An intervertebral spacer adapted for implanting between adjacent vertebral bodies of a human spine as a load-bearing replacement for a spinal disc. The spacing member may include an external, non-porous, concavo-convex contour with respect to one dimension of the spacing member. The spacing member may be constructed from a rigid, non-resilient load-bearing material that is incapable of elastic deformation. The spacing member may be inserted with the aid of a sheathed trocar device that is releasably attached to the spacer, to enable implantation and selective positioning of the spacer by the surgeon from the posterior side of the spine, without the need to retract the dural nerve or the posterior longitudinal ligament.