Finite Element Analysis of Vertebral Augmentation Using Metal Stents Combined with Artificial Bone versus Polymethyl Methacrylate (PMMA).

Background: With the increasing use of polymethyl methacrylate (PMMA) for vertebral augmentation, the complications caused by PMMA have also increased. In order to avoid the complications, metal stents combined with artificial bone are currently used in clinical practice for vertebral augmentation. We conducted finite element analysis on the biomechanical differences between metal stents combined with artificial bone versus PMMA on adjacent vertebrae and intervertebral discs, in order to find whether metal stents combined with artificial bone have more advantages.

Methods: Finite element models of a functional spinal unit from T11 to L1 were created based on computed tomography data. The T12 vertebra was augmented using three different materials: one metal stent with artificial bone, two metal stents with artificial bone, and PMMA. The model assumed fixation of the lower endplate of L1. A 350 N follower load was applied at the centre of the upper endplate of T11, with flexion, extension, lateral bending, and axial rotation under a 7.5 Nm moment.

Results: Compared to the PMMA augmentation model, the maximum von Mises stress within the augmented vertebra significantly increased with metal stents combined with artificial bone. Meanwhile, the augmentation materials in the vertebral body among the three models showed no significant difference. Furthermore, compared to the PMMA augmentation model, metal stents combined with artificial bone models exhibited reduced stress on adjacent vertebrae and intervertebral discs during flexion-extension and lateral bending. No significant biomechanical differences were observed between one or two metal stents combined with artificial bone models.

Conclusions: Metal stents combined with artificial bone and PMMA can enhance the strength and rigidity of the augmented vertebra, aiding reconstruction of vertebral function. Metal stents combined with artificial bone offer biomechanical advantages over PMMA for adjacent vertebrae and intervertebral discs.