Tips for General Practitioners – AC Joint Injection
Acromioclavicular (AC) Joint Arthritis

The principal causes of AC joint arthritis are overuse injuries or previous trauma to the AC joint. Any activity that can put pressure on the joint, either normal or excessive, may eventually cause this condition.

Constant overhead lifting, such as is engaged in by weightlifters or manual laborers who work overhead can increase the incidence of the disease. Other susceptible individuals are athletes participating in contact sports or engaging in any activity which may result in a fall on the end of the shoulder.

Typical symptoms of AC joint arthritis are pain and tenderness on the top of the shoulder around the AC joint. Sleeping on the side may cause pain and restlessness. There may be a decrease in shoulder motion. Compression of the joint, such as bringing the arm across the chest may result in increased pain.

First-line treatment consists of non-steroidal anti-inflammatory drugs (NSAIDs) and activity modification with physiotherapy. Steroid and local anesthetic injections are quite useful in recalcitrant cases.

Indications

Steroid and Local anaesthetic injections are commonly used as part of the orthopedic surgeon’s armamentarium when dealing with AC joint arthritis. They are useful both for diagnosis and treatment.

Injection with lignocaine is useful as a diagnostic tool to confirm the diagnosis of AC joint pain and can be used to exclude pain from subacromial impingement and rotator cuff tendonitis as well as referred pain from the neck.

Equipment

• Use a 10 mL syringe and a 21-Gauge needle. A 23-Gauge needle is also acceptable.
• Lignocaine can be used safely in dosages of less than 2 mg/kg bodyweight. Generally, 50 mg (5 mL of a one percent preparation) provides adequate analgesia within safe limits.
• Triamcinolone or other steroid preparations are equally acceptable.
• Aseptic techniques should be strictly adhered to.

Location

The landmarks for Acromioclavicular injections are the acromion, the distal clavicle and the coracoid process (Figure 1).

Identify the soft spot between the distal edge of the clavicle and the medial aspect of the acromion.
This is the landmark for entering the AC joint joint (Figure 2).

Palpate the soft spot and mark out the AC joint. This will give you the “target” with which to approach the subacromial space (Figure 3).

By aligning your syringe and needle with the “soft spot”, you will be able to enter and infiltrate AC joint easily.
There should be no resistance to flow and the patient should be comfortable throughout the procedure (Figure 4).