14.2: Acromioclavicular Joint Separation

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Acromioclavicular (AC) Joint Separation/Dislocation

Case

Acromioclavicular joint dislocation

Clinical:

History – 21 year old female injured her shoulder while wrestling.

Symptoms – This patient complained of a deformed, painful, end of her right collar bone.

Physical – There was swelling and tenderness of the region of the acromioclavicular joint.

DDx:

Acromioclavicular Joint Separation

Clavicle Fracture

Acromion Fracture

Hematoma

Imaging Recommendation

ACR – MSK – Acute Shoulder Pain, Variant 1

Shoulder X-ray

ODIN Link to AC Joint Separation images, Figure 14.2A and B: mistr.usask.ca/odin/?caseID=20150209202015857

Figure 14.2A X-ray of the right shoulder, Y-view, with AC joint separation

Figure 14.2B X-ray of the right shoulder, AP, with AC joint separation

Imaging Assessment

Findings:

The lateral clavicle was displaced cranially and the acromioclavicular joint was widened. The coracoclavicular distance was also widened.

Interpretation:

Acromioclavicular joint dislocation, Type 3.

Diagnosis:

Acromioclavicular joint dislocation

Discussion:

Acromioclavicular joint injuries can be graded on the 6-point Rockwood scale:

Type	AC Joint	CC Joint	Reducibility	Treatment
I	Sprain	Normal	NA	Conservative
II	Torn	Sprain – CC distance <25% of the contralateral side	Reducible	Conservative
III	Torn	Torn – CC distance increased 25 – 100 % of the contralateral side	Reducible or Non-Reducible	Conservative or Surgical
IV	Torn	Torn – Posterior displacement of clavicle into the trapezius muscle	Not Reducible	Surgery
V	Torn	Torn – CC distance > 100% of the contralateral side with the clavicle protruding through the delto-trapezial fascia	Not Reducible	Surgery
VI	Torn	Torn – Clavicle caudal to the subacromial or subcoracoid	Not Reducible	Surgery

Figure 14.3 Acromioclavicular injury classification

X-ray findings may include:

Minor injuries of this joint space usually involve only the joint capsule and the acromioclavicular ligament.
With more severe injuries the coracoclavicular ligament may be torn leading to a more displaced clavicle and a wider coracoclavicular distance.
Severe injuries can involve the coracoclavicular ligament, the deltoid muscle and the trapezius muscle.

Attributions

Figure 14.2A X-ray of the right shoulder with AC joint separation by Dr. Brent Burbridge MD, FRCPC, University Medical Imaging Consultants, College of Medicine, University of Saskatchewan is used under a CC-BY-NC-SA 4.0 license.

Figure 14.2B X-ray of the right shoulder with AC joint separation by Dr. Brent Burbridge MD, FRCPC, University Medical Imaging Consultants, College of Medicine, University of Saskatchewan is used under a CC-BY-NC-SA 4.0 license.

Figure 14.3 Acromioclavicular injury classification. Courtesy of Dr. Roberto Schubert, Radiopaedia.org, RID: 19124. Originally published at https://radiopaedia.org/cases/rockwood-classification-system-of-acromioclavicular-joint-injuries under a Creative Commons Attribution-Non-commercial-Share Alike 3.0 License.