Morphologic Study on a Vascularized Composite Flap for Tracheal Reconstruction in Rabbit: I. Light Microsopic Study

Kim, Eun Seo; Hong, Won Pyo; Lee, Jeung Gweon; Chung, Yoo Sam; Choi, Young Joon; Kong, Seok Cheol

Abstract

Successful regeneration of a cartilage framework using perichondrium has been reported by several authors but there are some arguments surrounding mucosal regeneration. Some authors report that regeneration of mucosa is completed by ingrowth from neighboring tissue but others insist that it occurs via metaplasia from the squamous epithelium. This study was designed to investigate the differences in regeneration between nonvascularized and vascularized flaps. A 5 X 15mm sized vascularized composite flap composed of vascularized perichondrium pedicled on the central auricular artery and free buccal mucosa which was harvested from the oral cavity and sutured on the vascularized perichondrium was fabricated in a rabbit ear. It was transferred to a pre-created 4 X 12mm tracheal defect. A morphologic study was carried out to determine the outcome of the grafted mucosa at regular intervals under light microscopy after H and E staining. A nonvascularized perichondrial-mucosal composite flap with the same dimension was transferred in the control group. The results are as follows;1) The control group showed necrosis of the grafted mucosa and defective area was covered by ingrowth of the neighboring normal mucosa. The periphery of the defective area regenerated earlier than the central area and immature epithelia were still found 6 weeks after the graft. Regeneration of cilia was rather inconsistently observed 8 weeks after the transfer. 2) In the experimental group, the grafted mucosa survived on the vascularized perichondrium which was thought to act as a vascularizing bed. Two weeks after reconstruction, the covering epithelium appeared almost as normal as the tracheal columnar epithelium. At 4 weeks, the regenerated mucosa could hardly be distinguished from the normal mucosa. Regeneration of cilia was consistent at 6 weeks in the experimental group. Mucosal regeneration in the experimental group was superior to the control group in terms of degree and quality. Mucosal coverage of the control group occurred by ingrowth from the neighboring mucosa. In the experimental group, survival of the grafted mucosa relied upon revascularization through the vascular pedicle. It can be conceived that metaplasia of the grafted mucosa occurs in a vascularized composite flap transferred group. In conclusion, maintenance of vascularization is essential to successful regeneration of grafted mucosa with good quality.