ACROMIOCLAVICULAR DISLOCATION

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Facts

• More common in males
• Occurs due to downward force applied to superior shoulder with upper extremity adducted
• Joint is covered by fibrocartilage and contains an intraarticular disc
• Joint inclination can be vertical to 50° medial
• AC ligaments reinforce thin joint capsule
  1. Fibers of the deltoid and trapezius (deltotrapezial fascia) blend with ligaments
  2. Confers AP stability to joint
• Vertical stability is provided by coracoclavicular (CC) ligaments: trapezoid (lateral), conoid (medial)
• Patients typically present with pain and swelling
• Abrasions over the distal clavicle are common
• Examine the seated patient with arm in dependent position
  1. Assess NV status and identify associated injuries
  2. Asymmetrical clavicular prominence may be apparent
     • This must be differentiated from a clavicle fracture
  3. Identify step offs and assess skin condition
  4. Point tenderness at the AC joint is common
  5. Pain is increased with attemped abduction of the arm
  6. Cross-body adduction test: most sensitive
     • From a position of 90° abduction and elbow extension, adduct arm across chest
     • Reproduction of pain is suggestive of AC joint pathology

Imaging

Radiographs

• AP, scapular Y (45° from coronal plane) and axillary (shoulder abducted 70° and beam shot through the axilla) views of the shoulder should be obtained
  1. Axillary view can visualize anterioposterior displacement
  2. Comparison with the contralateral shoulder is helpful

Normal AP shoulder

Normal scapular Y view

Normal axillary shoulder

• Zanca view: AP angled 20° cephalad
  1. Removes AC joint overlap with scapular spine
• Stress views: can be performed when suspicion is high but radiographs are negative
  1. AP view of both shoulders with 10 lb weights strapped to both wrists
  2. Differential CC widening suggests complete CC ligament disruption

Classification

• Rockwood:
  Type I: sprain
  1. Tenderness but radiographically normal

Type II: AC ligaments disrupted, CC ligaments intact 

1. AC joint may be widened (> 6 mm)
2. AP instability of joint

Type III: AC and CC ligaments disrupted 

1. Visible deformity, reducible with upward elbow pressure
2. AP and superior-inferior instability of joint
3. Widened AC and CC intervals

Type IV: posterior displacement of the distal clavicle through deltotrapezial fascia 

1. Prominence of clavicle over scapular spine
2. Clavicle posterior to acromion on axillary radiograph
3. Widened CC interval and dislocation of AC on AP radiograph

Type V: wide CC separation, distal clavicle through deltotrapezial fascia 

1. Visible deformity, nonreducible (buttonholed through deltotrapezial fascia)
2. Wide CC displacement

Type VI: inferior displacement of distal clavicle under coracoid 

Rockwood classification

• OTA: acromioclavicular (10-B)
  1. Anterior (theoretical)
  2. Posterior
  3. Superior
  4. Inferior
  5. Other

 

Treatment

• Nonoperative treatment: sling for comfort for 7-10 days followed by shoulder exercises, resume activities as tolerated
• Treatment by type:
  Type I: nonoperative
  Type II: nonoperative
  1. Persistent pain that cannot be controlled by NSAIDs or cortisone may require distal clavicle resection, ligament reconstruction and capsular plication

Type III: nonoperative treatment initially 

1. Most regain function (but deformity will persist)
2. Failed nonoperative treatment requires reconstruction of the CC ligaments
   • Most common is the Weaver-Dunn procedure (resect 2 cm of distal clavicle, CA ligament transfer to clavicle ± intraosseous sutures between coracoid and clavicle)
   • Allograft or autograft augmentation can also be performed
   • Deltotrapezial aponeurosis and capsule should be repaired

Type IV: early surgical treatment as in Type III
Type V: early surgical treatment as in Type III
Type VI: early surgical treatment as in Type III 

Complications

• Distal clavicle osteolysis: idiopathic process
• Pneumothorax: most commonly with type IV separation

 

 

Acromioclavicular joint dislocation Examination corner