Acromioclavicular Instability: Arthroscopic Repair and Reconstruction

Nathaniel Cohen

Phil Davidson

Treg Brown

INTRODUCTION

The treatment of acromioclavicular (AC) injuries continues to evolve. These injuries commonly occur from a fall on the lateral aspect of the shoulder or from a direct blow in a collision sport such as hockey or American football. The caudally directed force onto the superior aspect of the acromion process leads to injury and disruption of the AC ligaments. In higher-grade injuries disruption of the coracoclavicular (CC) ligaments also occurs. While lower-grade, minimally displaced injuries are treated nonoperatively, higher-grade displaced injuries are often managed surgically.

Over 150 different surgical techniques have been described in the literature for the management of AC injuries and dislocations.¹^,² Open and arthroscopic techniques frequently involve the use of a tendon graft to reconstruct the ligaments, while temporary stabilization of the AC joint is achieved with a plate, screw, suture loop, button, suture anchors, or similar devices. Unfortunately, the surgical treatment of AC joint injuries has been fraught with high rates of failure and complications. Reports show up to 80% of patients have loss of radiographic reduction and 20% to 30% of patients managed surgically undergo reoperation due to complications.²^,³ Many techniques, both open and arthroscopic, require drilling tunnels through the coracoid process, the clavicle, or both.⁴^,⁵ Unfortunately, it has been shown that these techniques can often lead to fracture of the coracoid, clavicle, or both.⁶^, ⁷ ^and ⁸ In this report we describe an arthroscopically assisted tunnel-free technique involving the use of a broad polyester suture band (4 or 7 mm) with a preattached metal buckle and allograft augmentation. This arthroscopically assisted approach has the advantage of minimal tissue dissection and preservation of the deltoid fibers. Moreover, an arthroscopically assisted approach allows visualization of the glenohumeral joint where tears of the labrum and/or rotator cuff are frequently found in conjunction with high-grade AC injuries.⁹

PREOPERATIVE PREPARATION

History

Patients with AC injuries and CC disruptions present after a traumatic injury to the superior aspect of the shoulder. Typical injuries occur during collision sports such as American football and hockey, skiing, and snowboarding, as well as cycling and motorcycling. It is important to be alert for additional injuries, such as labral or tendon injury, as CC disruptions are usually high-energy injuries. In our observation, approximately 30% or more of AC dislocations treated surgically have concomitant pathology requiring repair.

Patients will report pain on the superior aspect of the shoulder. They also may report pain with cross-body adduction of the shoulder and pain along the shoulder girdle. They often complain of pain with loading of the AC joint, particularly with pushups. Patients with symptomatic AC disruptions may describe clicking or pain with cross-body maneuvers.

Physical Examination

Patients presenting with an AC disruption will present with a typical deformity over the AC joint. There may be disruptions to the skin due to a fall directly on the superior shoulder. Patients with
higher-grade dislocations will have foreshortening of the shoulder, as measured from the mid-sternum to the lateral acromion. This mechanical alteration of shoulder mechanics in its unstable and foreshortened status can yield clicking, “clunking,” and periscapular pain associated with compensatory motions.

Patients may have pain with cross-body adduction. As previously mentioned, care should be taken to assess for additional injuries such as superior labral tears and rotator cuff tears.⁹

Radiographic Examination

Complete radiographic evaluation for AC injuries includes anteroposterior (AP) and angled views of both the glenohumeral and AC joints. This allows for assessment of the CC distance to assess for Rockwood Grade disruption. In addition to clavicle views, axillary views of the affected shoulder should be obtained to assess for posterior subluxation of the clavicle with respect to the acromion.

The most commonly used radiographic classification of AC injuries is the Rockwood classification. The Rockwood classification is determined by the degree of change in the CC distance with respect to the unaffected side. Rockwood I injuries have no displacement of the clavicle with respect to the acromion. Rockwood II injuries have an increase in the CC distance of <25%. Rockwood III injuries have displacement of 25% to 100%. Rockwood IV injuries have similar displacement to Rockwood III injuries, but they have posterior displacement of the clavicle with respect to the acromion. Rockwood V injuries have displacement of 100% to 300% of the CC distance. These injuries are associated with disruption of the deltotrapezial fascia. Rockwood VI injuries involve an inferior dislocation of the clavicle with respect to the coracoid and are quite rare.¹⁰

In addition to radiographs, the authors will obtain magnetic resonance imaging (MRI) of the shoulder to assess the degree of disruption of the CC ligaments and the continuity of the deltotrapezial fascia. In addition, MRI allows for assessment of additional pathology, such as rotator cuff and superior labral injuries.

INDICATIONS

Typical indications for arthroscopically assisted AC reconstruction is similar to that of open AC reconstruction. Patients with high-grade AC dislocations (Rockwood IV and V) or patients with symptomatic medium-grade (Rockwood III) dislocations can be considered for surgery. In some cases, particularly those with posterior clavicular translation, Rockwood II cases may need surgery when persistently symptomatic. Additionally, patients with distal clavicle fractures who have disruption of the CC ligaments are candidates for an arthroscopically assisted reconstruction of the CC ligaments using our technique.

SURGICAL TECHNIQUE

AC dislocations can be successfully and safely treated using predominantly arthroscopic techniques. A small incision is required superiorly, atop the clavicle, to allow for fixation of the M-Fix implant (Coracoid Solutions, Menlo Park, CA), a woven polyester band with an attached metal, fixation buckle (Figure 4-1). The M-Fix is passed under the coracoid process and over the clavicle. Subcoracoid passage is facilitated by the J-Pass (Coracoid Solutions), an incremental passing device that allows suture to be passed under the coracoid process (Figure 4-2). The M-Fix is used to maintain reduction of the AC joint and protect the torn CC ligaments as they heal following an AC repair. The implant also protects any soft tissue graft used to replace the CC ligaments during an AC reconstruction. Acute and chronic injuries utilize similar techniques, although some surgeons may prefer to use solely the M-Fix implant for acute repairs (less than 3-4 weeks from date of injury). Chronic injuries require more soft tissue dissection in the CC interval to allow a reduction of the diastasis. If there is ossification of the CC ligaments, then open dissection may be indicated to allow safe reduction of the interval between the coracoid and clavicle.

FIGURE 4-1 M-Fix (Coracoid Solutions, Menlo Park, CA, USA).

Implant is woven polyester with an attached metal buckle. This device is passed under the coracoid and clavicle. It can hold provisional fixation while the reduction is confirmed radiographically. M-Fix accessory tools include the Countertraction Tool and Punch. The Countertraction Tool is used to reduce the coracoclavicular distance, and the Punch is a tool designed to lock the M-Fix buckle.

FIGURE 4-2 J-Pass (Coracoid Solutions, Menlo Park, CA, USA) is used to pass a nitinol wire with an attached shuttle suture.

It can be used for limited tissue dissection as well.

Patient Positioning

The patient is placed in a standard beach chair position. The ability to achieve the proper trajectory during graft passage is a critical component of the arthroscopic technique. Unfortunately, many of the commercially available beach chair positioning attachments utilize head-stabilizing components that may impede the surgeon’s access to the superior aspect of the clavicle. Therefore, in order allow sufficient access to the operative field, it may be necessary to place the patient on a standard operating room (OR) table and maneuver the table into a beach chair position. The patient’s torso is moved near the edge of the table sufficiently to later allow a routine posterior viewing portal. The
torso needs to be secured to the table around the upper thorax and beneath the axilla to stabilize the patient. A standard foam head support is used to keep the head in a neutral position, protective goggles are applied, and the head is secured to the table with an elastic wrap followed by 2-inch silk tape. Some surgeons may prefer to use a C-arm during the preparation for passage of the implant and/or graft and later to confirm proper reduction of the AC joint. To obviate the need for moving the C-arm repeatedly in and out of the operative field, the surgeon may first use the C-arm to confirm adequate visualization of the AC joint and then move the machine medially toward the contralateral shoulder prior to prepping. The operative shoulder and arm are then sterilely prepped and the C-arm covered beneath the superior drape, allowing the machine to be moved in and out of the operative field without risk of contamination. Finally, a commercially available antimicrobial incision drape (Ioban 3M) can be applied to the operative site and then the arm may be placed in a mechanical arm holder (Figure 4-3).

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