Most commonly occur with a direct blow to the shoulder. 9-12% of shoulder injuries have Acromioclavicular (AC) joint involvement.

• Peak incidence is ages of 20-29, most commonly males who play contact sports.
• The majority of patients with an isolated, low-grade (Type I-III) AC separation can be discharged home and managed on an outpatient basis.
• Higher grade separations (Type IV-VI) may require surgical repair.

History

• Direct lateral or superior blow to the acromion, usually with the arm in an adducted position.
• Less commonly with a fall on outstretched hand (FOOSH) injury.
• Pain, deformity, or instability over the AC joint, worsened by arm elevation.

Physical

• Rule out brachial plexus involvement – cervical spine screen, distal neurological and vascular examination.
• Rule out injury to associated structures via palpation (Sternoclavicular joint, clavicle, acromion, scapula, coracoid process, humerus).
• Swelling and tenderness located at the AC joint; deformity, prominence or displacement of the clavicle may be noted in higher-grade injuries.

If the injury is mild and diagnosis unclear, special testing can be performed (see Related Information for videos):

• • Cross-body adduction test (77% sensitivity, 79% specificity).
    • Passively hold the patient’s straight arm at 90 degrees of shoulder flexion, in neutral rotation; then passively horizontally adduct across the patient’s body.
    • A positive test is indicated by the reproduction of pain.

Source: Musculoskeletal Key

O’Brien (active compression) test (41% sensitivity; 94% specificity).

• • Instruct patient to flex shoulder to 90 degrees, and horizontally adduct by 10-15 degrees.
  • Passively internally rotate the arm maximally, and ask the patient to resist an inferiorly directed force (positive test = provocation of pain).
  • Repeat with arm in an externally rotated position (pain should be reduced/absent).

Source: BMJ (https://bjsm.bmj.com/content/42/8/628).

Imaging

Radiographs

• Suspected AC joint injury should initially be evaluated with a plain x-ray.
  • Recommend single AP radiograph of both shoulders for maximal detail; arm placed in internal rotation.
  • If initial views are non-diagnostic, consider an AP glenoid, or Zanca view: Xray taken with a 10-15 cephalad angle to better demonstrate the acromioclavicular joint free from superimposition.
  • An axillary view can be used to rule out coracoid fracture or to confirm clavicle position in Type III-IV separations (see Grading).
• Stress (weighted) views are no longer recommended due to limited diagnostic value and pain.

Other

• Ultrasound or MRI for detailed evaluation are typically ordered on an outpatient basis – not an ED order.
• Evaluation with CT is not recommended.

Grading

Created by Ella Barrett-Chan, UBC MSI3, 2023

Conservative Management

• Rest, ice, and analgesics PRN.
• Shoulder immobilization (see below for specific recommendations by injury type).
• Shoulder range of motion exercises as soon as tolerated to minimize the risk of adhesive capsulitis.
• Referral to primary care physician and/or physiotherapy for ongoing management.

Management by Injury Type

Type I-II

• Conservative management.
• Sling for <3-7 days.
• Recovery timelines: Type I = 1-2 weeks; Type II = 3-4 weeks.

Type III

• Urgent referral (3-7 days) to orthopedics indicated for consideration of operative repair, though conservative management usually adequate.
• Sling for <2-3 weeks.
• Recovery timeline: 6-12 weeks.

Type IV-VI

• Requires referral for orthopedic evaluation for consideration of operative repair.
• If neurovascular compromise is present, referral should be emergent.
• Prognosis variable.

1. Acromioclavicular joint injuries (“separated” shoulder)
   Koehler SM. Updated Feb 4, 2021. Accessed Apr 15, 2021.
   – UpToDate.

   
   

2. Acute Shoulder Injuries in Adults.
   Monica J, Vredenburgh Z, Korsh J, et al.  2016;94(2):119-127.
   – American Family Physician Journal

   
   

3. Acromioclavicular Separation – Emergency Management. 
   Silverio L.   Updated Nov 30, 2018. Accessed Apr 15, 2021.
   – Dynamed.

   
   

4. Special test links:

   The shoulder
   Musculoskeletal key
   – Musculoskeletal Insight Engine