Long-Term Histologic Changes and Effects of Perichondrium Preservation of Auricular Cartilage Grafted in Rabbit Tympanic Bullae

Abstract

Introduction: This study evaluated the long-term histologic changes of grafted auricular cartilage in rabbit tympanic bullae. Materials and Methods: Auricular cartilage with or without perichondrium was prepared and cut into small pieces to obliterate the rabbit tympanic bullae. The histologic changes of the grafted cartilage in both groups were compared 20 months after surgery. Results: Remarkable spongy bony trabeculae of mature lamellar bone with red bone marrow formation were observed in the perichondrium-preserved group. Parts of the grafted cartilage pieces were invaded and replaced by bone and bone marrow. The grafted cartilage pieces grossly maintained their original polygonal shapes, and no osteochondral tissue regeneration was observed in the perichondrium-removed group. The viable chondrocyte ratios were 46.21 ± 5.58 versus 27.80 ± 4.81%, and the minimal resorption ratios were 10.31 ± 3.27 versus 2.98 ± 1.48% in the perichondrium-preserved (n = 14) and -removed groups (n = 12, p < 0.05). The tissue ratios were cartilage: 38.18 ± 8.76 versus 52.97 ± 9.30%; lamellar bone: 18.49 ± 5.31 versus 0.82 ± 0.43%; bone marrow: 20.72 ± 6.27 versus 0.00 ± 0.00%; fibrous tissue: 10.13 ± 2.74 versus 5.81 ± 2.20%, and adipose tissue: 12.01 ± 4.48 versus 40.70 ± 7.83% in the perichondrium-preserved and -removed groups. The differences were all statistically significant (p < 0.05). Conclusion: A space-filling mass effect with minimal resorption of the cartilage pieces was observed in the perichondrium-removed group. In addition to this mass effect, the progenitor cells in the preserved perichondrium allowed active bone tissue regeneration and cartilage resorption in the perichondrium-preserved group.