# Biomechanical Comparison of Three Fixation Constructs for Tile Type C1.2 Pelvic Ring Fractures: A Finite Element Analysis

## TL;DR

This study compares three surgical methods for fixing Tile type C1.2 pelvic fractures using computer modeling to determine which provides the best stability.

## Contribution

The study introduces a finite element analysis comparing three fixation constructs for Tile C1.2 pelvic fractures, revealing biomechanical differences in stability.

## Key findings

- The iliosacral screw construct showed the lowest displacement and highest stiffness under vertical loads.
- The transiliac plate construct had larger displacements compared to the iliosacral screw.
- The anterior reconstruction plate provided intermediate stability but higher joint stresses.

## Abstract

Fractures of the pelvic ring are among the most severe injuries in orthopaedic practice and Tile type C lesions are characterized by complete disruption of the posterior arch with both vertical and rotational instability. The optimal construct for posterior ring fixation remains a matter of debate. The aim of this study was to compare, by means of finite element analysis, the biomechanical performance of three different methods of osteosynthesis for Tile type C1.2 pelvic ring fractures: a transiliac plate, one iliosacral screw and two anterior reconstruction plates on the sacroiliac joint. A three-dimensional model of an intact pelvis was reconstructed from computed tomography images of a healthy adult male. A Tile type C1.2 injury pattern was created virtually, and three fixation constructs were designed in Ansys SpaceClaim according to manufacturer specifications. All materials were assumed to be homogeneous, isotropic and linearly elastic. Vertical loads of 400 N and 800 N were applied to the sacral endplate to simulate partial and full weight bearing, while the acetabular regions were constrained to represent standing stance. In this study, mechanical stability was operationally defined as resistance to global displacement under applied vertical load, with lower displacement indicating higher construct stiffness. Construct stiffness, total deformation and von Mises stress were assessed for bone and implants. For both loading conditions, the iliosacral screw construct showed the lowest overall displacement and provided the greatest stiffness. The transiliac plate construct presented larger displacements, whereas the anterior reconstruction plate construct provided intermediate stability with higher stresses at the sacroiliac joint. Among the analyzed constructs, the iliosacral screw provided the greatest stiffness and lowest overall displacement, suggesting superior mechanical performance under vertical loading conditions.