Efficacy of perichondrium and a trabecular demineralized bone matrix for generating cartilage

A pedicled auricular perichondrial flap wrapped around trabecular demineralized bovine bone matrix can generate an autologous cartilage graft. In earlier experimental studies, it was demonstrated that this graft could be used for nasal and cricoid reconstruction. It was assumed that the vascularization of the perichondrial flap was obligatory, but it was never proven that the flap should be pedicled. Moreover, for clinical use, the dimensions of the auricle would set restrictions to the size of the graft generated. Therefore, the possibility to generate cartilage with a composite graft of a free perichondrial flap wrapped around demineralized bovine bone matrix, by using young New Zealand White rabbits, was studied. This composite graft was implanted at poorly (subcutaneously in the abdominal wall; n = 12), fairly (subcutaneously in the pinna; n = 12), and well-vascularized sites (quadriceps muscle; n = 12). As a control, trabecular demineralized bovine bone matrix was implanted without perichondrial cover. Half of these grafts (n = 6) were harvested after 3 weeks, and the remaining grafts (n = 6) after 6 weeks of implantation. In histologic sections of these grafts, the incidence of cartilage formation was scored. Furthermore, the amount of newly formed cartilage was calculated by computerized histomorphometry. Trabecular demineralized bovine bone matrix without perichondrial cover demonstrated early resorption; no cartilage or bone was formed. In demineralized bovine bone matrix wrapped in perichondrium, early cartilage formed after 3 weeks at well- and fairly vascularized sites. No cartilage could be detected in grafts placed at a poorly vascularized site after 3 weeks; minimal cartilage formed after 6 weeks. In summary, the highest incidence of cartilage formed when trabecular demineralized bovine bone matrix was wrapped either in a pedicled auricular perichondrial flap or in a free perichondrial flap, which was placed at a well-vascularized site. Second, a significantly higher percentage of the total area of the graft was cartilaginized at well-vascularized sites after 3 weeks. The newly generated cartilage contained collagen type II and proteoglycans with hyaluronic acid binding regions, whereas collagen type I was absent, indicating the presence of hyaline cartilage. This study demonstrates that new cartilage suitable for a graft can be generated by free perichondrial flaps, provided that the site of implantation is well vascularized. Consequently, the size of such a graft is no longer limited to the dimensions of the auricle.