Intervertebral fusion remote monitoring device

Abstract

Disclosed is an invasive intervertebral fusion cage, the intervertebral fusion cage including: a vibration sensor; and a frame configured to support surrounding tissues used to create a bone fusion process; wherein the vibration sensor is integral with the frame in order to measure the mechanical vibrations the vibrations arising from the medium consisting of the frame, the surrounding tissues and/or the fusionned bone, and wherein the intervertebral fusion cage does not include a vibration excitation transducer. Also disclosed is a remote medical monitoring device including a receiver for receiving data from an intervertebral fusion cage, reflecting the mechanical vibrations of a medium and a calculator computing from the received data a medium indicator by: determining at least one vibration pattern of the received data; comparing the at least one vibration pattern with at least one reference model; generating a medium indicator in function of the comparing step.

Claims

1. An invasive intervertebral fusion cage (10), said intervertebral fusion cage (10) comprising: a frame (13), configured to support surrounding tissues (20) used to create a bone fusion process upon a bone; at least one vibration sensor (11) located in an interior of a structure of the frame (13); a non-transitory computer-readable data carrier storing data acquired by the vibration sensor; a wireless interface for transmitting said stored data to an external device; and a sensor actuator, wherein the vibration sensor (11) is integral with the frame (13) and measures mechanical vibrations arising from a medium consisting of one or more of the frame (13), the surrounding tissues (20), and the bone subject to the bone fusion process, wherein the intervertebral fusion cage does not comprise a vibration excitation transducer, wherein the intervertebral fusion cage is configured to be placed in an initial position between two vertebrae (L1, L2), wherein the vibration sensor, in an activated state, emits mechanical or ultrasound waves, and wherein the sensor actuator is configured to activate the vibration sensor, the vibration sensor emitting said mechanical or ultrasound waves when activated by said sensor actuator, and the vibration sensor and the sensor actuator together form a control loop wherein information from the vibration sensor of the measured mechanical vibrations controls said sensor actuator in order for said sensor actuator to activate the vibration sensor for emission of the mechanical or ultrasound waves.

2. The intervertebral fusion cage (10) according to claim 1, further comprising: at least two hollow or empty holes (12) arranged to allow the bone fusion process between the two vertebrae.

3. The intervertebral fusion cage (10) according to claim 1, further comprising: at least one support element configured to control a space between the two vertebrae.

4. The intervertebral fusion cage (10) according to claim 1, wherein said intervertebral fusion cage comprises only one sensor.

5. The intervertebral fusion cage (10) according to claim 1, wherein said intervertebral fusion cage comprises an accelerometer, or wherein the sensor is an accelerometer.

6. A medical system, comprising an intervertebral fusion cage (10) according to claim 1, and a medical monitoring device, wherein the medical monitoring device comprises: a receiver that receives data from the intervertebral fusion cage, the data received by the receiver reflecting mechanical vibrations of a medium consisting of one or more of the frame of the intervertebral fusion cage, surrounding tissues (20), and a bone to undergo a bone fusion process; and a calculator configured to compute, from the data received by the receiver, a medium indicator (MI) by: determining at least one vibration pattern (VP) of said received data; comparing said at least one vibration pattern (VP) with at least one reference model; generating the medium indicator (MI), which includes at least one of: a data related to the progress of the bone fusion process, a density of the bone, a thickness of a bone layer, a stiffness of the bone layer, and a stiffness of the intervertebral fusion cage, from which a physical integrity information of the intervertebral fusion cage is deduced; wherein the medical system further comprises an interface which activates a transmission of vibration data measured into the intervertebral fusion cage in order to be received by the medical monitoring device.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 is a drawing of the intervertebral fusion cage according to one embodiment of the present invention.

(2) FIG. 2 is a drawing of the intervertebral fusion cage according to one embodiment between two vertebrae.

(3) FIG. 3 is a cross-sectional view of the intervertebral fusion cage between two vertebrae and surrounded internally and externally by a bone grafting material according to one embodiment of the present invention.

(4) FIG. 4 is a cross-sectional view in the direction of the AA axis of the intervertebral fusion cage surrounded internally and externally by a bone grafting material.

(5) FIG. 5 is a drawing of the intervertebral fusion cage according to one embodiment of the present invention between two vertebrae.

(6) FIG. 6 is a graph of the vibration response measured by the vibration sensor in function of the frequency.

(7) FIG. 7 is a graph of the frequency of the two resonant frequencies in function of the Young's Modulus of the bone grafting material.

(8) FIG. 8 is a graph of the frequency of two resonant frequencies in function of the intervertebral fusion cage migration along the x-axis of FIG. 5.

(9) FIG. 9 is a graph of the frequency of two resonant frequencies in function of the intervertebral fusion cage migration along the y-axis of FIG. 5.

(10) FIG. 10 is a graph of a time history from an accelerometer signal embedded in the intervertebral fusion cage.

REFERENCES

(11) 10—Intervertebral fusion cage 11—Vibration sensor 12—Empty hole of the intervertebral fusion cage 13—Frame 20—Surrounding tissues L1—Vertebrae L2—Vertebrae F1—First resonant frequency F2—Second resonant frequency

EXAMPLES

(12) The present invention is further illustrated by the following examples.

(13) In said example, the vibration pattern chosen was the resonant frequency.

Example 1: Measuring of the at Least One Resonant Frequencies

(14) Materials and Methods

(15) Material

(16) An intervertebral fusion cage according to the present invention is implemented in a simulator simulating vibration. The simulator allows generating vibrations which can occurred between the human vertebrae. In this example, the intervertebral fusion cage is externally and internally surrounded by a bone grafting material.

(17) According to one setup, the bone grafting material Young's modulus has been set to 1 GPa, which corresponds to a fusion bone completion.

(18) The migration of the implant has been set to 0 mm.

(19) Methods

(20) During the simulation, the frequencies and the vibration responses were measured by the vibration sensor.

(21) Results

(22) The vibration response measured is illustrated on FIG. 6. It can be seen that the vibration response of the bone grafting material is increased at two specific frequencies: around 4800 Hz (F2) and 3500 Hz (F1). For the other frequencies, the vibration response is sensibly the same for a spectrum of frequency from 2000 Hz to 5000 Hz.

(23) The resonant frequencies are so 4800 Hz and 3500 Hz.

Example 2: Bone Fusion Process Impact on Resonant Frequencies

(24) Materials and Methods

(25) Material

(26) A medical device according to the present invention was used in a simulator simulating vibration which can be caused between the human vertebrae.

(27) Methods

(28) The migration of the implant has been set to 0 mm.

(29) The Young's modulus of the bone grafting material has been ranging from 50 MPa (no bone fusion) to 1000 MPa (fusion bone completion).

(30) Results

(31) The calculated resonant frequencies for each bone grafting material's Young's modulus are illustrated on FIG. 7. Both resonant frequencies increase with a progression of the fusion process. Both resonant frequencies could be considered for bone fusion monitoring.

Example 3: Cage Displacement Impact on Resonant Frequencies

(32) Materials and Methods

(33) Material

(34) According to one example, a medical device according to the present invention is implemented in a simulator simulating vibrations. The vibrations generated are preferably in the same range of those caused between the human vertebrae.

(35) Methods

(36) The Young's modulus of the bone grafting material has been set to 50 MPa (no bone fusion).

(37) The position of the implant has been moved from its initial position according to the x or they axis illustrated on FIG. 5.

(38) Results

(39) The calculated resonant frequencies when the cage has been displaced along the x axis are illustrated on FIG. 8 and the calculated resonant frequencies when the cage has been displaced along the y axis are illustrated on FIG. 9.

(40) Both resonant frequencies present a sensitivity to a displacement of the implant in the x or y direction. After their implantation into the user body, when there is still no bone fusion, the present invention allows checking the position of the intervertebral fusion cage and calculating the migration of said intervertebral fusion cage around its initial position.

(41) As it can see on FIGS. 8 and 9, the bone grafting material comprises two resonant frequencies. Both resonant frequencies have not the same evolution when the migration of the implant is varying. The resonant frequency F2 cannot be used to monitor the migration of the implant.

(42) By using the two resonant frequencies F1 and F2, the medical monitoring system is able to calculate at least two indicators. The first indicator corresponds to the Young's modulus of medium related to the progress of the bone fusion process. The second indicator corresponds to the offset indicator of the intervertebral fusion cage.