Summary

Horizontal instability of the AC joint is often missed or poorly understood, and is associated with worse patient outcomes in terms of pain and disability; this systematic review describes techniques for diagnosing, evaluating, and treating horizontal instability of the AC joint in order to aid in better management of these injuries by orthopaedic surgeons.

Abstract

Background

Injuries to the acromioclavicular (AC) joint are common and should be suspected in patients who present with shoulder pain in the region of the acromion and clavicle. These injuries occur as a result of trauma to the shoulder, and are often caused by a direct blow or fall on an adducted arm. The AC ligament attaches to the distal clavicle and provides horizontal (anterior-posterior) stability to the AC joint. Injuries to the AC ligament can cause horizontal instability and are often neglected or underdiagnosed, which can lead to poor patient outcomes in terms of pain and disability.

Purpose

To perform a systematic review of the literature on the diagnosis and treatment of horizontal instability of the AC joint.

Methods

The authors performed a systematic review using the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. PubMed and Embase were searched for studies that investigated diagnosis, treatment, and failure of operative management of acute and chronic AC separations. Studies that did not specifically evaluate AC joint injuries, were not written in English, or were specific only to vertical instability of the AC joint were excluded.

Results

Overall, 23 articles met the inclusion criteria and were therefore included in this systematic review. Horizontal instability is commonly present in AC joint injuries and leads to worse outcomes for patients. Current literature indicates that it is difficult to diagnose horizontal instability of the AC joint using standard X-ray views. To better evaluate horizontal instability, studies described varied X-ray techniques including modified Alexander view, Zanca view, axillary lateral view, and supine dynamic lateral view. Dynamic views were shown in some cases to better detect horizontal instability than with static views. There are >60 published procedures for treating AC joint injuries, but many focus on vertical rather than horizontal instability. Most authors agreed that current surgical techniques, such as Weaver-Dunn reconstruction of the CC ligament, did not adequately address horizontal instability of the AC joint, but there was no consensus on the most appropriate treatment. Modifications to current surgical procedures to incorporate reconstruction of the horizontal component showed improved patient outcomes. Such modifications included additional AC joint suture cord cerclage, combined AC and coracoclavicular (CC) ligament reconstruction, and the Twin Tail TightRope triple button technique. Failure after surgical stabilization of AC joint separation has been reported to occur in 15-80% of cases.

Conclusion

There is currently no consensus regarding the best practices for diagnosis, evaluation, and treatment of acute or chronic horizontal instability of the AC joint. Moreover, horizontal instability injuries are often neglected or poorly understood, making diagnosis difficult, which may lead to high complication and failure rates.