CASE 138
By: Dr. Nizar Al-Nakshabandi MD, FRCPC
HISTORY: 39-year-old complaining of shoulder pain following direct blow to the shoulder.
What are your findings?
What is the diagnosis?
What are the causes?
FINDINGS:
The AP plain radiograph of the right shoulder [A] demonstrates a superior dislocation of the clavicle in relation to the acromion with increased distance reaching 1.5 cm. Furthermore, the coracoclavicular distance is markedly increased reaching 3.1 cm. Ultrasound of the right shoulder [B] short axis at the supraspinatus level demonstrates a full rupture of the supraspinatus tendon with retraction by approximately 3 cm.
Ultrasound of the right shoulder [C] at the level of the acromioclavicular joint demonstrates widening of the acromioclavicular distance reaching 1.5 cm confirming the plain radiograph finding.
DIAGNOSIS:
Type IV acromioclavicular joint separation.
CAUSES OF INJURY:
Direct blow to the acromioclavicular injury or fall on an abducted arm which pushes the acromion posteriorly.
Features of acromioclavicular joint injury include:
Soft tissue injury may be the only finding being grade 1 injuries.
Widening of the acromioclavicular distance by more than 2-4 mm asymmetry with and without weights should raise the suspicion of AC separation.
The coracoclavicular distance has a normal distance of 10-13 mm, whereas in grade 3 separation it is doubled.
The Rockwood classification of acromioclavicular joint injury is as follows:
· Type I: Clavicle not elevated with respect to the acromion.
o Acromioclavicular ligament: mild sprain.
o Coracoclavicular ligament: intact.
· Type II: Clavicle elevated but not above the superior border of the acromion.
o AC ligament: ruptured.
o CC ligament: sprain.
· Type III: Clavicle elevated above the superior border of the acromion but CC distance is less than twice normal (i.e. <25 mm).
o AC ligament: ruptured.
o CC ligament: ruptured.
· Type IV: Clavicle displaced posteriorly into trapezius.
o AC ligament: ruptured.
o CC ligament: ruptured.
· Type V: Clavicle is markedly elevated and CC distance is more than double normal (i.e. >25 mm).
o AC ligament: ruptured.
o CC ligament: ruptured.
· Type VI: Clavicle inferiorly displaced behind coracobrachialis and biceps tendons, which is rare.
o AC ligament: ruptured.
o CC ligament: ruptured.
FURTHER READING:
1. Rockwood CA, Williams GR, Young DC. Acromioclavicular injuries. In: Rockwood CA, Green DP, Bucholz RW, Heckman JD, editors. Fractures in Adults. 4th ed. Vol I. Philadelphia, PA: Lippincott-Raven; 1996. pp. 1341–1413.
2. Weissleder R, Wittenberg J, Harisinghani MG. Primer of diagnostic imaging. Mosby Inc. (2003) ISBN:0323023282.
