Biomechanical properties of repairs for dislocated AC joints using suture button systems with integrated tendon augmentation

Purpose: To evaluate the biomechanical performance of different techniques for CC reconstruction using suture button systems with integrated tendon augmentation. Hypothesis was that (1) reconstructions using a cortical button combined with a biological augmentation (semitendinosus allograft) will demonstrate improved stability than a modified Weaver-Dunn procedure and (2) constructs using two tunnels at the clavicle for fixation will show superior horizontal stability than single-tunnel constructs. Methods: The acromioclavicular joints of 47 cadaveric shoulders were tested for anterior, posterior, and superior translations (70 N load) and maximal load to failure (superior). Shoulders were assigned to 4 groups: (1) native (n = 18) and after sectioning the AC and CC ligaments; (2) CC reconstruction with 1 clavicular and 1 coracoid tunnel (GR-ST) augmented with semitendinosus graft (n = 15); (3) CC reconstruction augmented with semitendinosus tendon (GR-DT) with 2 clavicular and 1 coracoid tunnel (n = 8); and (4) modified Weaver-Dunn reconstruction (n = 6). Results: The Weaver-Dunn demonstrated statistically more translation than the native joint for posterior direction (P = 0. 038). The GR-ST had significantly less translation than the Weaver-Dunn for anterior and posterior translations (P = 0. 003, P = 0. 004) and compared to the native for superior translation (P = 0. 028). The GR-DT differed significantly in anterior and posterior translations compared to the Weaver-Dunn (P = 0. 002, P = 0. 001). The modified Weaver-Dunn failed at significantly less load to failure compared to all other groups (P = 0. 002, P = 0. 002, P = 0. 005). There was no significant difference between the native and the other reconstructions. Conclusion: The evaluated techniques for isolated CC ligament reconstruction (GR-ST) in AC joint dislocation showed biomechanical stability superior to the modified Weaver-Dunn procedure and obtained similar measures compared to the native control. A modified technique (GR-DT), which used two fixation points at the clavicle, did not result in decreased horizontal or vertical translation and therefore no superiority of the GR-DT technique could be shown compared to the GR-ST. Level of evidence: Controlled laboratory study.