Abstract:
This study uses finite element (FE) analysis to provide a theoretical framework for understanding and optimizing the biomechanics of vertebroplasty, a procedure that uses bone cement to stabilize fractured vertebrae. An experimentally calibrated, anatomically accurate FE model of an elderly L1 vertebral body was created from CT scans. Mechanical damage was first simulated in the model by applying a compressive load that exceeded the bone's yield strain and reducing the material modulus of yielded elements according to empirical data. Subsequently, virtual vertebroplasty was performed on this damaged model to investigate how the volume and spatial distribution of the cement affect stiffness recovery. The simulations tested cement volumes from 1 to 7 cm³ delivered via four different surgical approaches: unipedicular (left and right), bipedicular, and posterolateral. The results showed that a surprisingly small amount of bone cement—approximately 3.5 cm³, or a 14% volume fill—was sufficient to restore the vertebra's compressive stiffness to its pre-damaged level. A 30% fill increased stiffness by more than 50% above the original value. While unipedicular (single-sided) approaches provided good stiffness recovery, they induced a medial-lateral bending motion, or "toggle," under a uniform pressure load, especially with larger cement volumes. The study concludes that large fill volumes may not be biomechanically optimal; a better approach might be to use a lower volume of cement with a more symmetric placement to restore stiffness while minimizing unstable load transfer.
