Comparison of optimal screw configurations in two locking plate systems for proximal humerus fixation - a finite element analysis study. (August 2020)

• Record Type: Journal Article
• Authors: Mischler, Dominic; Babu, Satish; Osterhoff, Georg; Pari, Carlotta; Fletcher, James; Windolf, Markus; Gueorguiev, Boyko; Varga, Peter
• Is Part Of: Clinical biomechanics. Volume 78(2020)
• Publication Date: 2020-08
• Subjects: Proximal humerus -- Fracture fixation -- Shoulder -- Finite element analysis -- Locking plates; Biomechanics -- Periodicals; Osteopathic medicine -- Periodicals; Biomechanics -- Periodicals; Osteopathic Medicine -- Periodicals; 612.76
• DOI: 10.1016/j.clinbiomech.2020.105097
• Languages: English
• ISSNs: 0268-0033

Abstract

Abstract: Background: Management of proximal humerus fractures is challenging, especially in elderly. Locking plating is a common surgical treatment option. The Proximal Humerus Internal Locking System (plate-A) has shown to lower complication rates compared to conventional plates, but is associated with impingement risk, which could be avoided using Peri-articular Proximal Humerus Plate (plate-B). Nevertheless, biomechanical performance and optimal screw configuration of plate-B is unknown. The aim of this study was to evaluate different screw configurations of plate-B and compare with plate-A using finite element analyses. Methods: Twenty-six proximal humerus models were osteotomised to create unstable three-part fractures, fixed with either of the two plates, and tested under three anatomical loading conditions using a previous established and validated finite element simulation framework. Various clinically relevant screw configurations were investigated for both plates and compared based on the predicted peri-implant bone strain, being a validated surrogate of cyclic cut-out failure. Findings: Besides increasing the number of screws, the placement of the posterior screws in combination with the calcar screw in the plate-B significantly decreased the predicted failure risk. Generally, plate-A had a lower predicted failure risk than plate-B. Interpretation: The posterior and calcar screws may be prioritized in plate-B. Compared to plate-A, the more distal positioning, less purchase in the posterior aspect and a smaller screw spread due to not fitting of the most distal calcar screw in most investigated subjects led to a significantly higher predicted failure risk for most plate-B configurations. The findings of the simulations study require clinical corroboration. Highlights: Evaluation of the effect of screw configuration in a proximal humerus plate Comparison with another clinically often used implant. Established and validated finite element methodology used to predict failure risk. Posterior and calcar screws are the most beneficial in the first plate. Second plate has generally lower predicted failure risk, but may induce impingement.