Acromioclavicular Joint Injury

The acromioclavicular joint is stabilised horizontally by its capsule and ligaments (the posterior part is most important) and vertically by the coracoclavicular ligaments (conoid and trapezoid), with additional support from the deltotrapezial fascia. Injury follows a fall onto the point of the shoulder with the arm adducted, common in contact sport and cycling, and about 9% of shoulder girdle injuries. Young men are most affected.

Types (by direction and degree of displacement):

• Type I: sprain of the joint ligaments, normal alignment
• Type II: torn acromioclavicular ligaments, sprained coracoclavicular ligaments, mild widening
• Type III: both torn, the clavicle displaced upward (the coracoclavicular distance increased 25 to 100%)
• Type IV: the clavicle displaced backward into the trapezius
• Type V: gross upward displacement (over 100%) with deltotrapezial detachment
• Type VI: inferior displacement beneath the coracoid (rare)

Complications are persistent pain, post-traumatic acromioclavicular arthritis, distal clavicle osteolysis, chronic instability, skin tenting, and associated clavicle, coracoid or rib fracture.

• Pain and swelling over the joint, a step off deformity, tenderness at the joint, and pain with cross body adduction
• A piano key sign (the clavicle depresses with downward pressure and springs back)
• Painful elevation beyond 90 degrees
• Red flags: skin tenting or threatened skin, neurovascular compromise, dyspnoea (pneumothorax), a mass of the medial clavicle (a concurrent injury) and high energy mechanism

• Radiographs: bilateral anteroposterior views with a 10 to 15 degree cephalic tilt, and an axillary view for posterior displacement. Weighted views are not needed.
• Measurements: the coracoclavicular distance is about 11 to 13 mm, and an increase of 25% or more compared with the other side indicates coracoclavicular injury. The acromioclavicular interval is normally under 7 mm.
• CT for fracture and posterior displacement. Ultrasound for dynamic assessment.
• MRI when associated labral or cuff injury is suspected.

Differentials: distal clavicle fracture, coracoid fracture, sternoclavicular injury, cuff tear, labral tear, glenohumeral dislocation.

Types I and II: sling for 1 to 2 weeks, ice, paracetamol 1 g orally every 6 hours (maximum 4 g a day), ibuprofen 400 mg orally every 8 hours with food for up to 7 days, early motion and strengthening. Return to contact sport at 2 to 4 weeks (type I) and 6 to 12 weeks (type II).

Type III: begin non-operatively with a sling for 2 to 4 weeks and 6 to 12 weeks of rehabilitation. Surgery for persistent pain or instability, overhead athletes and heavy manual workers.

Types IV to VI: surgery.

• Within 3 weeks: repair or reconstruct the coracoclavicular ligaments, using a graft (semitendinosus or similar) through tunnels in the clavicle and coracoid with cortical button devices. A hook plate is an option, removed at 3 to 6 months. Repair the deltotrapezial fascia.
• Chronic: graft reconstruction.
• Cefazolin 2 g IV before incision (3 g if over 120 kg).
• Postoperative: sling for 4 to 6 weeks, no lifting for 3 months, sport at 4 to 6 months.

Post-traumatic arthritis: injection of triamcinolone acetonide 10 mg with lidocaine 1% 1 mL into the joint under ultrasound guidance. Distal clavicle excision of 5 to 10 mm for refractory pain.

Complications of surgery: loss of reduction (10 to 30%), fracture through tunnels, infection, hardware irritation, osteolysis and wound problems.

Follow up at 2 weeks, 6 weeks, 3 months and 6 months. Counsel that a bump may persist without functional loss.