[Angel]

A MEDICAL team of 80 was last night tackling a marathon operation to separate 10-month-old siamese twins in Los Angeles.

Doctors said it would be the longest and most complex separation of siamese twins ever attempted at Childrens Hospital Los Angeles.

Ten-month-old Regina and Renata Salinas Fierros were to go on the operating table at 11pm last night and will be there for at least 24 hours.

They are rare even among conjoined twins, joined face-to-face, and share many organs: liver, intestine, urinary, reproductive, vascular and musculo-skeletal systems.

Their parents are Sonia Fierros, 23 and Federico Salinas, 36, both from Mexico.

At home, Sonia said, when one twin sleeps, the other one often does as well -- though there can be trouble when only one of them wants to sleep. When one feeds, the other helps lift the bottle.

James Stein, who heads the team, said the operation would involve a lot of cutting: "From the breast bone down to the pelvis and everything in between. That would include their liver, their intestine, genital organs, bladders, bony pelvis."

Dominic Femino heads the orthopaedic surgery team, which goes to work once the twins are apart: "What we have to do is to cut the pelvic bones in the back on each side and then rotate the hips and legs forward, so they're not pointing backward any more, rotate them into a more normal position and close the pelvic ring in the front."

Doctors have implanted inflatable balloons under the girls' skin to stretch it so that it would expand enough to close up the surgical wound.

Dr Stein will oversee the 80 medical personnel involved.

"Their tissues and bones at this age tend to be both firm and pliable enough -- and also of a reasonable size -- to manipulate them easily," Dr Stein said.

"If the surgery were not performed, the twins' anatomy would begin to limit their quality of life over time -- taking away their individuality, their ability to walk and to develop normally," Dr Stein said.

Regina is much smaller than her sister, despite a healthy appetite. Stein said he believes more of Renata's blood vessels may be supplying the girls' intestines, thereby robbing Regina of essential nutrients.

"Our goal is to create two very functional children at the conclusion of this and we have every expectation this will run smoothly and that will be our eventual outcome," he said.

The girls' mother Sonia said she looked forward to the twins leading separate lives.

"It's strange to see them together, but I'll be happy to see them separated," she said.