Method and system for computer assisted surgery for bicompartmental knee replacement

A system for resecting distal and anterior portions of a distal portion of a femur, comprising:

• a geometric representation of the distal portion of the femur;
• a virtual anterior resection plane within the geometric representation of the distal portion of the femur at a predetermined depth on the anterior portion of the distal femur, the virtual anterior resection plane being oriented at a predetermined angle relative to the femur in internal/external rotation wherein the virtual anterior resection plane includes an intersection point as a distal-most point of a lateral portion on the geometric representation of the virtual anterior resection plane;
• an AP line on the geometric representation of the distal portion of the femur, the geometric representation having an anterior-posterior distance perpendicular to the AP line between a posterior portion of a condyle of the femur and the intersection point;
• computer code configured to calculate a varus/valgus angle between a plane perpendicular to the mechanical axis of the femur and a plane passing through the intersection point and the AP line;
• an anterior resection guide positioned perpendicular to the AP line at a depth determined by the anterior-posterior distance between the posterior portion of the condyle of the femur and the intersection point;
• and
• a distal resection guide positioned according to the varus/valgus angle.