Functional gradients in natural and biomimetic spinal disk structures

Naturally occurring gradients have been identified in the natural spinal disk joint. Emulating these gradients within a total joint arthroplasty may allow the motion-moderating function of the disk to be more closely replicated. Biomimetic functionally gradient materials have been developed for providing rigid bone-engaging caudal and coronal bioactive surfaces that transition to a flexible fibrocartilage-like portion. Methods are detailed for forming thermoplastic elastomers, bioactive reinforcement, radially aligned anisotropic composites and functionally graded materials with axial and radial gradients. Employing these methods to the vertebral-interlocking spinal disk design provides a biomimetic approach to reduce risk of hypermobility, stress concentration and implant migration.