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AC Joint Separation


  • tears of AC & CC ligaments (from fall on tip of shoulder) allows upper limb to drop away from clavicle, producing separation of AC joint;

differential diagnosis

  • distal clavicular physeal separation
    • childhood equivalent of AC separation;
  • atraumatic AC joint laxity (from ligamentous laxity)



Rockwood Classification

  • type I
    • sprain of joint with out a complete tear of either ligament
  • type II
    • tear of AC ligaments w/ coracoclavicular ligaments intact;
    • will not show marked elevation of lateral end of clavicle;
  • type III
    • in this injury both AC & CC ligaments are torn;
    • > 5 mm elevation of AC joint w/o weights is consistent w/ severe type II or a type III injury;
    • need to distinguish this from type III clavicular fracture
  • type IV
    • distal clavicle impaled posteriorly into trapezial fascia;
  • type V

SHO99 SHO100 SHO161





Basamania Classification

  • essentially relies on whether the distal clavicle is stable or unstable;
  • w/ more than 50-75 % displacement on static films or more than 100% displacement on a cross arm AP, there will be disruption of not only the AC ligaments but also the CC ligaments;
  • clinically, an unstable AC separation will cause significant prominence of the distal end of the clavicle when the arm is distracted in adduction;

SHO82AC Separation 6AC Separation 4 AC Separation 5






  • Cross Body Adduction View
    • (from C.J. Basamania MD personal communication, 1997);

SHO99 SHO100 SHO161





case example

AC Joint 1 AC Joint 2 AC Joint 3 AC Joint 4





  • 20-year-old who fell on tip of right shoulder, but did not show radiographic signs of AC joint injury in the ER;
  • one month later the patient continued to have pain, and radiographs demonstrated greater than 100 percent displacement of AC joint on both AP and Cross Body AP (Cross Adduction View);

Operative Treatment