Mastering Acromioclavicular Joint Reduction: TightRope Fixation

Introduction and Epidemiology

Acromioclavicular separations represent a distinct spectrum of shoulder girdle trauma characterized by the disruption of the acromioclavicular complex. While relatively rare in the context of all skeletal trauma, overall incidence is estimated at 3 to 4 per 100,000 individuals in the general population. The demographic distribution is heavily skewed toward young, active males, with up to 52 percent of cases occurring during sporting events, particularly contact sports such as rugby, American football, and ice hockey. High-velocity trauma, including motorcycle collisions and cycling accidents, accounts for the majority of non-sports-related acromioclavicular joint disruptions.

The degree of injury is dictated by the magnitude and vector of force transmitted through the acromion to the distal clavicle and the surrounding deltotrapezial fascia. Pathogenesis typically involves a direct force applied to the lateral aspect of the shoulder with the arm adducted, such as a direct fall onto the point of the shoulder. This mechanism drives the acromion inferiorly and medially. The clavicle remains in its anatomic position, stabilized by the sternoclavicular ligaments and the strong sternocleidomastoid muscle, resulting in a shear force across the acromioclavicular and coracoclavicular intervals. Increased force transmission sequentially leads to dissociation of the acromioclavicular joint, tearing of the acromioclavicular ligaments, and ultimately, rupture of the coracoclavicular ligaments. Severe arm abduction during the injury sequence can result in atypical displacement patterns, including subacromial or subcoracoid dislocation of the distal clavicle. Determination of the precise injury type and morphological grade is critical, as it directly guides the algorithm for operative versus nonoperative management.

Surgical Anatomy and Biomechanics

A profound understanding of the local anatomy and biomechanics is paramount for achieving anatomic reduction and restoring shoulder kinematics. The acromioclavicular joint is a diarthrodial joint composed of the medial acromial margin and the distal end of the clavicle. The articular surfaces are incongruent and variable in orientation, typically sloping inferomedially. A fibrocartilaginous intra-articular disc is interposed between the two bony ends, serving to decrease contact stresses and accommodate the morphological incongruity. This meniscus-like structure undergoes rapid degeneration, often becoming functionally obsolete by the fourth decade of life.

Dynamic and Static Stabilizers

Dynamic stability of the acromioclavicular joint is provided by the robust deltotrapezial fascia, which blends with the superior joint capsule. The trapezial fascia and the overlying anterior deltoid act as a superior tension band, resisting inferior displacement of the scapula relative to the clavicle.

Static stability is conferred by two distinct ligamentous complexes. The acromioclavicular ligaments are capsular thickenings that control horizontal translation. The superior acromioclavicular ligament is the most robust and provides the greatest restraint to anterior and posterior translation of the distal clavicle. The anterior, posterior, and inferior ligaments add secondary horizontal stability to the joint.

The coracoclavicular ligaments provide the primary restraint to superior translation of the clavicle relative to the acromion and are the main suspensory ligaments of the upper extremity. They consist of two distinct fascicles:

• Conoid Ligament Arises from the posteromedial aspect of the coracoid process base and inserts on the conoid tubercle of the posteromedial clavicle, approximately 4.5 centimeters medial to the distal clavicular articular surface. It measures about 2.5 centimeters long and 1 centimeter wide. Biomechanically, the conoid provides the primary resistance against anterior and superior loading of the clavicle.
• Trapezoid Ligament Arises from the anterolateral coracoid, just posterior to the insertion of the pectoralis minor, and attaches to the trapezoid line on the lateral or central inferior surface of the clavicle, approximately 3 centimeters medial to the distal clavicular articular surface. It measures about 2.5 centimeters long and 2.5 centimeters wide. The trapezoid provides primary resistance against posterior loading and axial compression of the clavicle.

Biomechanical Considerations for Cortical Button Fixation

The native coracoclavicular ligament complex has a load to failure of approximately 500 to 725 Newtons. Modern suspensory fixation devices, such as the TightRope system, utilize ultra-high-molecular-weight polyethylene sutures paired with metallic cortical buttons. These constructs exhibit biomechanical properties that closely mimic, and often exceed, the ultimate tensile strength of the native ligaments, typically failing at loads greater than 800 Newtons. However, the non-biologic nature of the construct means it is subject to creep and cyclic elongation over time. Therefore, biological healing of the native ligaments or a supplemental biological graft is required for long-term success.

Indications and Contraindications

The management of acromioclavicular joint dislocations is guided by the Rockwood classification system, which categorizes injuries based on the direction and degree of clavicular displacement. Most low-grade injuries involve only the acromioclavicular joint capsule and are self-limited, whereas higher-grade injuries with complete coracoclavicular ligament disruption produce significant deformity and scapular dyskinesia, necessitating operative intervention.

Rockwood Types I and II are universally treated nonoperatively with a brief period of sling immobilization, ice, and early range of motion. Rockwood Types IV, V, and VI are widely accepted indications for surgical reduction and stabilization. Type IV injuries involve posterior displacement of the clavicle into the trapezius fascia. Type V injuries are characterized by severe superior displacement (greater than 100 percent to 300 percent of the contralateral side) with extensive deltotrapezial fascial stripping. Type VI injuries are rare subcoracoid dislocations.

The management of acute Rockwood Type III injuries (100 percent superior displacement) remains highly controversial. Current literature suggests nonoperative management as the initial treatment of choice for the general population. However, early operative intervention is considered for elite overhead athletes, heavy manual laborers, and patients with profound scapular dyskinesia or severe aesthetic concerns.

Summary of Operative and Nonoperative Management

Contraindications to arthroscopic-assisted TightRope fixation include active local or systemic infection, severe medical comorbidities precluding anesthesia, and chronic injuries (typically defined as greater than 3 to 6 weeks old). In chronic settings, the native ligaments lose their healing potential, and isolated TightRope fixation is contraindicated due to the high risk of construct fatigue and failure. Chronic injuries require biological augmentation, such as a free semitendinosus autograft or allograft reconstruction (e.g., modified Weaver-Dunn or anatomic coracoclavicular reconstruction).

Pre Operative Planning and Patient Positioning

A comprehensive physical examination of both upper extremities with the patient appropriately attired and in the upright position is standard. Evaluation of the cervical spine and a complete neurovascular examination are essential, as higher-grade, high-energy injuries may manifest with concomitant brachial plexus compromise or vascular shear injuries.

Low-grade injuries will present with localized tenderness to palpation at the acromioclavicular joint, with mild elevation possible. Increased clinical deformity is commonly seen as the injury grade increases, but acutely, the true extent of the deformity may be masked by significant soft tissue swelling.

Clinical Diagnostic Maneuvers

Methods for examining the acromioclavicular joint include several provocative tests designed to isolate pathology:
* Acromioclavicular Joint Compression Shear Test Isolated painful movement at the acromioclavicular joint in conjunction with a history of direct trauma indicates joint pathology. The examiner places one hand on the clavicle and one on the spine of the scapula, squeezing them together.
* Cross Arm Adduction Test The patient elevates the arm to 90 degrees of forward flexion, and the examiner passively adducts the arm across the chest. Look for pain specifically localized to the acromioclavicular joint. Pain at the posterior aspect of the shoulder might indicate posterior capsular tightness, while lateral shoulder pain suggests subacromial impingement.
* Paxino Test The examiner places their thumb under the posterolateral aspect of the acromion and the index and long fingers of the same hand over the middle part of the clavicle. Pressure is applied anterosuperiorly to the acromion and inferiorly to the clavicle. This is highly sensitive for acromioclavicular joint pathology.
* O Brien Active Compression Test Symptoms at the top of the joint must be confirmed by the examiner palpating the acromioclavicular joint during the maneuver. Deep anterior glenohumeral joint pain suggests labral or biceps pathology rather than acromioclavicular pathology.
* Targeted Palpation Local point tenderness at the acromioclavicular joint while the glenohumeral joint is kept still strongly suggests localized joint pathology.

Imaging Modalities

Standard shoulder radiographs can be useful for initial diagnosis, but overpenetrance may result in poor visualization of the distal clavicle. A dedicated Zanca view (10 to 15 degrees cephalic tilt) is mandatory to accurately assess the joint without superimposition of the scapular spine. An axillary lateral view is critical to evaluate for posterior displacement (Type IV). Historically, bilateral anteroposterior views with weights strapped to the wrists were used to unmask subtle Type III injuries; however, this practice has largely been abandoned as it causes unnecessary pain and rarely alters the surgical decision-making process.

Patient Positioning and Operating Room Setup

The procedure is typically performed under general anesthesia supplemented with an interscalene regional nerve block. The patient is placed in the beach chair position with the head secured and the operative arm completely free to allow for dynamic manipulation during reduction. The medial border of the scapula must be supported, but the acromion should be free of the bed to allow the scapula to be translated superiorly during the reduction maneuver. A C-arm fluoroscopy unit is positioned on the contralateral side of the table, coming in perpendicular to the patient to obtain intraoperative Zanca views.

Detailed Surgical Approach and Technique

Arthroscopic-assisted coracoclavicular stabilization utilizing cortical button fixation (TightRope) combines the advantages of minimal soft tissue dissection, direct visualization of the coracoid base, and the ability to address concomitant glenohumeral pathology, which is present in up to 15 to 30 percent of high-grade acromioclavicular separations.

Diagnostic Arthroscopy and Coracoid Preparation

A standard posterior viewing portal is established. A diagnostic arthroscopy is performed to evaluate the labrum, rotator cuff, and biceps anchor. An anterior working portal is established in the rotator interval using an outside-in technique with a spinal needle, ensuring the trajectory allows access to the undersurface of the coracoid.

The arthroscope is advanced into the subcoracoid space. Using a radiofrequency wand and an arthroscopic shaver through the anterior portal, the soft tissue at the base of the coracoid is meticulously cleared. It is imperative to visualize the medial and lateral borders of the coracoid base to ensure central placement of the drill hole. The musculocutaneous nerve and neurovascular bundle lie medial and inferior to the coracoid; therefore, dissection should remain strictly on the osseous footprint.

Clavicular Exposure and Drilling

Attention is turned to the superior aspect of the shoulder. A 3 to 4 centimeter sagittal incision is made over the distal clavicle, approximately 3.5 centimeters medial to the acromioclavicular joint. The deltotrapezial fascia is carefully incised in line with the clavicle, creating full-thickness anterior and posterior flaps. This exposes the superior surface of the clavicle.

A specialized coracoclavicular drill guide is introduced through the anterior arthroscopic portal and positioned precisely at the central base of the coracoid. The superior sleeve of the guide is positioned on the superior aspect of the clavicle, approximately 35 to 40 millimeters medial to the distal end, corresponding to the anatomic footprint of the conoid ligament.

Under direct arthroscopic visualization, a guide pin is drilled from the superior clavicle, through the clavicle, and down through the central axis of the coracoid base. Fluoroscopy can be utilized at this stage to confirm the trajectory. Once the guide pin position is confirmed, a cannulated drill (typically 4.0 millimeters for a single TightRope or 3.0 millimeters if a double TightRope technique is utilized) is passed over the pin.

Implant Passage and Deployment

A suture passing wire is inserted through the cannulated drill before the drill is removed. This wire is used to shuttle the TightRope implant down through the clavicle and coracoid tunnels. The oblong cortical button is advanced through the coracoid hole. Under arthroscopic visualization, the button is flipped and seated flush against the inferior cortex of the coracoid base. It is critical to ensure that no soft tissue is interposed between the button and the bone to prevent postoperative loosening.

Joint Reduction and Fixation

Reduction of the acromioclavicular joint is a critical step that requires coordinated movement. The surgeon applies a superiorly directed force to the patient's elbow, elevating the scapula and acromion, while simultaneously applying a direct inferior force to the distal clavicle. Once anatomic reduction is achieved and verified clinically and fluoroscopically, the superior round button of the TightRope is seated against the superior clavicular cortex.

The tensioning sutures are pulled sequentially and symmetrically to lock the construct. The knotless mechanism or sliding knots are secured. Over-reduction must be avoided, as it can lead to anterior translation of the clavicle and impingement.

Deltotrapezial Fascia Repair

The final, yet equally important, step is the meticulous repair of the deltotrapezial fascia. The fascia is closed over the superior button in a pants-over-vest fashion using heavy nonabsorbable sutures. This provides dynamic stability to the construct and acts as a biological barrier over the hardware. The subcutaneous tissues and skin are closed in a standard fashion.

Complications and Management

While arthroscopic-assisted cortical button fixation yields excellent clinical outcomes, it is not without risks. The transition from rigid hook plates and screw fixation to flexible, high-tensile suture constructs has altered the complication profile. Hardware failure, loss of reduction, and peri-implant fractures are the most significant concerns.

Coracoid fractures typically occur due to eccentric drill hole placement or utilizing a drill diameter that is too large relative to the native coracoid width. Clavicle fractures can occur through the drill hole, especially if the hole is placed too anteriorly or if multiple passes are made. Loss of reduction (creep) is frequently observed radiographically but does not always correlate with poor clinical outcomes.

Complications and Salvage Strategies

Post Operative Rehabilitation Protocols

The postoperative rehabilitation protocol is designed to protect the non-biologic mechanical fixation while biological healing of the coracoclavicular ligaments and deltotrapezial fascia occurs. Premature stress on the construct is the leading cause of suture creep and clinical failure.

Phased Rehabilitation Strategy

• Phase I Maximum Protection (Weeks 0 to 4) The patient is immobilized in a standard shoulder sling at all times, except for hygiene and specific exercises. Rehabilitation is strictly limited to passive range of motion. Forward flexion is limited to 90 degrees, and abduction is limited to 90 degrees.

Clinical & Radiographic Imaging