To review, this is a 50 year-old woman with right shoulder pain after direct fall. Her physical examination shows tenderness to palpation over the distal clavicle.
Questions and Answers:
1) What is the suspected diagnosis based on history, examination, and imaging?
The patient has tenderness at the distal clavicle and just inferior to the distal clavicle; this is the location of the AC joint and indicates some level of acromioclavicular (AC) injury with the possibility of further shoulder separation. See below for normal shoulder joint and ligamentous anatomy.
Shoulder separations are classically defined using the Rockwell classification schema, which is described below:
Any patient who has AC joint tenderness on physical examination should undergo axial strain testing to evaluate for any joint instability. To perform axial strain testing, the examiner places one hand on the AC joint and assesses the distance between clavicle and acromion process without axial strain. The examiner places the other hand on the upper arm and applies gentle axial traction to the humerus. Any widening of the AC joint when axial traction is applied to the shoulder girdle is concerning for a separation that is greater than grade I.
Based on the above schema, this patient has clear widening of her AC joint of less than 50%, and therefore has at least a grade II shoulder separation based on Rockwell classification.
2) What are the next steps in evaluation?
Based on this patient's initial radiographs, she has a grade II shoulder separation and can be sent home with a sling and instructions to follow-up as needed. However, this patient may have a more serious shoulder injury that could be unmasked with further imaging. Approximately 51% of patients with normal AC joints have significantly underriding clavicles at baseline and threfore may have undetected grade III and grade V injuries, as even a displacement of < 50% may actually be a significant deviation from their baseline anatomy and indicate full rupture of both the AC and coracoclavicular (CC) joints.
To account for this, Rockwood's initial classification schema required bilateral shoulder radiographs in the diagnosis of normal anatomy. Recent studies have redemonstrated the importance of bilateral films in the appropriate diagnosis of AC injuries. 52% of patients patients with grade II or grade III shoulder separations on unilateral films were upgraded to grade V shoulder separations after the addition of bilateral films. Any patient with AC laxity on axial strain or radiographically visible shoulder separation on unilateral shoulder film should receive bilateral shoulder films for appropriate CC comparison and diagnosis of operative shoulder separations.
3) What are the next steps in management?
All patients with shoulder separations should be given a sling and appropriate analgesic. Patients who have diagnosed grade IV or V separations should receive orthopedic follow-up within 3-5 days to discuss operative fixation. patients with grades I-II shoulder separation after confirmatory radiographs can be instructed to follow-up with their primary care as needed, and those with grade III shoulder separations should follow-up with an orthopedist or their primary care physician within 1-2 weeks.
Anatomy image courtesy of Taylor Nichols
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Schneider et al. Inter- and intraobserver reliability of the Rockwood classification in acute acromioclavicular joint dislocations. Knee Surg Sports Traumatol Arthrosc (2016)24:2192-2196