Acromio-clavicular Joint Problems

The acromioclavicular (AC) joint is the articulation between the acromion process of the scapula and the lateral end of the clavicle. It is one of the important functional joints that allows a full range of movement at the glenohumeral joint. A joint capsule and several ligaments hold the joint in-situ, assisted by the trapezoid and conoid coracoclavicular (CC) ligaments that connect the coracoid process of the scapula to the mid/lateral clavicle.

It is difficult to know how common such injuries are since there are no reliable population data, but they seem to be highly prevalent among players of high-impact contact sports. One series found that 41% of collegiate American Football players had suffered AC injury.¹ Forty-five per cent of first class rugby players gave a history of suffering AC disruption, although functional outcome in the long term appeared to be good in this group.²

Shoulder pain is a common symptom. Causes include:

• Rotator cuff pathology
• Bursitis
• Biceps tendonitis
• Labral tears
• Joint pathology e.g. acromioclavicular, sternoclavicular and scapulothoracic

1. AC joint disruption - when trauma leads to varying degrees of displacement of the distal clavicle from the local ligaments and muscles
2. Osteoarthritis and/or osteolysis of the AC joint

Mechanism of Injury

This usually follows trauma e.g. due to a direct blow to the acromion with the humerus adducted as in collision in high-impact contact sports, or after a fall onto the apex of the shoulder. Injury may occur as a consequence of throwing sports or chronic irritation due to activities that require repetitive overhead motions, particularly weight lifting. Its aetiology is uncertain but may be due to repeated stress fractures of the lateral clavicle.

• OA of the AC may occur after injury, repetitive overuse or more rarely as a primary phenomenon.⁴
• Distal Clavicular Osteolysis may occur spontaneously in rheumatoid arthritis, hyperparathyroidism, myeloma, systemic sclerosis, due to infection and in those who are involved in throwing sports/extensive upper-limb weight training.

AC Joint disruption

• There will usually be a history of relevant trauma and severe pain over the lateral shoulder.
• There may be marked tenderness of the AC joint and a visible/palpable 'step' if there is clavicular separation. This is best viewed with the arm adducted across the body.
• The position of the clavicle should be determined along its whole length (associated sternoclavicular abnormalities may occur as well as fracture of clavicle).
• Brachial and radial pulses should be checked along with sensory and motor function in the affected arm due to the possibility of injury to brachial plexus and axillary/subclavian vessels.
• Patients may also present with acute complications of AC joint disruption e.g.
  • Injury to axillary/subclavian vessels
  • Injury to brachial plexus
  • Muscular avulsion, particularly deltoid and trapezius
  • Rarely pneumothorax if associated clavicular fracture

OA and Distal Clavicular Osteolysis

• Diffuse lateral shoulder pain and/or localised AC joint pain.
• Maybe simply an ache in deltoid area.
• Often worse at night.
• Local tenderness with exacerbation on passive and active shoulder movements.
• Cross-adduction (i.e. reach over front of opposite shoulder) often worsens pain and further passive cross-adduction by examiner may aggravate this.⁴
• Reduced range of movement is rare unless prolonged period of arthritis.

• Clavicular fracture
• Shoulder (glenohumeral) dislocation
• Cervical spine fracture
• Bursitis (especially in cases of OA and osteolysis)
• Tendonitis (especially in cases of OA and osteolysis)
• Other causes of shoulder pain (see above)

• Plain radiographs are the initial choice.
• Type I and II injuries may be differentiated using stressed radiographs where weights are hung from the patient's wrists, although many consider this technique to be unhelpful.
• A Zanca view (AP view where beam is directed at the AC joint with 10º cephalic tilt) optimises the view of the joint.
• CXR and full clavicle views may be needed in some cases.
• Carefully inspect scapula to rule out associated scapular fracture.
• A variety of images may be required to assess the degree of AC joint disruption.

AC joint disruption

• Type I and II injuries are managed conservatively with ice, a sling for 1-3 weeks and NSAIDS followed by physiotherapy to strengthen muscles and ligaments after the acute phase.
• Type III injuries should be managed conservatively but carefully selected cases may benefit from surgical intervention if conservative therapy fails.⁵
• Type IV-VI are nearly always treated with open reduction and internal fixation.
• All acute lesions thought to be worse than type II should be referred urgently for an orthopaedic opinion.

OA/Osteolysis

• Activity modification, physiotherapy and NSAIDs/other analgesia.
• Intraarticular corticosteroids may provide relief of symptoms for up to 3 months in expert hands. Currently there is no consensus in terms of dosage and injections should be limited to less than 4 per year.⁶ Duration of analgesia is very variable with ranges of 2 hours to 3 months reported.
• In severe cases of OA or osteolysis distal clavicular resection may need to be considered. This can be performed openly or arthroscopically.⁷
• In OA consider surgery for severe cases where there is failure of response to conservative management after 6 months.

• Impingement syndrome of supraspinatus tendon due to narrowing of scapular outlet
• OA of AC joint
• Frozen shoulder and chronic shoulder pain/limitation of movement⁸