Compact mechanical joint balancer

Patent metadata

Field	Value
Publication number	US-10952873-B2
Application number	US-202016938178-A
Country	US
Kind code	B2
Filing date	Jul 24, 2020
Priority date	Jan 25, 2018
Publication date	Mar 23, 2021
Grant date	Mar 23, 2021

Abstract

The present invention relates to devices and methods for balancing joints, including knee joints. The devices convert unequal forces at a joint to a rotation or displacement of a pointer or gauge. The devices are able to display the relative difference in force between the lateral and medial sides of a joint from flexion to extension. In certain aspects, the devices are useful for balancing the knee during total knee surgery. The devices can be inserted between the trial femoral and tibial components of the knee and measures whether one condyle experiences more force than the other.

First claim

What is claimed is:

1. A joint balancer device, comprising:
a handle having a gauge;
a lower plate attached to the handle; and
an upper plate aligned in parallel with the lower plate by a gap space, wherein the upper plate is displaceable relative to the lower plate;
wherein the upper plate is connected by a mechanical link to the gauge, and wherein the mechanical link magnifies displacement of the upper plate such that the gauge displays the magnified displacement, wherein the mechanical link comprises:
a first and a second long beam adjacently positioned within a hollow interior of the handle, each long beam having an anterior end as a pointer of the gauge;
a first short beam extending from an interior of the lower plate in a lateral direction underneath a left side of the upper plate such that the first short beam attaches to a posterior end of the first long beam, wherein the first short beam is further connected to the upper plate by a short vertical beam;
a second short beam extending from an interior of the lower plate in a lateral direction underneath a right side of the upper plate such that the second short beam attaches to a posterior end of the second long beam, wherein the second short beam is further connected to the upper plate by a short vertical beam;
a first fulcrum beam extending from an interior of the lower plate in a lateral direction underneath a left side of the upper plate, the first fulcrum beam positioned anterior to the first short beam such that the first fulcrum beam attaches to the first long beam at a position anterior to the first short beam; and
a second fulcrum beam extending from an interior of the lower plate in a lateral direction underneath a right side of the upper plate, the second fulcrum beam positioned anterior to the second short beam such that the second fulcrum beam attaches to the second long beam at a position anterior to the second short beam.

2. The device of claim 1 , wherein an inferior displacement of a side of the upper plate inferiorly displaces the respective short beam underneath the side of the upper plate, such that the respective connected long beam is actuated about the respective fulcrum beam to shift the pointer of the gauge in a superior direction.

3. The device of claim 2 , wherein the upper plate comprises flexible membranes above the first and second short beams.

4. The device of claim 1 , wherein the upper plate has an upper surface contoured to fit a femur's condyles or a trial femoral component of a total knee replacement, and the lower plate has a lower surface contoured to fit a resected surface of a tibia in a total knee replacement.

5. The device of claim 1 , wherein the upper plate and the lower plate are separated by a substantially parallel distance between about 1 and 3 mm.

6. The device of claim 5 , wherein the upper plate is cantilevered over the lower plate by the distance.

7. The device of claim 5 , wherein the distance is maintained in a neutral state by one or more springs positioned between the upper plate and the lower plate, the one or more springs selected from the group consisting of: coil springs, conical springs, wave springs, and leaf springs.

8. The device of claim 1 , wherein the gauge includes a scale having at least one of force units, distance units, angle degrees, or unitless markings.

9. The device of claim 1 , wherein the device is configured to measure a relative difference in force between a lateral side and a medial side of a joint.

10. A method of balancing a joint, comprising the steps of:
providing the balancer device of claim 1 ;
inserting the balancer device into a joint in need of balancing such that the upper and lower plates rest against opposing surfaces of the joint;
flexing the joint through at least part of its full range of motion;
recording magnitudes of displacement or force between left and right sides of the joint indicated by the gauge throughout the flexing of the joint;
removing the balancer device from the joint; and
modifying a balance of the joint based on the magnitudes of displacement or force between left and right sides of the joint.

11. The method of claim 10 , wherein the joint is a knee joint or an elbow joint.

12. The method of claim 10 , wherein the opposing joint surfaces are opposing bone surfaces, opposing implant surfaces, or combinations thereof.

13. The method of claim 10 , wherein the balance of the joint is modified by trimming the opposing surfaces, raising the opposing surfaces, adjusting a spacer component between the opposing surfaces, or combinations thereof.

14. The method of claim 10 , wherein contact forces are increased between the joint and the balancer device by adding one or more additional spacer plates to the upper plate and/or lower plate.

Assignees

• Univ New York

Inventors

• Walker Peter Stanley
• Einhorn Thomas Alfred

Classifications

• A61B5/4585

  Evaluating the knee · CPC title

• A61B17/56

  Surgical instruments or methods for treatment of bones or joints; Devices specially adapted therefor · CPC title

• A61F2002/4666

  for measuring force, pressure or mechanical tension · CPC title

• A61F2/4657

  Measuring instruments used for implanting artificial joints (for surgical instruments A61B90/06) · CPC title

• A61B2017/0268

  for the knee · CPC title