High Yield Topics

Acromioclavicular Separations (Types 1–6)

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Acromioclavicular Separations (Types 1–6)
Anne S. Boyd
Shannon Woods
Basics
  • Separation of the clavicle and acromion due to injury of the acromioclavicular (AC) and coracoclavicular (CC) ligaments
  • Classified based on the degree of separation and the anatomical structures that are involved (types I–VI)
  • AC ligament is the main static stabilizing force for the AC joint in the anterior-posterior direction:
    • This ligament blends with the trapezius and deltoid fascia to form the AC capsule and provide static stability to the joint (1).
  • CC ligament is the main static stabilizing force for the AC joint in the superior and inferior direction:
    • This ligament comprises the trapezoid and conoid ligaments (2).
  • Synonym(s): Shoulder separation; Shoulder sprain; AC sprain; AC dislocation; Shoulder dislocation (misname; term primarily refers to glenohumeral dislocation)
Description
  • Type I:
    • Mild sprain of the AC ligament, some fiber disruption
    • Position of clavicle: No change
  • Type II:
    • Complete tear of the AC ligament with an intact CC ligament
    • Position of clavicle: Slight subluxation of the AC joint
  • Type III:
    • Complete AC and CC ligament tear
    • Position of clavicle: 100% AC joint dislocation in a superior direction, representing 25–100% increase in coracoclavicular separation vs the noninvolved side
  • Type IV:
    • Complete AC and CC ligament tear
    • Clavicle displaced posteriorly into trapezius
    • Deltoid and trapezius detached
    • Axillary view on radiographs reveals injury extent
    • Surgical referral immediately
  • Type V:
    • Complete AC and CC ligament tear
    • Position of clavicle: Also thought of as a large type III, there is 100–300% change in CC separation and may see disruption of the deltoid and trapezius attachments to the clavicle
  • Type VI:
    • Complete AC and CC ligament tear
    • Position of clavicle: 100% inferior AC joint displacement, usually with distal clavicle wedged underneath coracoid process. There is potential damage to the underlying brachial plexus and subclavian vessels.
Epidemiology
  • Direct trauma to an unprotected shoulder, such as when tackling an opponent without shoulder pads
  • Falling directly upon the “point” of shoulder, such as when diving for a baseball
  • Upward indirect force, fall on outstretched hand, force directed cranially through humeral head to AC joint
  • Downward indirect force, sudden change in load through upper extremity, usually heavier weight
Incidence
  • Males are 5 times more likely to suffer injuries than females.
  • Nearly 45% of all AC dislocations occur to individuals in their 20s.
  • Type I and II injuries account for the majority of AC dislocations.
Commonly Associated Conditions
  • Fracture injuries are associated with a type III–V AC dislocation in 5% of patients (3).
  • Intra-articular injuries are associated with a type III–V AC dislocation in 18% of patients:
    • Shoulder labrum/SLAP tears reported in 5–14% (3).
    • Rotator cuff tears reported in ∼4% (3).
Diagnosis
History
  • Exact mechanism of injury (to assess the severity of the injury and the possibility of associated injuries)
  • Neurologic symptoms or vascular symptoms (which indicate a more severe injury and may require immediate surgery)
Physical Exam
  • Pain at the AC joint
  • Pain during forward flexion and/or adduction of the shoulder, over shoulder motions, direct weight-bearing, abduction of shoulder
  • Deformity (step-off) of AC joint with type III injuries and higher
  • Inspection (asymmetry of the shoulders)
  • Palpation (point tenderness of the affected AC joint) (2)
  • Range of motion decrease due to pain adduction > abduction > flexion
  • Crossover or scarf test: Flexion of shoulder to 90 degrees and forced adduction across chest to reproduce pain over the AC joint (2)
  • Careful neurovascular examination
Diagnostic Tests & Interpretation
Imaging
  • True shoulder anteroposterior (AP), scapular Y, and axillary views are the standard views for the shoulder:
    • Zanca views of both shoulders (try to get on same cassette): To identify fractures of the clavicle, acromion, or coracoid, and to preliminarily evaluate AC joint separation and CC ligament disruption (2)
    • Axillary lateral view helps to distinguish a type III dislocation from a type IV. A type IV will show the scapula anterior to the clavicle. Many patients may be unable to tolerate this view, and a computed tomography scan may be required (2).

    • P.15


  • Zanca view: An AP of the shoulder with the central beam directed 10–15 degrees cephalad towards the clavicle, and with slightly reduced penetration (since the AC joint is superficial and will be overpenetrated with regular beam strength).
  • Stress views (weighted views) can be used to differentiate types I–III, but are not recommended, as the results do not affect treatment, and disruption of the CC ligament (larger space between coracoid and clavicle on the affected side) can be seen on the standard AP.
  • Stryker notch views to assess for coracoid fracture when indicated (2)
  • The average distance between the inferior aspect of the clavicle and the coracoid is 1.1–1.3 cm. This value can vary, so it is important to compare to the unaffected side.
Diagnostic Procedures/Surgery
  • CT scan may be required to assess for other bony injuries not well visualized on plain radiographs.
  • Magnetic resonance imaging (MRI) may be utilized to assess for concomitant soft tissue injuries, especially in older patients or those with systemic ailments that may make the patient at increased risk, such as diabetes.
  • Rarely is an injection required to confirm diagnosis.
Differential Diagnosis
  • Fractures of the coracoid, acromion, or clavicle
  • Rotator cuff injuries
  • SLAP/shoulder labrum lesion
  • Glenohumeral dislocation
  • Burner/stinger (neurogenic)
  • Cervical spine injuries
  • Pneumothorax (rare)
  • Gorhams massive osteolysis
  • Gout
  • Neoplasm (multiple myeloma)
Treatment
  • Types I and II:
    • Shoulder sling for several days (average of 3–7 days) for pain reduction and comfort
    • Ice and analgesics for pain and swelling:
      • Generally, fewer than 1–2 wks of analgesia are needed.
    • Range of motion exercises early in course; the sooner the better (4).
    • Rotator cuff, scapular stabilization, and trunk strengthening exercises as pain resolves
  • Type III:
    • Dependent upon patient usage/expectations: Nonsurgical vs surgical repair. Studies indicate good outcome with nonsurgical management, as detailed under types I and II:
      • ∼80% of individuals are subjectively satisfied with their nonoperative outcomes based on pain and function.
      • Some strength loss might occur after injury, particularly with bench press. Some evidence to suggest less strength loss with operative treatment (4).
    • Consider surgical referral, particularly in throwers, heavy manual laborers, high-level athletes, patients unwilling to tolerate cosmetic deformity, and those who fail nonoperative management (4).
  • Types IV–VI:
    • Surgical referral
Additional Treatment
Additional Therapies
  • Types I and II: Shoulder range of motion and strengthening exercise are introduced as pain subsides. Full return to contact when full, painless range of motion and normal strength resumes.
  • Type III: Shoulder strengthening exercises are introduced when range of motion and pain are improved. Return to contact sports usually is anticipated in 6 wks–6 mos, depending on resumption of full painless range of motion and normal strength.
Surgery/Other Procedures
Types IV–VI usually require operative treatment.
Ongoing Care
  • Type IV–VI refer to orthopedics.
  • Refer type III in high-level athletes, patients unwilling to have conservative therapy, heavy manual laborers, patients unwilling to tolerate the deformity, and patients who have failed nonoperative treatment after 3–6 mos
Prognosis
Reports suggest that up to 40% of individuals with type I or II injures will go on to develop osteoarthritis at the AC joint (1).
Complications
  • Cosmetic deformity and AC joint arthritis are common complications.
  • Many patients note intermittent pain and/or clicking, often referred to as nuisance symptoms. These symptoms may require an injection or further physical therapy.
  • Rarely, distal clavicle osteolysis may occur.
References
1. Rudzki JR, Matava MJ, Paletta GA. Complications of treatment of acromioclavicular and sternoclavicular joint injuries. Clin Sports Med. 2003;22:387–405.
2. Mazzocca AD, Arciero RA, Bicos J. Evaluation and treatment of acromioclavicular joint injuries. Am J Sports Med. 2007;35:316–329.
3. Tischer T, Salzmann GM, El-Azab H, et al. Incidence of associated injuries with acute acromioclavicular joint dislocations types III through V. Am J Sports Med. 2008;37:136–139.
4. Buss DD, Watts JD. Acromioclavicular injuries in the throwing athlete. Clin Sports Med. 2003;22:327–341, vii.
Codes
ICD9
831.04 Closed dislocation of acromioclavicular (joint)
Clinical Pearls
  • In general, full return to contact sports is possible when painless range of motion and normal strength are achieved. However, type I sprains are stable, so the athlete may return immediately if strength is normal and pain is tolerable and will not limit his athletic abilities.
  • Cosmetic deformity and AC joint arthritis are common complications.


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