A spinal fusion device for implantation between adjacent vertebrae is formed in the approximate shape of a hollow cube. The device has an upper section and a lower section relatively movable with regard to each other. The sidewalls of the upper section and the lower section terminate in complementary inclined planes so that as the sections move away from each other the height of the device lessens and as the sections move toward each other the height of the device increases. A distractor is placed within the hollow body and contacts the upper and lower sections by a link which is used to adjust the height of the device.