Subacromial Erosion After Hook Plate Fixation in Acute Acromioclavicular Joint Dislocation

Objectives: To determine the incidence of subacromial erosion, perform quantitative analysis, and identify risk factors after locking hook plate fixation for acute acromioclavicular joint injury. Design: A retrospective case series study. Setting: A single tertiary university hospital. Patients/Participants: The study was conducted on 35 patients who had acute acromioclavicular joint injury. Intervention: Patients underwent the locking hook plate fixation. Main Outcome Measurements: The computed tomography (CT) was conducted to measure the subacromial erosion. The acromioclavicular slope (AC slope) of the unaffected side, the acromion-hook angle, the acromioclavicular anteroposterior distance (AC-AP distance), and the preoperative acromioclavicular interval of the affected side were analyzed to identify the risk factors of subacromial erosion. Results: According to the CT findings, subacromial erosion was found in all cases, and the mean value was 5.0 mm, which is 53% of the entire acromion thickness. The AC slope (B = −0.159, P < 0.001) and AC-AP distance (B = 0.233, P = 0.004) were found to have a significant influence on postoperative subacromial erosion. The AC slope showed a negative correlation with the amount of erosion, whereas the AC-AP distance showed a positive correlation with erosion. Conclusion: The CT findings revealed that subacromial erosion occurred in all cases, and the mean erosion depth was about 50% of the acromial thickness. If the preoperative AC slope of the unaffected side was more acute and the AC-AP distance was larger, the incidence of subacromial erosion was higher. Level of Evidence: Therapeutic Level IV. See Instructions for Authors for a complete description of levels of evidence.