US Patent 7578848 Intervertebral stabilizer

An intervertebral stabilizer includes: a first surface operable to engage an endplate of a first vertebral bone of a spine; a second surface spaced apart from the first surface and operable to engage an endplate of an adjacent second vertebral bone of the spine; a spring element between the first and second surfaces and operable to provide reactive force in response to compression loads from the first and second vertebral bones, wherein a cross-sectional profile taken through the surfaces is hourglass shaped.