Knee replacement surgical cut planes estimation for restoring pre-arthritic alignment

A computer-aided method using an interactive pre-operative planning software analysis tool of total knee replacement for selecting femoral and tibial implant size and positioning and cut plane orientations based upon patient-specific images of a leg, the method comprising:

• obtaining, and inputting as image data into a computer system, a series of images of a leg of a patient, including at least one whole-leg coronal image showing hip, knee, and ankle, and a set of coronal, axial and sagittal image slices of respective hip, knee, and ankle joints representing a current anatomical condition of a patient;
• marking, by means of the interactive software analysis tool in the computer system operating upon the image data, of coordinate positions and sizes of a femoral head, distal tibia ankle joint, and of a knee joint in at least a selected subset of the respective coronal, axial and sagittal image slices;
• performing by the computer system a joint anatomical-matching and wear mechanism analysis based upon the marked coordinate positions to estimate from the image data, a pre-arthritic tibio-femoral mechanical alignment of the leg;
• performing by the computer system a best fit analysis of femur and tibia implant size and positioning from at least a selected subset of the respective coronal, axial and sagittal image slices in the image data;
• offering by the interactive software analysis tool a range of surgeon choices for the implant size and positioning including the computed best fit size and positioning and at least one adjacent size and positioning that is displayed overlaid with corresponding image slices and saving a surgeon implant size and positioning choice;
• offering by the interactive software analysis tool a range of surgeon choices for tibial-femoral mechanical alignment including the estimated pre-arthritic alignment and at least one closer-to-neutral alignment and saving a surgeon alignment choice;
• determining by the computer system respective cut planes for femoral and tibial surgical jigs in accord with the surgeon alignment choice and that is displayed overlaid with corresponding image slices for surgeon verification;
• and
• constructing femoral and tibial surgical jigs with a set of bone-jig contact surfaces dimensioned from the series of images such that the jig has one and only one mechanical self-locking position, each jig having a bone cutting guide that defines its respective cut plane as per the surgeon alignment choice.