ACJ Separation

The clavicle and acromium articulate with each other via a cartilaginous meniscus.  Joint integrity is maintained by the acromioclavicular ligament, between the acromium and the clavicle and the coracohumeral and corcoacromial ligaments beneath the joint.  Injury results in separation of the joint and can be classified according to Post and Rockwood’s definitions.

Injury results in separation of the joint.







Fracture Type
Injury Pattern


Sprain of Acromioclavicular Ligament AC joint in tact Coracoclavicular ligaments intact Deltoid and trapezius muscles intact A mild force , usually to the point of the shoulder produces a minor strain to the fibres of the acromioclavicular ligaments but they stay intact and the join remains stable.

Not indicated

Acromioclavicular joint disrupted Acromioclavicular joint wider : may be a slight vertical displacement compared to the other side. Sprain of the coracoclavicular ligaments. Coracoclavicular interspace may be slightly increased Deltoid and trapezius muscles intact A moderate force to the point of the shoulder is severe enough to rupture the ligaments of the acromioclavicular joint. The distal end of the clavicle is unstable in the horizontal plane (AP) but stable in the vertical plane (superoinferiorly) as the coracoclavicular ligament is intact. The scapula may rotate medially further widening the ACJ. The distal end of the clavicle may be slightly raised.


Not indicated
Acromioclavicular ligaments disrupted Acromioclavicular joint dislocated and the shoulder complex displaced inferiorly Coracoclavicular ligaments disrupted Coracoclavicular interspace 25% to 100% greater than the normal shoulder. Deltoid and trapezius muscles usually detached from the distal end of the clavicle. Variants “Pseudodislocation” through intact periosteal sleeve Physeal injury Coracoid process fracture A severe enough force causes complete dislocation of the ACJ. The distal end of the clavicle is displaced superiorly and the scapular and shoulder joint droop inferomedially. The deltoid and trapezius muscles are displaced from the distal clavicle.


Acromioclavicular ligaments disrupted ACJ dislocated and clavicle anatomically displaced posteriorly into or through the trapezius muscle. Coracoclavicular ligaments totally disrupted Corcoclavicular space may be displaced but may appear the same as the normal shoulder Deltoid and trapezius muscles detached from the distal clavicle The clavicle is posteriorly displaced into or through the trapezius muscle as the force applied to the acromium drives the scapular anteriorly and inferiorly.It may otherwise be known as anterior scapular dislocation. Bipolar clavicular dislocation ie sternoclavicular and acromioclavicular dislocation,is even more rare.


Acromioclavicular ligaments disrupted Coracoclavicular ligaments disprupted Acromioclvicular joint dislocated and gross disparity between the clavicle and the scapula (100%to 300% greater) Deltoid and trapezius muscles detached from the distal half of the clavicle. The distal clavicle is stripped of all its soft tissue attachments( acromioclavicular ligaments , coracoclavicular ligament, and the deltotrapezius muscle attachments) and lies subcutaneously near the base of the neck. When combined with superior displacement of the clavicle owing to unopposed pull of the sternocleomastoid muscle, the severe downward droop of the arm.


Acromioclavicular ligaments are disrupted. Coracoclavicular ligaments
also disrupted in subcoracoid type and intact in subacromial type.
Acromioclavicular joint is dislocated and clavicle displaced
inferiorly to the acromium or coracoid process. Coracoclavicular
interspace reversed in the subcoracoid type (ie clavicle inferior to
the coracoid) or decreased in the subcromial type (ie clavicle
inferior to the acromium).
Deltoid and trapezius muscles detached from the distal clavicle. This
type is very rare and often accompanied by multiple injuies.The
mechanism of injury is thought to be severe hyperabduction and
external rotation of the armcombined with retraction of the scapula.



Types I and II do not, in isolation, require early surgical intervention.
However, late post traumatic, osteoarthritis can occur, which may be significantly symptomatic (pain when carrying weights and high elevation) to warrant treatment in the form of injections or surgery.

When surgery is indicated to reconstruct the ACJ, this is best done very early after injury, ideally within the first 3 weeks. Surgical intervention is designed to reduce the clavicle (replace it in the correct position) and stabilize the clavicle by reconstructing the coracoclavicular ligaments (which will have been torn), as well as the coracoacromial ligaments. Some of the surgical reconstruction options include the ” Tightrope” or the “Surgilig” implants.

Further more the joint itself will have been disrupted , often a tear of the meniscus ( internal “floating” cartilage) will occur. Sometimes it is possible to repair and reconstruct this meniscus and the joint; but often the degree of disruption and damage is so great as to preclude successful reconstruction. In this case, an excision hemi arthroplasty can be considered, which entails removing a small section of the lateral end of the clavicle and half the A.C.Joint, leaving a gap of approx 10 mm. These options should be discussed with the surgeon.