Dr David Genecov, craniofacial surgeon at Medical City Dallas, said two-year-old Ahmad and Muhammad Ibrahim will probably have synthetic materials used in reconstructing their misshapen heads, and the reconstruction process, that is set to start soon, will be long.
"It involves, ultimately, the creation of a new skull," Genecov told a press conference.
On Thursday, the boys left Children's Medical Centre in Dallas, where they were separated in a 34-hour operation a month ago, and moved to Medical City Dallas - the hospital that had overseen their care for about a year prior to the separation surgery.
"Ultimately, their final reconstruction may not really be apparent until they are 18 years of age," Genecov said.
The hospital will offer more details of the reconstruction process on Monday at a news conference, he said.
The boys avoided for the most part post-operative complications such as infection, blood clots, or brain swelling - all of which could have proven fatal. They are both in good condition and have been fitted for special head bands to protect their skulls.
The boys were born in a town 800 km (500 miles) south of Cairo on 2 June, 2001.
Ahmad and Muhammad before the remarkable operation
In an emotional press conference on Thursday, the boys' father Ibrahim Muhammad said through an interpreter that the successful surgery was "a miracle".
"I would love to take them back to Egypt with them walking on their own feet," he said.