Optimization of Bone Cement Stiffness in Metastatic Vertebral Augmentation: Balancing Strength Restoration and Stress...

The goal of this study was to investigate the mechanical performance of vertebral augmentation with various polymer-based materials across different defect sizes. Specifically, this study aimed to identify the optimal stiffness of bone cement that maximizes vertebral strength while minimizing stress redistribution.

A calibrated quantitative computed tomography-based finite element analysis (QCT/FEA) approach was developed and calibrated against cadaveric experimental data. Lytic metastatic defects were simulated in human vertebrae at two augmentation volumes (20 and 50%) and filled with materials spanning a wide range of elastic moduli (50 to 2500 MPa). Stress distributions and fracture forces were analyzed in six vertebrae to evaluate the influence of material stiffness and augmentation size.

The QCT/FEA models accurately predicted vertebral strength (R² = 0.96) and showed that increased material stiffness leads to higher fracture force but also significantly elevates stress concentrations. An augmentation material with an elastic modulus of approximately 300 MPa offered a favorable balance between strength restoration and minimal stress elevation, especially for 50% augmentation size. Paired t-tests revealed that materials with moduli ≤ 300 MPa did not produce statistically significant stress redistribution compared to intact bones, while stiffer materials (≥1000 MPa) did.

The findings suggest that a bone cement stiffness of approximately 300 MPa may provide optimal mechanical benefits by enhancing vertebral strength without inducing excessive stress redistribution. The study also highlights that augmentation size strongly influences the mechanical outcomes, with larger augmentation volumes showing greater sensitivity to material stiffness. The proposed patient-specific QCT/FEA framework provides a cost-efficient, adaptable tool for preclinical evaluation and personalized planning of vertebral augmentation These insights can assist material developers in optimizing bone cement formulations for patient-specific treatments.