Granted Patent B2

US 12,599,377 · App. 18/307,403 · Granted Apr 14, 2026

Inventors: Franz W. Kellar (Gastonia, NC); Michael D. Bissette (Belmont, NC); Harold L. Crowder (Concord, NC)

Assignee: DYNAMIC BALANCER SYSTEMS LLC

A61B17/025A61B5/4585A61B17/149A61B17/154A61B34/10A61B34/30A61B5/6885A61B2017/00398A61B2017/0268A61B2034/105A61B2034/2051

Abstract

Claims (27)

1 . A method of evaluating a human knee joint which includes a femur bone, a tibia bone, and ligaments, wherein the ligaments are under anatomical tension to connect the femur and tibia together, creating a load-bearing articulating joint, the method comprising:

inserting into the knee joint a tensioner-balancer that includes a femoral interface surface, and at least one force sensor;

providing an electronic receiving device;

moving the knee joint through at least a portion of its range of motion;

while moving the knee joint, using the electronic receiving device to collect data from the at least one force sensor;

processing the collected force data to produce a digital geometric model of the knee joint, wherein the digital geometric model includes:

a medial spline representing a locus of points of contact of a medial condyle of the femur with the femoral interface surface, over a range of knee flexion angles, each of the points of contact characterized by a location, a direction, and a first and second derivative; and

a lateral spline representing a locus of points of contact of the femur with the femoral interface surface over a range of knee flexion angles, each of the points of contact characterized by a location, a direction, and a first and second derivative; and

storing the digital geometric model for further use.

2 . The method of claim 1 , wherein the femoral interface surface is defined by a top plate, the top plate including a lateral cantilevered pad and a medial cantilevered pad, wherein each cantilevered pad is provided with two or more spaced-apart strain gages at the intersection between the respective cantilevered pad and a stationary portion of the top plate.

3 . The method of claim 1 further comprising:

connecting at least one tracking marker to the knee joint;

collecting position data from the tracking marker while moving the knee joint; and,

using the position data and the force data to produce the geometric model.

4 . The method of claim 1 further comprising:

computing one or more tool paths passing through the knee joint;

coupling at least one tracking marker to the knee joint;

receiving data representing an actual position and orientation of a tool relative to the at least one tracking marker;

moving a tool along the one or more tool paths, with reference to the data, so as to remove bone from the knee joint, thereby forming a machined feature in the knee joint.

5 . The method of claim 1 wherein the patella remains in its native anatomical position during all steps of the method.

6 . The method of claim 1 further comprising using the tensioner-balancer to distract the knee joint.

7 . The method of claim 6 wherein the distraction is carried out by:

inserting the tensioner-balancer between the tibia and the femur, with the tensioner-balancer in a retracted position; and

moving the tensioner-balancer towards an extended position, so as to urge the tibia and the femur apart and apply tension to ligaments of the knee joint.

8 . The method of claim 6 wherein the tensioner-balancer applies a substantially constant force while permitting variable deflection.

9 . The method of claim 6 wherein the tensioner-balancer applies a predetermined variable force as the data is collected while moving the knee joint, where the predetermined variable force is correlated to knee joint position.

10 . The method of claim 6 wherein the tensioner-balancer maintains a predetermined distraction gap as the data is collected while moving the knee joint.

Assignments (2)

Continuity (3)

References Cited (83)