Subacromial erosion after clavicular hook plate fixation

Abstract

Introduction I aimed to identify the anatomical factors related to the subacromial erosion following surgical fixation of the acromioclavicular (AC) joint using hook plate, and to describe the characteristics of these anatomical factors in normal population.

Materials and methods The current study is consisted of two part. In Part I study, 23 patients with AC joint injury surgically treated with a hook plate were included. Several anatomical factors, including AC angle, the plate to hook angle (PH angle), the angular mismatch between these two angles (angular mismatch), the depth of the acromion, the depth of the hook, the mismatch between these two depths (depth mismatch), the subacromial erosion ratio (SET) were measured on computed tomography (CT) scans performed three months after surgery. A correlation analysis was performed between SET and the anatomical factors, and the groups with and without erosion were compared. In Part II study, the CT of the AC joint of 101 patients with no AC joint pathology were examined, and the anatomical factors related to the postoperative subacromial erosion found in Part I study were analyzed.

Results In Part I, the angular mismatch demonstrated the highest correlation with SET (rho=0.61, p=0.002). The mean AC angle and the angular mismatch were significantly higher in the erosion group (p=0.013, p=0.004, respectively). In Part II, the mean AC angle was 17.1° (range, -8.0 to 39.0; SD, 10.51) and showed very high individual variability (coefficients of variation= 62.6%) in normal population.

Conclusion A high AC angle, a mismatch between the AC angle and the PH angle might be related to postoperative subacromial erosion. These anatomical factors show high individual variability in normal population. I think that my observations could be helpful in improving the future design of the hook plate and could also be the cornerstone for future studies investigating the relationship between postoperative complications of hook plate fixation and the AC joint anatomy.