Construction of a three-dimensional finite element model of proximal humerus and related biomechanical analyses

Abstract

Objective To investigate a method of rapidly constructing a three-dimensional finite element model of the proximal humerus and to characterize the state and distribution of stresses on the model under a physiological state. Methods A normal adult male volunteer was subjected to spiral 64-row CT scanning of the shoulder joints. The DICOM data were input into the Mimics to generate a three-dimensional geometric model of the proximal humerus. The three-dimensional model was input into the ALGOR to create a finite element model following meshing and material property assignment. In the finite element model, boundary conditions were constrained and axial loads applied to simulate a physiological state. Stress distribution and strain results on the finite element model of the proximal humerus were obtained for analyses. Results The established finite element model of the proximal humerus could be rotated arbitrarily for observation from any perspective in three dimensions. All the units had 4 nodes. The units of cortical bone were 9, 346, and those of cancellous bone 25, 732. The total unit number was 35, 078, and the total node number 6, 819. When an axial load of 600 N was applied in a physiological state of shoulder abduction of 90°, the stress at the proximal humerus increased from the proximal to the distal end, peaking at lateral regions of the humeral shaft (9.8 MPa Max) and the stress was emphasized at the calcar region of the cortical area (5.2 MPa max). Conclusions The Mimics software provides a simple and rapid method to construct a three-dimensional finite element model of proximal humerus. Biomechanical analysis on the model shows stress at the proximal humerus is emphasized at the calcar region and lateral regions of the humeral shaft. This indicates that, in internal fixation of fractures of proximal humerus, locked plating in a lateral tension-band position should be done first and mechanical support to the inferomedial region of the proximal humerus seems to be important for maintaining fracture reduction. Key words: Shoulder joint; Finite element analysis; Biomechanics