A femoral osteotomy is a surgical procedure to cut the femur bone and realign it in an attempt to improve limb mechanics.
This is an X-ray through the plaster post op of a distal femoral osteotomy. You can see the plate and screwss. This was actually a double osteotomy as the alignment of the tibia was also changed, and you get a glimpse of this at the bottom of the image.
The common osteotomy is the distal femoral osteotomy, in the femur bone just above the knee. The other kind of osteotomies may be that of the neck of the femur for torsional deformity or of the shaft for badly-healed fractures that need de-rotation or re-alignment.