What is tibial derotation osteotomy along with femoral derotation osteotomy?

Good question. Osteotimy is a cut in the bone. In a derotational osteotimy, the bone is cut and then rotated to a better position and this corrected position is usually then held in place by a plate and screws. In this case, the surgery is done on the tibia and femur. The most common indication would be severe malalignment of the leg such as a severe case of "in- toeing."