Description

• The acromioclavicular (AC) joint is formed by the articulation of the distal clavicle and the scapular acromion
• It is stabilized by the AC ligament, coracoclavicular (CC) ligament, and attachments from deltoid and trapezius muscles
  • AC ligament is responsible for horizontal stability
  • CC ligament is responsible for vertical stability
• Rockwood classification (sequential injury pattern):
  • Type I:
    • No visible deformity
    • Sprained AC ligament (AC joint tender)
    • Intact joint capsule
    • No CC ligament injury (nontender)
    • No deltoid or trapezius injury
    • No radiographic abnormality (clinical diagnosis)
  • Type II:
    • Ruptured AC ligament (AC joint tender) (distal clavicle horizontally unstable)
    • Ruptured joint capsule
    • Sprained CC ligament (CC ligament tender)
    • Minimal deltoid and trapezius injury
    • Radiographs show slight widening of AC joint (normal <5 mm)
    • Normal CC space (11–13 mm)
  • Type III:
    • Ruptured AC ligament (AC joint tender) (distal clavicle horizontally unstable)
    • Ruptured joint capsule
    • Ruptured CC ligament (CC ligament tender) (distal clavicle vertically unstable)
    • Detached deltoid and trapezius
    • Complete AC dislocation
    • Radiographs show widening of AC joint
    • Increased CC space, with distal clavicle above superior aspect of acromion (100% displaced)
  • Types IV, V, and VI:
    • Cause more significant pain than types I, II, and III
    • Best visualized on lateral/axillary radiographs
    • All require operative treatment
    • Greater risk for prolonged disability
  • Type IV:
    • Identical ligamentous/muscular injury pattern to type III
    • Clavicle is displaced posteriorly into trapezius muscle
    • Posteriorly displaced clavicle may be palpable on exam
    • May cause tenting of skin posteriorly
  • Type V:
    • Rare
    • Identical ligamentous/muscular injury pattern to type III
    • Clavicle is displaced superiorly above the trapezius (100–300% increase in CC space)
    • Shoulder droops severely
    • Clavicle may be palpated subcutaneously
    • May cause tenting, ischemia, or disruption of skin
  • Type VI:
    • Usually associated with severe trauma with multiple injuries
    • Identical ligamentous/muscular injury pattern to type III
    • Clavicle is displaced inferiorly into subacromial or subcoracoid location
    • Shoulder appears flattened
    • Associated neurovascular injury is common

Etiology

• Injury most commonly seen in young, active males during contact sports
• Most common mechanism is direct trauma to superior or lateral shoulder while arm is adducted, usually in the setting of a fall:
  • Acromion is displaced inferomedially
  • Clavicle remains stabilized by sternoclavicular ligaments
• May also occur indirectly via a fall on an outstretched hand or elbow, with transmission of force to the AC joint

Signs and Symptoms

• Pain to anterior or superior aspect of the shoulder following trauma
• Pain exacerbated by moving arm across the chest, behind the back, or overhead
• Mechanism/force will dictate suspicion for and pattern of injury
• Associated neurovascular symptoms
• Cervical spine symptoms

• Exam in standing or sitting position, as supine position negates force of gravity which can mask joint instability
• Inspection: Ecchymosis, abrasion, swelling, symmetry, deformity of AC joint, skin tenting, or laceration
  • Prominence of clavicle with sagging of the acromion indicates rupture of AC joint (Rockwood type II injury or greater)
• Palpation: Sequential exam of sternoclavicular joint, length of clavicle, AC joint, CC ligament, coracoid process, scapular spine, and proximal humerus
  • Tenderness over AC joint indicates AC ligament injury (Rockwood type I injury or greater)
  • Horizontal instability of distal clavicle indicates AC ligament rupture (Rockwood type II injury or greater)
  • Tenderness over CC ligament indicates CC ligament injury (Rockwood type II injury or greater)
  • Vertical instability of distal clavicle indicates CC ligament rupture (Rockwood type III injury or greater)
• Special tests:
  • Cross-body adduction test:
    • Arm elevated to 90 degrees with elbow flexed at 90 degrees, and adducted across chest
    • Pain confirms AC injury by specifically compressing the joint
    • Sensitivity 77%, specificity 79%
  • O'Brien test:
    • Arm elevated to 90 degrees with elbow in extension, adduction of 10–15 degrees and maximum forearm pronation
    • Examiner applies downward force against resistance
    • Pain over top of shoulder confirms AC injury
    • Sensitivity 16–93%, specificity 90–95%
• Complete distal neurovascular exam, including brachial plexus
• Careful cervical spine exam

Essential Workup

• History to seek mechanisms that commonly cause AC joint injury and associated force
• Physical exam to evaluate for injury pattern, neurovascular compromise and exclude other causes of pain
• Radiographic evaluation as outlined below

Diagnostic Tests and Interpretation

• Specific AC joint radiograph:
  • Recommended if AC injury suspected
  • Should include bilateral AC joints (for comparison)
  • Standard shoulder views will over penetrate AC joint and may obscure subtle injuries
  • Stress views no longer recommended
• Zanca view (10–15 degrees cephalic tilt to remove scapula from field) for limited initial views
• Axillary view for type III–VI injuries to determine position of distal clavicle
• CT or MRI for further evaluation of surgical cases (Rockwood types IV–VI)
  • Angiography may be used to evaluate associated neurovascular injuries
  • US if CT/MRI is not available

Differential Diagnosis

• Shoulder dislocation
• Fractures of acromion or clavicle
• Rotator cuff injury
• Tendinitis
• Capsulitis
• Cervical radiculopathy
• Osteoarthritis
• Osteomyelitis

• Pediatric clavicle encased in periosteal tube:
  • CC ligament within tube
  • AC ligament external to tube (more vulnerable)
• AC joint injury rarely occurs in isolation in the pediatric population
• When injury does occur, it is more often type I or II
• Distal clavicular fractures through physis are more common than type III AC joint dislocations

Pre Hospital

• Ice packs
• Sling immobilization
• Cervical spine immobilization if indicated

Initial Stabilization/Therapy

• Ice packs
• Sling immobilization
• Cervical spine immobilization if indicated
• Analgesia (NSAIDs, other analgesics)

Ed Treatment/Procedures

• Types I and II:
  • Rest, ice, analgesics
  • Brief sling immobilization (typically 3–7 d)
  • Range of motion (ROM) and strengthening exercises as soon as can be tolerated
  • Resume normal activities once painless ROM and strength have returned (2–4 wk)
• Type III:
  • Rest, ice, analgesics
  • Sling immobilization and early (within 72 hr) orthopedic referral
• Treatment plan is controversial as insufficient evidence exists to favor one management strategy over the other (conservative vs. surgical)
  • Which approach is chosen may depend on general health of patient, level of activity, occupation, hand dominance, and risk for reinjury
  • Current trend is toward nonoperative management except for those with persistent symptoms and functional limitations after 6–12 wk
• Types IV, V, and VI:
  • Rest, ice, analgesics
  • Sling immobilization and immediate orthopedic referral
  • Require early surgical intervention
• Special circumstance: Potential future complication of AC joint injury is arthritis of the joint

• Types I and II:
  • Conservative management (rest, ice, analgesics, sling)
  • Should heal without major sequelae
• Type III:
  • Age <15 yr, conservative management
  • Age ≥15 yr may require more aggressive treatment
• Types IV, V, and VI:
  • Operative repair

Medication

• Ibuprofen: 600 mg (peds: 4–10 mg/kg) PO q.i.d
• Ketorolac: 30 mg (peds: 0.5 mg/kg up to 30 mg if >6 mo) IM/IV q6h (15 mg IM/IV q6h if >65 yr or <50 kg)

Disposition

• Open injury
• Types IV, V, and VI require admission for operative repair

• Types I and II can be discharged with orthopedic referral
• Type III should have urgent orthopedic referral

Follow-Up Recommendations

• Type I and II: Orthopedic follow-up within 2–4 wk
• Type III: Early (within 72 hr) orthopedic follow-up
• Type IV–VI: Immediate orthopedic referral
• All pediatric injuries should have prompt orthopedic follow-up, with type IV–VI injuries requiring immediate referral

See Also

• Clavicle Fracture
• Shoulder Dislocation
• Sternoclavicular Joint Injury