In vivo joint space measurement device and method

• US 20050010301A1
• Filed: 07/09/2004
• Published: 01/13/2005
• Est. Priority Date: 07/11/2003
• Status: Active Grant

• Current Assignee: Depuy Products Incorporated (Johnson & Johnson)
• Original Assignee: Depuy Products Incorporated (Johnson & Johnson)
• Inventors: Sherman, Jason T., Dietz, Terry L., Disilvestro, Mark R.
• Granted Patent: US 7,195,645 B2
• Time in Patent Office: Days
• US Class Current: 623/18.120
• CPC Class Codes: A61B 2090/061 for measuring dimensions, e.g. length
• CPC Class Codes: A61B 5/076 Permanent implantations telemetry using implanted circuitry A61B5/0031; implanted stimulators for therapy A61N1/3605, A61N1/362, A61N1/372
• CPC Class Codes: A61B 5/1076 for measuring dimensions inside body cavities, e.g. using catheters A61B3/1005 takes precedence
• CPC Class Codes: A61B 5/4528 Joints A61B5/4533, A61B5/4538 take precedence
• CPC Class Codes: A61B 90/06 Measuring instruments not otherwise provided for
• CPC Class Codes: A61F 2/32 for the hip
• CPC Class Codes: A61F 2/34 Acetabular cups
• CPC Class Codes: A61F 2/36 Femoral heads ; Femoral endoprostheses
• CPC Class Codes: A61F 2/367 Proximal or metaphyseal parts of shafts trochanteric devices connected to said proximal parts A61F2/30739
• CPC Class Codes: A61F 2/38 for elbows or knees
• CPC Class Codes: A61F 2/3859 Femoral components
• CPC Class Codes: A61F 2/389 Tibial components A61F2/3868 takes precedence
• CPC Class Codes: A61F 2/40 for shoulders
• CPC Class Codes: A61F 2/4081 Glenoid components, e.g. cups
• CPC Class Codes: A61F 2/4657 Measuring instruments used for implanting artificial joints for surgical instruments A61B90/06
• CPC Class Codes: A61F 2/488 Means for detecting or monitoring wear
• CPC Class Codes: A61F 2002/30079 magnetic
• CPC Class Codes: A61F 2002/30133 kidney-shaped or bean-shaped
• CPC Class Codes: A61F 2002/30326 differing in height or in length
• CPC Class Codes: A61F 2002/30589 Sealing means
• CPC Class Codes: A61F 2002/30668 : Means for transferring electromagnetic energy to implants
• CPC Class Codes: A61F 2002/3067 : for data transfer
• CPC Class Codes: A61F 2002/30795 : Blind bores, e.g. of circular cross-section
• CPC Class Codes: A61F 2002/30807 : Plurality of blind bores
• CPC Class Codes: A61F 2002/30878 : with non-sharp protrusions, for instance contacting the bone for anchoring, e.g. keels, pegs, pins, posts, shanks, stems, struts
• CPC Class Codes: A61F 2002/30884 : Fins or wings, e.g. longitudinal wings for preventing rotation within the bone cavity
• CPC Class Codes: A61F 2002/30892 : parallel
• CPC Class Codes: A61F 2002/3611 : Heads or epiphyseal parts of femur
• CPC Class Codes: A61F 2002/4018 : Heads or epiphyseal parts of humerus
• CPC Class Codes: A61F 2002/4062 : Proximal or metaphyseal parts of shafts
• CPC Class Codes: A61F 2002/4661 : for measuring thickness
• CPC Class Codes: A61F 2002/4698 : magnetic
• CPC Class Codes: A61F 2210/009 : magnetic
• CPC Class Codes: A61F 2230/0015 : Kidney-shaped, e.g. bean-shaped
• CPC Class Codes: A61F 2250/0001 : Means for transferring electromagnetic energy to implants
• CPC Class Codes: A61F 2250/0002 : for data transfer
• CPC Class Codes: A61F 2250/0037 : differing in height or in length

Abstract

A joint endoprosthesis system has first and second prosthetic components. The second prosthetic component has a bearing surface. The interface of the bearing surface and the first prosthetic component defines the joint articulation. A signal source and sensor are affixed on opposite sides of the joint articulation. The signal source generates a first signal that is received by the sensor. The sensor generates a second signal that has a characteristic that varies depending on the distance between the sensor and the signal source. A transmitter transmits a signal. The signal has a characteristic that varies depending on the characteristic of the second signal. This system can be used to measure a dimension of the joint space and to determine whether a dimension of the joint space has changed over time. The system may alternatively use magnets and magnetic sensors.

Claims

1. A joint endoprosthesis system for use in a joint comprising two bones interfacing at a joint articulation in a patient'"'"'s body, the joint endoprosthesis system comprising:

a first prosthetic component;

a second prosthetic component having a bearing surface to be placed against the first prosthetic component, the interface of the first prosthetic component and the bearing surface of the second prosthetic component defining a joint articulation;

a signal source to be affixed within the patient'"'"'s body on one side of the joint articulation for generating a first signal;

a distance reference to be affixed within the patient'"'"'s body across the joint articulation from the signal source; and

an internal transmitter to be affixed within the patient'"'"'s body, the internal transmitter being capable of producing a transmitter signal having a characteristic that varies depending on the distance between the signal source and the distance reference and that is capable of being transmitted from within the patient'"'"'s body to a location outside of the patient'"'"'s body.

2. The joint endoprosthesis system of claim 1 wherein the signal source comprises an eddy current sensor and the distance reference comprises a target.

3. The joint endoprosthesis system of claim 2 wherein the first prosthetic component comprises a distal femoral prosthesis having condyles, the second prosthetic component comprises a tibial bearing, the joint endoprosthesis further comprising a proximal tibial prosthesis having a surface that contacts the tibial bearing.

4. The joint endoprosthesis system of claim 3 wherein the target comprises at least part of the surface of at least one of the condyles of the distal femoral prosthesis.

5. The joint endoprosthesis system of claim 3 wherein the target comprises at least part of the surface of the proximal tibial prosthesis.

6. The joint endoprosthesis system of claim 2 wherein the first prosthetic component comprises an acetabular liner and the second prosthetic component comprises a proximal femoral component having a femoral head with a surface for bearing against the acetabular liner, the joint endoprosthesis further comprising an acetabular shell.

7. The joint endoprosthesis system of claim 6 wherein the target comprises at least part of the surface of the acetabular shell.

8. The joint endoprosthesis system of claim 6 wherein the target comprises at least part of the surface of the femoral head.

9. The joint endoprosthesis system of claim 2 wherein the first prosthetic component comprises a humeral component and the second prosthetic component comprises a glenoid component.

10. The joint endoprosthesis system of claim 1 wherein:

the distance reference comprises a sensor that is capable of generating a second signal having a characteristic that varies depending on the distance between the signal source and the sensor; and

the characteristic of the transmitter signal that varies depending on the distance between the signal source and the distance reference is dependent on the characteristic of the second signal.

11. The joint endoprosthesis system of claim 10 wherein the signal source, sensor and transmitter are capable of generating the first signal, second signal and transmitter signal within the patient'"'"'s body.

12. The joint endoprosthesis system of claim 10 wherein:

the variable characteristic of the second signal includes at least one of the following;

voltage;

wave frequency;

wave amplitude; and

wave phase; and

the characteristic of the transmitter signal includes at least one of the following;

wave frequency;

wave amplitude; and

wave phase.

13. The joint endoprosthesis system of claim 11 wherein:

the sensor comprises a Hall effect transducer;

the signal source comprises a permanent magnet;

the transmitter comprises a radio-frequency transmitter;

the first signal comprises a magnetic field;

the second signal comprises an electrical voltage; and

the transmitter signal comprises a radio-frequency wave.

14. The joint endoprosthesis system of claim 11 including an antenna coupled to the radio-frequency transmitter for transmitting the transmitter signal to a position outside of the patient'"'"'s body.

15. The joint endoprosthesis system of claim 11 wherein the first signal includes at least one of the following:

a magnetic field;

an electric field; and

a radio-frequency wave.

16. The joint endoprosthesis of claim 11 wherein the second signal includes at least one of the following:

an electric voltage;

an electric current; and

a radio-frequency wave.

17. The joint endoprosthesis system of claim 11 wherein:

the sensor comprises a radio-frequency transponder;

the signal source comprises a source of radio-frequency waves;

the first signal, second signal and transmitter signals comprise radio-frequency waves.

18. The joint endoprosthesis system of claim 11 further comprising a power source to be implanted in the patient'"'"'s body.

19. The joint endoprosthesis system of claim 11 further comprising an electronic component to be implanted in the patient'"'"'s body and electrically connected to the sensor and to the transmitter for converting the second signal to the transmitter signal.

20. The joint endoprosthesis system of claim 11 wherein the signal source is affixed to the first prosthetic component and the sensor is affixed to another prosthetic component.

21. The joint endoprosthesis system of claim 1 wherein the distance reference is separate from both the first prosthetic component and the second prosthetic component.

22. The joint endoprosthesis system of claim 11 wherein the signal source is separate from both the first prosthetic component and the second prosthetic component.

23. The joint endoprosthesis system of claim 22 wherein the distance reference is separate from both the first prosthetic component and the second prosthetic component.

24. The joint endoprosthesis system of claim 11 wherein the first prosthetic component comprises a distal femoral component and the second prosthetic component comprises a tibial bearing.

25. The joint endoprosthesis system of claim 11 wherein the first prosthetic component comprises a femoral head, the second prosthetic component comprises an acetabular liner.

26. The joint endoprosthesis system of claim 11 wherein the first prosthetic component comprises a humeral component and the second prosthetic component comprises a glenoid component.

27. The joint endoprosthesis system of claim 1 wherein the first signal generated by the signal source comprises an electric field and wherein the distance reference comprises part of a capacitor.

28. A method of determining a dimension of a joint space in the body of a patient wherein the patient has a joint endoprosthesis that includes a first prosthetic component and a bearing occupying the joint space adjacent the first prosthetic component, the method comprising:

generating a distance-related signal that has a characteristic that relates to a dimension of the joint space;

transmitting a signal from within the patient'"'"'s body to a location outside of the patient'"'"'s body, wherein the signal has a characteristic that relates to the characteristic of the distance-related signal;

determining a dimension of the joint space based on the value of the characteristic of the signal transmitted outside of the patient'"'"'s body.

29. The method of claim 28 wherein the step of generating a distance-related signal comprises generating a magnetic field across the joint space.

30. The method of claim 29 wherein the magnetic field is generated on one side of the joint space and where the step of generating a distance-related signal further comprises creating a voltage on the opposite side of the joint space, the voltage having a magnitude that relates to a characteristic of the magnetic field on said opposite side of the joint space.

31. The method of claim 30 the step of transmitting a signal to a location outside of the patient'"'"'s body comprises producing a radio-frequency wave.

32. The method of claim 28 wherein the step of generating a distance-related signal comprises generating a first radio-frequency wave at a first fixed location on one side of the joint space and generating a second radio-frequency wave at a second fixed location on the opposite side of the joint space and wherein the second radio-frequency wave has a characteristic dependent on the distance between the first fixed location and the second fixed location.

33. The method of claim 32 wherein the characteristic of the second radio-frequency wave dependent on distance includes at least one of the following:

frequency, amplitude and phase.

34. The method of claim 32 wherein the step of transmitting a signal to a location outside of the patient'"'"'s body comprises generating a radio-frequency wave having a characteristic dependent on a characteristic of the second radio-frequency wave.

35. The method of claim 34 wherein the characteristic of the signal transmitted includes at least one of the following:

frequency, amplitude and phase.

36. The method of claim 28 wherein the joint comprises the knee, the first prosthetic component comprises a distal femoral component and the bearing comprises a tibial bearing occupying a joint space adjacent the distal femoral component.

37. The method of claim 28 wherein the joint comprises the hip, the first prosthetic component comprises a proximal femoral component and the bearing comprises an acetabular liner.

38. The method of claim 28 wherein the joint comprises the shoulder, the first prosthetic component comprises a humeral component and the bearing comprises a glenoid component.

39. The method of claim 28 wherein the step of generating a distance-related signal comprises generating an electric field across the joint space.

40. The method of claim 28 wherein the step of generating a distance-related signal comprises generating an eddy current and determining eddy current change across the joint space.

41. A method of determining a change in a dimension of a joint space in the body of a patient wherein the patient has a joint endoprosthesis that includes a first prosthetic component and a bearing occupying the joint space adjacent the first prosthetic component, the method comprising:

generating a first signal from one side of the joint space at a first location within the patient'"'"'s body;

receiving the first signal on the opposite side of the joint space at a second location within the patient'"'"'s body;

transmitting a signal from within the patient'"'"'s body to an external location, wherein the signal transmitted to the external location has a characteristic that relates to distance between the first location and the second location;

determining the extent of change in a dimension of the joint space based on said characteristic of the signal transmitted to the external location.

42. The method of claim 41 wherein the step of generating a first signal creates a magnetic field at the second location.

43. The method of claim 41 wherein the step of generating a first signal includes generating a radio-frequency wave.

44. The method of claim 41 wherein the step of generating a first signal includes creating an electric field at the second location.

45. The method of claim 41 wherein the step of generating a first signal includes creating an eddy current.

46. The method of claim 41 wherein the step of transmitting a signal to an external location includes generating a radio-frequency wave.

47. The method of claim 46 wherein the characteristic of the radio-frequency wave that relates to distance between the first location and the second location includes at least one of the following:

frequency, amplitude and phase.

48. The method of claim 41 wherein the joint comprises the knee, the first prosthetic component comprises a distal femoral component and the bearing comprises a tibial bearing occupying a joint space adjacent the distal femoral component.

49. The method of claim 41 wherein the joint comprises the hip, the first prosthetic component comprises a proximal femoral component and the bearing comprises an acetabular liner.

50. The method of claim 41 wherein the joint comprises the shoulder, the first prosthetic component comprises a humeral component and the bearing comprises a glenoid component.

51. An implantable medical device comprising a material that acts selectively as a magnet.

52. The implantable medical device of claim 51 wherein the material that acts selectively as a magnet comprises a superparamagnet.

53. The implantable medical device of claim 51 wherein the device comprises a bone prosthesis.

54. A medical system comprising an implantable prosthetic component, a material that acts selectively as a magnet carried by the implantable prosthetic component and an external sensor for sensing a characteristic produced by the material that acts selectively as a magnet.

55. The medical system of claim 54 wherein the material that acts selectively as a magnet comprises a superparamagnet.

56. The medical system of claim 54 wherein the sensor comprises a Hall effect sensor.

57. The medical system of claim 54 wherein the Hall effect sensor comprises a three-dimension Hall effect sensor.

58. The medical system of claim 54 further comprising an additional sensor.

59. The medical system of claim 58 further comprising a plurality of additional sensors.

60. The medical system of claim 54 further comprising a cuff carrying the sensor.

61. The medical system of claim 54 further comprising a field source for selectively magnetizing the material that selectively acts as a magnet.

62. A joint endoprosthesis system for use in a joint comprising two bones interfacing at a joint articulation in a patient'"'"'s body, the joint endoprosthesis system comprising:

a first prosthetic component;

a second prosthetic component having a bearing surface to be placed against the first prosthetic component, the interface of the first prosthetic component and the bearing surface of the second prosthetic component defining a joint articulation;

a magnet to be affixed within the patient'"'"'s body;

a sensor to be affixed within the patient'"'"'s body, the sensor being capable of sensing a property of the magnetic field of the magnet; and

an internal transmitter to be affixed within the patient'"'"'s body, the internal transmitter being capable of producing a signal having a characteristic that varies depending on the property sensed by the sensor and that is capable of being transmitted from within the patient'"'"'s body to a location outside of the patient'"'"'s body.

63. The joint endoprosthesis system of claim 62 wherein the sensor is selected from the group consisting of:

a Hall effect sensor;

a three-dimensional Hall effect sensor;

a variable reluctance sensor;

a magnetoelastic sensor;

a magnetoresistive sensor;

a magnetorestrictive sensor;

a saturation core sensor;

a superconducting quantum interference device;

a nuclear magnetic resonance sensor;

am induction core magnetometer;

a proton precession magnetometer; and

an optically pumped magnetometer.

64. The joint endoprosthesis of claim 62 further comprising a power source to be implanted in the patient'"'"'s body.

65. The joint endoprosthesis system of claim 62 wherein the magnet is carried by one of the prosthetic components and the sensor is carried by the other prosthetic component.

66. A joint endoprosthesis system for use in a joint comprising two bones interfacing at a joint articulation in a patient'"'"'s body, the joint endoprosthesis system comprising:

a first prosthetic component;

a second prosthetic component having a bearing surface to be placed against the first prosthetic component, the interface of the first prosthetic component and the bearing surface of the second prosthetic component defining a joint articulation;

a magnet to be affixed within the patient'"'"'s body; and

a sensor to be maintained outside of the patient'"'"'s body, the sensor being capable of sensing a property of the magnetic field of the magnet.

67. The joint endoprosthesis system of claim 66 wherein the effect sensor is selected from the group consisting of:

a Hall effect sensor;

a three-dimensional Hall effect sensor;

a variable reluctance sensor;

a magnetoelastic sensor;

a magnetoresistive sensor;

a magnetorestrictive sensor;

a saturation core sensor;

a superconducting quantum interference device;

a nuclear magnetic resonance sensor;

am induction core magnetometer;

a proton precession magnetometer; and

an optically pumped magnetometer.

68. The joint endoprosthesis system of claim 66 further comprising an external cuff carrying the sensor.

69. The joint endoprosthesis system of claim 66 further comprising an additional sensor to be maintained outside of the patient'"'"'s body.

70. The joint endoprosthesis system of claim 66 further comprising an additional plurality of sensors to be maintained outside of the patient'"'"'s body.