Magnetic kyphoplasty: A novel drug delivery system for the spinal column

Vertebral compression fractures (VCFs) caused by metastatic malignancies or osteoporosis are devastating injuries with debilitating outcomes for patients. Minimally invasive kyphoplasty is a common procedure used for symptomatic amelioration. However, it fails in treating the underlying etiologies of VCFs. Use of systemic therapy is limited due to low perfusion to the spinal column and systemic toxicity. Localized delivery of drugs to the vertebral column can provide a promising alternative approach. A porcine kyphoplasty model was developed to study the magnetically guided drug delivery of systemically injected magnetic nanoparticles (MNPs). Jamshidi cannulated pedicle needles were placed into the thoracic vertebra and, following inflatable bone tamp expansion, magnetic bone cement was injected to the vertebral body. Histological analysis was performed after intravenous injection of MNPs. Qualitative analysis of harvested tissues revealed successful placement of magnetic cement into the vertebral body. Further quantitative analysis of histological sections of several vertebral bodies demonstrated enhanced accumulation of MNPs to regions that had magnetic cement injected during kyphoplasty compared to those that did not. By modifying the kyphoplasty bone cement to include magnets, thereby providing a guidance stimulus and a localizer, we were successfully able to guide intravenously injected magnetic nanoparticles to the thoracic vertebra. These results demonstrate an in-vivo proof of concept of a novel drug delivery strategy that has the potential to treat the underlying causes of VCFs, in addition to providing symptomatic support.