AC Joint Fixation

Arthroscopy

AC Joint Fixation

The acromioclavicular (AC) joint, situated in the shoulder, is where two bones converge. One of these bones is the collarbone, also known as the clavicle, while the other is a part of the shoulder blade, called the acromion, which is the prominent bone behind the shoulder forming part of the shoulder joint. The juncture where the clavicle meets the acromion is termed the AC joint.

Functioning as a crucial connection between the axial skeleton and the upper extremity, the AC joint facilitates movement between bones through cartilage, the white tissue between bones enabling their mobility. Unlike rigid structures, this joint is movable in all planes owing to dynamic and static stabilizers. Its intricate ligamentous setup is vital for the shoulder girdle’s normal operation, with the acromioclavicular and coracoclavicular ligaments serving as static stabilizers, while the dynamic stabilizers include the deltoid and trapezoid muscles.

Before & After Repair

An AC joint injury occurs when the joint connecting the collarbone and the acromion separates, indicating torn ligaments and misalignment of the collarbone. The severity of the injury can range from mild to severe.

Classification:

Type I: This involves a sprain of the AC ligament with no complete tear, and both the AC and CC ligaments remain intact.

Type II: In this case, the AC ligament is torn but not the CC ligaments.

Type III: Here, both the AC and CC ligaments are torn, resulting in a displacement of the clavicle by 25% to 100% compared to the opposite side.

Type IV: In this injury, both the AC and CC ligaments are torn, and the distal clavicle is pushed backward into the trapezius fascia.

Type V (Rockwood type): This complex injury involves tears in the AC and CC ligaments, along with damage to the deltoid origin and trapezius insertion, leading to extreme instability of the AC joint. The clavicle displacement is significant, with the CC distance increased by 100% to 300%.

Type VI: This injury results from inferior displacement of the distal clavicle into the subcoracoid position.

The traditional literature advocates for conservative treatment for grade I and II injuries, while operative intervention is recommended for grade IV, V, and VI injuries. Grade III injuries remain a subject of controversy in terms of treatment.

Various surgical techniques have been outlined, including the use of screws, plates, muscle transfers, ligamentoplasty procedures, and ligament reconstruction utilizing either autografts or allografts. Anatomical ligament reconstruction with a tendon graft can be performed using either open or arthroscopic methods. Open surgery necessitates detachment of the deltoid from the clavicle and extensive soft-tissue dissection to access the coracoid process, posing risks to neurovascular structures due to limited visibility during tendon transfer around the coracoid.

Recent approaches to AC joint dislocation treatment have focused on either CC ligament reconstruction or CC interval fixation. Various devices such as screws, plates, suture anchors, or synthetic tapes have been employed for fixation, but none are devoid of complications such as implant failure, migration, bony erosions, clavicle fractures, and recurrent dislocation. The evolution of arthroscopic techniques has shifted the management of AC joint injuries from open surgical procedures to less invasive, arthroscopically-assisted, or all-arthroscopic procedures.

One primary advantage of arthroscopy is early discharge from the hospital, shorter rehabilitation duration, and quicker return to activity for patients. Arthroscopy provides superior visibility around the coracoid without the need for extensive dissection of the deltotrapezial fascia, thereby reducing the risk to vital neurovascular structures. The suprascapular nerve and artery, in particular, are closely situated to any implanted material. Furthermore, arthroscopy enables direct visualization of the inferior aspect of the coracoid base, a critical anatomical region, especially during placement of CC fixation systems.