US Patent 7182783 Selectively expandable composite structures for spinal arthroplasty

Embodiments include selectively expandable composite structures useful as spinal arthroplasty devices such as intervertebral disc prostheses. The structures may comprise an outer shell comprised of a non-hydrogel polymer material. The structures also may comprise at least one core positioned within the outer shell. The core may be comprised of a hydrophilic polymer. The core may expand upon hydration, thereby deforming the outer shell. The selectively expandable composite structures may be implanted in a dehydrated form and then expand during re-hydration following implantation.