Induction in vivo of cartilage grafts for craniofacial reconstruction.

In the craniofacial region, defects of cartilage structures are preferably reconstructed with autologous cartilage. Donor-site morbidity related to the creation of a new defect elsewhere, and a lack of growth potential of the graft--mandatory in children--have stimulated investigators to find other ways to generate new "extra" cartilage. Several biomaterials have been tested as a matrix for the ingrowth of (peri)chondroblasts in experimental animals. In young (growing) rabbits we have developed a process of heterotopic cartilage induction with the use of a demineralized (bovine) bone matrix which is enfolded in a pedicled flap of ear perichondrium for at least three weeks. During this period the demineralized matrix is colonized by macrophages and polymorphonuclear cells which start a process of complete biodegradation of the material. Simultaneously, the collagen matrix is invaded by mesenchymal cells, originating from the perichondrium and differentiating into chondroblasts and later, into chondrocytes forming the intercellular substance. The developing, very young cartilage could be demonstrated as collagen type II, thus, hyaline cartilage. When applied with its adherent perichondrium as a graft, it merges easily with the more matured host cartilage and even appears to be capable of further growth. Therefore, it seems suitable for the reconstruction of a cartilaginous defect in growing cartilaginous structures like the nasal septum or the larynx.