Posterior Positioning of a Clavicle Hook Plate Is a Risk Factor for Acromial Fractures after Acromioclavicular Joint Dislocation

Abstract

Purpose: Acromioclavicular (AC) joint dislocation is commonly treated using a clavicle hook plate (HP). However, previous reports have indicated that acromial fractures may occur after HP fixation. The purpose of this study was to identify risk factors for acromial fractures. Methods: A retrospective study was conducted on 39 patients with AC joint dislocation who were treated using clavicle HP fixation in our hospital between 2006 and 2017. Related parameters, including Rockwood classification, hook angle, the degree of reduction, the coverage of the hook under the acromion, and the anteroposterior position of the hook under the acromion, were evaluated to identify risk factors for acromial fractures. Results: The mean age of the participants was 51.7 (range 19 - 81) years; 34 were men and 5 were women. Injury occurred on the right side in 18 patients and on the left side in 21. Injuries were categorized as follows: 24 were Rockwood type III, one was type IV, and 14 were type V. Four of the 39 patients (10%) experienced acromial fractures. Statistical analyses indicated that the degree of reduction at the final follow-up was moderately correlated with the Constant score. Posterior positioning of the hook was the only identified risk factor for acromial fractures. Hook angle and the degree of reduction at the time of surgery were not significantly associated with acromial fractures. Conclusions: Postoperative shoulder function was associated with the degree of reduction at the final follow-up, suggesting that anatomical reduction is recommended for AC joint dislocation. Posterior positioning of the hook is a risk factor for acromial fractures; however, clavicle HP fixation provides a positive outcome for AC joint dislocation. Therefore, careful positioning of the hook is required for preventing acromial fractures.