Biomechanical study of a novel polyanhydride-based biodegradable intervertebral cage in spinal surgery

Biomechanical study of a novel polyanhydride-based biodegradable intervertebral cage in spinal surgery Intervertebral disc degeneration may result in disc herniation, spondylolisthesis, discogenic pain, cervical or lumbar kyphosis. Intervertebral cages can restore the sagittal alignments, restore disc heights, reduce the loading of facet joints, increase the stability of the fixed segments, improve bone fusion rate, and expand the neural foramens to relieve nerve root compression. Intervertebral cages are mainly made of titanium or polyether ether ketone (PEEK). But there are still shortcomings: Their Young's modulus are much higher than the cortical bones, which may cause implant subsidence into endplates. Implant subsidence is associated with pseudoarthorsis. Clinical studies have shown delayed bacterial infection because of long-term foreign body in the spine. Besides, titanium and PEEK cages can not be used as drug carriers to promote osteogenesis. Biodegradable intervertebral cages, such as polylactic acid (PLA) or polycaprolactone (PCL) have been widely studied. But these polymers are associated with poor cell affinity. Besides, hydrolysis of ester bonds results in low pH value, which causes non-infectious inflammation. The mechanical strength decreases rapidly through the degradation process. The pseudoarthrosis rate is high in PLA and PCL intervertebral cages. Polyanhydrides are biodegradable polymers with good biocompatibility. The pH value decreases slightly without affecting cell viability. Surface degradation can maintain mechanial strength through the process of degradation. As drug carriers, they can protect protein activty. Hydroxyapatite is the main component of bone tissue. It can enhance osteoblast affinity and prevent fibrous tissue formation at the bony gaps. In this study, the research team will use hydroxyapatite and polyanhydride copolymer to fabricate intervertebral cages. In the first year, material preparation, property evaluation, in vitro cell experiment and small animal biocompatibility test will be performed. We will fabricate a new composite with mechanial strength slightly higher than the cortial bone. The new composite is characteristic with slow degradation, high cell affinity and stable drug release profile. In the second and third years, mechanical tests and large animal experiments will be peformed. The spinal bone union rate will be determined by computer tomography and material testing machine. This innovative research is expected to benefit patients with degenerative spine disease.

Project ID:PB10202-1560
External Project ID:NSC101-2221-E182-079-MY2