Biomechanic Evaluation of AC Joint Reconstruction Techniques: A Systematic Review
Hoelscher, Skyler MD
Webb, Brian MD
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Background. Acromioclavicular (AC) joint disruption comprises 3.2% of all shoulder injuries, yet there is still broad debate on the optimal surgical approach. Over 150 surgical variations have been proposed, however the lack of common terminology and experimental standards make it challenging to draw any conclusions. For such predicaments, systematic reviews that provide a methodical approach for navigating the literature and have proven useful for identifying areas for improvement, standardizing protocols, and providing direction for a comprehensive analysis. Objective. The purpose of this review is to: 1) systematically evaluate the current state of the literature concerning the biomechanical testing of AC reconstruction; 2) to summarize the surgical techniques and testing procedures; and 3) to identify biomechanical areas that are not well represented in the existing literature. Methods. We completed a literature search to identify biomechanical studies on AC joint fixation using Medline, Scopus, and Excerpta Medica Database (EMBASE) following the 2009 PRISMA statement. Articles were independently reviewed by two investigators and any disagreements were reconciled by consensus in consultation with a third investigator. Investigators independently abstracted data from each study, focusing on surgical techniques and characteristics of the testing protocol. Results. The most popular techniques were the Modified Weaver Dunn and suture button techniques with a tunnel through or looping under the coracoid. To assess construct performance, 28 out of 39 studies included a load to failure protocol to evaluate strength and stiffness of the construct. 18 studies measured vertical plane translation, 16 studies measured horizontal motion, and 5 studies measured rotation. Conclusion. Overall, the most common techniques involved graft with suture augmentation. Techniques looping under the coracoid decreased the likelihood of fracture whereas techniques going through the coracoid improved stability and better maintained reduction. Free graft and hookplates have been found to be biomechanically or clinically inferior. Elastic stiffness serves as a reliable indicator for quantifying early construct stability while strength and translation better represent long-term functional stability. While general conclusions can be made from current biomechanic literature, a more objective verdict requires better standardization of terminology and testing procedures.