Helical coil electrode radiofrequency ablation designed for application in osteolytic vertebral tumors--initial evaluation in a porcine model

Impact of radiofrequency ablation (RFA) on bone quality in a murine model of bone metastases

Thermal therapies such as radiofrequency ablation (RFA) are gaining widespread clinical adoption in the local treatment of skeletal metastases. RFA has been shown to successfully destroy tumor cells, yet the impact of RFA on the quality of the surrounding bone has not been well characterized. RFA treatment was performed on femora of rats with bone metastases (osteolytic and osteoblastic) and healthy age matched rats. Histopathology, second harmonic generation imaging and backscatter electron imaging were used to characterize changes in the structure, organic and mineral components of the bone after RFA. RFA treatment was shown to be effective in targeting tumor cells and promoting subsequent new bone formation without impacting the surrounding bone negatively. Mineralization profiles of metastatic models were significantly improved post-RFA treatment with respect to mineral content and homogeneity, suggesting a positive impact of RFA treatment on the quality of cancer involved bone. Evaluating the impact of RFA on bone quality is important in directing the growth of this minimally invasive therapeutic approach with respect to fracture risk assessment, patient selection, and multimodal treatment planning.

Comparison of the effect of two different bone-targeted radiofrequency ablation (RFA) systems alone and in combination with percutaneous vertebroplasty (PVP) on the biomechanical stability of the metastatic spine

INTRODUCTION

Radiofrequency ablation (RFA) and percutaneous vertebroplasty (PVP) are used independently and in combination to treat metastatically involved vertebrae with the aim of relieving pain, reducing tumour burden and providing bony mechanical stabilization.

PURPOSE

The aim of this work was to characterize the effect of two bone-targeted RFA devices, alone and in combination with PVP, to improve strength and mechanical stability in vertebrae with osteolytic metastatic disease.

METHODS

Simulated spinal metastases (n = 12) were treated with one of two bone-targeted RFA devices (bipolar cooled or bone coil RF electrodes), followed by PVP. Under axial compressive loading, spinal canal narrowing was measured in the intact specimen, after tumour simulation, post-RFA and post-PVP.

RESULTS

RFA alone resulted in successful tumour shrinkage and cavitation, but further increased canal narrowing under loading. RFA combined with PVP significantly reduced posterior wall stability in samples where sufficient tumour shrinkage and cavitation were coupled with a pattern of cement deposition which extended to posterior vertebral body.

CONCLUSIONS

RFA combined with cement deposition in the posterior vertebral body demonstrates significantly more stable vertebrae under axial loading.