Acromioclavicular (AC) joint dislocation

By Jaime Moran MD, PGY-3

Edited by Dr. deSouza

Acromioclavicular joint dislocations: the “Separated” shoulder

EPIDEMIOLOGY & MECHANISM OF INJURY

9-12% of shoulder girdle injuries
More common in males
Usually results as a direct blow to the shoulder; less commonly fall onto an outstretched arm.
- Most commonly falling onto the shoulder while the arm is adducted to the side.

ANATOMY

Acromioclavicular joint: stabilized by 2 ligaments
- Acromioclavicular (AC) ligament provides horizontal stability; AC joint width is normally <3mm
- Coracoclavicular (CC) ligaments (trapezoid and conoid) provide vertical stability; CC joint distance is normally <5mm

PHYSICAL EXAM

Tenderness over the AC joint
In cases of significant ligamentous disruption, the distal clavicle may be superiorly displaced and be seen as a deformity at the top of the shoulder.

AC Compression test:
- AC joint cross-body adduction
- Pain elicited by passively adducting the patient’s arm, thereby compressing the AC joint

IMAGING

Routine shoulder XR
Consider different views:
- Bilateral AP to compare displacement to contralateral side
- Axillary lateral view is required to diagnose Type IV injury
- Zanca view – tilt the x-ray beam 10-15^O towards the head to avoid superimposing the scapular spine

ROCKWOOD CLASSIFICATION: 6 Types

Type	AC	CC	Displacement / XRs	Tx
I = sprain	Sprain	Intact	None	Sling 1-2 weeks; early ROM
II = subluxation	Torn	Sprain	Slight elevation of distal clavicle; CC distance <25%	Sling; ortho referral
III = dislocation	Torn	Torn	Elevated distal clavicle; increased CC distance 25-100%	Conservative v surgery?
IV = displacement	Torn	Torn	Posterior displacement of distal clavicle through the trapezius	Surgery
V = displacement	Torn	Torn	Superior displacement of distal clavicle; CC distance > 100%; disruption of muscular and fascial attachments of distal clavicle	Surgery
VI = displacement	Torn	Torn	Inferior displacement of distal clavicle into subacromial or subcoracoid position; Rare	Surgery

TREATMENT

Type I
- Sling, RICE, early ROM
Type II
- Sling until pain resolves
- Early ROM (helps prevent development of adhesive capsulitis)
- PT and rehab
- Avoid heavy lifting and contact sports for 3 mos. (while the ligaments heal so as not to convert the injury into a complete ligamentous tear)
Type III
- Controversial – immobilization v surgery?
- Bone Joint J 2013;95-B:1595–1602.
  - Systematic review
  - 28 studies – meta-analyses, systematic reviews, RCTs, case series
  - Limited evidence; most of the studies include heterogenous populations, different surgical techniques, and varying severities and chronicity of injury.
  - Conclusion: operative management results in better cosmetic and radiological results and similar functional outcomes, at the expense of longer time off work and increased complication rates. HOWEVER the lack of high-quality evidence makes it difficult to draw conclusions from this study.
- Sling
- Ortho referral
Types IV – VI
- Acute management with a sling
- Definitive treatment is surgical fixation

REFERENCES

Acromioclavicular joint injuries (“separated” shoulder). Uptodate. Accessed on 02/04/16 via http://www.uptodate.com/contents/acromioclavicular-joint-injuries-separated-shoulder?source=search_result&search=ac+joint+separation&selectedTitle=1~150.
Acromioclavicular Injuries. Orthobullets. Accessed on 02/04/26 via http://www.orthobullets.com/sports/3047/acromio-clavicular-injuries-ac-separation.
Modi CS. Controversies relating to the management of acromioclavicular joint dislocations. Bone Joint J 2013;95-B:1595–1602.
Rivers, C. 2011. “Shoulder Dislocations and Ligamentous Tears.” In Preparing for the Written board Exam in Emergency Medicine. 6^th Edition. Ohio ACEP. 411-412.
Simon R, Sherman S. 2011. “Shoulder”. In Emergency Orthopedics. 6^th Edition. McGraw-Hill. 338-340.