Shanghai ? A 2-month-old Chinese boy was recovering Tuesday after surgery to remove an unusually well-formed third arm.

Neither of the boy’s two left arms was fully functional, but surgeons decided to remove the one growing closer to his chest after tests showed it was less developed.

Dr. Chen Bochang, the chief surgeon, said the three-hour operation at Shanghai Children’s Medical Center went much better than expected.

“We found the nerves and blood vessels for the arm were formed just as they would be for a normal arm,” Chen said.

Chen said the baby will require long-term physical therapy to gain function in his remaining hand, which has no palm and flexes in either direction.

“We’re hoping to exchange information with doctors who’ve dealt with similar cases anywhere in the world,” said Chen, head of the orthopedics department at Shanghai Children’s Medical Center. “This is so rare that we have virtually no information to go on.”