Ceramic implants, such as spinal implants, may comprise a dense shell and a porous core. In some implementations, methods for manufacturing the implants may comprise one or more stages at which the core material abuts the shell so as to form a mechanical attachment therewith while both the core and the shell are in a green state. The core and the shell may be fired together, and the resultant implant may, in some embodiments, comprise a unitary piece of ceramic material. Some embodiments may comprise silicon nitride ceramic materials.