Biomechanical evaluation of Pi clamp fixation method under torsional loading for distal radius fractures

Distal radius fractures are prevalent injuries. Unstable fractures with joint involvement generally require surgical fixation to optimize outcomes. One of the ways to treat unstable fractures is percutaneous pinning, which usually has less stiffness compared to the common method of plating in treating this type of fracture. Still, it has some advantages compared to the plating method. Pi clamp fixation method is one of the novel approaches for stabilizing distal radius fractures that utilizes a set of K-wires and a small clamp. This study uses the finite element method (FEM) to examine the effect of the four factors that are expected to have an effect on the stability of fixation. To conduct this research, first, a Taguchi design of experiments was performed to determine the effects of parameters. A geometric model of a fractured bone with an extra-articular transverse fracture, including cortical and cancellous bones, was created. Then, according to the experimental design, eight different fixation patterns were modeled and subjected to torsional loading 1 N.m. The goal of optimization was to increase stiffness, which is equivalent to reducing rotation against torsion. Therefore, each experiment’s maximum rotation under torsion loading was calculated using finite element analysis, and Taguchi analysis was performed on the results. so that the average maximum rotation for two levels of pin diameter is about and for two levels of number of pins is about 0.9°, and for the corresponding levels of the angle relative to the transverse plane in the planes A and B are less than 0.5°. This study showed that pin diameter and number of pins are more influential factors on stiffness, and increasing their values leads to increased stiffness. Additionally, a smaller angle of the pins relative to the transverse plane is desired for higher stiffness under torsional loading.