Computational Simulations of Vertebral Body for Optimal Instrumentation Design

The engineering design of surgical instrumentation to exert forces and torques/moments on bones during operations constitutes a rather difficult task. This technical difficulty is caused mainly by the natural, pathological, and individual irregularities of the human bone morphologies and surfaces. Usually, mechanical forces are applied on determined parts of bone surfaces, so-called regions of interest (ROIs). We describe a computational method (CAD) to digitalize, simulate, and fit mathematically the anterior vertebral body morphometric. Based on experimental data from 17 cadaveric specimens, large sets of surface digital points were generated. Complete anterior vertebral body morphologies were visualized and analyzed with subroutines, which are initially used to select these natural ROIs. Subsequently, an optimized fitting model was implemented for the ROIs. 3D surface equations of the anterior vertebral body (L3, L4, L5, and S1) were determined. Statistics and determination coefficients which define the error boundaries and goodness of the model, were calculated and mathematically analyzed. A bioengineering application is the use of these equations for the industrial design of an innovative vertebral distractor. The device separates two adjacent vertebrae in parallel, and minimizes the force to carry out the surgical maneuver.