Joshua and Jacob Spates, who spent their first seven months outside the womb as conjoined twins, are recovering in the pediatric intensive care unit of a Memphis hospital after a successful 13-hour surgery to separate them.

Dr. Max Langham, team leader for the separation, said on Wednesday that all involved are enjoying a celebratory mood of how well Joshua and Jacob are doing.

The twins, who were joined at the spine, were separated August 29. Two weeks later, not only are the boys healthy, both of them are using their legs and getting ready to try to crawl out of bed, Langham said.

Most conjoined twins don't ever get a chance to get to separation because they die from complications at delivery, said Langham, chief of pediatric surgery at Le Bonheur Children's Hospital.

Conjoined twins occur in one out of 100,000 births. These boys were born pygopagus twins, joined back-to-back at the pelvis and lower spine, but with separate hearts, heads and limbs.

This condition occurs in just 15 percent of the cases of conjoined twins, according to Le Bonheur.

It took a 34-member pediatric surgical team 13 hours to separate the Memphis brothers' spinal column bone, nerves and muscles and to complete gastrointestinal repairs.

An ultrasounds last November confirmed that the two boys were conjoined. After being monitored for eight weeks, the babies -- who had a shared rectum, muscles and nerves -- were delivered via Caesarean on January 24.

Two days later, surgeons performed a colostomy and inserted a gastrostomy tube to assist with nutrition and waste elimination, according to the hospital press office.

Doctors had to deal with a number of other conditions in the following months. Joshua had a single kidney, a heart defect and calcifications in the spleen and Jacob had a two-vessel umbilical cord and a heart defect.

Langham said members of the medical team spent over a month planning and rehearsing the operation.

The doctor said the trickiest part of the surgery involved dealing with the part of the spine shared by the boys.