Penttilä H (1), Tulamo R-M (2), Waris T (3), Ellä V (4), Kellomäki M (4), Törmälä P (4), Ashammakhi N (3,4)

1. Department of Maxillofacial Surgery, Helsinki University Central Hospital, Helsinki, Finland.
2. Department of Veterinary Medicine, University of Helsinki, Helsinki, Finland.
3. Department of Surgery, Division of Plastic Surgery, Oulu University Hospital, Oulu, Finland.
4. Institute of Biomaterials, Tampere University of Technology, Tampere, Finland.

Introduction
It has been demonstrated that cartilage can be grown by using free perichondrial transfers in muscle tissue. The size of such grown cartilage pieces is, however, limited by the ability of nutrients and oxygen diffusion into the growing tissue because of the lack of vascularity. Growth factors have been tried to improve the outcome but none have been successful so far to induce permanent vascularity to the constructed tissue.

Aim
The aim of this experiment is to demonstrate whether it is possible to grow definitely larger and eventually thicker constructs of cartilage by using a composite of prefabricated grafts. These would provide vascularity and favourable environment for the chondrocytes to migrate into and grow.

Materials and methods
We used rabbits as experimental animals. As the source of perichondrium we used dorsal ear perichondrium with central artery and vein. As scaffold we used non-woven PLDLA 96/4 (poly-L/D-lactic acid 96/4) 1 mm thick 80 x 30 x1 mm sized pieces. The perichondrial flaps were raised and the pedicular vessels were dissected free and separated. Each scaffold was cut to the size of the flap and rounded at the corners. The flaps were placed under the ventral skin of each rabbit. The pedicular vessels were anastomosed to the femoral vessels, as end-to-end for arteries and side-to-end for veins. The ear skin was closed over the existing cartilage and the inguinal incision over the anastomosis area. The follow-up groups were 1 month, 3 months and five months. As controls we used three animals, one with biodegradable scaffold only, one with perichondrial flap and scaffold without microvascular method and one with microvascular pericohndrial flap without biodegradable scaffold. All controls were in the 5-month follow-up group.

Results
Preliminary results have shown that the procedure is feasible and the animals as well as the flaps have survived the procedure. Specimens were harvested and they are being prepared for histological examination, the results of which will be reported on soon.

Conclusions
Microvacularised perichondrial flaps combined with biodegradable scaffolds can be used to tissue-engineer cartilage constructs in a rabbit model. This may have an impact in staged clinical cartilage reconstruction in human.

Key words
biodegradable scaffolds, cartilage, microsurgery, tissue engineering