Articular cartilage evaluator and method for using the same

• US 5,673,708 A
• Filed: 04/24/1995
• Issued: 10/07/1997
• Est. Priority Date: 04/21/1992
• Status: Expired due to Term

• Current Assignee: Board of Regents of the University of Texas System (University of Texas System)
• Original Assignee: Board of Regents of the University of Texas System (University of Texas System)
• Inventors: Athanasiou, Kyriacos A., Lanctot, Dan R., Constantinides, George
• Primary Examiner(s): HINDENBURG, MAX F
• Application Number:
  US08/427,058
• Time in Patent Office: 897 Days
• Field of Search: 128/737, 128/739, 128/740, 128/744, 128/774, 128/782, 73/81, 73/82, 73/85, 73/87, 73/573, 73/781, 73/855, 364/413.02, 364/505, 364/506, 364/508, 364/512
• US Class Current: 600/587
• CPC Class Codes: A61B 2562/227 Sensors with electrical connectors
• CPC Class Codes: A61B 5/103 Detecting, measuring or recording devices for testing the shape, pattern, colour, size or movement of the body or parts thereof, for diagnostic purposes A61B5/08 takes precedence; measuring aids for tailors A41H1/00; measuring instruments specially adapted for dentistry A61C19/04
• CPC Class Codes: A61B 5/224 Measuring muscular strength
• CPC Class Codes: A61B 5/4514 Cartilage
• CPC Class Codes: A61B 5/4528 Joints A61B5/4533, A61B5/4538 take precedence
• CPC Class Codes: A61B 5/6847 mounted on an invasive device
• CPC Class Codes: G01N 2203/0071 Creep
• CPC Class Codes: G01N 2203/0089 Biorheological properties
• CPC Class Codes: G01N 2203/0208 Specific programs of loading, e.g. incremental loading or pre-loading
• CPC Class Codes: G01N 2203/0244 Tests performed "in situ" or after "in situ" use
• CPC Class Codes: G01N 2203/0676 Force, weight, load, energy, speed or acceleration
• CPC Class Codes: G01N 3/42 by performing impressions under a steady load by indentors, e.g. sphere, pyramid G01N3/54 takes precedence

Abstract

An articular cartilage evaluator for determining the Index of Structural Integrity of articular cartilage. This computer-based system measures deformation or reaction force of articular cartilage through closed loop control of a testing tip and allows the measurement of peak force, stress relaxation behavior or creep behavior in vivo and in situ. This evaluator also allows the calculation of the tissue'"'"'s material properties. A calibrator is also provided for calibrating the evaluator and attaching and removing a replaceable tip assembly.

Claims

1. A cartilage evaluator adapted to measure force exerted by the cartilage against the evaluator during use;

comprising;

(a) a hand-held component comprising;

(1) a loading system comprising a testing tip for placement proximate to, and adapted for indenting the cartilage a predetermined distance during use;

(2) an alignment system adapted to align the testing tip substantially perpendicular to the surface of the cartilage during use;

(3) a force detection system adapted to detect force exerted by the cartilage against the testing tip over time during use;

(b) a computer operatively connected to said loading system and to the force detection system, the computer being adapted to control the loading system and measure said force.

2. The cartilage evaluator of claim 1 wherein said loading system comprises a motor operatively connected to a motor shaft adapted to exert an axial force during use.

3. The cartilage evaluator of claim 2 wherein said loading system further comprises a force translation system connected to said motor shaft and said testing tip for changing the direction of the motion imparted to said testing tip by said motor shaft during use.

4. The cartilage evaluator of claim 3 wherein said force translation system comprises a slider fixedly attached to said motor shaft, said slider being adapted to move at an angle to said motor shaft in response to force imparted by said motor shaft during use.

5. The cartilage evaluator of claim 4 wherein said force translation system is adapted to change the speed of the motion of the motor shaft imparted to the testing tip during use.

6. The cartilage evaluator of claim 1 comprising a force transducer between the slide and the testing tip operatively connected to said computer whereby the force exerted by the cartilage against the testing tip is measured during use.

7. The cartilage evaluator of claim 1 comprising a position detector operatively connected to said computer and said loading system whereby the position of the testing tip with respect to the cartilage is measured and controlled during use.

8. The cartilage evaluator of claim 1 wherein said alignment system comprises a perpendicularity rim operatively connected to said testing tip.

9. The cartilage evaluator of claim 8 wherein the testing tip has a diameter, and wherein the perpendicularity rim has an inside diameter which is at least about 5 times greater than the diameter of the testing tip.

10. The cartilage evaluator of claim 1 comprising a replaceable testing tip assembly comprising a perpendicularity rim and a testing tip.

11. The cartilage evaluator of claim 1 comprising a disposable probe assembly and a reusable motor assembly.

12. The cartilage evaluator of claim 1 comprising means for standardizing the amount of force communicated to the distal end of the evaluator as a result of activating the evaluator, said means comprising a thumb trigger switch activated by a predetermined thumb pressure.

13. The cartilage evaluator of claim 12 wherein said means for standardizing force also comprise a pistol-type hand grip.

14. The cartilage evaluator of claim 1 comprising a head at an angle from the shaft thereof between about 30°

and about 80°

.

15. The cartilage evaluator of claim 14 comprising electrical means for informing the computer of the head angle, and for compensating for said head angle in calculating force exerted by the cartilage against the testing tip.

16. The cartilage evaluator of claim 1 wherein said computer is comprised within a battery-operated controller and comprises an EEPROM programmed to operate said hand-held component.

17. The cartilage evaluator of claim 1 wherein the loading system is adapted to indent less than about 50 microns during use.

18. The cartilage evaluator of claim 1 wherein the loading system is adapted to indent less than about 10 microns during use.

19. The cartilage evaluator of claim 1 wherein the cartilage evaluator is adapted to measure the response of cartilage in less than about 10 seconds during use.

20. The cartilage evaluator of claim 1 wherein the cartilage evaluator is adapted to measure the response of cartilage in less than about 5 seconds during use.

21. The cartilage evaluator of claim 1 wherein the cartilage evaluator is adapted to evaluate the cartilage during use without harming any portion of the cartilage.

22. The cartilage evaluator of claim 1 wherein the cartilage evaluator is adapted to evaluate the cartilage without determining the thickness of the cartilage.

23. The cartilage evaluator of claim 1 wherein the cartilage evaluator is adapted to evaluate articular cartilage of a human knee.

24. A system for evaluating cartilage comprising:

(a) a hand-held component comprising;

(1) a loading system comprising a testing tip for placement proximate to, and adapted for indenting the cartilage a predetermined distance during use;

(2) an alignment system adapted to align the testing tip substantially perpendicular to the surface of the cartilage during use;

(3) a force detection system adapted to detect force exerted by the cartilage against the testing tip over time during use;

(b) a calibrator for said cartilage evaluator comprising a calibration pad having a known stiffness, said calibration pad also comprising means for attaching a replaceable tip assembly to said evaluator.

25. The system of claim 24 wherein said calibrator also comprises means for removing said replaceable tip assembly from said evaluator.

26. A computerized device for determining the state of health or disease of cartilage tissue comprising:

(a) a force measurement system adapted to measure force exerted by the cartilage against a testing tip that is indenting the cartilage to a predetermined displacement during use;

(b) a computer system adapted to compare the ratio of said force measurement to at least one corresponding measurement of tissue of the same type having a known state of health;

(c) a system for expressing said ratio.

27. The device of claim 26 comprising a system for measuring force over time, a system for calculating a number representing the peak force value multiplied by the time in seconds to reach said peak value and a system for comparing said numbers with the corresponding calculated number for tissue having a known state of health.

28. The device of claim 27 wherein said corresponding tissue measurement comprises the mean of at least about twelve measurements of healthy tissue of the same type.

29. The device of claim 27 wherein said corresponding force measurement of healthy tissue is assigned a value of ten and said ratio is expressed as an integer from one to ten.

30. A method of determining the response of cartilage to indentation, comprising:

(a) positioning a testing tip through skin substantially perpendicular to underlying cartilage;

(b) displacing a portion of the cartilage with the testing tip by applying force against the cartilage with the testing tip; and

(c) using a computer to detect and measure the response of the cartilage in terms of force exerted against the testing tip by the cartilage at a set displacement.

31. A method of determining the response of cartilage to indentation, comprising:

(a) positioning a testing tip through skin substantially perpendicular to underlying cartilage;

(b) displacing a portion of the cartilage with the testing tip by applying force against the cartilage with the testing tip; and

(c) using a computer to detect and measure the response of the cartilage in terms of displacement of the cartilage at a constant force applied by the testing tip.

32. A method of determining the response of cartilage to indentation, comprising:

(a) positioning a testing tip through skin substantially perpendicular to underlying cartilage;

(b) displacing a portion of the cartilage with the testing tip by applying force against the cartilage with the testing tip; and

(c) using a computer to detect and measure the response of the cartilage and display the results.

33. A method for determining the state of health or disease of cartilage tissue comprising:

(a) indenting the cartilage to a predetermined displacement using a testing tip and measuring the force required to achieve said displacement;

(b) using a computer to determine the ratio of said force measurement to at least one corresponding measurement of healthy tissue of the same type, wherein said measurement for healthy tissue is assigned a value of 10;

(c) displaying said ratio as an integer from one to ten.

34. The method of claim 33 wherein said force measurement is the peak force value multiplied by the time in seconds to reach said peak value.

35. The method of claim 33 wherein said force measurement for healthy tissue is the mean of at least about twelve measurements of healthy tissue of the same type.