Arthroscopic Acromioclavicular Joint Stabilization

 

 

 

DEFINITION

Acromioclavicular (AC) separations are relatively rare injuries that result in disruption of the AC joint complex.

Overall incidence of injury is 3 to 4 per 100,000 in the general population, with up to 52% occurring during sporting events.4

The degree of injury is based on the amount of force transmitted through the acromion to the distal clavicle and the surrounding deltotrapezial fascia.1,18,24

Increasing force leads to dissociation of the AC joint and tearing of the coracoclavicular ligaments. Determination of the injury type will indicate operative versus nonoperative management.18

 

 

ANATOMY

 

The AC joint is a diarthrodial joint composed of the medial acromial margin and distal clavicle.

 

 

 

A fibrocartilaginous intra-articular disc between the two bony ends decreases contact stresses.17,18,19 Dynamic stability of the AC joint is provided by the trapezial fascia and the overlying anterior deltoid.

 

The AC joint is statically stabilized by the following:

 

 

AC ligaments

 

 

 

Anterior and posterior capsular thickenings Superior and inferior capsular thickenings

 

Coracoclavicular ligaments

 

 

 

Conoid: arises from the posteromedial aspect of the coracoid and inserts on the posteromedial clavicle Measures up to 2.5 cm long and 1 cm wide5,18,20

 

Provides resistance to anterior and superior loading6,8,13,14

 

Trapezoid: arises from the anterolateral coracoid just posterior to the pectoralis minor and attaches to the lateral/central clavicle

 

 

Measures up to 2.5 cm long and 2.5 cm wide5,18,20

 

Provides resistance to compression and posterior loading6,8,14

 

PATHOGENESIS

Mechanism of Injury

 

AC separations are the result of a direct force to the lateral aspect of the shoulder with the arm adducted (ie, fall on point of the shoulder).1,8,10,14,18,19,24

 

The degree of injury to the AC joint, deltotrapezial fascia, and/or coracoclavicular ligaments will determine the resultant deformity.

 

Most low-grade injuries involve only the AC ligaments and are often self-limited.

 

 

 

Severe arm abduction can result in subacromial or subcoracoid displacement of the clavicle.18 Pain localized to the AC joint and a visual deformity will be present with high-grade injuries.

PHYSICAL FINDINGS

 

A complete physical examination of both upper extremities with the patient appropriately attired and in the upright position is critical.

 

Evaluation of the neck is also important as with any upper extremity examination.

 

Complete neurologic examination is essential as higher grade injuries may manifest brachial plexus compromise.

 

Low-grade injuries will be tender to palpation at the AC joint, with mild elevation possible. Increased deformity will be seen as injury grade increases, but acutely may be masked by swelling.

 

Classification

 

Rockwood (modification of Allman, Tossy, and Bannister's work) described six types of injuries to the AC joint.1,2,18,24

 

This classification scheme has proven to be effective for prognosis and treatment.

 

 

Type I: The AC and coracoclavicular ligaments are intact.

 

Type II: The AC ligament is completely torn but the coracoclavicular ligaments are intact with partial subluxation of the AC joint.

 

Type III: complete disruption of the AC ligaments and coracoclavicular ligaments. Degree of separation is up to 100% of the coracoclavicular interval.

 

Type IV: posterior displacement of the clavicle through the trapezius muscle

 

Type V: severe displacement with 100% to 300% increase in coracoclavicular interval (Bannister III-C); includes injury to the deltotrapezial fascia

 

Type VI: inferior displacement of the clavicle to a subacromial or subcoracoid position

 

IMAGING STUDIES

 

Standard shoulder radiographs can be useful for diagnosis, but overpenetrance may result in poor visualization of the AC joint.

 

Include an axillary view to avoid missing a dislocation and to help assess anteroposterior translation of the clavicle.

 

A 10- to 15-degree cephalic tilt (Zanca) view avoids the scapular spine and allows improved view of the AC joint. This view also allows evaluation for loose bodies or small fractures that may be missed with standard

views of the shoulder18 (FIG 1).

 

 

P.115

 

 

 

 

FIG 1 • Zanca view.

 

 

Stress radiographs

 

 

Standing views with 10 to 15 pounds of traction applied to the wrists are recommended by some authors to help distinguish the grade of injury as the patient may guard with standard standing views.

 

Recent literature does not support the routine use of stress radiographs. They do not affect the decision-making process for operative versus nonoperative management.18,19,26

DIFFERENTIAL DIAGNOSIS

 

 

 

 

Distal clavicle fracture Sternoclavicular dislocation Glenohumeral dislocation Scapulothoracic dissociation

NONOPERATIVE MANAGEMENT

 

Types I and II

 

 

Most authors agree that nonoperative management is the treatment of choice of these incomplete injuries.1,9,12,17,18,19,22,24,25

 

 

A simple sling for comfort is used, with progression to range of motion as tolerated in 1 to 2 weeks. Return to sports is authorized when the patient has painfree range of motion and normal strength.

 

Type III

 

Controversial. Conservative treatment is often successful.2,3,12,17,18,21,22

 

Sling for comfort, range-of-motion exercises, and avoidance of contact sports for 6 to 8 weeks may suffice. Padding the residual deformity for contact athletes may be necessary. Recurrence of injury may lead to a higher grade injury.

 

Types IV to VI are typically treated operatively.2,4,7,11,12,14,16,18,19,22,23,24

 

SURGICAL MANAGEMENT

Indications

Rockwood types III to VI in active patients unwilling to accept the dysfunction and the cosmetic deformity of the affected shoulder

Arthroscopic AC resection should be considered even in younger patients without degenerative changes as the potential exists for the development of painful AC joint arthrosis.

Currently, we rarely perform a distal clavicle resection when managing acute injuries.

 

 

Preoperative Planning

 

Thorough evaluation of all radiologic studies to rule out associated fractures of the clavicle, coracoid, or glenoid is mandatory.

 

Scrutinize films together with a careful physical examination to diagnose sternoclavicular or glenohumeral injuries.

 

Positioning

 

Standard beach-chair positioning is used, with all bony and soft tissue prominences well padded.

 

The use of an arm holder (McConnell Orthopaedics, Greenville, TX; the Spider, Tenet Medical Engineering, Inc., Calgary, Canada; or Trimano, Arthrex, Inc., Naples, FL) is optional.

 

Preparation is done in the standard fashion. We prefer to use an arthroscopy drape.

TECHNIQUES

• Dog Bone Button Fixation (Arthrex, Inc., Naples, FL)

The Dog Bone Button is a precontoured titanium button that allows the use of multiple FiberTapes for AC joint reduction.

The technique allows for a quick and relatively simple arthroscopic fixation of acute and subacute AC separations.

The Dog Bone Button technique uses FiberTape, which has increased tensile strength over the Tightrope system, which uses no. 5 FiberWire.

Standard shoulder arthroscopy portals are used. Identify anatomy and portals.

Coracoid Acromion

Extent of clavicle length and width

 

 

 

AC joint Posterior portal

 

Anterior superior lateral portal slightly more anterior and inferior than normal, coming in at a slight angle in both the coronal and axial plane

 

Low anterior portal lateral to the coracoid

 

Posterior portal is created for viewing 2 cm inferior and 2 cm medial to the posterolateral edge of the acromion in the “soft spot.”

 

Enter the glenohumeral joint using standard technique.

 

An 18-gauge spinal needle can be used to create the anterior superior lateral portal with an “outside-in technique.”

 

Introduce an 8-mm cannula to assist with pressure control.

 

Use a shaver or electrocautery probe through the anterior superior lateral portal to open the rotator interval and expose the coracoid along the inferior border all the way to the base (TECH FIG 1A).

 

Create a low anterior portal lateral to the coracoid and insert a 10-mm PassPort Button Cannula.

 

Tip: Cut a small wedge out of the articular portion of the PassPort to allow for a better fit next to the coracoid.

 

Tip: A 70-degree arthroscope can aid in visualization of the inferior coracoid.

 

Place the appropriate AC guide under the coracoid base through the low anterior portal (TECH FIG 1B).

 

 

P.116

 

 

Make a small incision in line with Langer lines over the distal clavicle (TECH FIG 1C). Drill through the clavicle and coracoid with a 2.4-mm cannulated drill (TECH FIG 1D).

 

Remove the trocar from the drill and pass the SutureLasso SD Wire Loop through the drill cannulation loop first and retrieve it through the low anterior cannula (TECH FIG 1E).

 

Insert the FiberTape Loop and a TigerTape Loop into the slots of a Dog Bone Button so that the tapes form a U-shape (TECH FIG 1F).

 

Pull the suture and Dog Bone Button through the low anterior cannula until the Dog Bone Button abuts the inferior coracoid (TECH FIG 1G).

 

Tip: Use a grasping instrument to turn the button sideways and push it through the cannula.

 

 

 

TECH FIG 1 • A. Coracoid base. B. Drill guide through low anterior portal straddling the undersurface of the coracoid. C. Distal clavicle superior incision. D. Cannulated 2.4-mm drill passing through distal clavicle and coracoid. E. Passing the SutureLasso through the cannulated drill bit. F. FiberTape and TigerTape inserted into Dog Bone Button. G. Dog Bone Button seated on the inferior coracoid. H. Square knots on superior button.

 

 

Insert the suture limbs exiting the superior clavicle into a second Dog Bone Button.

 

 

The upper extremity is then elevated with the arm in adduction and the AC joint is maximally reduced. Square knots are placed over the superior suture button (TECH FIG 1H).

 

The suture ends should be left about 1 cm long to allow the knot to lay flat under the soft tissues.

 

For additional stability, the soft tissue capsule of the AC joint can be sutured as this is an important component to AC stability. Tears in the deltotrapezial fascia can also be oversewn.

 

The wounds are closed and dressed in the usual fashion.

 

 

P.117

Pearls

Pitfalls

• Trim the internal portion of the

PassPort to allow better access to the coracoid.

• A 70-degree arthroscope through the

posterior portal can enhance visualization.

• Trying to use a 30-degree scope for the entire case

will require additional portals and still not optimize the view.

• The AC joint should be slightly

overreduced to allow for potential creep.

• Use the 2.4-mm drill for the coracoid.

• A 3.5-mm drill if slightly off can predispose the patient

to a coracoid fracture and lack of fixation.

PEARLS AND PITFALLS

 

 

POSTOPERATIVE CARE

 

 

 

This fixation is secure, but a supportive sling should be used for 6 weeks. Range of motion about the elbow, wrist, and hand is permitted immediately. Gentle Codman or pendulum exercises in the sling are also permitted.

 

 

Motion is limited until the 6-week mark, at which time full motion is permitted. No heavy work or athletics are permitted for 3 months.

 

Radiographs postoperatively are compared to radiographs at the 6 week return visit.

 

Weight lifting is allowed at 3 months, and when strength and fitness allows, sports may be resumed.

COMPLICATIONS

Coracoid fracture15 Suture failure Clavicle fracture Loss of reduction Infection

Suprascapular neurovascular bundle injury Loss of range of motion

Repeat procedure

 

 

 

 

OUTCOMES

The Dog Bone fixation system is a relatively new system for treatment of acute and subacute high-grade AC separations. It is not intended for chronic injuries. No longterm studies or prospective randomized trials are currently available.

 

 

REFERENCES

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