FREE FLAP TRANSFER IN RABBITS USING IRRADIATED RECIPIENT VESSELS

By E. TAN, F.R.A.C.S., B. McC. O’BRIEN, M.Sc., M.S., F.R.A.C.S., F.R.C.S., F.A.C.S. and M. BRENNEN, F.R.C.S.

Microsurgery Research Unit, St Vincent’s Hospital, Melbourne, Australia

THE free flap is well established as a method of obtaining soft tissue cover. As more indications arise for its use, the prospect of transferring a free flap with anastomoses to vessels which are not normal arises. When a free flap is used for cover in an area previously treated by radiotherapy, the most accessible recipient vessels may have been irradiated.

The purpose of the following experiments was to ascertain the results of free flap transfer using previously irradiated recipient vessels especially since free flaps in 2 patients had failed following the use of irradiated vessels,

MATERIALS AND METHODS

New Zealand-strain white rabbits of mixed sexes and averaging 2.0 kg were used. Ten rabbits acted as controls, and 48 rabbits were reserved for the experiment and irradiated in the left groin. The dose of irradiation was 2,000 rad, using a Siemens 250 KV machine with HVL 0.9 mm of copper, delivered to a circular field 2.5 cm in diameter, centred around the left femoral artery palpated just below the left inguinal ligament. This relatively low dosage resulted in loss of hair over the field but none of the rabbits had ulceration or moist desquamation.

The experimental animals were divided into 2 groups of 24 each. At 6 weeks after irradiation, the first group of 24 rabbits had composite free flaps taken from the right groin and transferred to the left groin, by the technique of O’Brien and Shanmugan (1973) and using the irradiated left femoral artery and vein as recipient vessels (Figs. I and 2). At 16 weeks after irradiation, the second group of 24 rabbits had similar free flap transfers. Ten control transfers were conducted, interspersed with the experi- mental animals. Anaesthesia was administered with intravenous Nembutal followed by nitrous oxide and oxygen inhalation by mask. No anticoagulants or antibiotics were used.

RESULTS

In the experimental groups there were 38 rabbits remaining after: anaesthetic deaths (4); upper respiratory tract infection (2); haemorrhage (2); unsuitable vessels (2). All IO control animals were available.

Of the 38 rabbits, 19 had free flap transfers 6 weeks after irradiation and 19 had them 16 weeks afterwards. In each group 9 out of 19 flaps necrosed. Necrosis began on the 3rd and 4th postoperative days and usually started at one margin or corner. It then progressed rapidly and was complete by the 7th or 8th day.

In the IO non-irradiated controls, 9 had viable flaps. The single necrotic flap was found to have a 180” rotation at the venous anastomosis.

Address for reprints: Mr B. McC. O’Brien, Director, Microsurgery Research Unit, St Vincent’s Hospital, Melbourne 3065, Australia.

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122 BRITISH JOURNAL OF PLASTIC SURGERY

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FIG. I. The free groin flap is supplied by the superficial inferior epigastric arteries and removed with these vessels and short lengths of the femoral artery and vein. It is anastomosed to the femoral vessels on the

other side with IO/O Nylon.

FIG. 2. (a) The flap isolated on its vascular pedicle. (b) After transfer to the non-irradiated side, the donor area is closed directly.

DISCUSSION

With the technique used here, O’Brien and Sharmmgan achieved IOO per cent survival in 27 free flaps in rabbits, and apart from the single technical error the same results were obtained in this control series. The death of almost half the flaps anasto- mosed to irradiated vessels is therefore highly significant. It is also significant that there was no difference in the results whether the rabbit had been irradiated 6 or 16 weeks previously.

Ohtsuka et al. (1976) reported a case in which a human free groin flap was success- fully transferred to a facial defect by anastomosis to heavily irradiated vessels. On the other hand we have had no success and indeed have lost 3 flaps using irradiated vessels. Dr Kiyonori Harii (personal communication) has had a similar experience. It is now our practice to avoid the use of irradiated vessels by mapping out the precise field of the previous irradiation and then use interpositioned vein grafts to reach suitable normal vessels or transplants with long vascular pedicles.

FREE FLAP TRANSFER IN RABBITS 123

SUMMARY

In rabbits free flaps anastomosed to irradiated vessels have about a 50 : 50 chance of

survival.

This project has been supported in part by the National Hea?th and Medical Research Council a?zd the Anti-Cancer Council of Victoria.

The authors express their gratitude to St Vincent’s Hospital for its unfailing support of the laboratories.

REFERENCES

O'BRIEN, B. McC. and SHANMUGAN, N. (1973). Experimental transfer of composite free flaps with microvascular anastomoses. Australian and Nero Zealmd Journal of Surgery,

OHT$I?I~?~& KAMIISHI H SAITO H ITO M. and SHIOYA, N. (1976) Successful fret flap kn8fers with diseiied rec;pie& vekels. British Journal of PIask Surgery, 29, 5.