Mechanics of coracoacromial ligament transfer augmentation for acromioclavicular joint injuries

The objective of this study was to determine how effectively the Weaver–Dunn repair (both unaugmented and augmented with a suture and suture anchor) restores joint translation in response to applied loads to normal. Translation of a reference point on the clavicle relative to a reference point on the acromion was assessed in five cadaver shoulders by applying anterior, posterior and superior loads of 50 N to the clavicle using a specially designed test rig while measuring movement of the acromion and clavicle with an optical measurement system. Translation was determined for the intact joint, after simulated injury and Weaver–Dunn repair, and after augmentation of the Weaver–Dunn repair with a suture fixed to a suture anchor in the coracoid process. Joints were significantly more mobile after Weaver–Dunn repair (16.1 mm anterior, 15.7 mm posterior, 11.1 mm superior) than when intact (4.1 mm anterior, 3.2 mm posterior, 4.0 mm superior) (p<0.05). Augmentation with a suture and suture anchor reduced separation of the Weaver–Dunn reconstruction significantly (to 5.3 mm anterior, 4.1 mm posterior, 2.0 mm superior) (p<0.05). Joints reconstructed using an augmented Weaver–Dunn repair were not significantly more (or less) mobile than normal joints (p>0.05), although the power of the test to detect this difference was low (power=0.107). We anticipate that, when surgery is indicated for treating acromioclavicular joint injury, an augmented Weaver–Dunn reconstruction will yield a joint that is less painful, more functional and less likely to require revision