Evaluation of the Clavicle Hook Plate for Treatment of Acromioclavicular Joint Dislocation: A Cadaveric Study

Objectives:To describe surgical technique for proper placement of the clavicle hook plate, determine whether there is subacromial impingement caused by hook plate fixation, and evaluate the mechanical strength of the clavicle hook plate construct.Methods:Eight fresh-frozen cadaveric shoulders with a mean age of 48 years (range, 37-69) were used. Open reduction and internal fixation of simulated Rockwood type V AC joint dislocation was performed with the clavicle hook plate. Three-dimensional computed tomography studies and arthroscopic evaluation were performed with the glenohumeral joint in different orientations to assess the position of the hook plate relative to relevant joint structures. The clavicle was then superiorly loaded to mechanical failure.Results:Computed tomography evaluations showed no contact between the humerus and the hook plate. Distance between the greater tuberosity and hook plate ranged from 14 to 31 mm with maximal shoulder forward flexion and 8.1-25.4 mm with maximal shoulder abduction. Arthroscopic evaluation of the subacromial space demonstrated that with maximal abduction/forward flexion, there was abutment of the rotator cuff with the hook plate in 6 of 8 specimens. In mechanical testing, mean failure load was determined to be 1011 N (range, 380-1563 N). Failure mechanisms included acromion fracture (4), slippage of the hook under acromion (3), and distal clavicle fracture (1).Conclusions:This study demonstrates that the clavicle hook plate reduces AC joint dislocation or distal clavicle fractures anatomically, has supra-physiologic mechanical strength, does not cause bony impingement, and exhibits rotator cuff impingement only with maximal abduction/forward flexion of the shoulder.