Osseogenesis refers to a bone formation with no indication of cellular origin. When the new bone is formed on or about a graft, it may be either of graft origin (i.e., from cells that survive the transfer and are capable of forming bone) or from cells of host origin. Surface cells on cortical and cancellous grafts that are properly handled can survive and produce new bone. This early bone formed by viable graft cells is often critical in callus formation during the first 4 to 8 weeks after surgery. Cancellous bone, with its large surface area covered by quiescent lining cells or active osteoblasts, obviously has the potential for more graft-origin new bone formation than does cortical bone.
Corticocancellous and cortical allografts provide structural support and are osteoconductive to a limited degree. Corticocancellous grafts may be prepared from the ilium, the distal femur, or the proximal tibia. A cortical bone may be cut longitudinally to yield struts, which are generally used to buttress preexisting bone or constructs. Full-thickness fibulas may also be used as struts. Full-thickness cortical bone grafts, ranging from short ringlike structures to entire diaphyses, are available and are generally used to fill defects and to buttress constructs.