Preoperatively planning an arthroplasty procedure and generating a corresponding patient specific arthroplasty resection guide

A method of manufacturing a custom arthroplasty resection guide, the method comprising:

• generate a three dimensional tibia bone computer model from MRI knee coil two dimensional images, wherein the MRI knee coil two dimensional images include a knee region of a patient;
• locate positions of an approximate ankle center and an approximate tibia knee center in coronal view MRI body coil two dimensional images, wherein the positions are relative to at least two axes in a global coordinate system of a computer environment and wherein the MRI body coil two dimensional images include an ankle region of the patient and the knee region of the patient;
• cause the three dimensional tibia bone computer model and approximate ankle center and approximate tibia knee center to generally correspond with each other with respect to location and orientation in the global coordinate system of the computer environment by aligning first locations of knee landmarks in the MRI knee coil two dimensional images and second locations of the knee landmarks in the MRI body coil two dimensional images;
• define across the three dimensional tibia bone computer model a tibial mechanical axis between the approximate tibia knee center and the approximate ankle center;
• locate a condylar point of the three dimensional tibia bone computer model;
• define a proximal plane that is orthogonal to the tibial mechanical axis in a coronal view of the three dimensional tibia bone computer model, wherein the proximal plane also passes through a condylar point;
• define a resection plane that is parallel to the proximal plane and distally offset a distance along the tibial mechanical axis from the proximal plane;
• and
• manufacture the custom arthroplasty resection guide by using data associated with the resection plane to define a resection guide in the custom arthroplasty resection guide.

A method of manufacturing a custom arthroplasty resection guide, the method comprising:

• a) locate coordinate system points in a computer environment, the coordinate system points approximating hip, knee and ankle centers in coronal two dimensional images of a first set of two dimensional images;
• b) generate in a computer environment a three dimensional knee computer model from a second set of two dimensional images;
• c) employ computer processing to cause the three dimensional knee computer model and the coordinate system points to be positioned relative to each other as a combined computer model in a global coordinate system generally as if the three dimensional knee computer model were generated from the first set of two dimensional images;
• d) preoperatively plan an arthroplasty procedure with the combined computer model of step c) via a method including:
• define a mechanical axis across the three dimensional knee computer model between a pair of the coordinate system points including the coordinate system point approximating the knee center and at least one of the coordinate system points approximating the hip center or approximating the ankle center;
• and
• define a resection plane parallel to, and offset a distance along the mechanical axis from, a reference plane that:
• 1) is orthogonal to the mechanical axis in a coronal view and
• 2) extends through a condylar point on the three dimensional knee computer model, wherein the condylar point is either a most distal femoral condyle point or a tibial condyle point;
• and
• e) manufacture the custom arthroplasty resection guide by using data associated with the resection plane to define a resection guide in the custom arthroplasty resection guide.