Sunday, November 3, 2002 - 2:33 PM

Autogenous Ear Reconstruction: Prefabrication and Prelamination in a Rat Model

Tzu Ying Tammy Wu, MD and Michael W. Neumeister, MD.

Introduction: Prefabrication and prelamination of flaps and tissue engineering provide an enriched armamentarium in difficult reconstructions. The current study employs these techniques to create a vascularized autogenous ear construct that is readily transferable on its own vascular pedicle.

Methods: Male Wistar rats (250-350g) were anesthetized. An incision was made over the right lower abdominal wall. A pocket was formed by blunt dissection just below the panniculus carnosus. A separate incision was made over the right femoral vessels, which were then isolated and transected distally. The vessels were transposed in a subcutaneous plane to the abdominal wound. A silicone mold in the shape of an ear (2 cm x 1.5 cm) was placed over the transposed vessels in the abdominal wound pocket. The mold and the vessels were secured with 6.0 vicryl sutures. The wounds were closed. In one group of rats, auricular cartilage was harvested at this setting, minced, washed, and cultured using standard chondrocyte culturing techniques. After 14 days, the chondrocyte culturing was complete and a vascularized capsule based on the incorporated, transposed femoral vessels was formed. The cultured chondrocytes were then introduced into the molded capsule with or without fibrin glue through an incision along the lateral aspect of the vascularized capsule. Another group of rats received intact auricular cartilage which was harvested at this setting (no cell culture) and placed directly into the molded capsule. Study groups included capsules filled with intact auricular cartilage, cultured chondrocytes only, cultured chondrocytes and a fibrin glue carrier, and the fibrin glue only. The capsule was closed and the wounds sutured. An additional group of rats received intact auricular cartilage placed into the subcutaneous plane, juxtaposed to the abdominal muscle fascia with the femoral vessels transposed directly on top of the auricular cartilage without the capsule. The prefabricated, prelaminated construct was isolated on its vascular pedicle at various time points. Gross examination and histological analysis were performed.

Results: All of the capsules were completely vascularized and could be reliably isolated on the transposed femoral vessels. The pedicle, being incorporated directly into the capsule, provided the dominant blood supply to the construct. None of the capsules with the fibrin glue only retained any shape and were devoid of cartilage. Similarly, there was no evidence of retained cartilage in the capsules filled with cultured chondrocytes alone. All capsules with the cultured chondrocytes and the fibrin glue carrier had mature shaped cartilage preserved. Those with intact auricular cartilage with and without capsule maintained the original shape of the cartilage and had as its main blood supply the transposed femoral vessels.

Discussion: We have shown that transposing a vascular pedicle to a subcutaneously placed silicone block will result in a vascular capsule that can be mobilized and transferred based solely on the pedicle. Similarly, intact autogenous auricular cartilage can be vascularized by the transposed pedicle without presence of the capsule; the shape of the cartilage is maintained as well with or without the capsule. On the other hand, cultured chondrocytes require a vascularized capsule along with an appropriate carrier such as fibrin glue to grow and thrive.

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