Acromioclavicular Joint Injury

Basics

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

Etiology

  • Injury mostly seen in young, active males during contact sports. One of the most common injuries of the shoulder girdle (4–12%)
  • 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 as the humeral head compresses the acromion

Diagnosis

Signs And Symptoms

History

  • 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

Physical Exam

  • Exam in standing or sitting position, as supine position negates force of gravity which can mask joint instability
  • Inspection: Arm held in adduction, 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° with elbow flexed at 90°, and adducted across chest
      • Pain confirms AC injury by specifically compressing the joint
      • Sensitivity 77%, specificity 79%
    • O’Brien test:
      • Arm elevated to 90° with elbow in extension, adduction of 10–15° 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

Imaging

  • 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° 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
  • Shoulder appears flattened
  • Associated neurovascular injury is common

Pediatric Considerations

  • 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

Treatment

Prehospital

  • 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

Pediatric Considerations

  • 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: 10 mg/kg) PO q6h PRN pain
  • 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)

Follow-Up

Disposition

Admission Criteria

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

Discharge Criteria

  • 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

Pearls And Pitfalls

  • Poor correlation between Rockwood classification and pain
  • Type I and II AC injuries:
    • No increase in CC space
    • Conservative management with rest, ice, sling, and ROM/strength exercises
  • Type III injuries:
    • 100% superior displacement of distal clavicle
    • Management somewhat controversial
    • Require early orthopedic follow-up
  • Type IV–VI injuries:
    • Identical ligamentous and muscular injuries to type III
    • Difference according to position of distal clavicle
    • Operative management is standard of care

Additional Readings

  1. Boström Windhamre H, von Heideken J, Une-Larsson V, Ekström W, Ekelund A. No difference in clinical outcome at 2-year follow-up in patients with type III and V acromioclavicular joint dislocation treated with hook plate or physiotherapy: a randomized controlled trial. J Shoulder Elbow Surg. 2022;31(6):1122–1136.  [PMID:35007749]
  2. Granville-Chapman J, Torrance E, Rashid A, Funk L. The Rockwood classification in acute acromioclavicular joint injury does not correlate with symptoms. J Orthop Surg (Hong Kong). 2018;26(2):2309499018777886.
  3. Shaw KA, Synovec J, Eichinger J, Tucker CJ, Grassbaugh JA, Parada SA. Stress radiographs for evaluating acromioclavicular joint separations in an active-duty patient population: what have we learned? J Orthop. 2018;15(1):159–163.  [PMID:29657459]
  4. Stucken C, Cohen SB. Management of acromioclavicular joint injuries. Orthop Clin N Am. 2015;46(1):57–66.
  5. Tamaoki MJS, Lenza M, Matsunaga FT, Belloti JC, Matsumoto MH, Faloppa F. Surgical versus conservative interventions for treating acromioclavicular dislocation of the shoulder in adults. Cochrane Database Syst Rev. 2019;10(10)CD007429.
  6. Wahal N, Kendirci AS, Abondano C, Tauber M, Martetschläger F. Acromioclavicular joint lesions in adolescents: a systematic review and treatment guidelines. J Clin Med. 2023;12(17):5650.  [PMID:37685716]
  7. Younis F, Ajwani S, Bibi A, Riley E, Hughes PJ. Operative versus non-operative treatment of grade III acromioclavicular joint dislocations and the use of SurgiLig: a retrospective review. Ortop Traumatol Rehabil. 2017;19(6):523–530.  [PMID:29493522]

See Also (Topic, Algorithm, Electronic Media Element)

Authors

Grant M. Schumaker

Robert Steele