Method and apparatus for distance based detection of wear and the like in joints

• US 6,573,706 B2
• Filed: 01/31/2001
• Issued: 06/03/2003
• Est. Priority Date: 11/18/1999
• Status: Expired due to Fees

• Current Assignee: Intellijoint Systems Limited
• Original Assignee: Intellijoint Systems Limited
• Inventors: Mendes, David, Mendes, Emanuel, Barak, Gilad, Beer, Ruth
• Primary Examiner(s): Strecker, Gerard R.
• Application Number:
  US09/774,017
• Publication Number:
  US 20020101232A1
• Time in Patent Office: 853 Days
• Field of Search: 324/207.16, 324/207-7-2, 324/207-2-2, 324/219, 324/234, 324/236, 324/239, 324/655, 340/551, 340/572.5, 600/409, 600/424, 600/595, 901/35, 901/46
• US Class Current: 324/207.17
• CPC Class Codes: A61B 17/70 Spinal positioners or stabilisers ; Bone stabilisers comprising fluid filler in an implant
• CPC Class Codes: A61B 2034/102 Modelling of surgical devices, implants or prosthesis
• CPC Class Codes: A61B 2034/105 Modelling of the patient, e.g. for ligaments or bones
• CPC Class Codes: A61B 2034/2051 Electromagnetic tracking systems
• CPC Class Codes: A61B 2034/2072 Reference field transducer attached to an instrument or patient
• CPC Class Codes: A61B 2560/0219 of externally powered implanted units
• CPC Class Codes: A61B 34/20 Surgical navigation systems; Devices for tracking or guiding surgical instruments, e.g. for frameless stereotaxis
• CPC Class Codes: A61B 5/06 Devices, other than using radiation, for detecting or locating foreign bodies for removing same A61B17/50 ; determining position of probes within or on the body of the patient
• CPC Class Codes: A61B 5/062 using magnetic field
• 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 5/4504 Bones A61B5/4547 takes precedence
• CPC Class Codes: A61B 5/4528 Joints A61B5/4533, A61B5/4538 take precedence
• CPC Class Codes: A61B 5/4547 Evaluating teeth
• CPC Class Codes: A61C 19/04 Measuring instruments specially adapted for dentistry A61C5/44 takes precedence; testing vitality of teeth A61B5/0534; radiation diagnosis specially adapted for dentistry A61B6/51
• CPC Class Codes: A61C 8/00 Means to be fixed to the jaw-bone for consolidating natural teeth or for fixing dental prostheses thereon; Dental implants; Implanting tools fastening of peg-teeth in the mouth A61C13/30
• CPC Class Codes: A61F 2/28 Bones joints A61F2/30
• CPC Class Codes: A61F 2/30 Joints
• CPC Class Codes: A61F 2/30767 Special external or bone-contacting surface, e.g. coating for improving bone ingrowth
• 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 2/38 : 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 2/4261 : for wrists
• 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 2/468 : Testing instruments for artificial joints for testing non-implantable prostheses A61F2/76
• CPC Class Codes: A61F 2/488 : Means for detecting or monitoring wear
• CPC Class Codes: A61F 2002/30079 : magnetic
• CPC Class Codes: A61F 2002/3067 : for data transfer
• CPC Class Codes: A61F 2002/30912 : made of expanded metal, e.g. diamond mesh or metal nets having lozenge-shaped apertures
• CPC Class Codes: A61F 2002/4233 : for metatarso-phalangeal joints, i.e. MTP joints
• CPC Class Codes: A61F 2002/4243 : for interphalangeal joints, i.e. IP joints
• CPC Class Codes: A61F 2002/4251 : for metacarpo-phalangeal joints, i.e. MCP or MP joints, e.g. knuckle joints
• CPC Class Codes: A61F 2002/4256 : for carpo-metacarpal joints, i.e. CMC joints
• CPC Class Codes: A61F 2002/4631 : the prosthesis being specially adapted for being cemented
• CPC Class Codes: A61F 2002/4658 : for measuring dimensions, e.g. length
• CPC Class Codes: A61F 2002/4671 : for measuring resonant frequency
• CPC Class Codes: A61F 2210/009 : magnetic
• CPC Class Codes: A61F 2250/0002 : for data transfer
• CPC Class Codes: A61F 2310/00017 : Iron- or Fe-based alloys, e.g. stainless steel
• CPC Class Codes: A61F 2310/00023 : Titanium or titanium-based alloys, e.g. Ti-Ni alloys
• CPC Class Codes: A61F 2310/00029 : Cobalt-based alloys, e.g. Co-Cr alloys or Vitallium
• CPC Class Codes: A61F 2310/00179 : Ceramics or ceramic-like structures
• CPC Class Codes: A61F 2310/00407 : Coating made of titanium or of Ti-based alloys
• CPC Class Codes: A61F 2310/00796 : Coating or prosthesis-covering structure made of a phosphorus-containing compound, e.g. hydroxy(l)apatite
• CPC Class Codes: G01B 7/023 : for measuring distance between sensor and object G01B7/082 and G01B7/102 take precedence

Abstract

A distance measurement system, comprising at least one resonant circuit, at least one magnetic element with predetermined magnetic properties, a transmitter operable to transmit an electromagnetic pulse, a receiver operable to detect oscillations emitted by said resonant circuit in response to said electromagnetic pulse, and an analyzer operable to analyze an amplitude envelope property of said oscillations, to thereby determine a distance between the resonant circuit and the magnetic element.

Claims

1. A distance measurement system, comprising:

at least one resonant circuit;

at least one magnetic element with predetermined magnetic properties located remotely from said resonant circuit by a first distance; and

a separate device, not connected to said resonant circuit, said separate device comprising;

a transmitter operable to transmit an electromagnetic pulse;

a receiver operable to detect oscillations emitted by said resonant circuit in response to said electromagnetic pulse; and

,

an analyzer operable to analyze an amplitude envelope decay pattern of said oscillations following said electromagnetic pulse, therefrom to determine an eddy current factor effecting said decay pattern and therefrom to determine said first distance.

2. A distance measurement system according to claim 1, wherein said magnetic element is ferromagnetic.

3. A distance measurement system according to claim 1, wherein said magnetic element is paramagnetic.

4. A distance measurement system according to claim 1, wherein said analyzer is operable to determine said amplitude envelope property from an absolute value of amplitudes of said oscillations.

5. A distance measurement system according to claim 1, wherein said analyzer is operable to determine said amplitude envelope property from relative amplitude values of more than one cycle of said oscillations.

6. A distance measurement system according to claim 1, wherein said amplitude envelope property is an amplitude rate of decay.

7. A distance measurement system according to claim 1, wherein said analyzer is operable to determine the distance between said resonant circuit and said magnetic element additionally from frequency properties of said oscillations.

8. A distance measurement system according to claim 1, comprising more than one resonant circuit, to thereby determine more than one distance between said resonant circuits and said at least one magnetic element.

9. A distance measurement system according to claim 8, operable to determine the distance between said resonant circuits and said at least one magnetic element in more than one dimension.

10. A distance measurement system according to claim 8, wherein said more than one resonant circuits are operable to resonate at different frequencies.

11. A distance measurement system according to claim 1, comprising more than one magnetic element, to thereby determine more than one distance between said at least one resonant circuit and said magnetic elements.

12. A distance measurement system according to claim 11, operable to determine the distance between said at least one resonant circuit and said magnetic elements in more than one dimension.

13. A distance measurement system according to claim 1, comprising more than one resonant circuit and more than one magnetic element, to thereby determine more than one distance between said resonant circuits and said magnetic elements.

14. A distance measurement system according to claim 13, operable to determine the distance between said resonant circuits and said at least one magnetic element in more than one dimension.

15. A distance measurement system according to claim 1, wherein said analyzer comprises a look-up table, comprising relationships between measured oscillations and distances.

16. A distance measurement system according to claim 15, wherein said relationships are per-system relationships.

17. A distance measurement system according to claim 15, wherein said relationships comprise in-situ calibrations.

18. A method for assembling a distance measurement system, comprising the steps of:

placing a resonant circuit at a first location;

placing a magnetic element with predetermined magnetic properties at a second location remote from said first location by a first distance;

separately from said resonant circuit providing;

a transmitter for transmitting an electromagnetic pulse to said resonant circuit;

a detector for detecting oscillations emitted by said resonant circuit in response to said electromagnetic pulse; and

,

an analyzer for analyzing an amplitude envelope decay pattern, following said electromagnetic pulse, of said detected oscillations, therefrom to determine an eddy current factor effecting said decay pattern and therefrom to determine said first distance.

19. A method for assembling a distance measurement system according to claim 18, wherein said analyzer comprises a look-up table of relationships between measured oscillations and distances, and wherein said look-up table values are established for each one of a predetermined set of distances by performing for each predetermined distance the steps of:

transmitting an electromagnetic pulse to said resonant circuit;

detecting oscillations emitted by said resonant circuit in response to said electromagnetic pulse; and

,

measuring an amplitude envelope property of said detected oscillations, to thereby establish a look-up table value for said distance.

20. A method for measuring the distance between a first location comprising a resonant circuit and a second location comprising a magnetic element and having a first distance therebetween, comprising remotely from said first and said second locations carrying out the steps of:

transmitting an electromagnetic pulse to said resonant circuit;

detecting oscillations emitted by said resonant circuit in response to said electromagnetic pulse; and

,

analyzing an amplitude envelope decay pattern of said detected oscillations following said electromagnetic pulse, therefrom to determine an eddy current factor effecting said decay pattern and therefrom to determine said distance.

21. A method for measuring the distance between locations according to claim 20, wherein the step of analyzing an amplitude envelope property further comprises:

comparing information detected from said emitted oscillations to information in a look-up table, of relationships between measured oscillations and distances.

22. A method for measuring the distance between locations according to claim 20, comprising obtaining said amplitude envelope property from an absolute value of amplitudes of said oscillations.

23. A method for measuring the distance between locations according to claim 20, comprising obtaining said amplitude envelope property from relative amplitude values of more than one cycle of said oscillations.

24. A method for measuring the distance between locations according to claim 20, comprising making use of an amplitude rate of decay as said amplitude envelope property.

25. A method for measuring the distance between locations according to claim 20, comprising additionally detecting the distance from frequency properties of said detected oscillations.

26. A distance measurement system utilizing eddy currents for energy dissipation, the system comprising:

at least one resonant circuit;

at least one magnetic element with predetermined magnetic properties located at a first distance from said resonant circuit;

a transmitter operable to transmit an electromagnetic pulse; and

a separate device, not connected to said resonant circuit, said separate device comprising;

a receiver operable to detect oscillations emitted by said resonant circuit in response to said electromagnetic pulse; and

,

an analyzer operable to analyze an amplitude envelope decay pattern of said oscillations following said electromagnetic pulse as an indicator of eddy current induced energy dissipation, to thereby determine said first distance between said resonant circuit and said magnetic element.