Materials and design of spinal implants--a review

Man-made devices have been implanted into the body to relieve pain, to restore function, and to facilitate healing. The subjects of this review are the materials, and to a lesser extent, the design aspects of the numerous implants that are available to the surgeon in dealing with the ailing spine. Often it is the material aspects of such devices that are responsible for their success or failure. It may be that osteoconductive properties are desired for implants to assist fusion, whereas as inert a material as possible would be preferred for interpositional barriers. The materials composing the instrumentation used to facilitate healing of spinal fractures would ideally have properties that optimize strength and biocompatibility, while at the same time minimizing imaging artifacts and allowing a gradual transfer of load from the instrumentation to the vertebral body (i.e., viscoelastic effects). The application of biomaterials and biomechanics to the design of spinal devices is obvious; what may be more subtle though is what the in vivo interactions of these will be. The study of such aspects must continue in order to better evolve the designs and subsequent results of implanted spinal devices.