Acromioclavicular Joint Injuries: Rockwood Classification, Clinical Features and Treatment

Acromioclavicular joint injuries are common in athletes and workers who use heavy equipment and they occur in any age, specially 20-40 years age group, they represent more than 40% of all shoulder injuries.

Mild injuries are not associated with any significant morbidity while severe injuries are associated with chronic pain and significant loss of shoulder function.

Mechanism of injury

A fall on the shoulder with arm adducted → AC ligaments are torn first → CC ligaments are torn with higher forces leading to complete dislocation of the joint.

Fall onto an outstretched hand or elbow may also result in AC joint injures.

Classification

Injury is graded according to the Rockwood classification of AC joint injuries.

Rockwood classification is a 6 grade system and it is a modification of Allman and Tossy’s 3 grade system, the first and second grades are same in both systems, while grade three in Allman and Tossy classification is subdivided into four grades in Rockwood classification.

Rockwood classification classify AC joint injures based on:

• Acromioclavicular joint alignment
• Coracoclavicular ligament status
• Deltoid and trapezius muscles status (both attach to the lateral part of the clavicle)

Acromioclavicular joint normal anatomy

• The inferior edge of the clavicle bone and inferior edge of the acromion should be leveled (on the same line) on clavicle AP view with 20 degree cephalic tilt
• It is okay if the superior edges don’t match up
• The joint space should be uniform and joint distance less than 8 mm (normal 5-8 mm)
• Normal Coracoclavicular distance is between 11-13 mm and there should be no greater than 5 mm difference between right and left
• No soft tissue swelling

Normal Acromioclavicular joint

Rockwood Grade I

Described as AC joint sprain.

• The clavicle is not elevated in respect to acromion (X ray appears normal)
• Acromioclavicular ligament: sprained
• Coracoclavicular ligament: normal
• AC Joint capsule: normal
• Trapezius muscle: attached
• Deltoid muscle: attached

Rockwood Grade I, Yosi I, CC0, via Wikimedia Commons

Rockwood Grade II

Described as AC joint subluxation.

• Clavicle elevated but not above superior border of acromion
• Acromioclavicular ligament: torn
• Coracoclavicular ligament: sprained
• Joint capsule: torn
• Trapezius muscle: minimal detachment
• Deltoid muscle: minimal detachment

Rockwood Grade II, Yosi I, CC0, via Wikimedia Commons

Rockwood Grade III

AC joint dislocation.

• Clavicle elevated above the superior border of acromion, the coracoclavicular distance is less than 25 mm
• Acromioclavicular ligament: torn
• Coracoclavicular ligament: torn
• Joint capsule: torn and joint is dislocated
• Trapezius muscle: complete detachment
• Deltoid muscle: complete detachment

Rockwood Grade III, Yosi I, CC0, via Wikimedia Commons

Rockwood Grade IV

Result from posteriorly directed forces that make the clavicle penetrates the trapezius muscle, sometimes completely.

• Acromioclavicular ligament: torn
• Coracoclavicular ligament: torn
• Joint capsule: torn
• Trapezius muscle: complete detachment
• Deltoid muscle: complete detachment

Rockwood Grade IV, Yosi I, CC0, via Wikimedia Commons

Rockwood Grade V

• Clavicle is markedly elevated and coracoclavicular distance is more than 25 mm
• Acromioclavicular ligament: torn
• Coracoclavicular ligament: torn
• Joint capsule: torn
• Trapezius muscle: complete detachment
• Deltoid muscle: complete detachment

Rockwood Grade V, Yosi I, CC0, via Wikimedia Commons

Rockwood Grade VI

• Inferior displacement of clavicle beneath the coracoid process
• Acromioclavicular ligament: torn
• Coracoclavicular ligament: torn
• Joint capsule: torn
• Trapezius muscle: detached
• Deltoid muscle: detached

Rockwood Grade VI, Yosi I, CC0, via Wikimedia Commons

Clinical features

Patient complain of shoulder pain and swelling; and they can locate where the pain exactly is (AC joint).

On examination, there is tenderness while palpating the shoulder, if there is no deformity seen then the injury is either Grade I or II, but if there is deformity then it is Grade III, IV, V, VI.

Shoulder movements are limited due to pain but active abduction to 45 degrees would exclude rotator cuff tear.

Imaging

• AP clavicle with 20 degrees cephalic tilt: this view show inferior edge of the clavicle at the same line as the inferior edge of acromion
• Axillary views: confirm whether there is posterior displacement of the clavicle (Rockwood type IV)

Emergency management

• ATLS trauma protocol
• Closed reduction is not helpful in these injures
• Provide a sling and pain relief

Definitive management

• Grade 1 and 2 (sprains and subluxations) are treated with sling immobilization for around 1 week until pain subsides and patient encouraged to exercise shoulder, elbow and fingers
• Grade 3 (dislocations) is treated non operatively unless there is extreme prominence of the clavicle, or in patients who want to resume their strenuous overarm or overhead activities then treated operatively
• Grade 4, 5, 6 are treated operatively

Operative treatment include accurate reduction, and fixation of the clavicle with the acromion is done using a hook plate.

There is also the modified Weaver-Dunn procedure.

Modified Weaver-Dunn procedure

Modified Weaver-Dunn include excision of the lateral end of the clavicle and coracoacromial ligaments are transferred to the outer end of the clavicle and attached by trans osseous sutures.

Clavicle is anchored to the coracoid with anchors or slings to reduce the tension on the repair during the healing phase.

Elbow and forearm exercises begun one day after operation and assisted shoulder exercises are started 2 weeks later, active movements are started 4-6 weeks after and strenuous lifting is avoided for 6 months.

Complications

• Supraspinatus tendonitis: is sometimes associated with AC joint injures and supraspinatus tendinitis may occur directly due to the primary injury or may result from edema or inflammation occurring after the initial injury
• Unreduced dislocation: affects function, treated with reconstruction of CC ligaments, if failed then Modified Weaver-Dunn procedure is done
• Ossification of ligaments: especially in severe injures, ossification of ligaments lead to late rotator cuff dysfunction
• Osteoarthritis: is a late complication that might occur with these injures