LYON, FRANCE – Doctors in France said they had performed the world’s first partial face transplant, forging into a risky medical frontier with their operation on a woman disfigured by a dog bite.

The 38-year-old woman, who wants to remain anonymous, had a nose, lips and chin grafted onto her face from a brain-dead donor whose family gave consent. The operation, performed Sunday, included a surgeon already famous for transplant breakthroughs, Dr. Jean-Michel Dubernard.

“The patient’s general condition is excellent and the transplant looks normal,” said a statement issued yesterday from the hospital in the northern city of Amiens where the operation took place. Dr. Dubernard would not discuss the surgery, but confirmed that it involved the nose, lips, and chin.

“We still don’t know when the patient will get out,” he said. A news conference is planned for Friday.

Scientists in China have performed scalp and ear transplants, but experts say the mouth and nose are the most difficult parts of the face to transplant. In 2000, Dr. Dubernard did the world’s first double forearm transplant.

The surgery drew both praise and sobering warnings over its potential risks and ethical and psychological ramifications. If successful – something that may not be known for months or even years – the procedure offers hope to people horribly disfigured by burns, accidents, or other tragedies.

The woman was “severely disfigured” by a dog bite in May that made it difficult for her to speak and chew, according to a joint statement from the hospital in Amiens and another in the southern city of Lyon where Dr. Dubernard works.

Such injuries are “extremely difficult, if not impossible” to repair using normal surgical techniques, the statement said.

“For pushing the bounds of science, they are to be applauded, as long as they have got full informed consent from the patient and the donor’s family,” the chief executive of the London based Facial Surgery Research Foundation, Dr. Iain Hutchison, added.

Scientists around the world are working to perfect techniques involved in transplanting faces. Today’s best treatments leave many people with facial disfigurement and scar tissue that doesn’t look or move like natural skin.

A complete face transplant, which involves applying a sheet of skin in one operation, has never been done before. The procedure is complex, but uses standard surgical techniques.

Critics say the surgery is too risky for something that is not a matter of life or death, as regular organ transplants are.

The main worry for both a full face transplant and a partial effort is organ rejection, causing the skin to slough off.