A method of promoting fusion of adjacent vertebral bodies include providing a conically-shaped cage body having bone engaging projections on an outer surface thereof, the cage body including a leading end having a first diameter and a trailing end having a second diameter that is larger than the first diameter. The method also includes positioning the leading end of the cage body adjacent an intervertebral disc space between an upper vertebral body and a lower vertebral body, whereby the upper and lower vertebral bodies have opposing end faces that define upper and lower limits of the intervertebral disc space. While urging the leading end of the cage body into the intervertebral disc space, the cage body is turned so that the bone engaging projections bite into the opposing end faces of the upper and lower vertebral bodies for anchoring the cage body to the upper and lower vertebral bodies.