INSTRUMENT ASSEMBLY FOR USE IN KNEE JOINT REPLACEMENT SURGERY

• US 20090138021A1
• Filed: 09/21/2006
• Published: 05/28/2009
• Est. Priority Date: 09/30/2005
• Status: Active Grant

• Current Assignee: Depuy International Limited (Johnson & Johnson)
• Original Assignee: Depuy International Limited (Johnson & Johnson)
• Inventors: Rock, Michael, Colquhoun, Callum
• Granted Patent: US 8,998,917 B2
• Time in Patent Office: Days
• US Class Current: 606/88
• CPC Class Codes: A61B 17/025 Joint distractors
• CPC Class Codes: A61B 17/155 Cutting femur
• CPC Class Codes: A61B 17/157 Cutting tibia
• CPC Class Codes: A61B 2017/0268 for the knee
• CPC Class Codes: A61B 2090/061 for measuring dimensions, e.g. length

Abstract

An instrument assembly for use in knee joint replacement surgery is provided including a base instrument having a tibial plate, a femoral plate, a tibial arm having a plate end and a control end, a femoral arm having a plate end and a control end, wherein the femoral plate is rotatably fastened to the plate end of the femoral arm. The assembly also includes a distractor mechanism configured to act between the tibial arm and the femoral arm at a point between their respective plate ends and control ends by which the distance between the plate ends of the arms can be adjusted and an ancillary instrument mountable on the base instrument and configured such that the position of the ancillary instrument relative to the tibial plate is fixed during subsequent steps in the knee replacement procedure, while the knee joint is distracted as a result of forces applied across the joint between the tibial plate and the femoral plate.

Claims

1. An instrument assembly for use in knee joint replacement surgery, comprising:

a base instrument that comprises;

a tibial plate;

a femoral plate;

a tibial arm having a plate end and a control end, wherein the tibial plate is fastened to the plate end of the tibial arm at its anterior edge, and wherein, when the tibial plate contacts the tibia, the tibial arm is configured to extend from the tibial plate generally medially or laterally of the knee joint;

a femoral arm having a plate end and a control end, wherein the femoral plate is rotatably fastened to the plate end of the femoral arm, and wherein, when the femoral plate contacts the femur, the femoral arm extends from the femoral plate generally aligned with the tibial arm; and

a distractor mechanism configured to act between the tibial arm and the femoral arm at a point between their respective plate ends and control ends by which the distance between the plate ends of the arms can be adjusted, and

an ancillary instrument mountable on the base instrument and configured such that the position of the ancillary instrument relative to the tibial plate is fixed during subsequent steps in the knee replacement procedure, while the knee joint is distracted as a result of forces applied across the joint between the tibial plate and the femoral plate.

2. The instrument assembly of claim 1, wherein the ancillary instrument and the base instrument have complimentary formations of a spigot and socket assembly that can be used to connect one to the other.

3. The instrument assembly of claim 1, wherein the distractor mechanism comprises a pivot by which the tibial and femoral arms are connected to one another at a point between their plate and control ends so that pivotal movement of the femoral arm relative to the tibial arm to reduce the distance between their control ends causes the distance between their plate ends to increase.

4. The instrument assembly of claim 1, wherein the base instrument includes a device configured to lock the tibial arm and the femoral arm against the relative movement between the tibial arm and the femoral arm by reducing the distance between their respective plate ends.

5. The instrument assembly of claim 4, wherein the locking device includes a ratchet mechanism.

6. The instrument assembly of claim 1, further comprising a biasing device configured to act on the tibial arm and the femoral arm so as to reduce the distance between their respective plate ends.

7. The instrument assembly of claim 1, wherein the femoral plate has a pair of recesses formed therein configured to received the femoral condyles.

8. The instrument assembly of claim 1, wherein the femoral plate is fastened to the femoral arm such that the femoral plate may rotate to minimize differences in the forces that are applied across the medial and lateral compartments of the knee joint.

9. The instrument assembly of claim 2, wherein the spigot is in the form of a plate and the socket is in the form of a slot wherein the plate can be received.

10. The instrument assembly of claim 2, wherein the part of the spigot and socket assembly provided on the base instrument is provided on the tibial arm.

11. The instrument assembly of claim 1, wherein the ancillary instrument is selected from:

a probe configured to contact the femur to measure the gap between the tibia and the femur;

a cutting guide having a slot formed therein for receiving the blade of a saw or other cutting device;

a pin guide having at least one hole extending therethrough to define the location for a hole to be prepared in the femur.

12. The instrument assembly of claim 1, wherein the face of the tibial plate that faces towards the resected tibia has at least one projection for locating the plate relative to the tibia.