ACROMIOCLAVICULAR SEPARATIONS: ROCKWOOD SCREW TECHNIQUE FOR CHRONIC PROBLEMS

Acromioclavicular Separations

Rockwood Screw Technique for Chronic Problems

David M. Burt, Michael A. Wirth, and Charles A. Rockwood

Rockwood classified acromioclavicular (AC) joint injuries into six types:

1. A type I injury is a sprain of the AC ligament.

2. A type II injury involves disruption of the AC joint but the coracoclavicular (CC) ligaments remain intact.

3. Type III injuries occur when the AC joint is disrupted and the CC ligaments are completely torn, resulting in separation of the scapula from the clavicle. The radiographic appearance on anterior-posterior view shows an increase in distance between the coracoid and the clavicle of 25 to 100% when compared with the contralateral side.

4. In a type IV injury the clavicle is displaced posteriorly into or through the trapezius muscle.

5. Type V injuries are the same as type III but with greater distance between the coracoid and the clavicle. There may be displacement of 100 to 300% when compared with the contralateral side.

6. A type VI injury is an inferior dislocation of the clavicle, with the clavicle resting either below the acromion or below the coracoid.

Most authors agree that nonoperative management is the treatment of choice for types I and II injuries and that operative management is necessary for type IV and type VI injuries. Controversy exists over the appropriate management of type III and type V injuries. Those who advocate operative treatment are matched by an equal number of authors who prefer nonoperative management for these injuries. To date, no author has reported a randomized prospective trial comparing operative to nonoperative treatment of complete AC joint dislocations of similar grade (type III or type V).

Many procedures have been described to stabilize a complete disruption of the AC joint. In 1972, Weaver and Dunn described their technique of operative stabilization for acute and chronic complete AC joint dislocations. The procedure consists of resectional arthroplasty of the distal clavicle and transfer of the coracoacromial (CA) ligament into the medullary canal of the distal end of the clavicle. Rockwood has modified this technique in chronic AC joint dislocation, with the addition of a temporary coracoclavicular screw. The screw is similar to that originally described by Bosworth; however, the Rockwood screw has a nipple at the tip of the screw to more easily find the hole in the base of the coracoid. The purpose of the screw is to protect the CA ligament transfer while it heals. The screw is removed at 10 to 12 weeks.

Indications

Indications include chronic Rockwood types III, IV, V, and VI injuries of the AC joint.

Mechanism of Injury

The injury is produced by a direct blow to the superior aspect of the shoulder. This drives the scapula and humerus inferiorly, first disrupting the AC ligaments and then disrupting the CC ligaments.

Physical Examination

1. Tenderness and bruising over the AC joint.

2. Prominent distal end of the clavicle.

Diagnostic Tests

1. Standard radiographs of the shoulder should demonstrate the lesion.

2. It is essential to obtain an axillary lateral to determine if the clavicle is displaced posterior, resulting in a type IV problem.

3. Stress anteroposterior radiographs of both shoulders with 10 pound weights strapped to each wrist may better demonstrate the degree of displacement.

Special Considerations

We believe that a person with an acute grade III or greater AC dislocation who does heavy labor, and in certain young people (under age 25) who have not made up their minds for their future plans for work or sports, a surgical repair should performed. An exception to this would be the case of a person who regularly subjects his or her shoulder to violent, unprotected trauma (e.g., soccer, rugby, and hockey players). American football players after an acute grade III injury can perform quite well with special extra padding in their shoulder pads. Throwers can usually return to their sports with a grade III injury after 4 to 8 weeks. Of all the various operative procedures described for an acute (less than 4 weeks) injury to the acromioclavicular joint, primary excision of the distal clavicle seems to be the most unreasonable. When injuries are chronic (greater than 4 weeks), distal clavicle resection with transfer of the CA ligament and temporary CC lag screw fixation provides a very satisfactory method of reconstruction.

Special Instruments

We use a standard shoulder instrument set, which includes all items required for placement of the Rockwood screw (DePuy, Warsaw, IN). This includes screws, washers, depth gauge, drill bits, and self-retaining screwdriver. The Rockwood screw is a partially threaded cancellous lag screw with a nipple at the tip. The screw is inserted using a modified screwdriver, which captures and firmly holds the screw. This feature, as well as the nipple end of the screw, aids in accuracy of insertion. A 3/16–inch drill bit and 9/64-inch drill bit are required to drill the near and far cortices, respectively.

Anesthetic Options

1. General anesthesia is the preferred method.

2. Regional blocks are difficult and usually insufficient.

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