Corticocancellous bone grafting from the iliac crest is widely used for repair of primary palate clefts. In most protocols this procedure is delayed until mid childhood. Donor site morbidity is considerable, requiring hospitalization in most cases. Consolidation of the site depends upon the survival of the graft. Osteoconduction (replacement of the transferred bone by autogenous bone) also takes place. For these reasons the ulimate“fill” of the cleft site can be quite irregular, sometimes as low as 20%.
The mesenchymal source for craniofacial bone, the skull base excluded, is the neural crest. These cells all have membrane-receptors for bone morphogenetic protein (BMP). They are found in the cambium layer of the periosteum and are responsible for the membranous ossification process by which the maxilla develops. Stimulation of periosteal mesenchymal stem cells (MSCs) by recombinant human bone morphogenetic protein-2 (rhBMP-2) results in membranous bone formation in a variety of animal and human models. This process is known as osteoinduction.
The mesenchymal source for all bones below the skull is mesoderm, not neural crest. Because dissection of an alveolar cleft involves exposure of its original mucoperiosteal lining, BMP-2 mediated osteoinduction of local neural crest MSCs is more logical than transfer of a non-neural crest mesenchymal graft. Dosing of rhBMP-2 is species-specific. Humans respond best to 1.5 mg/cc. This is delivered in a uniform concentration by saturation of an absorbable collagen sponge (ACS) of fixed size, by a predetermined amount of reconstituted rhBMP-2. This technique of bone synthesis is called in situ osteogenesis (ISO).
We report the use of rhBMP-2/ACS implantation in human cleft sites. Graft take was evaluated by a combination of dental radiographs and 3-dimensional CT scans. Grafting was successful in 64/65 sites. One site required re-entry and healed well subsequently. Bone formation within the clefts was remarkably uniform. Successful osteoinduction took place regardless of cleft size. All surgeries were done on an outpatient basis. Alveolar cleft reconstruction using ISO is highly effective, fast, and carries minimal morbidity when compared to conventional grafting techniques.