Abstract No. 262: Bone healing in vertebroplasty

Abstract

Pain improvement with vertebral body augmentation using PMMA is seen in greater than 90% of patients. Reduction in pain is due to reduction or elimination of micro-motion. PMMA polymerizes through an exothermic process, potentially causing thermal necrosis and eliciting a response of fibrous tissue layer around the polymer. Its application results in a permanent divide which prohibits fusion of fractured bone interfaces. Presented is the first USA series of vertebroplasty with a bi-phasic ceramic bone substitute, Cerament™ (Bone Support AB), with mechanical properties similar to cancellous bone. Cerament is designed to eliminate micro-motion of fragments and resorb in balance with bone remodeling. Cerament™ is a bi-phasic material comprising a powder of synthetic calcium sulfate (60% by weight) and a balance of sintered hydroxyapatite. Calcium sulfate is targeted by osteoclasts which trigger resorption. A carbonated apatite layer on HA particles attracts osteoblasts which progresses the second phase, bone remodeling, in balance with the resorption. When the Cerament™ powder is mixed with iohexol, an injectable paste is produced. This is demonstrated in the attached micrograph by Voor which illustrates the creeping substitution of new bone within Cerament™ filled critical defects in a rabbit model. Ease of injectability and flow provides a consistent and reproducible percutaneous application. The process is non-exothermic. Its construction delivers a compressive strength similar to cancellous bone when implanted and this restores initial strength. The stiffness is similar to cancellous bone to help prevent additional fractures in adjacent vertebrae. 20 patients have been treated in this first USA vertebroplasty series. 90% of patients have complete pain relief. Pain improved using a VAS score (in the 0 to 10 range) improved from 8.4 pre-op to 1.9 at one week on average. To date 2 patients have maintained an average VAS score of 1.8 at one year. No adjacent level fractures have been experienced to date. No post-operative complications have been reported in the series to date. Further details of the long term clinical results shall be discussed.