Influence of Gap Shape on Biomechanical Properties of Extra-Articular Distal Humeral Fracture - A Finite Element Study

The aim of the study was to assess the influence of gap shape on biomechanical results in extra-articular distal humeral fracture: with contact on the posterior part (by anterior gap) and contact on ulnar column (by radial gap). The goal was to examine if and to what extent did displacements decrease in comparison with previously examined parallel gap without bony contact. The finite element analysis on the three different plate constructs was performed, i.e. parallel, perpendicular and newly designed Y shape plate were considered. Displacements were measured on articular surface and gap point. The most visible decrease of maximum displacements in the distal part of the model was detected in the Y plate model with axial loading: in case of anterior gap 58.5% and especially at radially formed gap 60.9%. Similarly, at axial loading, displacement at the analyzed point on fracture gap most significantly decreased in Y plate model (by 49.4%) at posterior bony contact. Moreover, the latter showed displacement decrease by 68.5% at ulnar bone contact. Furthermore, if a longer radial plate than the ulnar one was used, varus stress could have been avoided. Study results suggested that sufficient stability could be ensured with the newly designed Y shape plate.