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Acromioclavicular Joint Separation

  • AC joint injuries range from a mild sprain of the supporting ligaments to a complete separation of the AC joint.
  • The AC joint is a diarthrodial joint formed by the distal clavicle and the medial facet of the acromion.
    • Interposed in the joint is a fibrocartilaginous disc, which helps distribute the forces from the upper extremity to the axial skeleton.
  • The AC joint has a thin capsule that is stabilized by anterior, posterior, superior, and inferior AC ligaments.
    • These AC ligaments provide horizontal joint stability to the AC joint.
    • The superior AC ligament is the most important of these 4 ligaments.
  • The coracoclavicular (the trapezoid and conoid) ligaments pass from the inferior surface of the clavicle to the base of the coracoid process of the scapula.
    • These strong ligaments provide vertical stability to the AC joint.
  • Tossy et al. originally classified AC joint injuries into 3 types; Rockwood et al. later added 3 more types to complete the current classification system based on physical examination findings and radiographs.
    • Type I: Sprain of the AC ligaments only; no displacement of the distal clavicle
    • Type II: Disrupted AC ligaments and joint capsule; intact coracoclavicular ligaments; <10% vertical subluxation of the clavicle
    • Type III: Disrupted AC ligaments, coracoclavicular ligaments, and joint capsule; complete separation of the AC joint with the clavicle displaced superiorly; complete loss of contact between the clavicle and acromion
    • Type IV: Disrupted AC ligaments, coracoclavicular ligaments, and joint capsule; completely displaced AC joint with the clavicle displaced posteriorly into or through the trapezius muscle
    • Type V: Disrupted AC ligaments, coracoclavicular ligaments, and joint capsule; completely displaced AC joint with the clavicle displaced superiorly (>300%); distal clavicle detached from the deltoid and the trapezius.
    • Type VI: Disrupted AC ligaments, coracoclavicular ligaments, and joint capsule; completely displaced AC joint with the clavicle displaced inferiorly to the acromion and coracoid process.
General Prevention
No effective preventive measures are known.
  • AC joint injuries represent approximately 40% of shoulder injuries in athletes.
  • This injury is especially common in athletes participating in hockey, rugby, football, wrestling, and lacrosse.
  • Peak incidence is in the second decade of life.
  • The injury is rare in skeletally immature patients.
  • The injury is 5 times more common in males than in females.
  • Type I and type II injuries each occur twice as frequently as the other types.
  • Most of these injuries result from direct trauma; classically, when an individual lands on the point of the shoulder.
  • The AC joint is at risk for traumatic injury because of its subcutaneous position on the top of the shoulder.
  • The magnitude of the force determines the injury severity and the structures involved.
    • Typically, the force is absorbed initially by the AC ligaments.
    • If the force is great enough, the coracoclavicular ligaments and deltotrapezial fascia are affected.
  • Indirect trauma, such as a fall on a flexed elbow or outstretched arm, also may lead to AC joint injury.
Associated Conditions
  • Fractures of the distal clavicle or the coracoid
  • Brachial plexopathy
Signs and Symptoms
Injury to the AC joint should be suspected in anyone with pain after a traumatic injury to the shoulder region.
Physical Exam
  • Inspection may reveal prominence of the outer end of the clavicle, abrasion, or swelling in the area of the AC joint.
  • Palpation reveals local tenderness and swelling.
  • A palpable step-off may be felt in type III to VI separations.
  • Pain is associated with arm movements.
  • Hypermobility of the clavicle is difficult to appreciate in the acute situation because of patient discomfort.
  • In type VI injuries, the shoulder has a flat appearance with a prominent acromion.
  • Radiographic evaluation should include an AP view of the AC joint and an axillary view of the shoulder.
    • Axillary views are useful for evaluating the position of the distal clavicle with respect to the acromion in the anteroposterior plane, particularly in type IV injuries.
  • A 15° cephalic-tilt view (Zanca view) is useful for assessing joint displacement and intra-articular fractures.
  • Stress or weighted radiographs are not recommended because of their ineffectiveness and because of patient discomfort.
Differential Diagnosis
  • Clavicle fracture, in which tenderness usually is located more medially and more swelling is present
  • Epiphyseal separation of the clavicle
  • Shoulder dislocation
General Measures
  • Type I injuries lack evidence of instability and should be treated nonoperatively: A sling (for up to 1 week), analgesic medication to provide comfort, and ice to reduce swelling.
  • Type II injuries are treated similarly to type I injuries: A sling (for up to 2 weeks), analgesics, and ice as necessary for patient comfort.
  • Treatment of type III injuries remains controversial.
    • Surgical treatment has no proven distinct advantage over nonoperative care, and currently most authors recommend nonoperative treatment except for overhead athletes and heavy manual laborers, open injuries, and patients with brachial plexopathy.
    • Nonoperative treatment is similar to that used for type I and II injuries: A sling (up to 4 weeks) followed by gentle mobilization and strengthening.
  • Early surgical treatment is recommended for all type IV, V, and VI injuries.
  • Type I injuries:
    • Return to sports should not be allowed until the athlete has painless ROM.
    • Most athletes return to competition within 2 weeks.
  • Type II injuries:
    • Return to athletic activity is predicated on the restoration of painless motion and strength.
    • Most athletes return to competition by 8 weeks.
  • Type III injuries:
    • Guarded return to sports and work are allowed after a period of sling immobilization, depending on the return of full painless ROM and the stability of the joint.
    • The time to return to sports is controversial, and many high-level athletes never return to their previous levels of function with nonoperative treatment.
Medication (Drugs)
First Line
An analgesic of choice is given for 4 weeks.
  • Surgical treatment is recommended for:
    • Open injuries
    • Closed type IV, V, and VI injuries
    • Patients who sustain type III injuries but continue to have pain and discomfort despite an adequate trial of nonoperative therapy
  • Some clinicians (2,4) also recommend surgery for:
    • Type III injuries in overhead athletes and heavy manual laborers
    • Patients with brachial plexopathy
  • Surgical treatment options for type III injuries include:
    • Dynamic muscle transfers
    • Primary AC joint fixation
    • Primary coracoclavicular ligament fixation
    • Distal clavicle excision with or without coracoclavicular ligament reconstruction
  • A dynamic muscle transfer may be performed as the tip of the coracoid process and the attached coracobrachialis and short head of the biceps are transferred to the undersurface of the clavicle. This technique:
    • Risks nonunion and musculocutaneous nerve injury
    • Has a high rate of failure with persistent pain
    • Is recommended only for patients with chronic injuries that failed nonoperative treatment
  • Primary AC joint transfixion may be performed using wires, pins, plates, or screws. This procedure:
    • Usually is undertaken with repair or reconstruction of the AC or coracoclavicular ligaments
    • Currently is unpopular because of risks of loss of fixation, pin breakage, and pin migration, and the necessity for a 2nd surgical procedure for hardware removal
  • Primary coracoclavicular ligament fixation with a coracoclavicular screw may be performed with or without supplemental repair of the coracoclavicular ligaments.
    • This procedure is limited by the necessity for a 2nd surgical procedure for hardware removal.
  • The most commonly performed surgical intervention for AC separation is an anatomic reconstruction of the injured ligaments.
    • Reconstruction of the coracoclavicular ligaments is performed by using the coracoacromial ligament as a substitute, and by the placement of a synthetic augmentation device (such as a band made of absorbable braid or ribbon) between the coracoid and clavicle.
    • Distal clavicle excision often is used to supplement this procedure.
  • Increasingly popular is reconstruction at the coracoclavicular ligaments with a free tendon graft, which allows anatomic reconstruction and obviates the need for supplemental fixation.
  • Surgical treatment options for type IV injuries include:
    • Closed reduction, converting the injury to a type III, and then treating nonoperatively or with open reduction (see Surgery outlined earlier)
    • Meticulous closure of the deltotrapezial fascia over the clavicle augments stability
  • Type V injuries are treated surgically with one of the procedures described earlier. Again, care is taken to close meticulously the deltotrapezial fascia.
  • Type VI injuries are rare.
    • Reduction is rarely achieved in a closed fashion.
    • Distal clavicle excision aids in reduction.
  • Excellent results in >90% of all patients (5)
  • Excellent results in nearly 100% of patients with type I and type II injuries
  • Most patients return to their usual activities in several months.
  • Complications may occur as a result of the injury or its treatment.
  • Complications related to the injury include:
    • Associated fractures of the distal clavicle or the coracoid
    • Propensity toward degenerative arthritis of the AC joint and osteolysis of the distal clavicle
  • Complications related to surgical treatment include:
    • Injury to the great vessels
    • Possible mortality related to pin migration
    • Continued pain if resection of the distal clavicle is inadequate, particularly if the joint remains unstable
    • Compromised stability if clavicle resection is excessive
    • Erosion into the clavicle by synthetic augmentation devices
    • Wound infection
    • Osteomyelitis
    • AC arthritis
    • Late fracture
    • Recurrent deformity


Q: Are stress views recommended in the evaluation of AC separations?
A: No. They only subject the patient to unnecessary pain, without providing additional useful information.
Q: What is the role of braces to reduce the joint (such as a Kenny-Howard brace)?
A: These braces are no longer widely used because of the risk of pressure sores and because of good results with only a simple sling.
Q: If an athlete suffers an AC separation, what is the timeframe for return to sports/competition?
A: The answer depends on the severity of the injury:
  • Type I: 2 weeks for most
  • Type II: 8 weeks for most
  • Type III: 3 months or more
  • Types IV, V, and VI: 6 months after surgical stabilization

1 comment to Acromioclavicular Joint Separation

  • Спасибо за объяснение. Все гениальное просто….




    AC joint injuries range from a mild sprain of the supporting ligaments to a complete separation of the AC joint…..