Reduction of subacromial osteolysis by bending the hook arthroscopically in clavicle hook plate fixation for distal clavicle fractures

Abstract Background: Subacromial osteolysis is a serious complication caused by clavicle hook plates. Incongruency between the hook and undersurface of the acromion has been reported as a cause of subacromial osteolysis. The aim of this study was to retrospectively examine the effectiveness of hook bending in reducing subacromial osteolysis. Methods: Twenty-two patients with unstable distal clavicle fractures were treated with clavicle hook plates. There were 19 males and 3 females, with a mean age of 55.0 years. They were followed for a mean period of 9.5 months. The patients were divided into two groups; there were 10 patients whose hook was bent (the bending group) and 12 patients whose hook was not bent (the nonbending group). In the bending group, the hook was bent using a dedicated bender such that the hook and the undersurface of the acromion were parallel, and the direction of the hook was confirmed arthroscopically. At plate removal, arthroscopy was performed in both groups to observe the subacromial bony defect and the rotator cuff injury. Results: One patient in the nonbending group had a fibrous union, but bone union was achieved in all other patients. In the bending group, the angle at which the hook was inclined downward with respect to the distal portion of the plate (hook inclination angle) was 9.3 ± 6.1˚ (range, 2-23˚). The subacromial bony defects were significantly smaller in the bending group (1.7 ± 2.4 mm) than in the nonbending group (4.7 ± 2.3 mm) (P<0.05). Partial-thickness rotator cuff tears localized around the hook were observed arthroscopically in 6 patients in the bending group (60%) and in 7 patients in the nonbending group (58%). Conclusions: When the hook was bent such that it was parallel to the undersurface of the acromion, the degree of subacromial osteolysis was reduced.