Interactive anterior-posterior axis determination

A system for adjusting a varus-valgus angle in a surgical plan for a distal femur of a patient, the system comprising:

• a display device;
• an input device;
• at least one processor;
• and
• at least one computer-readable medium coupled to the at least one processor storing instructions that, when executed by the at least one processor, cause the system to:
• display, on the display device, a three-dimensional model of the distal femur of the patient including an intercondylar surface,
• receive, from the input device, user input comprising at least two points on the intercondylar surface, thereby defining a datum line;
• perform a plurality of iterative revisions, wherein each of the plurality of iterative revisions comprises:
• generating a plurality of planes, each plane forming a predetermined angle with the datum line and intersecting the intercondylar surface,
• identifying a saddle point of the intercondylar surface on each of the plurality of planes, thereby forming a saddle point set, and
• calculating a fitted line for the saddle point set, wherein the datum line is re-defined as the fitted line for a subsequent iterative revision;
• generate an anterior-posterior (AP) axis based on the fitted line;
• rotate the three-dimensional model about the AP axis to alter an orientation of the three-dimensional model, thereby adjusting the varus-valgus angle of the distal femur;
• and
• update the surgical plan based on the altered orientation of the three-dimensional model;
• wherein the AP axis is generated based on the fitted line of a final iterative revision.

A system for adjusting a varus-valgus angle in a surgical plan for a distal femur of a patient, the system comprising:

• a display device;
• an input device;
• at least one processor configured to cause the system to:
• display, on the display device, a three-dimensional model of the distal femur of the patient including an intercondylar surface,
• receive, from the input device, user input comprising at least two points on the intercondylar surface, thereby defining a datum line;
• perform one or more iterative revisions, wherein each iterative revision comprises:
• generating a plurality of planes, each plane forming a predetermined angle with the datum line and intersecting the intercondylar surface,
• identifying a saddle point of the intercondylar surface on each of the plurality of planes, thereby forming a saddle point set, and
• calculating a fitted line for the saddle point set, wherein the datum line is re-defined as the fitted line for a subsequent iterative revision;
• generate an anterior-posterior (AP) axis based on the fitted line;
• rotate the three-dimensional model about the AP axis to alter an orientation of the three-dimensional model, thereby adjusting the varus-valgus angle of the distal femur;
• and
• update the surgical plan based on the altered orientation of the three-dimensional model;
• wherein each iterative revision further comprises assessing whether to perform a subsequent iterative revision based on at least one iteration criterion.