Fact-sheet: Acromio clavicular dislocation
  • Acromioclavicular dislocation


Updated on 09/30/2019 at 10:33 AM

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Definition

Acromioclavicular dislocation is defined as partial/complete loss of contact between the acromion and the clavicle following elongation/rupture of one or more (or even all) of the acromioclavicular, coracoacromial, and coracoclavicular ligaments

Clinical features

Acromioclavicular dislocation most often occurs in young patients following a direct blow/a fall onto the shoulder.

Prominence of the distal clavicle (downward and posteriorly), more or less pronounced depending on the stage and the patient's build.

Point tenderness over the acromioclavicular joint. The presence of a piano-key mobility is then assessed. This refers to the finding of reduction of the dislocation or subluxation of the distal clavicle with simple manual pressure (stage II and III). In cases of incarceration or perforation of the deltotrapezial fascia by the clavicle (stage IV), this reduction may become impossible. The anteroposterior drawer sign is seen in stages III and IV.

Shoulder mobility examination may be normal but painful beyond 90° of abduction, as the acromioclavicular joint comes into play at this point.

Radiography

On radiographs, the dislocation manifests as a step-off between the acromion and the clavicle.

  • Stage I lesions: radiographs are normal
  • Stage II lesions: a slight widening of the joint space may be seen with preserved contact of the articular surfaces. There is sometimes slight superior displacement
  • Stage III and IV lesions: there is complete loss of contact between the two articular surfaces, both on the frontal view superiorly and on the lateral view posteriorly

Radiographs also allow an associated fracture to be ruled out.

Ultrasound

Ultrasound allows for:

  • assessment of the ligaments (visualization of a hematoma, in the form of a collection and hypoechoic infiltration in the soft tissues between the clavicle and the coracoid process, which can be considered an indirect sign of coracoclavicular ligament rupture)
  • assessment of instability
  • characterization of the inflammatory nature
  • guidance of the infiltration

CT

No indication

MRI

Preoperative workup for evaluation of the acromioclavicular, coracoacromial, and coracoclavicular ligaments, with detection of ligamentous thickening, T2 FAT SAT hyperintensity, or a discontinuity in cases of complete or partial rupture

Management

In isolated involvement of the acromioclavicular ligaments, without injury to the coracoclavicular ligaments, functional or orthopedic treatment appears to be sufficient.

In stage III and IV injuries, depending on the patient's age and any sports practiced, surgical treatment may be proposed.

Orthopedic treatment: consists of simple immobilization with an arm sling

Surgical treatment: numerous surgical techniques exist, aimed at restoring both the coracoclavicular and acromioclavicular ligamentous structures, with transient stabilization in some cases by acromioclavicular pinning or screw fixation

Classification

Several authors have proposed classifications.

Patte described acromioclavicular dislocations in 4 stages, a classification frequently used by surgeons:

  • Stage 1: simple sprain, partial ligament injury without clavicular instability
  • Stage 2: the acromioclavicular ligaments are stretched but not torn. Slight “piano key” mobility of the clavicle (vertical mobility), without any anteroposterior mobility
  • Stage 3: complete acromioclavicular dislocation with complete rupture of the acromioclavicular and coracoclavicular ligaments. Visible shoulder deformity with marked prominence of the distal clavicle, reducible by simple pressure ("piano key" sign). Abnormal anteroposterior mobility is also present.
  • Stage 4: same as stage 3, with rupture of the deltotrapezial fascia and subcutaneous prominence of the clavicle.

The radiographic classification is that of Rockwood, which comprises 4 stages:

  • Stage I: a simple acromioclavicular sprain with stretching but no rupture of the acromioclavicular ligaments. No instability is noted
  • Stage II: an acromioclavicular subluxation with rupture of the acromioclavicular ligaments, the coracoclavicular ligaments being stretched but not torn. A slight joint gapping is seen, with mild vertical "piano key" mobility and no abnormal anteroposterior mobility
  • Stage III: an acromioclavicular dislocation with complete and permanent loss of contact between the articular surfaces due to complete rupture of the acromioclavicular and coracoclavicular ligaments. The deformity is visible, with prominence of the distal clavicle reducible by simple pressure ("piano key" sign). Anteroposterior mobility (anteroposterior drawer) is also present
  • Stage IV: a stage III acromioclavicular dislocation in which the clavicle has perforated the deltotrapezial fascia. The distal clavicle is directly palpable under the skin. The distinction between stages III and IV can sometimes be difficult to establish.