SENSING FORCE DURING PARTIAL AND TOTAL KNEE REPLACEMENT SURGERY

• US 20100217156A1
• Filed: 08/20/2009
• Published: 08/26/2010
• Est. Priority Date: 08/20/2008
• Status: Active Grant

• Current Assignee: Synvasive Technology Incorporated (Zimmer Biomet Holdings, Inc.)
• Original Assignee: Synvasive Technology Incorporated (Zimmer Biomet Holdings, Inc.)
• Inventors: Berend, Keith R., Sizelove, Andrew, Murray, David, Fisher, Michael G.
• Granted Patent: US 8,211,041 B2
• Time in Patent Office: Days
• US Class Current: 600/587
• CPC Class Codes: A61B 17/88 Osteosynthesis instruments; Methods or means for implanting or extracting internal or external fixation devices A61B17/7074 takes precedence
• CPC Class Codes: A61F 2/32 for the hip
• CPC Class Codes: A61F 2/38 for elbows or knees
• CPC Class Codes: A61F 2/3804 for elbows
• CPC Class Codes: A61F 2/40 for shoulders
• CPC Class Codes: A61F 2/4202 for ankles
• CPC Class Codes: A61F 2/44 for the spine, e.g. vertebrae, spinal discs
• CPC Class Codes: A61F 2/4657 Measuring instruments used for implanting artificial joints for surgical instruments A61B90/06
• CPC Class Codes: A61F 2/4684 Trial or dummy prostheses
• CPC Class Codes: A61F 2002/4666 for measuring force, pressure or mechanical tension
• CPC Class Codes: A61F 2002/4687 Mechanical guides for implantation instruments

Abstract

Systems, devices, and methods are provided for measuring forces in the space of a knee during surgery. Such forces can be caused by tension in the ligaments of the knee. A femoral member is engaged with a distal femur. While the knee is flexed, partially extended, or fully extended, a force sensor and a gauge shim can be placed in the gap between the femoral member and the tibial plateau to measure the forces therebetween. The force sensor provides an accurate and quantifiable measurement of force, making knee replacement surgery and ligament tension balancing more accurate, standardized and repeatable. The force sensor comprises an elongate housing which comprises a thin force sensing distal portion and a proximal handle portion.

Claims

1. A system for measuring forces in the space of an anatomical joint, the system comprising:

a force sensor comprising an elongate housing and a sensor element, the elongate housing comprising a thin force sensing distal portion and a proximal handle portion, wherein the thin force sensing distal portion includes the sensor element.

2. The system of claim 1, wherein the anatomical joint is a knee and the forces in the space of the anatomical joint are caused by ligaments adjacent the knee.

3. The system of claim 1, wherein the anatomical joint is selected from the group consisting of an elbow joint, an intervertebral joint, a hip joint, an ankle joint, and a shoulder joint.

4. The system of claim 1, wherein the elongate housing further comprises a stop portion proximal of the thin distal portion and distal of the proximal handle portion.

5. The system of claim 1, wherein the sensor element comprises a force sensing member.

6. The system of claim 5, wherein the force sensing member is selected from the group consisting of piezoelectric sensors, force sensing resistors, force sensing capacitors, strain gages, load cells, pressure sensors, and other force sensors.

7. The system of claim 5, wherein the thin distal portion of the elongate housing comprises a wide distal region and a thin proximal region, and the force sensing member of the sensor element is disposed within the wide distal region of the elongate housing.

8. The system of claim 7, wherein the sensor element further comprises a distal wiring portion extending proximally of the force sensing member.

9. The system of claim 1 further comprising:

a processor coupled with the sensor element for processing sensed force data into usable data for providing to a user; and

a visual display coupled with the processor and adapted to display the usable data.

10. The system of claim 9, wherein the visual display is attached to the proximal handle portion.

11. The system of claim 9, wherein the visual display comprises a plurality of different colored lights, wherein a light is illuminated in response to discrete incremental changes in force applied to the sensor element, wherein further, each illuminated light corresponds to an increase of force applied to the sensor.

12. The system of claim 9, wherein the visual display comprises a plurality of different colored lights, wherein each light is separately illuminated in response to a different predetermined force detected by the sensor element.

13. The system of claim 9 wherein the visual display is wirelessly coupled with the processor.

14. The system of claim 13 wherein the visual display is wireless coupled with the processor through at least one of an infrared connection, a radiofrequency connection, a BlueTooth®

connection, a Z-Wave connection, and a Zigbee®

connection

15. The system of claim 9 further comprising tangible media coupled to the at least one of the processor and visual display, the tangible media configured to store a value of the measured force.

16. The system of claim 1 further comprising at least one gauge shim, the at least one gauge shim being concave and having a condylar contact area.

17. The system of claim 16, wherein a length of the thin distal force sensing portion matches a length of the condylar contact area of the at least one gauge shim.

18. The system of claim 16, wherein the elongate bar has a flat first side and a tapered second side opposite the first side.

19. The system of claim 18, wherein the flat first side is adapted to match the at least one gauge shim.

20. The system of claim 18, wherein the tapered second side is tapered towards a distal end of the elongate bar.

21. The system of claim 4, wherein the stop portion is thicker than the thin distal portion.

22. The system of claim 4, wherein the stop portion is attached perpendicular to the distal end of the thin portion to limit the insertion distance of the handheld force sensor into an anatomical joint.

23. The system of claim 1, wherein the proximal handle portion is thicker than the thin distal force sensing portion.

24. The system of claim 1 further comprising a light source attached to the proximal handle portion, wherein the light source is configured to emit a line of visible light across the force sensing pad toward the anterior portion of the distal femur so as to capture the midline of the condylar center of the femoral component when the force sensor is disposed in a gap between a femoral member and a tibial plateau with the knee in approximately 90 degrees of flexion.

25. The system of claim 24, wherein the light indicates rotational alignment with the condylar center of the femoral component during flexion.

26. The system of claim 1 further comprising a light source attached to the proximal handle portion, wherein the light source is configured to emit a line of visible light across the force sensing pad toward the hip so as to capture the location of the hip center when the force sensor is disposed in a gap between a femoral member and a tibial plateau with the knee in extension.

27. The system of claim 24 or 26, wherein the light is a laser.

28. A handheld device for measuring forces in the space of an anatomical joint, the device comprising:

an elongate housing and a sensor element, the elongate housing comprising a thin force sensing distal portion and a proximal handle portion, wherein the thin force sensing distal portion includes the sensor element.

29. The device of claim 28, wherein the elongate housing further comprises a stop portion proximal of the thin distal portion and distal the proximal handle portion.

30. The device of claim 28, wherein the anatomical joint is a knee and forces in the space of the anatomical joint are caused by ligaments adjacent the knee.

31. The device of claim 28, wherein the anatomical joint is selected from the group consisting of an elbow joint, an intervertebral joint, a hip joint, an ankle joint, and a shoulder joint

32. The device of claim 28, wherein the sensor element comprises a force sensing member.

33. The device of claim 32, wherein the force sensing member is selected from the group consisting of piezoelectric sensors, force sensing resistors, force sensing capacitors, strain gages, load cells, pressure sensors, and other force sensors.

34. The device of claim 32, wherein the thin distal portion of the elongate housing comprises a wide distal region and a thin proximal region and the force sensing member includes the sensor element.

35. The device of claim 34, wherein the sensor element further comprises a distal wiring portion extending proximally of the force sensing member.

36. The device of claim 28 further comprising a processor coupled with the sensor element for processing sensed force data into usable data for providing to a user;

and a visual display coupled with the processor and adapted to display the usable data.

37. The device of claim 36 further comprising a power source coupled with the sensor element and the processor.

38. The device of claim 28, wherein the elongate housing has a flat first side and a tapered second side opposite the first side.

39. The device of claim 38, wherein the tapered second side is tapered towards a distal end of the elongate housing.

40. The device of claim 28, wherein the stop portion is thicker than the thin distal force sensing portion.

41. The device of claim 28, wherein the proximal handle portion is thicker than the thin distal portion.

42. A method for measuring forces in the space of a knee during surgery, the method comprising:

placing a force sensor in a gap between the distal femur and the proximal tibia; and

measuring a force exerted by the ligaments of the knee on the force sensing portion of the force sensor.

43. The method of claim 42, wherein placing a force sensor in a gap between the distal femur and the proximal tibia comprises placing a distal portion of the force sensor over the proximal tibial plateau.

44. The method of claim 43, wherein the force sensor is placed in the gap and the force is measured when the knee is in flexion.

45. The method of claim 43, wherein the force sensor is placed in the gap and the force is measured when the knee is partially extended.

46. The method of claim 43, wherein the force sensor is placed in the gap and the force is measured when the knee is in full extension.

47. The method of claim 42, wherein the method further comprises placing the force sensor in the gap along with a gauge shim moveably coupled to the force sensor to measure the forces in the gap that has been increased due to bone being resected from one of the proximal tibia or distal femur.

48. The method of claim 47, wherein natural tension in the ligaments of the knee is achieved when the combination of the thickness of the moveably coupled gauge shim and the thickness of the force sensor provide a force measurement indicating the ligaments of the knee have toned to an acceptable tension.

49. The method of claim 42 further comprising:

processing data based on the measured force into usable data for providing to a user; and

displaying the usable data on a visual display.

50. The method of claim 42 further comprising:

placing the force sensor in a gap a multitude of times in a repeatable fashion so as to align the force sensor to one of identified anatomical or surgical landmarks or devices.

51. The method of claim 50 further comprising placing the force sensor in a gap a multitude of times entering from the anterior aspect of the gap and stopping at the same position in the posterior aspect of the gap.

52. The method of claim 51 further comprising stopping at the same posterior aspect of the gap by abutting the force sensor against one of identified anatomical or surgical landmarks or devices.

53. The method of claim 50 further comprising placing the force sensor in a gap a multitude of times entering from the anterior aspect of the gap and stopping at the same position in the posterior aspect of the gap and rotationally aligning the force sensor in the same orientation relative to one of anatomical or surgical landmarks or devices.

54. The method of claim 53 further comprising rotationally aligning the force sensor in the same orientation relative to one of anatomical or surgical landmarks, or devices by visualizing a line or beam of light upon or cast from the force sensor.

55. The method of claim 42 further comprising storing the usable data on a tangible medium coupled to the visual display.

56. The method of claim 42, wherein measuring a force exerted by the ligaments of the knee on the force sensing portion of the force sensor comprises:

transmitting a voltage to a sensor element of the 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.

57. A method for measuring forces in the space of an anatomical joint during surgery, the anatomical joint comprising a first bone having a first end and a second bone having a second end opposing the first end, the method comprising:

engaging a prosthesis with the first end of the first bone;

placing a force sensor in a gap between the prosthesis and the second end of the second bone;

measuring a force exerted between the first end of the first bone and the second end of the second bone against one another with a force sensing portion of the force sensor; and

removing the force sensor from the gap.

58. The method of claim 57, wherein placing the force sensor in the gap comprises placing a distal portion of the force sensor over the second end of the second bone.

59. The method of claim 57, wherein the method further comprises:

placing a gauge shim in the gap.

60. The method of claim 57 further comprising:

processing data based on the measured force into usable data for providing to a user; and

displaying the usable data on a visual display.

61. The method of claim 60 further comprising storing the usable data on a tangible medium coupled to the visual display.

62. The method of claim 57, wherein measuring the force comprises:

transmitting a voltage to a sensor element of the 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.

63. The method of claim 57, wherein the anatomical joint is selected from the group consisting of a knee joint, an elbow joint, an intervertebral joint, a hip joint, an ankle joint, and a shoulder joint.