Removal of rods from broken femur?

HelloMy son is 6 years old and 6 months ago he was in a car accident. He walked away with a broken femur and was rushed into the hospital and had a surgery the same day. He had rods installed into his femur bone. Two months later he walked like nothing happened. Leg healed properly. Now our doctor says that he has to remove those rods removed. My wonder now is how will the remove the rods since his bone healed and they were installed through a cut made on his upper part of left leg and the fracture was in the lower part of the femur bone, maybe 10 cm from the knee. How will the rods be removed? How long does that kind of surgery last? How long will it take for him to walk normally again?

Thank you

Sanja, mom