US Patent 7018415 Expandable spinal fusion device and methods of promoting spinal fusion

An intervertebral disc space implant includes spaced-apart bone engagement portions that define an intermediate chamber that holds bone growth inducing material into contact with adjacent vertebral bodies. The implant is expandable to establish and maintain desired intervertebral spacing during fusion. The implant includes a first member and a second member arranged to move relative to each other by action of an expansion member, the first member being engageable with the vertebral body below the disc space.