Biomechanic Comparison of Reconstruction Techniques for AC joint Dislocation

Background: Acromioclavicular (AC) joint disruption comprises 8% of all shoulder injuries. There is still broad debate on when treatment with surgery is indicated and what surgery technique will provide optimal results. Purpose: In this study, we propose a modified technique that we hypothesize will provide the most security to a Rockwood type III AC joint dislocation with the least amount of post-operative complications. Materials and Methods: A rig to mount the cadaver specimens was constructed using a steel rails, screws, and L-brackets and fastened securely to the MTS apparatus. A total of 20 cadaveric shoulders will be gathered and each randomly assigned to one of three groups: 1) reconstruction with graft loop with fibertape augmentation and 2) reconstruction loop using two fibertapes and 3) reconstruction with the Mazzocca technique. The AC and CC ligaments will be released to simulate a Rockwood type III injury and reconstructed using one of the techniques listed above. The reconstructed specimen will then undergo load to failure (120 mm/min) in the superior direction to evaluate maximal loading capacity of the repair construct. Discussion: Difference compared to native for vertical migration of the AC joint, load to failure and mode of failure of the technique will be analyzed for variance if statistical significance is found (P< 0.05) followed by a Bonferroni post hoc analysis. With trials still underway, we anticipate the AC joint repair with augmented graft loop will decrease vertical migration and increase strength compared to previously described techniques.