A lateral approach (described here) is commonly used and not difficult to do.
Subacromial bursitis, supraspinatus tendonitis, and calcific tendonitis may be indistinguishable in their manifestations and response to injection therapy.
The subacromial bursa lies between bone and overlying tendons. Because it is deep, subacromial bursitis seldom causes visible swelling or erythema. However, bedside ultrasonography for subacromial evaluation and needle guidance is usually unnecessary.
(See also Bursitis Bursitis Bursitis is acute or chronic inflammation of a bursa. The cause is usually unknown, but trauma, repetitive or acute, may contribute, as may infection and crystal-induced disease. Symptoms include... read more .)
For injections of corticosteroid to treat inflammation
Symptoms of nonseptic bursitis are often effectively treated with rest and nonsteroidal anti-inflammatory drugs. However, when needed, bursal injection therapy provides rapid relief, which may be beneficial for subacromial bursitis that persists or recurs despite conservative measures.
Overlying cellulitis or skin ulcer, bacteremia, adjacent prosthetic shoulder joint
Hypersensitivity to an injected substance
For corticosteroid injection, suspected septic bursitis
Unrecognized tendon injury: Analgesia provided by a corticosteroid injection could delay accurate diagnosis.
Poorly controlled diabetes: Any benefit of corticosteroids is weighed against risk of worsening glycemic control.
Previous corticosteroid injection into same site: Many experts advise waiting 3 to 4 months between injections and not exceeding a lifetime total of 4 injections.
Complications are uncommon and include
Subcutaneous fat atrophy, skin atrophy and sinus tracts, and temporary skin depigmentation due to inadvertent subcutaneous corticosteroid injection
Painful local reaction (sometimes called steroid flare) occurring within a few hours of depot corticosteroid injection and usually lasting ≤ 48 hours (probably an irritation due to crystals in the injection vehicle or to injecting into a calcific deposit, common in this anatomic area)
In diabetic patients, hyperglycemia that may persist for weeks after a depot corticosteroid injection
Tendon, nerve, or blood vessel damage or misdirected corticosteroid injection due to errant needle insertion
Antiseptic solution (eg, chlorhexidine, povidone iodine, isopropyl alcohol)
Sterile gauze, sterile gloves, sterile adhesive bandage
Needle insertion site anesthesia (eg, topical freezing spray and/or injectable 1% lidocaine without epinephrine, in a 3-mL syringe)
Optional: For therapeutic injection, 1% lidocaine without epinephrine, with injectable depot corticosteroid (eg, triamcinolone acetate, 20 to 40 mg)
27-gauge, 1.5-inch needle
Some 3-, 5-, and 10-mL syringes
Having an assistant is helpful.
For bursal injection therapy, local anesthetic and depot corticosteroid often are mixed in a single syringe (the anesthetic eliminates the pain of the corticosteroid).
If the history or physical examination suggests possible septic bursitis (eg, marked regional warmth, erythema, distention), withhold corticosteroid injection.
Immediate analgesia after injection of local anesthetic helps confirm correct needle placement and that the subacromial bursa is the source of pain.
Subacromial bursitis and supraspinatus tendinitis cannot always be differentiated clinically and tendinitis may be calcific, sometimes with spread to the bursa (calcareous tendinitis).
Injection therapy can be effective for any of these disorders; however, the injection path may differ for tendinitis.
Consider doing a shoulder x-ray before injection in patients with longstanding chronic shoulder pain or if symptoms persist to identify other possible causes of pain (eg, glenohumeral osteoarthritis, fracture).
The subacromial bursa lies immediately superior and lateral to the supraspinatus tendon and inferior to the coracoacromial arch.
Injection into a tendon or muscle will meet resistance and is to be avoided; injection into a bursa (or sometimes into a tendon sheath) is desired and will not meet resistance.
Shoulder anatomy (anterior view)
Seat the patient with the forearm resting in the lap. The seated position allows gravity to distract the humerus and widen the subacromial space.
To avoid vasovagal episodes, avert the patient's head and orient your work area so that the patient does not see the needles.
Step-by-Step Description of Procedure
Do the procedure using sterile technique.
Prepare the site
Mark the needle entry site on the skin.
Prepare the area with antiseptic solution.
Optional: Apply sterile drapes (eg, if obtaining a fluid sample for microbiology studies).
Spray freezing spray at the needle insertion site until it just blanches and/or inject a skin wheal of local anesthetic (≤ 1 mL).
Inject the bursa
Wear sterile gloves.
Posterior needle insertion approach: Insert the needle 2 to 3 cm inferior to the posterolateral corner of the acromion and direct it anteriorly toward the coracoid process, aiming upward at a 10° angle.
Lateral needle insertion approach: Insert the needle 2 cm below the lateral acromion border and over the humeral head.
If the needle encounters the acromion, retract the needle about 1 mm.
Gently pull back on the plunger as you advance to rule out intravascular placement.
Slowly inject the anesthetic/corticosteroid mixture and withdraw the needle.
If the injection meets resistance, the needle tip may be within the supraspinatus tendon. Stop injecting, partially withdraw the needle, and then readvance it more superiorly until the injection does not meet resistance.
Pain is immediately relieved after a properly placed injection of anesthetic.
Apply an adhesive bandage or sterile dressing.
Prescribe limited activity but do not immobilize the shoulder (to avoid a frozen joint).
Advise use of ice, and oral nonsteroidal anti-inflammatory drugs (NSAIDs) until pain subsides.
Instruct the patient to return for reassessment to exclude infection if pain is continuously and progressively increasing after several hours or persists for > 48 hours.
Begin gentle range-of-motion exercises after 24 hours and increase the intensity after 2 weeks.
Warnings and Common Errors
To avoid damaging tendons, do not inject corticosteroids against resistance.
Tips and Tricks
To increase opening into the subacromial space when using the lateral approach, have the patient hook their fingers around the cushion of the examination table, relax the shoulder muscles, and lean to the contralateral side.