Determining a range of motion of an artificial knee joint

Abstract

A data processing method for determining a range of motion of an artificial knee joint which connects a femur and a tibia via a medial ligament and a lateral ligament, wherein at least the femur comprises an implant which forms a medial condyle and a lateral condyle, the method comprising the steps of: acquiring the maximum lengths of the lateral ligament and the medial ligament: for a particular flexion angle of the knee joint; calculating a first virtual position between the femur and the tibia in which the lateral condyle of the femoral implant touches the tibia and the medial ligament is stretched to its maximum length; calculating a maximum valgus angle of the range of motion from the first virtual position; calculating a second virtual position between the femur and the tibia in which the medial condyle of the femoral implant touches the tibia and the lateral ligament is stretched to its maximum length; and calculating a maximum yarns angle of the range, of motion from the second virtual position.

1 - 18 . (canceled) 
     
     
         19 . A computer-implemented method for use in association with a knee arthroplasty performed on a knee joint of a patient, the knee joint comprising a lateral ligament and a medial ligament, the method comprising:
 determining, by a computer system, at one or more flexion angles of the knee joint:
 a first relative position of a tibia and a femur in response to the knee joint being under a  varus  stress, and 
 a second relative position of the tibia and the femur in response to the knee joint being under a valgus stress; 
   determining, by the computer system for each of the flexion angles, a change in a length of each of the lateral ligament and the medial ligament based on the first and second relative positions;   determining, by the computer system for each of the flexion angles, a  varus  angle and a valgus angle for an implant based on the change in the length of each of the lateral ligament and the medial ligament; and   outputting, by the computer system, a range of motion of the knee joint across the one or more flexion angles based on the determined  varus  angle and the determined valgus angle.   
     
     
         20 . The method of  claim 19 , wherein the first and second relative positions are determined subsequent to a cut of a proximal end of the tibia and an insertion of a spreading device between the femur and the tibia. 
     
     
         21 . The method of  claim 19 , wherein the change in the length of each of the lateral ligament and the medial ligament are measured perpendicular to a tibial cutting plane. 
     
     
         22 . The method of  claim 19 , wherein the change in the length of each of the lateral ligament and the medial ligament are determined based on a distance between a point on the femur and a tibial cutting plane. 
     
     
         23 . The method of  claim 19 , wherein the  varus  stress and the valgus stress are applied via a spreading device inserted into the knee joint. 
     
     
         24 . The method of  claim 19 , further comprising:
 receiving, by the computer system, at least one position or size parameter for the implant; and   modifying, by the computer system, an output of the range of motion based on the at least one position or size parameter.   
     
     
         25 . A computer system for use in association with a knee arthroplasty performed on a knee joint of a patient, the knee joint comprising a lateral ligament and a medial ligament, the system comprising:
 a display device; and   a computer system comprising:
 a processor, and 
 a memory coupled to the processor, the memory storing instructions that, when executed by the processor, cause the processor to:
 determining for one or more flexion angles of the knee joint:
 a first relative position of a tibia and a femur in response to the knee joint being under a  varus  stress, and 
 a second relative position of the tibia and the femur in response to the knee joint being under a valgus stress, 
 
 determining, for each of the flexion angles, a change in a length of each of the lateral ligament and the medial ligament based on the first and second relative positions, 
 determining, for each of the flexion angles, a  varus  angle and a valgus angle for a femoral implant or a tibial implant based on the change in the length of each of the lateral ligament and the medial ligament, and 
 outputting, via the display device, a range of motion of the knee joint across the one or more flexion angles based on the determined  varus  angle and the determined valgus angle. 
 
   
     
     
         26 . The computer system of  claim 25 , wherein the first and second relative positions are determined subsequent to a cut of a proximal end of the tibia and an insertion of a spreading device between the femur and the tibia. 
     
     
         27 . The computer system of  claim 25 , wherein the change in the length of each of the lateral ligament and the medial ligament are measured perpendicular to a tibial cutting plane. 
     
     
         28 . The computer system of  claim 25 , wherein the change in the length of each of the lateral ligament and the medial ligament are determined based on a distance between a point on the femur and a tibial cutting plane. 
     
     
         29 . The computer system of  claim 25 , wherein the  varus  stress and the valgus stress are applied via a spreading device inserted into the knee joint. 
     
     
         30 . The computer system of  claim 25 , the memory stores instructions that, when executed by the processor, cause the processor to:
 receive at least one position or size parameter for the implant; and   modify an output of the range of motion based on the at least one position or size parameter.   
     
     
         31 . A method for use in performing a knee arthroplasty performed on a knee joint of a patient, the knee joint comprising a lateral ligament and a medial ligament, the method comprising:
 generating a cutting plane through a proximal end of a tibia of the knee joint of a patient;   resecting through the cutting plane;   inserting a spreading device between the resected proximal end of the tibia and a femur of the knee joint;   applying a  varus  stress and a valgus stress to the knee joint when the knee joint is at one or more flexion angles;   determining for each of the one or more flexion angles of the knee joint:
 a first relative position of the tibia and the femur in response to the knee joint being under the  varus  stress, and 
 a second relative position of the tibia and the femur in response to the knee joint being under the valgus stress; 
   determining, for each of the flexion angles, a change in a length of each of the lateral ligament and the medial ligament based on the first and second relative positions;   determining, for each of the flexion angles, a  varus  angle and a valgus angle for a femoral implant or a tibial implant based on the change in the length of each of the lateral ligament and the medial ligament; and   outputting a range of motion of the knee joint across the one or more flexion angles based on the determined  varus  angle and the determined valgus angle.   
     
     
         32 . The method of  claim 31 , wherein the change in the length of each of the lateral ligament and the medial ligament are measured perpendicular to a tibial cutting plane. 
     
     
         33 . The method of  claim 31 , wherein the change in the length of each of the lateral ligament and the medial ligament are determined based on a distance between a point on the femur and a tibial cutting plane. 
     
     
         34 . The method of  claim 31 , further comprising:
 placing a spreading device between the femur of the patient and the tibia, wherein the  varus  stress and the valgus stress are applied via the spreading device.   
     
     
         35 . The method of  claim 19 , further comprising:
 receiving at least one position or size parameter for the implant; and   modifying an output of the range of motion based on the at least one position or size parameter.