Acromioclavicular Joint Injuries

Introduction

The acromioclavicular joint is often overlooked when evaluating injuries to the shoulder girdle. This was noted back as far as 400 B.C. by Hypocrites. Whenever evaluating a patient for shoulder or neck pathology, evaluation of the acromioclavicular joint (AC joint) should be performed.

Anatomy

The shoulder complex is made up of multiple articulations including the sternoclavicular, scapulothoracic, glenohumeral, and the acromioclavicular joint. The AC joint allows transmission of force from the appendicular upper extremity to the axial skeleton. This is stabilized by the AC ligaments which are a condensation of the capsule at the AC joint. Further stabilization is afforded by the coracoclavicular ligament s, the trapezoid and the conoid.

Intra-articularly, there sits a small meniscoid disk which helps absorbs force in compression. This disk degenerates over time to the point where cadaveric studies show up to 50% degeneration of the disk. Also it has been shown that significant joint space narrowing occurs throughout life starting in the-second decade.

Acromioclavicular Separation

AC separation occurs with direct and, infrequently, indirect injuries to the shoulder. This is commonly seen with bicycling, where patients fall over the handlebars and land directly on their shoulder, or in skiing accidents.

The injury involves disruption of the AC as well as the coracoclavicular (CC) ligaments. In severe cases, injury to the deltotrapezial fascia also occurs.

Classification

The injuries are classified into six categories:

• Type I - Strain of the AC ligament with intact coracoclavicular ligament.
• Type II - Complete disruption of the AC ligament with a sprain of the CC ligament.
• Type III - Complete disruption of the AC and the CC ligaments with superior displacement of the clavicle, 25% - 100%.
• Type IV Posterior displacement of the clavicle.
• Type V Superior displacement of the clavicle in the subcutaneous position (more than l00% displacement).
• Type VI - Inferior displacement below the coracoid, this is rare.

Presentation

The patients usually present with a history of a direct blow to the shoulder with pain at the AC junction. InType II and more severe injuries, there will be a bump and swelling in this region.

Evaluation

Evaluation of the shoulder and neck should be performed at the time of the physical examination. often, hypermobility can be felt at the clavicle with respect to the acromion. Radiographic evaluation should include a shoulder series as well as a 200 cephalad AP of the clavicle. Weighted x-rays are not necessary.

Treatment

Initial treatment in the Emergency Room should be a sling for comfort, judicial use of analgesic medicines, and ice for swelling. orthopaedic consultation should be sought seven to ten days after the injury for further evaluation. If there is a neurologic deficit or an open injury, this becomes an open AC dislocation and should be emergently evaluated by an Orthopaedic Surgeon.

Subsequent treatment for the majority of these injuries include a sling for comfort for three to four weeks followed by a progressive range of motion and return to function. In type IV and V injuries, surgical reconstruction is appropriate. In type III, injuries that go on and become painful and unstable after six months to a year, reconstruction is also appropriate.

Acromioclavicular Osteoarthritis

This is common beginning with the second decade of life and can be associated with trauma or degeneration. 50% of adults over the age of 65 will have radiographic changes consistent with osteoarthritis of the AC joint. Symptoms usually are pain in the shoulder region especially with overhead activities and with abduction of the arm. For this reason, it is often misdiagnosed as rotator cuff tendonitis.

Physical therapy usually exacerbates this pain, whereas it usually improves rotator cuff tendonitis. Management of osteoarthritis of the AC joint includes: observation, nonsteroidal anti-inflammatories, iontophoresis, and judicious use of corticosteroid injections. If the patient continues to have pain and cannot live with this, then there is a role for distal clavicle excision, either arthroscopically or performed open depending upon the surgeon's preference.

Conclusion

AC joint injuries are an important source of pain in the shoulder region and must be evaluated. The management of these injuries is with nonoperative treatments in the majority of cases.