Patient-Specific Bone Material Modelling Can Improve the Predicted Biomechanical Outcomes of Sacral Fracture Fixation Techniques: A Comparative Finite Element Study

• Published in: Injury 2023-12, Vol.54 (12), p.111162-111162, Article 111162
• Main Authors: Turbucz, Mate, Pokorni, Agoston Jakab, Bigdon, Sebastian Frederick, Hajnal, Benjamin, Koch, Kristof, Szoverfi, Zsolt, Lazary, Aron, Eltes, Peter Endre
• Format: Article
• Language: English
• Subjects: Biomechanics; Finite Element Analysis; Iliosacral Screw Fixation; Patient-Specific Bone; QCT; Sacral Fracture
• ISSN: 0020-1383; 1879-0267
• DOI: 10.1016/j.injury.2023.111162

•All fixations can provide clinically sufficient stability, as the relative interfragmentary displacement on the fracture is below 0.5 mm.•The TISS12 is biomechanically superior, providing the greatest biomechanical stability with the lowest stress on the implant.•Both the LBM and PSM are suitable for performing biomechanical studies, with the bone modelling approach dependent on the study's specific objectives.•Patient-specific bone modelling reveals that insertion of a single screw at S1 is biomechanically more advantageous than at S2. To evaluate and compare the biomechanical efficacy of six iliosacral screw fixation techniques for treating unilateral AO Type B2 (Denis Type II) sacral fractures using literature-based and QCT-based bone material properties in finite element (FE) models. Two FE models of the intact pelvis were constructed: the literature-based model (LBM) with bone material properties taken from the literature, and the patient-specific model (PSM) with QCT-derived bone material properties. Unilateral transforaminal sacral fracture was modelled to assess different fixation techniques: iliosacral screw (ISS) at the first sacral vertebra (S1) (ISS1), ISS at the second sacral vertebra (S2) (ISS2), ISS at S1 and S2 (ISS12), transverse iliosacral screws (TISS) at S1 (TISS1), TISS at S2 (TISS2), and TISS at S1 and S2 (TISS12). A 600 N vertical load with both acetabula fixed was applied. Vertical stiffness (VS), relative interfragmentary displacement (RID), and the von Mises stress values in the screws and fracture interface were analysed. The lowest and highest normalised VS was given by ISS1 and TISS12 techniques for LBM and PSM, with 137% and 149%, and 375% and 472%, respectively. In comparison with the LBM, the patient-specific bone modelling increased the maximum screw stress values by 19.3, 16.3, 27.8, 2.3, 24.4 and 7.8 % for ISS1, ISS2, ISS12, TISS1, TISS2 and TISS12, respectively. The maximum RID values were between 0.10 mm and 0.47 mm for all fixation techniques in both models. The maximum von Mises stress results on the fracture interface show a substantial difference between the two models, as PSM (mean ± SD of 15.76 ± 8.26 MPa) gave lower stress values for all fixation techniques than LBM (mean ± SD of 28.95 ± 6.91 MPa). The differences in stress distribution underline the importance of considering locally defined bone material properties when investigating internal mechanical parameters. Based on the results, all techniques demonstra