TY - JOUR T1 - Parameterization of Proximal Humerus Locking Plate Impingement with In Vitro, In Silico, and In Vivo Techniques JF - bioRxiv DO - 10.1101/368258 SP - 368258 AU - Emily M. Bachner AU - Elaine C Schmidt AU - Matthew Chin AU - Surena Namdari AU - Josh R. Baxter AU - Michael W. Hast Y1 - 2018/01/01 UR - http://biorxiv.org/content/early/2018/07/13/368258.abstract N2 - Background Locked plating of displaced proximal humerus fractures is common, but rates of subacromial impingement remain high. Computational predictions of implant impingement have yet to be sufficiently explored in proximal humerus fixation. The goal of this study was to utilize a multidisciplinary approach to elucidate the relationships between common surgical parameters, anatomical variability, and the likelihood of plate impingement.Methods The experiment was completed in three phases. First, a controlled in vitro experiment was conducted to simulate impingement. Second, a dynamic in silico musculoskeletal model was developed to simulate changes to implant geometry, surgical techniques, and acromial anatomy, where a collision detection algorithm was used to simulate contact between the plate and acromion. Finally, in vivo shoulder kinematics were recorded for nine activities of daily living and motions that created a high likelihood of impingement were identified.Results Impingement was measured at 73.3±14.5° abduction in the cadaveric model and 92.0°±34.0° with computational simulations. Impingement events were limited to ranges of motion between 10–40° of cross-body adduction. Activities of daily living, such as combing one’s hair, lifting and object overhead, and reaching behind one’s head are likely to cause impingement.Discussion and Conclusion This multidisciplinary experiment quantified key preoperative factors to assist with implantation decisions. Results demonstrated that proximal implant placement, superior translation of the humeral center of rotation, increases in plate thickness, and increases in acromial tilt all increase the likelihood of impingement. Careful preoperative planning that includes these factors could help guide operative decision making and improve clinical outcomes.Level of Evidence: VAuthor Contribution SummaryEMB: Contributed to research design, acquisition, analysis, and interpretation of data. Drafted and revised the paper. Read and approved the final submitted manuscript.MC: Contributed to research design, acquisition, analysis, and interpretation of data. Drafted and revised the paper. Read and approved the final submitted manuscript.ECS: Contributed to research design, acquisition, analysis, and interpretation of data. Drafted and revised the paper. Read and approved the final submitted manuscript.SN: Contributed to research design and interpretation of data. Provided revisions of the paper. Read and approved the final submitted manuscript.JRB: Contributed to research design, acquisition, analysis and interpretation of data. Drafted and revised the paper. Read and approved the final submitted manuscript.MWH: Contributed to research design, acquisition, analysis and interpretation of data. Drafted and revised the paper. Read and approved the final submitted manuscript.The authors would also like to thank Anthony Cresap for his help with cadaveric testing and Todd Hullfish and Annelise Slater for their help collecting motion capture data. ER -