# US 11,439,467 B1 · Knee replacement surgical cut planes estimation for restoring pre-arthritic alignment > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 11,439,467 B1 - Document ID: US11439467B1 - Status: Granted - Kind: B1 - Application number: 16/565,818 - Filed: 2019-09-10 - Granted: 2022-09-13 - Earliest claimed: 2019-09-10 - Assignees: Lento Medical Inc. - Applicants: Lento Medical Inc. - Inventors: Ilwhan Park - Web page: https://patentgrep.com/patent/US11439467B1 ## CPC - A61B 34/10: Computer-aided planning, simulation or modelling of surgical operations - A61B 5/4528: {Joints (A61B5/4533, A61B5/4538 take precedence)} - A61B 17/155: {Cutting femur} - A61B 17/157: {Cutting tibia} - G16H 20/40: relating to mechanical, radiation or invasive therapies, e.g. surgery, laser therapy, dialysis or acupuncture - G16H 30/40: for processing medical images, e.g. editing - G16H 40/63: for local operation - A61B 2017/564: {Methods for bone or joint treatment} - A61B 2017/568: {produced with shape and dimensions specific for an individual patient} - A61B 2034/102: {Modelling of surgical devices, implants or prosthesis} - A61B 2034/105: {Modelling of the patient, e.g. for ligaments or bones} - A61B 2034/107: {Visualisation of planned trajectories or target regions} - A61B 2034/108: {Computer aided selection or customisation of medical implants or cutting guides} - A61B: DIAGNOSIS; SURGERY; IDENTIFICATION (usefulness limited to only animals A61D) - G16H: HEALTHCARE INFORMATICS, i.e. INFORMATION AND COMMUNICATION TECHNOLOGY [ICT] SPECIALLY ADAPTED FOR THE HANDLING OR PROCESSING OF MEDICAL OR HEALTHCARE DATA ## Abstract A computer-aided pre-operative planning tool with interactive surgeon interface for total knee replacement implements a method that allows implant size selection, implant positioning, and surgical cut planes estimation (with construction of corresponding surgical jig), based upon a series of coronal, axial and sagittal image slices of a patient's leg. Limb alignment and corresponding surgical cut planes are defined based upon joint anatomical-matching analysis to minimize joint wear and restore a pre-arthritic alignment (rather than an always fully neutral alignment). Using the interface, a surgeon has the option to adjust the varus/valgus alignment within recommended bounds between the pre-arthritic and fully neutral alignments. Implant size may be selected based on a best fit to the patient's leg obtained from analysis of the images. ## Claims ### Claim 1 A computer-aided method using an interactive pre-operative planning software analysis tool for establishing, from patient-specific images, femur and tibia cut planes and implant sizes for knee replacement surgery, 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; determining by the computer system a set of coordinates of selected hip, knee and ankle features in the image data; estimating from the determined set of coordinates, based upon a joint anatomical-matching wear mechanism carried out by the computer system, a pre-arthritic tibio-femoral mechanical alignment of the leg; establishing, through user interaction with the pre-operative planning software analysis tool in the computer system, a desired tibio-femoral mechanical alignment of the leg within bounds defined between the estimated pre-arthritic alignment and a fully neutral alignment; determining a cut plane for at least one of a femoral and tibial surgical jig in accord with the desired tibio-femoral mechanical alignment; and constructing the at least one surgical jig with a set of bone-jig contact surfaces that are dimensioned from the image data such that the jig has one and only one mechanical self-locking position, the jig having a bone cutting guide that defines the cut plane as per the desired alignment. ### Claim 2 (depends on 1) The method as in claim 1, wherein the pre-arthritic tibio-femoral mechanical alignment of the leg is estimated using coronal plane images of the entire limb from hip to knee to ankle. ### Claim 3 (depends on 2) The method as in claim 2, wherein the pre-arthritic tibio-femoral mechanical alignment of the leg is further estimated from an analysis of joint wear mechanisms using coronal, axial and sagittal image slices of the knee. ### Claim 4 (depends on 1) The method as in claim 1, wherein the pre-arthritic tibio-femoral mechanical alignment of the leg is estimated to within about 0.5 degree. ### Claim 5 (depends on 1) The method as in claim 1, wherein a desired tibio-femoral mechanical alignment is any one of a within two degrees of neutral alignment, a varus (bowlegged) alignment of more than two degrees from neutral alignment, and a valgus (knock-kneed) alignment of more than two degrees from neutral alignment. ### Claim 6 (depends on 1) The method as in claim 1, wherein a desired tibio-femoral mechanical alignment is selected to assure a total range of knee motion of at least 90 degrees. ### Claim 7 (depends on 1) The method as in claim 1, wherein a desired tibio-femoral mechanical alignment is selected by offering a range of surgeon choices including the estimated pre-arthritic alignment and one or more closer-to-neutral alignments within three degrees of the estimated pre-arthritic alignment. ### Claim 8 (depends on 7) The method as in claim 7, wherein a desired tibio-femoral mechanical alignment is selected by also taking due regard to any one or more of a condition of an associated hip joint, and an alignment of an opposite limb, as evidenced by the series of images. ### Claim 9 (depends on 1) The method as in claim 1, wherein determining a cut plane in accord with the desired tibio-femoral mechanical alignment includes separately establishing femoral and tibial cut planes for orienting respective femoral and tibial implants of an artificial replacement joint. ### Claim 10 (depends on 1) The method as in claim 1, further selecting, using the series of image slices of the knee, a best fit of femoral and tibial implant size and positioning. ### Claim 11 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. ### Claim 12 (depends on 11) The method as in claim 11, wherein coordinate positions of the knee joint include any one or more of distal femur center, medial-lateral distal femur length and contact points, anterior-posterior distal femur length and endpoints, femur segmentation, proximal tibia center, medial-lateral proximal tibia line and endpoints, anterior-posterior proximal tibia length and endpoints, and tibia segmentation. ### Claim 13 (depends on 12) The method as in claim 12, wherein coordinate positions are transformed onto orthogonal axes corresponding to left-right, anterior-posterior, and inferior-superior directions of the leg, the coordinates being separately transformed about marked coordinate positions of the respective distal femur center and posterior tibia center as origins. ### Claim 14 (depends on 12) The method as in claim 12, wherein the wear model analysis is performed based upon a lattice truss modeling of the marked coordinate positions of the femoral head, knee joint and ankle. ### Claim 15 (depends on 14) The method as in claim 14, wherein the wear model analysis is further performed based upon the femur segmentation and tibia segmentation in the knee joint and upon associated wear vectors, anticipated longitudinal (compression) stress and anticipated tangential (shear) stress of the knee joint, and applying calculated wear in reverse to obtain a pre-arthritic condition of the knee joint. ### Claim 16 (depends on 11) The method as in claim 11, wherein the at least one closer-to-neutral alignment for the surgeon alignment choice is limited to at most three degrees from the estimated pre-arthritic alignment.