Objective: Spinal metastatic disease occurs in up to one-third of all cancer patients. Metastasis can lead to vertebral burst fracture and consequent neurologic compromise. Percutaneous vertebroplasty (PV) is a minimally invasive procedure aimed at restoring vertebral stability by augmentation of weakened vertebrae with bone cement. PV is associated with a complication rate of 10% in treating vertebral metastases. Tumor ablation before cement injection has been suggested to improve PV outcome in the metastatic spine. The objectives of this study were to quantify the effects of volumetric tumor reduction and cement augmentation in the metastatic spine and to develop a protocol for recommended cement volume to achieve sufficient restoration of intact (nonpathologic) vertebral body stability.
Methods: A biphasic parametric finite element model of an L1 spinal motion segment was developed and validated against previously collected experimental data. Using this model, 12 scenarios were simulated to represent tumor volume reductions of up to 60% and cement augmentation from 1 to 8 mL.
Conclusions: Restoration of intact vertebral stability is possible in metastatic vertebrae after 30% tumor ablation and 1 to 2 mL bone cement augmentation. A protocol was developed on the basis of the findings of this study suggesting recommended cement volume for injection as a function of remaining tumor volume after ablation. These findings may motivate refined methods of prophylactic treatment of metastatic vertebrae.