Biomechanical Outcomes of Glenoid Bone Graft Fixation Techniques: A Systematic Review

Background:The Latarjet and other bony augmentation procedures are commonly used to treat anterior shoulder instability in the setting of significant glenoid bone loss. Although several fixation strategies have been reported, the biomechanical strength of these techniques remains poorly understood.Purpose:To perform a systematic review of the biomechanical strength of glenoid bony augmentation procedures for anterior shoulder instability.Study Design:Systematic review; Level of evidence, 4.Methods:A systematic search of the Medline, Embase, Web of Science, and Cochrane Library databases was performed to identify biomechanical studies evaluating various fixation strategies for coracoid and other bone transfer procedures for anterior shoulder instability. Biomechanical results included load to failure with both compression and traction forces, stiffness, and cyclic displacement. The quality of included articles was assessed based on the Quality Appraisal for Cadaveric Studies (QUACS) scale.Results:A total of 21 biomechanical studies comprising 486 specimens were included. The number of screws used and the addition of washers were found to significantly increase rigidity and load to failure. The comparison of fixation techniques demonstrated mixed results in load to failure between screw and alternative constructs including suture buttons and suture anchors. However, studies that tested graft displacement consistently found more graft displacement in buttons compared with screws. The median and mean of the QUACS scale were both 12, with a range of 10-13.Conclusion:Biomechanical studies consistently demonstrated that when glenoid bone grafts were fixed with screws, the number of screws and use of washers significantly increased construct rigidity and load to failure. Different metal screw materials and sizes did not consistently demonstrate a significant difference in biomechanical strength. There are mixed results when comparing suture buttons to screw fixation. The evaluated studies revealed that all double metal screw constructs and the majority of suture button and anchor constructs were able to withstand the glenohumeral load reflective of activities of daily living using a 150-N threshold.