Cement augmentation of calcar screws may provide the greatest reduction in predicted screw cut-out risk for proximal humerus plating based on validated parametric computational modelling: Augmenting proximal humerus fracture plating

Bone & Joint Research

Markus Windolf¹  James W. A. Fletcher¹  Peter Varga¹  Ladina Hofmann-Fliri¹  Jason A. Inzana¹  Prof. Dr. Norbert P. Südkamp²  Armin Runer³ 

[1] AO Research Institute Davos, Davos, Graubünden, Switzerland;Department of Orthopaedics and Trauma Surgery, University Hospital Freiburg, Freiburg, Germany;Medical University Innsbruck, Innsbruck, Tirol, Austria;

关键词: proximal humerus fracture;    locking plate fixation;    osteoporosis;    finite element analysis;    cement augmentation;   

DOI  :  10.1302/2046-3758.99.BJR-2020-0053.R1

来源: DOAJ

【 摘 要 】

Aims: Fixation of osteoporotic proximal humerus fractures remains challenging even with state-of-the-art locking plates. Despite the demonstrated biomechanical benefit of screw tip augmentation with bone cement, the clinical findings have remained unclear, potentially as the optimal augmentation combinations are unknown. The aim of this study was to systematically evaluate the biomechanical benefits of the augmentation options in a humeral locking plate using finite element analysis (FEA). Methods: A total of 64 cement augmentation configurations were analyzed using six screws of a locking plate to virtually fix unstable three-part fractures in 24 low-density proximal humerus models under three physiological loading cases (4,608 simulations). The biomechanical benefit of augmentation was evaluated through an established FEA methodology using the average peri-screw bone strain as a validated predictor of cyclic cut-out failure. Results: The biomechanical benefit was already significant with a single cemented screw and increased with the number of augmented screws, but the configuration was highly influential. The best two-screw (mean 23%, SD 3% reduction) and the worst four-screw (mean 22%, SD 5%) combinations performed similarly. The largest benefits were achieved with augmenting screws purchasing into the calcar and having posteriorly located tips. Local bone mineral density was not directly related to the improvement. Conclusion: The number and configuration of cemented screws strongly determined how augmentation can alleviate the predicted risk of cut-out failure. Screws purchasing in the calcar and posterior humeral head regions may be prioritized. Although requiring clinical corroborations, these findings may explain the controversial results of previous clinical studies not controlling the choices of screw augmentation.

【 授权许可】

Unknown