KNEE BALANCING FOR REVISION PROCEDURES

• US 20110093081A1
• Filed: 04/09/2010
• Published: 04/21/2011
• Est. Priority Date: 10/23/2008
• Status: Active Grant

• Current Assignee: Synvasive Technology Incorporated (Zimmer Biomet Holdings, Inc.)
• Original Assignee: Synvasive Technology Incorporated (Zimmer Biomet Holdings, Inc.)
• Inventors: Fisher, Michael, Chana, Barjinder
• Granted Patent: US 8,506,571 B2
• Time in Patent Office: Days
• US Class Current: 623/20.14
• CPC Class Codes: A61B 17/155 Cutting femur
• CPC Class Codes: A61B 17/157 Cutting tibia
• CPC Class Codes: A61B 17/1764 for the knee
• CPC Class Codes: A61B 17/72 Intramedullary pins, nails or other devices A61B17/744 takes precedence
• CPC Class Codes: A61F 2/38 for elbows or knees
• CPC Class Codes: A61F 2/4684 Trial or dummy prostheses

Abstract

Methods, systems and devices are provided for facilitating a surgical procedure on a knee, particularly, a revision total knee replacement procedure. Prior femoral and tibial prostheses are removed. A cut end of a distal femur is engaged with a femoral adjustment member, which will typically center itself about an intermedullary rod placed into the femur. The lateral and medial forces exerted by lateral and medial sides of the femoral adjustment member and the cut tibial plateau against each other are measured. The femoral adjustment member is adjusted to apply and/or adjust tension to the lateral collateral ligament and/or the medial collateral ligament based on the measured forces, for example, such that the measured lateral force and the measured medial force are matched. Based on the position of the adjusted femoral member, guided clean-up cuts for placement of a new femoral prostheses are made on the cut end of the distal femur.

Claims

1. A method for facilitating a surgical procedure on a knee, the method comprising:

inserting an intermedullary rod into the femoral intermedullary canal of a femur such that a portion of the intermedullary rod extends distally outward from a cut distal end of the femur;

sliding a femoral adjustment member over the distally extending portion of the intermedullary rod to engage the cut distal end of the femur with the femoral adjustment member, the femoral adjustment member comprising a lateral femoral portion and a medial femoral portion;

measuring a lateral force exerted by a lateral femoral portion of the femoral adjustment member and a lateral tibial portion of a tibial plateau against one another;

measuring a medial force exerted by a medial femoral portion of the femoral adjustment member and a medial tibial portion of the tibial plateau against one another; and

adjusting the femoral adjustment member based on the measured lateral force and the measured medial force to apply tension to at least one of the lateral collateral ligament and the medial collateral ligament.

2. The method of claim 1, wherein the femoral adjustment member is adapted to self-adjust and position itself about the intermedullary rod when slid over the distally extending portion of the intermedullary rod.

3. The method of claim 2, wherein the femoral adjustment member positions itself about the intermedullary rod off-center toward a medial side of the femoral adjustment member.

4. The method of claim 3, further comprising rotating the femur about the intermedullary rod, with the medial side of the femoral adjustment member as a balancing fulcrum.

5. The method of claim 1 further comprising locking the femoral adjustment member in a fixed position relative to the intermedullary rod wherein locking comprises sliding a locking clamp over the distally extending portion of the intermedullary rod and tightening the locking clamp.

6. The method of claim 1 further comprising inserting a force sensor between the engaged femoral adjustment member and the tibial plateau so that a lateral side of the force sensor is disposed between a lateral tibial portion of the tibial plateau and the lateral femoral portion of the femoral adjustment member, and a medial side of the force sensor is disposed between a medial tibial portion of the tibial plateau and the medial femoral portion of the femoral adjustment member.

7. The method of claim 6 wherein the lateral force and the medial force are measured with the force sensor.

8. The method of claim 6, wherein the force sensor comprises a sensor selected from the group consisting of piezoelectric sensors, force sensing resistors, strain gauges, load cells, other pressure sensors and other force sensors.

9. The method of claim 6, wherein at least one of measuring the lateral force or measuring the medial force comprises:

transmitting a voltage to a sensor element of a thin force sensing portion of the force sensor;

measuring the voltage after it has passed through the sensor element;

determining a percentage of the voltage passed through the sensor element relative to the voltage transmitted to the sensor element; and

deriving the measured force from the percentage.

10. The method of claim 6 further comprising displaying at least one of the measured lateral force or the measured medial force with a visual display coupled with the force sensor.

11. The method of claim 1, wherein the tibial plateau is engaged with a tibial member.

12. The method of claim 11, wherein the tibial member and femoral adjustment member are engaged primarily within a joint space between the cut surfaces of the proximal tibial and the distal femur.

13. The method of claim 1, wherein adjusting the femoral adjustment member comprises adjusting the femoral adjustment member such that the measured lateral force matches the medial force.

14. The method of claim 1, wherein adjusting the femoral adjustment member comprises adjusting tension in at least one of a medial collateral ligament and a lateral collateral ligament.

15. The method of claim 1, wherein adjusting the femoral adjustment member comprises enlarging a joint space between at least part of the distal femur and the tibial plateau to apply tension to at least one of the ligaments.

16. The method of claim 15, wherein enlarging the joint space comprises enlarging the space primarily at a medial side of the knee.

17. The method of claim 15, wherein enlarging the joint space comprises enlarging the space primarily at a lateral side of the knee.

18. The method of claim 1, wherein at least one of the lateral femoral portion and medial femoral portion of the femoral adjustment member is adjustable.

19. The method of claim 18, wherein the femoral adjustment member further comprises at least one stationary member.

20. The method of claim 19, wherein sliding the femoral adjustment member over the distally extending portion of the intermedullary rod to engage the cut distal end of the femur with the femoral adjustment member comprises attaching the at least one stationary member to the cut distal end of the femur, and wherein at least one of the lateral adjustment portion or medial adjustment portion are coupled with the at least one stationary member.

21. The method of claim 20, wherein adjusting the femoral adjustment member comprises adjusting the position of at least one of the lateral adjustment portion and the medial adjustment portion relative the at least one stationary member and the cut distal end of the femur.

22. The method of claim 21, wherein adjusting the position of at least one of the lateral adjustment portion and medial adjustment portion comprises turning at least one screw of at least one of the lateral adjustment portion and medial adjustment portion.

23. The method of claim 18, wherein both the lateral femoral portion and the medial femoral portion are adjustable and the lateral femoral portion and the medial femoral portion are separately adjustable.

24. The method of claim 23, wherein adjusting the femoral adjustment member comprises rotating the femoral adjustment member relative to the distal femur by adjusting the lateral femoral portion and medial femoral portion relative to each other.

25. The method of claim 1 further comprising engaging a first cutting guide with the adjusted femoral adjustment member and aligning the first cutting guide with the adjusted femoral adjustment member.

26. The method of claim 25 further comprising locking the first cutting guide in place relative to the adjusted femoral adjustment member and distal femur.

27. The method of claim 26 further comprising determining a position for placing a first at least one bone cut on the distal femur based on the relative position of the first cutting guide.

28. The method of claim 27 further comprising making the first at least one bone cut on the distal femur based on the relative position of the first cutting guide.

29. The method of claim 28 further comprising:

removing the first cutting guide from the femoral adjustment member;

removing the femoral adjustment member from the distal femur; and

engaging a second cutting guide on the distal femur based on the first at least one bone cut on the distal femur.

30. The method of claim 29 wherein engaging the second cutting guide on the distal femur based on the first at least one bone cut on the distal femur comprises engaging a reference tongue with the first at least one bone cut and positioning the second cutting guide based on the position of the reference tongue.

31. The method of claim 29 further comprising:

making a second at least one bone cut on the distal femur;

removing the second cutting guide from the distal femur; and

attaching a femoral prosthesis to the cut distal femur, the femoral prostheses being positioned relative to the cut distal femur based on the position of the second at least one bone cut.

32. A system for enhancing a surgical procedure on a knee, the system comprising:

a femoral adjustment member removably engagable with a cut distal end of a femur, the femoral adjustment member comprising;

a femoral body having a lateral side and a medial side;

a lateral adjustable member disposed on the lateral side of the femoral body and a medial adjustable member disposed on the medial side of the femoral body, the lateral adjustable member and medial adjustable member being separately adjustable to adjust the position of the femoral body relative to the cut distal end of the femur and to apply tension to at least one of the lateral collateral ligament or the medial collateral ligament of the knee; and

a self-centering sliding mechanism disposed on the femoral body between the lateral side and medial side, the sliding mechanism configured to slide over an intermedullary rod extending from the cut end of the distal femur and to position the femoral body about the cut end of the distal femur.

33. The system of claim 32, further comprising a force sensor adapted to measure a lateral force exerted between the lateral side of the femoral body and a lateral side of the tibial plateau, and to measure a medial force exerted between the medial side of the femoral body and a medial side of the tibial plateau.

34. The system of claim 33, wherein the force sensor comprises a sensor selected from the group consisting of piezoelectric sensors, force sensing resistors, strain gauges, load cells, other pressure sensors and other force sensors.

35. The system of claim 33, further comprising a visual display coupled to the force sensor, the visual display adapted to display the measured lateral force and the measured medial force.

36. The system of claim 32, further comprising a tibial member having a lateral side and a medial side.

37. The system of claim 32, wherein the sliding mechanism comprises a sliding bolt.

38. The system of claim 37, wherein the sliding bolt is translatable in a first direction, translatable in a second direction orthogonal to the first direction, and translatable in a third direction orthogonal to both the first direction and second direction.

39. The system of claim 32, wherein adjusting one adjustable member relative to the opposite adjustable member causes the femoral body to rotate relative to the cut distal end of the femur when the femoral adjustment member is coupled thereto.

40. The system of claim 32, wherein the lateral adjustable member comprises a lateral adjustment element and the medial adjustment member comprises a medial adjustment element.

41. The system of claim 40, wherein the lateral adjustment element and medial adjustment element are selected from the group consisting of screws, pins, levers, rods, springs, spring-loaded mechanisms and shape memory materials.

42. The system of claim 40, wherein the lateral adjustable member comprises a lateral paddle and the medial adjustable member comprises a medial paddle.

43. The system of claim 42, further comprising a set of augmenting members adapted to couple to the lateral paddle or the medial paddle.

44. The system of claim 40, wherein the femoral body comprises:

at least one distal femoral portion emulating the cut distal surface of the femur; and

at least one posterior condylar portion emulating the posterior condylar surfaces of the femur.

45. The system of claim 44, wherein the at least one posterior condylar portion comprises:

a lateral femoral posterior condylar member; and

a medial femoral posterior condylar member.

46. The system of claim 45, wherein at least a portion of the lateral adjustable element extends from the lateral femoral posterior condylar member and at least a portion of the medial adjustable element extends from the medial femoral posterior condylar member.

47. The system of claim 32, further comprising a locking clamp slidable over a distally extending portion of the intermedullary rod and adapted to lock the femoral adjustment member in a fixed position abutted flush against the cut distal end of the femur creating a balance plane from which to balance the extension axis to the flexion axis.

48. The system of claim 47, wherein the locking clamp is adapted to be tightened using a screwing tool, and the lateral adjustable member and medial adjustable member are adapted to be adjusted using the same screwing tool.

49. The system of claim 47 wherein the locking clamp comprises a rotatable body having a lumen offset from the center of the rotatable body.

50. The system of claim 32, further comprising a first cutting guide engagable with the femoral adjustment member, the first cutting guide adapted to facilitate making one or more bone cuts on the cut distal end of the femur.

51. The system of claim 50, further comprising a reference tongue adapted to couple to the one or more bone cuts made on the cut distal end of the femur.

52. The system of claim 50, further comprising a second cutting guide engagable with the cut distal end of the femur based on the position of the one or more bone cuts made on the distal femur facilitated by the first cutting guide.

53. A method for balancing tension of ligaments during knee replacement surgery, the method comprising:

inserting a first end of an intermedullary rod into an intermedullary canal of a femur such that the rod at least partially follows the bow of the femur to establish a first axis;

positioning a second end of the intermedullary rod to extend distally outward from a cut distal end of the femur, wherein the second end has a coupling configured for movement in at least the first axis and a second axis;

sliding a femoral adjustment member, having a lateral femoral portion and a medial femoral portion, over the second end to engage the cut distal end of the femur with the femoral adjustment member, wherein the coupling moves about the second axis independent of influence from the first axis when the femoral adjustable member is flush against the cut distal end of the femur;

measuring a lateral force exerted by a lateral femoral portion of the femoral adjustment member and a lateral tibial portion of a tibial plateau against one another;

measuring a medial force exerted by a medial femoral portion of the femoral adjustment member and a medial tibial portion of the tibial plateau against one another; and

adjusting the femoral adjustment member based on the measured lateral force and the measured medial force to apply tension to at least one of a first and a second knee ligament.

54. The method of claim 53, wherein the first axis is a flexion/extension direction and the second axis is a varus/valgus direction.

55. The method of claim 53, wherein the first knee ligament is the lateral collateral ligament and the second knee ligament is the medial collateral ligament.

56. The method of claim 53, wherein the coupling comprises an outer race and an inner race, wherein the inner race is a portion of a ball configured to allow the outer race to rotate around the inner race in a varus/valgus direction and in a flexion/extension direction.

57. The method of claim 53, wherein adjusting the femoral adjustment member allows full range patella tracking.

58. The method of claim 53, wherein the second end of the intermedullary rod is adjustable in at least the first axis and the second axis.

59. The method of claim 53, wherein the femoral adjustment member is adapted to self-adjust and position itself about the intermedullary rod when engaged with the distally extending portion of the intermedullary rod.

60. The method of claim 53 wherein measuring comprises inserting a force sensor having a lateral side and a medial side between the engaged femoral adjustment member and the tibial plateau so that the lateral side of the force sensor is disposed between the lateral tibial portion of the tibial plateau and the lateral femoral portion of the femoral adjustment member, and a medial side of the force sensor is disposed between the medial tibial portion of the tibial plateau and the medial femoral portion of the femoral adjustment member.

61. The method of claim 60 wherein the lateral force and the medial force are measured with the force sensor.

62. The method of claim 53, wherein at least one of measuring the lateral force or measuring the medial force comprises:

transmitting a voltage to a sensor element of a thin force sensing portion of the force sensor;

measuring the voltage after it has passed through the sensor element;

determining a percentage of the voltage passed through the sensor element relative to the voltage transmitted to the sensor element;

deriving the measured force from the percentage; and

displaying at least one of the measured lateral force or measured medial force with a visual display coupled with or integral with the force sensor.

63. The method of claim 53, wherein adjusting the femoral adjustment member comprises adjusting the femoral adjustment member such that the measured lateral force matches the medial force.

64. A system for enhancing a surgical procedure on a knee, the system comprising:

a femoral adjustment member removably engagable with a cut distal end of a femur, the femoral adjustment member comprising;

a femoral body having a lateral side and a medial side;

a lateral adjustable member disposed on the lateral side of the femoral body and a medial adjustable member disposed on the medial side of the femoral body, the lateral adjustable member and medial adjustable member being separately adjustable to adjust the position of the femoral body relative to the cut distal end of the femur and to apply tension to at least one of the lateral collateral ligament or the medial collateral ligament of the knee; and

a coupling mechanism disposed on the distal end of an intermedullary rod that self-centers the femoral adjustment member when coupled thereto.

65. The system of claim 64, wherein the coupling mechanism is not influenced by the intermedullary rod.

66. The system of claim 64, wherein the coupling mechanism self-centers the femoral adjustment in at least a flexion/extension direction and a varus/valgus direction.

67. The system of claim 64, further comprising a force sensor adapted to measure a lateral force exerted between the lateral side of the femoral body and a lateral side of the tibial plateau, and to measure a medial force exerted between the medial side of the femoral body and a medial side of the tibial plateau.

68. The system of claim 64, further comprising a visual display coupled to the force sensor, the visual display adapted to display the measured lateral force and the measured medial force.

69. The system of claim 64, wherein the lateral adjustable member and medial adjustable member are selected from the group consisting of screws, pins, levers, rods, springs, spring-loaded mechanisms and shape memory materials.

70. The system of claim 64, further comprising a key engagable with a distally extending portion of the intermedullary rod and adapted to rest atop the outer race of the intermedullary rod creating a balance plane from which to establish a cutting guide.