Acromioclavicular osteoarthritis is a common cause of shoulder pain and is a frequent finding in patients >50 years.
It is the most common disorder of the acromioclavicular joint.
Image credit: Grutter
Anatomy of Acromioclavicular Joint
The acromioclavicular joint is a diarthrodial joint between lateral end of clavicle and medial end of acromion.
The two articular ends are separated by a fibrocartilaginous disc which functions to correct bony incongruities, acts as a cushion.
A number of ligaments – capsular ligaments, extracapsular ligaments, and attachments from the surrounding musculature stabilize the joint.
Coracoclavicular and coracoacromial ligaments are external stabilizers of the acromioclavicular joint.
These ligaments extend from the coracoid to the inferior surface of the clavicle in a V-shaped configuration and resist vertical displacement under high-load.
The deltoid and trapezius muscles attach over the lateral clavicle and acromion, and their fiberst blend with those of the superior acromioclavicular ligament.
Acromioclavicular ligament is supplied by branches of the suprascapular and lateral pectoral nerves. Blood supply is through branches of the suprascapular and thoracoacromial arteries.
Cause and Pathophysiology of Acromioclavicular Osteoarthritis
Osteoarthritis in the acromioclavicular joint could be caused by
- Primary osteoarthritis – Due to age related degenerative changes
- Secondary osteoarthritis – Due to pre-existing cause
- Trauma
- Inflammatory arthritis
- Infection
Usually, the osteoarthritis of acromioclavicular joint causes pain in the joint but it can result in subacromial impingement of the rotator cuff termed extrinsic impingement, resulting in pain, weakness and even injury to rotator cuff tendons.
Presentation of Acromioclavicular Osteoarthritis – Symptoms and Signs
Patients generally present with progressively worsening shoulder pain. Sometimes, minor trauma and strenuous activity may cause an acute exacerbation of the pain.
The pain of acromioclavicular osteoarthritis is localized over the anterior aspect of the shoulder in the region of the acromioclavicular joint. The pain may be referred to the shoulder and upper arm, or base of the neck.
Some patients may have associated headaches.
Activities involving overhead activities, weight lifting, and cross-body movements may worsen the symptom.
The patient may also complain of night pain, especially when he lies on the affected shoulder, often disturbing the sleep.
Complaints of popping, clicking, grinding, or a catching may be present with movements of the shoulder.
Examination of the shoulder reveals tenderness over the joint and exacerbation of pain by provocative measures. [discussed below]
Stability of the clavicle is checked to rule out any instability.
Provocative Tests
Cross-body Adduction
This test is performed by passively bringing the patient’s arm into 90 degrees of forward flexion and maximal adduction, thus causing compression across the joint.
Acromioclavicular Resisted Extension Test
The patient’s arm is placed in 90 degrees of forward flexion and the patient is asked to actively extend against resistance.
O’Brien Active Compression Test
Arm placed in 90 degrees of forward flexion with 10 degrees of adduction. With the arm in the maximal internal rotation, the thumb gets pointed downward and the patient resists a uniform downward force applied by the examiner.
The arm is then externally rotated to make palm face upward and the maneuver repeated. The test is considered positive if the pain is present with internal rotation but decreases or resolves with external rotation. Pain localized to the acromioclavicular region during this test is indicative of acromioclavicular joint pathology, whereas pain located deep inside the shoulder may indicate labral pathology.
Imaging
Initial imaging should include a modified AP view, scapular Y-view, and Zanca view radiographs.
Modified AP View
In this, the x-ray is done as in routine but the voltage is reduced by 50%. This provides a better view of the acromioclavicular joint.
Scapular Y View
Zanca View
This provides optimal visualization of acromioclavicular joint. In Zanca view, the x-ray beam is angled with 10 degrees of cephalic tilt thus eliminating overlap from the scapula and other tissues seen on standard AP radiographs
Axillary Lateral View
It is done if there is a history of trauma.
Xrays show a decrease in joint space and marginal sclerosis [see image]
Magnetic resonance imaging
MRI can be used to further characterize the degree of arthrosis when radiographs are equivocal.
Procedures
Joint Injection
A combination of local anesthetic and corticosteroid is injected after the joint is located by palpation. The joint is approached from the superior side. Ultrasound guidance also has been shown to further improve the accuracy of proper intraarticular needle placement.
Treatment of Acromioclavicular Osteoarthritis
Goals of treatment of acromioclavicular osteoarthritis are pain reduction and allowing full range of motion.
The first line of treatment is nonoperative management, and options include rest, activity modification, nonsteroidal anti-inflammatory medications, corticosteroid injections, and physical therapy.
Rest
Rest is indicated in patients with acute exacerbation of their symptoms. Immobilization in a sling, cold or hot fomentation would help.
Warm or cold compress. Patients can loosen a stiff joint by using moist heat, such as a warming pad or whirlpool, for a few minutes before activity. Icing the shoulder joint for 15 or 20 minutes after activity can decrease swelling and give some immediate pain relief. These treatments provide temporary symptom relief and do not treat the underlying causes of acromioclavicular joint osteoarthritis.
Activity Modification
Repetitive, overhead, and cross-body movements should be avoided. Weight lifting and sports like golf should also be avoided.
Activity modification aims at reducing the stress on the acromioclavicular joint and prevents worsening of the symptoms.
Physical therapy
It includes strength and range of motion exercises of the shoulder girdle, stretching, ultrasound, and other modalities like cryotherapy. These are more effective in concomitant impingement or rotator cuff arthropathy than acromioclavicular osteoarthritis.
Medications
- Oral analgesics like acetaminophen
- Oral non-steroidal anti-inflammatory drugs (NSAIDs like aspirin, ibuprofen etc.
- Topical Applications like gels and sprays containing counter-irritant, like capsacin, eucalyptus, and NSAIDs
- Lidocaine is an anesthetic agent that interrupts pain signals to the brain. Adhesive patches containing 5% lidocaine applied directly to the affected joint may reduce or pain.
- Glucosamine and chondroitin sulfate – Equivocal results
Injections
Intra-articular steroid injections are used to reduce swelling and shoulder stiffness and pain. The degree of pain relief from injections is variable and temporary.
Surgery
Surgical treatment of acromioclavicular osteoarthritis is indicated when a patient with AC osteoarthritis has persistent symptoms despite conservative management.
The procedure performed is distal clavicle excision is the can be performed through either open or arthroscopic techniques.
The results of open and arthroscopic are almost comparable.
Other possible surgeries are arthroscopic to remove loose pieces of damaged cartilage and osteotomy to shave off osteophytes and reduce bone friction.
