Acromioclavicular Instability: Open Repair and Reconstruction

Berkcan Akpinar

Nicholas P. Perry

Mark D. Price

Augustus D. Mazzocca

ABSTRACT

Acromioclavicular (AC) joint separation injuries occur on a spectrum of severity depending upon the energy imparted during the time of trauma. Depending on the timing of treatment, severity of injury, and patient-specific factors, treatments range from nonoperative to operative management. Higher-grade AC separation injuries warrant surgical management especially in the setting of concomitant coracoclavicular (CC) ligament compromise. While many techniques have been described in the past, here we describe an AC joint reconstruction with a technical emphasis on distal clavicle mobilization, initial reduction tensioning using a suture-based cerclage system free of potential allograft creep limitations, and successful management of the deltotrapezial fascia to impart additional rotational and translational stability to the AC reconstruction.

INTRODUCTION

Operative management of AC joint separation has evolved with over 150 techniques described in the literature, each with its own set of advantages and disadvantages; however, no one technique has been shown to be superior to date.¹^, ²^, ³ ^and ⁴ While acute injuries may be amenable to soft tissue-based repairs, transarticular AC joint fixation, and CC fixation, chronic injuries often require reconstruction of the CC ligaments with or without AC ligament reconstruction as well to best restore stability to the AC joint. Distal clavicle excision and soft tissue transfer (modified Weaver-Dunn procedure) has also been described for chronic injury patterns.⁵^, ⁶ ^and ⁷ Unfortunately, current strategies while abundant have been demonstrated to have a high failure rate with a large portion of patients requiring revision procedures.⁸^,⁹ While individual techniques vary, the overall goal of surgery is to reduce the AC joint and restore biomechanical stability, which involves restoring the structural support provided originally by the torn AC and CC ligaments.

Pathoanatomy and Biomechanics

In discussing surgical management, a clear understanding of the pathoanatomy of an AC joint separation is critical. The native AC joint is diarthrodial in nature with an intra-articular fibrocartilaginous meniscus homologue.¹⁰ The posterior and superior portions of the capsule provide the most significant restraint to horizontal translation of the distal clavicle with respect to the acromion predominantly stabilizing posterior displacement. The CC ligaments collectively provide vertical stability predominantly to the AC joint. The trapezoid ligament lies approximately 2 cm medial to the distal clavicle edge while the conoid lies 4 cm medial.¹⁰ Furthermore, the deltotrapezial fascia, an aponeurotic layer that represents the continuation of the upper trapezial fascia over the clavicle forming the superficial fascia of the anterior deltoid has been recently shown to contribute to dynamic horizontal and rotational AC joint stability.⁴^,¹¹^,¹² In addition to horizontal instability, disruption of the AC joint capsule imparts a unique load distribution profile across both the CC ligaments. The trapezoid is subjected to greater force with posterior translation of the clavicle while the conoid is subjected to over two times the native force profile with anterior translation after capsular disruption.¹³ This differential loading pattern across the CC ligaments in addition to the loss of dynamic rotational
stability from concomitant deltotrapezial fascia injury during initial separation further underscores the importance of restoring the biomechanical effects of both CC ligaments during AC joint stabilization surgery. A successful AC joint reconstruction therefore requires effectively restoring the AC capsule, CC ligaments, and the deltotrapezial fascia in order to fully stabilize the joint.

PREOPERATIVE EVALUATION

Appropriate patient selection is critical to a successful outcome. A complete set of radiographs is needed including bilateral dedicated AC joint views as well as bilateral Zanca views to best evaluate the AC joint and an axillary lateral view to evaluate for a type IV separation on initial presentation.¹⁴ Typically, patients will not need further imaging; however, weighted stress views have been historically described to differentiate between type II and III separations. In addition to type IV-VI separations, acute type III separations are also addressed surgically in elite athletes, manual laborers, and patients with cosmetic issues. Chronic type III injuries are typically indicated for surgery depending on presence of refractory or recurrent symptoms, as well as a failure of nonoperative bracing/sling immobilization. Contraindications are rare and include patients who may not be suitable for surgery due to comorbidities, are unable to comply with postoperative rehabilitation or if there are wound concerns at the planned operative site. From a repair versus reconstruction standpoint, AC joint stabilization through CC ligament reconstruction is typically spared for patients with chronic injuries; however, acceptable for acute injury as well.

Surgical Technique

Here we describe a technique for an open AC joint reconstruction using an allograft-based CC ligament reconstruction alongside a differentially tensioned internal brace cerclage suture with subsequent repair of the deltotrapezial fascia. Advantages of our technique include tensioning the internal brace in line with the conoid limb of the ligament reconstruction after achieving anatomic reduction. Our internal brace tensioning technique allows independent fixation of the allograft, which reduces the risk of creep and suboptimal subsequent graft tensioning. Our described dissection and repair of the deltotrapezial fascia allows maximal exposure for the critical components of the case with excellent restoration of the dynamic stabilizers of the AC joint as described later.

Positioning

The patient is positioned in a slightly less upright beach chair position (45° vs 70° incline) with a bump under the ipsilateral scapula and all bony prominences well padded, the necessary deep vein thrombosis prophylaxis applied, and appropriate access to the operative upper extremity. Positional areas at risk including the hips, knees, and elbow are appropriately positioned in positions of minimal compression to nearby neurovascular structures. The head and neck are appropriately padded and secured working in concert with the anesthesia team (Figure 3-1).

FIGURE 3-1 Appropriate positioning of a patient for a left-sided acromioclavicular reconstruction.

There is a small bump underneath his ipsilateral scapula in order to further elevate the operative site.

Approach

Landmarks and Superficial Exposure

The operative extremity is prepped and draped in the standard, sterile fashion. While drawing bony landmarks (Figure 3-1), consider the patient’s specific anatomy in addition to the “S” shape of the lateral clavicle. Also consider deformation of anatomic landmarks as a result of the AC injury: the clavicle may be displaced posteriorly in the trapezius muscle and the Neviaser portal site may be obscured as a landmark. We find that the coracoid and the posterolateral edge of the acromion are consistently reliable. A vertical strap incision spanning just proximal to the posterior border of the clavicle to the tip of the coracoid should be made to allow for maximal exposure. This incision should ideally be placed 3.5 cm medial to the AC joint, which should be readily palpable on the shoulder. After superficial hemostasis is achieved with electrocautery, identify the deltotrapezial fascia (DTF) layer and raise subcutaneous skin flaps at this level (Figure 3-2).

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