 degrees. If tension is still high and the patient obviously anxious, ask the patient to take a deep breath and try to relax the shoulder muscles. If tension remains high, reposition the needle by 0.25 inch (about 0.5 cm) increments or by altering the angle of entry by 5 to 10 degrees. The subacromial bursa will accept only 2 to 3 mL of total volume before rupturing.
Courtesy of Bruce C Anderson, MD.
Graphic 60759 Version 4.0
