[Autologous meniscus replacement with rib perichondrium. Experimental results].

The purpose of our study was to examine the potential of autologous perichondrial tissue to form meniscal replacements. Eighteen mature sheep were used. In 12 animals a complete meniscal resection was performed; replacement was formed using strips of autologous perichondrial tissue explanted from the lower rib; six animals with a complete meniscal resection but without any replacement served as controls. In all animals restriction from weight-bearing was achieved by means of transsection and partial achillestendon resection. Six animals each, 4 of group T and 2 of group C, were sacrificed after 3, 6 and 12 months. Perichondrial grafts and the underlying articular cartilage were removed and investigated by gross macroscopic examination, by means of light and scanning electron microscopy, polarized light examination, and biomechanical tests evaluating the failure stress and tensile modulus. In all transplanted animals a new perichondrial meniscus developed. After 3 months the transplants resembled in size and thickness normal menisci, while in the control animals only small rims of spontaneously grown tissue were detectable. Microscopically, the perichondrial menisci exhibited similarity to normal collagen fiber orientation and cellular characteristics, but, in their central region, areas of calcification disturbed the regular tissue differentiation. In contrast, spontaneously grown tissue in control animals lacked normal fiber orientation and cellularity. Scanning electron-microscopy of perichondrial menisci revealed surface characteristics similar to normal sheep menisci without fissures and lacerations, while the control specimens exhibited such defects. The femoral and tibial cartilage being in contact with the new menisci showed normal surface characteristics apart from one animal with slight surface irregularities. Control animals showed superficial lesions after 3 months, and the extent increased from 6 to 12 months postoperatively. Exemplary microangiographies of the newly grown tissue exhibited a less intense vascularisation after three months when compared to normal menisci with an improving tendency after 6 and 12 months. Biomechanically, values of the failure stress as well as of the tensile modulus of perichondrial menisci were significantly lower than those of normal contralateral menisci. But, spontaneously regenerated tissue in meniscectomized animals exhibited even smaller values also with significant differences towards original menisci. There were no significant differences in values of newly grown perichondrial menisci and spontaneously grown tissue.