MATHEMATICAL MODELING OF INTERLOCKING NAILSBY THE FINITE ELEMENT METHOD

Abstract

Introduction. The implementation and using new types of orthopedic devices involves solving
complex biomechanical, biophysical, technological problems. In this paper, we consider a mathematical
model of a nail, described by the finite element method, and an imitation of phenomena occurring in this
system over time.
Materials and methods. At the first stage we define and execute the 3D model geometry.
Depending on the geometry type, we construct the model. At the second stage, it is necessary to
determine the shape and size of the finite elements to be applied to the grid model. At the stage of
specifying mechanical and strength properties, the composition of the material, its density, modulus of
elasticity, and temperature of the system during the experiment are indicated. To implement the
geometric model, two types of nails were chosen: the investigated elastic locking nail (sample 1) and the
intramedullary interlocking nail ChM (sample 2). The mesh was partitioned using a standard procedure
built into the SolidWorks software package.
Result. The minimum of stresses in sample 1 is 2200 times less than in sample 2. The maximum of
stresses in sample 1 is 14 times smaller than stresses in sample 2. In sample 2, in a similar comparison,
we obtain a maximum stress of 3.2 times less yield point. Thus, sample 1 has a significant margin of
strength, which allows it to be used at high loads and, accordingly, for patients with a higher body
weight.
In sample 1, the upper part undergoes minimal stresses, and the lower components are slightly
loaded, but the distribution of stress along their entire length is uniform and much lower than in sample
2. The maximum stress falls on the lower part of nail where locking screw place is located. Such a
distribution of stresses and their low values, in our opinion, are due to the peculiarity of the composite
design of the sample 1.
Conclusion. Elastic locking nail has high strength and performance characteristics in comparison
with the ChM’ nail.