ACROMIOCLAVICULAR SEPARATIONS: MODIFIED WEAVER-DUNN TECHNIQUE

Acromioclavicular Separations

Modified Weaver-Dunn Technique

David S. Morrison and Mark J. Scheer

The acromioclavicular (AC) joint is a diarthrodial joint, with fibrocartilage covering the articular surfaces between the medial end of the acromion and the distal end of the clavicle. The AC ligaments (anterior, posterior, superior, inferior) resist horizontal displacement of the joint, and the fibers of the deltoid and trapezius blend into the superior ligament to further resist displacement. The coracoclavicular (CC) ligaments (trapezoid and conoid) attach to the underside of the distal one third of the clavicle and resist vertical displacement. The average space between the coracoid and clavicle is 1.1 to 1.3 cm.

Classification

The current accepted classification of AC injuries is based on six types depending on amount of displacement from the coracoid and direction of the displacement (superior, posterior, or inferior).

1. Type I—sprain of the AC ligaments. X-rays normal.

2. Type II—tearing of AC ligaments. Distal end of the clavicle slightly superior to acromion and mobile in superior-inferior direction. X-rays show minimal upward displacement of distal clavicle with AC joint widened.

3. Type III—complete disruption of both AC and CC ligaments. X-rays show distal clavicle above the superior border of acromion. CC inter-space widened 25 to 100%, mobile in superior-inferior direction, slightly mobile in anteroposterior direction.

4. Type IV—type III with distal clavicle displaced posterior into or through the trapezius. Axillary view shows posterior displacement of distal clavicle, mobile in superior-inferior direction.

5. Type V—type III with distal clavicle severely displaced superiorly. Deltoid and trapezius aponeurosis avulsed from distal clavicle. Distal clavicle lies subcutaneously and often the overlying skin is blanched. X-rays show CC interspace widened 100 to 300%, mobile in superior-inferior direction, very mobile in anteroposterior direction.

6. Type VI—inferior displacement of distal clavicle under acromion (subacromial) or coracoid (subcoracoid). Usually results from direct blow to superior surface of distal clavicle with arm abducted and scapula retracted. X-rays show decreased CC interspace.

Indications

Acute

1. Types I and II—conservative management with sling and rest for 7 to 10 days; no heavy lifting for 6 weeks.

2. Type III—surgical intervention is controversial (athletes vs. laborers vs. sedentary; see “Special Considerations” subpoint 3). Surgery indicated for tenting of the skin with vascular compromise.

3. Types IV, V, VI—surgical intervention recommended.

Chronic Symptomatic

1. Type II—controversial (AC resection vs. AC resection with CC ligament reconstruction)

2. Type III—reconstruction with or without distal clavicle resection

3. Types IV, V, VI—reconstruction with or without distal clavicle resection

Contraindications

1. Patient uncooperative with postop restrictions

2. Medically contraindicated

Mechanism of Injury

Acromioclavicular separations occur from either a direct or an indirect mechanism. The majority of AC injuries occur as a result of a direct blow to the superior aspect of the shoulder with the arm adducted, causing a shearing force at the joint. An indirect mechanism usually results from a fall on an outstretched arm causing both shearing and compressive forces at the joint.

Physical Examination

1. Associated findings for AC injury:

a. Soft tissue abrasions or ecchymosis

b. Tenderness over AC joint

c. Prominent distal clavicle (types III and V)

d. Prominent acromion (types IV and VI)

e. Blanching of the skin (type V)

f. Superior-inferior ballottement: greater instability may help distinguish types III to V from type II (there is 3 to 5 mm of ballottement in type II)

g. Anterior-posterior displacement with traction on the arm in types III and V (there is no anteroposterior instability in type II)

2. Associated injuries:

a. Fracture of the coracoid, acromion, midclavicle, and/or distal clavicle into AC joint

b. Type VI: pneumothorax, pulmonary contusion

Diagnostic Tests

1. Routine radiographs:

a. Anteroposterior and anteroposterior in 20 degrees cephalad: assess degree of displacement of AC joint

b. Axillary view: assess position of distal clavicle

c. Weighted views of both shoulders are of questionable value (may help differentiate type II from type III)

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