The invention provides methods and apparatus for accurately
cutting bones with a surgical
cutting device, such as a sagittal saw, using a surgical
navigation system without use of a complex
cutting jig. A surgical
navigation system is used to navigate a
guide tube to be used to
drill a k-wire into the bone. The k-wire will act as a guide to control at least one degree of freedom of a saw blade for making a
cut in the bone. In an exemplary
high tibial osteotomy procedure, in which two intersecting planar cuts must be made in the
tibia in order to remove a wedge of bone, a surgical navigation marker is mounted on the
guide tube. The surgeon uses the surgical
navigation system to navigate the
guide tube to the desired varus-valgus angle and height of the first
cut and then drills a k-wire into the
tibia at that varus-valgus angle using the guide tube. The process is repeated for the second
cut. The surgeon then uses the two k-wires as guides for controlling the varus-valgus angle of a sagittal saw for the two planar cuts. The surgeon rests the saw blade flat on the respective k-wire to define the varus-valgus angle of the cut. The saw itself also is navigated, with the surgical navigation
system providing a display showing the surgeon at least (1) the varus-valgus angle, (2) the cut depth, and (3) the anterior-posterior slope. The anterior-posterior slope and the depth of the cut is controlled freehand by the surgeon.