Peri-implant failure in dual plating of the distal humerus—A biomechanical analysis with regard to screw and plate positioning

PurposeThe aim of this biomechanical study was to analyse the influence of plate and screw positioning on peri-implant failure in dual plate osteosynthesis. We hypothesized that screw positioning rather than plate configuration influences the risk of peri-implant fractures.MethodsTwenty macerated humerus specimens were available. 5 groups of 4 were built according to specimen size. Locking dual plates (Medartis, Switzerland) were randomly applied to the distal humerus of the specimens in 4 types of configuration:P1: Parallel plate endings; positioning of the outermost screws at different levels.A1: Antiparallel plate endings; positioning of the outermost screws at different levels.A0: Antiparallel plate endings; positioning of the outermost screws at the same level.P0: Parallel plate endings; positioning of the outermost screws at the same level.Bending forces were applied using a universal testing machine until peri-implant fracture occurred.ResultsMean failure loads for respective configuration types were as follows:P1: 428.7 (±84.2) N, A1: 410.0 (±54.7) N, A0: 297.8 (±48.3) N, P0: 261.0 (±65.0) N. Configurations with positioning of the most proximal screws at different levels (P1, A1) reached significantly higher failure loads when compared to screw placement at the same level (P0, A0) (0.01 ≤ p ≤ 0.03). Altering the plate configuration did not significantly influence failure loads (0.34 ≤ p ≤ 0.58).ConclusionsThe results of this study suggest that placement of the most proximal screws rather than the configuration of the plates is critical regarding the predetermined risk of peri-implant failure in dual plate osteosynthesis of the distal humerus. Varying levels of the outermost screws of corresponding double plates seem to be crucial to avoid complications related to the osteosynthesis.