Method and apparatus for determining osseous implant fixation integrity

• US 5,024,239 A
• Filed: 01/11/1990
• Issued: 06/18/1991
• Est. Priority Date: 12/21/1988
• Status: Expired due to Term

• Current Assignee: Alexander D. Rosenstein
• Original Assignee: Alexander D. Rosenstein
• Inventors: Rosenstein, Alexander D.
• Primary Examiner(s): Hindenburg, Max
• Assistant Examiner(s): Longo, Robin R.
• Application Number:
  US07/463,427
• Time in Patent Office: 523 Days
• Field of Search: 128/739-740, 128/773, 128/774, 128/660.06, 73/579, 73/582, 73/588, 73/662, 324/635, 324/636
• US Class Current: 600/587
• CPC Class Codes: A61B 5/0051 by applying vibrations
• 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: A61F 2/02 Prostheses implantable into the body closure means for urethra or rectum or for artificial body openings therefor A61F2/0004
• CPC Class Codes: A61F 2/36 Femoral heads ; Femoral endoprostheses
• CPC Class Codes: A61F 2/468 Testing instruments for artificial joints for testing non-implantable prostheses A61F2/76
• CPC Class Codes: A61F 2002/4671 for measuring resonant frequency
• CPC Class Codes: A61F 2240/008 Means for testing implantable prostheses
• CPC Class Codes: G01H 1/12 of longitudinal or not specified vibrations

Abstract

An apparatus for detecting loosening of an implant imbedded in a bone of a limb of a patient, includes a vibrator is pressed into engagement with the limb to impart vibratory motion to the bone. The vibrator is controlled to cause the vibratory motion to have a predetermined recurring pattern. A pickup device is pressed into engagement with the limb spaced from the vibrator over the same bone near the implant, for detecting the vibratory motion transmitted through the bone implant composite to generate an output signal. Implant loosening is determined when the recurring pattern of the output signal transmitted through the bone implant composite demonstrates sustained superimposition on the oscilloscope and/or significant secondary harmonics on the spectrum analyzer.

Claims

1. A method for determining, without the utilization of base line information, the integrity of a heterogeneous composite substrate of an implant fixation in a bone of a limb of a patient, the substrate including a bone to cement interface and a cement to implant fixation interface, comprising:

using a vibrator having a smoothly contoured member;

compressing firmly with the contoured member, the flesh of the limb to the bone and to the implant fixation, of the substrate, over a large outer surface area of the limb, to enable vibrations to be imparted through the compressed flesh and through said heterogeneous composite substrate, to the bone, with little discomfort or damage to the limb;

supplying to said vibrator an input energizing electrical signal having a predetermined recurring pattern of a single non-resonant frequency;

vibrating the heterogeneous composite substrate, including each one of the interfaces thereof in response to the vibrator being energized by said input signal;

using a single pick-up device;

pressing the pick-up device into engagement with the outer surface of the limb spaced from the vibrator at the same bone, for detecting the vibratory motion of the bone implant heterogeneous composite substrate, to generate a single output electrical signal;

analyzing said input energizing electrical signal relative to the recurring pattern only of the single output electrical signal transmitted through the bone implant heterogeneous composite substrate and each one of said interfaces, without the utilization of base line information; and

determining implant loosening when said recurring pattern of said output signal is persistently distorted.

2. An apparatus for determining, without the utilization of base line information, the integrity of a heterogeneous composite substrate of an implant fixation in a bone of a limb of a patient, the substrate including a bone to cement interface, and a cement to implant fixation interface, comprising:

vibrator means for imparting to the heterogeneous composite substrate, including each one of the interfaces thereof, vibratory motion having a predetermined recurring pattern, said vibrator means including a smoothly contoured member adopted to compress firmly the flesh of the limb to the bone and to the implant fixation, of the substrate, over a large outer surface area of the limb, to enable vibrations to be imparted through the compressed flesh and through said heterogeneous composite substrate, to the bone, with little discomfort or damage to the limb;

means for generating a vibrator energizing electrical signal having a predetermined recurring pattern of single non-resonant frequency;

single pick-up means adapted to be pressed into engagement with the outer surface of limb spaced from said vibrator means for detecting the vibratory motion of said bone implant heterogeneous composite substrate, to generate a recurring single output electrical signal; and

means for analyzing said input energizing electrical signal relative to the pattern of said single output electrical signal only transmitted through the bone implant heterogeneous composite substrate and each one of said interface, without the utilization of base line information, to determine implant fixation loosening when said single input recurring pattern is persistently distorted;

wherein said means for analyzing includes means for detecting subharmonic frequencies of said signal output signal to indicate a lack of implant fixation integrity.

3. An apparatus of claim 2, wherein said vibrator means includes a spherical head for engaging the limb, and means for vibrating said head.

4. An apparatus of claim 3, wherein said spherical head is between about 15 mm and about 25 mm in diameter.

5. An apparatus of claim 4, wherein said diameter is about 19 mm.

6. An apparatus of claim 2, wherein said signal generator means is a sine wave generator.

7. An apparatus of claim 2, wherein said pick-up device means is an accelerometer.

8. An apparatus of claim 2, further including an amplifier coupled to the output of said pick-up means.

9. An apparatus of claim 2, further including a spectrum analyzer means for analyzing the signal received via said pick-up means.

10. An apparatus of claim 2, wherein said means for analyzing the pattern of the single output electrical signal only includes an oscilloscope for analyzing the presence or absence of sustained wave superimposition.

11. An apparatus of claim 10, further including a chart recorder.

12. An apparatus of claim 2, wherein said means for analyzing the pattern of the single output electrical signal only is a spectrum analyzer said spectrum analyzer being adapted for analyzing the presence or absence of significant secondary harmonics in an output signal.

13. An apparatus of claim 12, further including an oscilloscope for displaying graphically said output signal.