U.S. patent application number 11/171869 was filed with the patent office on 2007-01-04 for apparatus, system, and method for transcutaneously transferring energy.
Invention is credited to Jason Sherman.
Application Number | 20070005141 11/171869 |
Document ID | / |
Family ID | 37103017 |
Filed Date | 2007-01-04 |
United States Patent
Application |
20070005141 |
Kind Code |
A1 |
Sherman; Jason |
January 4, 2007 |
Apparatus, system, and method for transcutaneously transferring
energy
Abstract
An apparatus for transcutaneously transferring an amount of
energy to an implantable orthopaedic device includes a primary
coil. The primary coil has a resonant frequency matched to a
resonant frequency of a secondary coil, which may form part of the
implantable orthopaedic device. The primary coil may have an
aperture configured to receive a portion of a patient's body or may
include a substantially "C"-shaped core. A power circuit may be
coupled with the primary coil to provide power to the coil. The
apparatus may also include a wireless receiver, a measuring device,
and/or a display.
Inventors: |
Sherman; Jason; (Warsaw,
IN) |
Correspondence
Address: |
BARNES & THORNBURG LLP
11 SOUTH MERIDIAN
INDIANAPOLIS
IN
46204
US
|
Family ID: |
37103017 |
Appl. No.: |
11/171869 |
Filed: |
June 30, 2005 |
Current U.S.
Class: |
623/18.12 ;
623/17.11 |
Current CPC
Class: |
A61F 2250/0002 20130101;
A61F 2002/3067 20130101; A61B 5/4528 20130101; A61F 2/389 20130101;
A61F 2/30 20130101; A61B 2560/0219 20130101; A61B 5/0031
20130101 |
Class at
Publication: |
623/018.12 ;
606/061 |
International
Class: |
A61F 2/30 20060101
A61F002/30 |
Claims
1. An apparatus for transcutaneously transferring an amount of
energy to an implantable orthopaedic device, the apparatus
comprising: a core having a substantially "C"-shaped side profile;
and a primary coil wound around a portion of the core, the primary
coil having a resonant frequency matched to a resonant frequency of
a secondary coil of the implantable orthopaedic device.
2. The apparatus of claim 1, wherein the core is a ferrite
core.
3. The apparatus of claim 1, wherein the core includes an elongated
middle portion, a first end portion extending from one distal end
of the elongated middle portion, and a second end portion extending
from an opposite distal end of the elongated portion, the first and
second end portions being coplanar with each other, the primary
coil being wound around the elongated middle portion.
4. The apparatus of claim 3, wherein the first and second end
portions extend substantially orthogonally from the elongated
middle portion.
5. The apparatus of claim 3, wherein a length of the elongated
portion is sized based on a length of the secondary coil of the
implantable orthopaedic device.
6. The apparatus of claim 3, wherein the elongated middle portion,
the first end portion, and the second end portion form a unitary
core.
7. The apparatus of claim 1, wherein the core has a substantially
circular cross-section profile.
8. The apparatus of claim 1, wherein the resonant frequency of the
primary coil is adjustable to match the resonant frequency of a
different secondary coil of an implantable orthopaedic device.
9. The apparatus of claim 1, wherein the resonant frequency of the
primary coil is less than about 9 kilohertz.
10. The apparatus of claim 9, wherein the resonant frequency of the
primary coil is about 5 kilohertz.
11. The apparatus of claim 1, wherein resonant frequency of the
primary coil is matched to the resonant frequency of a secondary
coil using a capacitive device.
12. The apparatus of claim 1, further comprising a bobbin having an
aperture, the core being positioned in the aperture and the primary
coil being wound around the bobbin and the core.
13. The apparatus of claim 1, wherein the implantable orthopaedic
device includes an electrical circuit configured to receive power
from the secondary coil.
14. The apparatus of claim 13, wherein the electrical circuit
includes a transmitter configured to transmit sensory data in
response to a power signal received from the secondary coil.
15. The apparatus of claim 1, wherein the primary coil is coupled
with a knee brace, the knee brace being configured to be coupled to
a leg of the patient.
16. The apparatus of claim 1, further comprising a power circuit
configured to supply a power signal to the primary coil to cause
the primary coil to generate an alternating magnetic field.
17. The apparatus of claim 16, wherein the power circuit includes a
wireless receiver configured to receive data signals from the
implantable orthopaedic device.
18. The apparatus of claim 16, wherein the power circuit includes a
measuring device and a display, the measuring device configured to
measure an amount of power used by the primary coil and display the
amount of power to a user of the apparatus via the display.
19. The apparatus of claim 16, wherein the power circuit includes a
direct current power source configured to produce a direct current
power signal and a converter configured to convert the direct
current power signal to an alternating current power signal.
20. The apparatus of claim 19, wherein the power circuit and the
primary coil are positioned in a portable housing.
21. A method for transcutaneously transferring an amount of energy
to a secondary coil of an orthopaedic device implanted in a portion
of a patient's body, the method comprising: positioning a primary
coil having a substantially "C"-shaped ferrite core near the
portion of the patient's body such that the primary coil is
substantially coplanar with the orthopaedic device; and supplying a
power signal to the primary coil to cause the primary coil to
generate an alternating magnetic field.
22. The method of claim 21, wherein the positioning step includes
positioning the primary coil such that the primary coil is spaced
away from a skin surface of the portion of the patient's body.
23. The method of claim 21, wherein the supplying step includes
supplying a power signal having a frequency matched to a resonant
frequency of the primary coil.
24. The method of claim 23, wherein the supplying step includes
supplying a power signal having a frequency of about 9 kilohertz or
less.
25. The method of claim 21, further comprising tuning a resonant
frequency of the primary coil to match a resonant frequency of the
secondary coil.
26. The method of claim 21, further comprising receiving a wireless
data signal from the orthopaedic device.
27. A method for determining a location of an orthopaedic device
implanted in a patient's body, the method comprising: moving a
primary coil over a portion of the patient's body having the
orthopaedic device implanted therein; measuring an amount of power
used by the primary coil; and determining the location of the
orthopaedic device based on the measuring step.
28. The method of claim 27, wherein the moving step includes
receiving the portion of the patient's body with an aperture
defined by the primary coil such that the primary coil
circumferentially surrounds the portion.
29. The method of claim 27, wherein the moving step includes
positioning a primary coil having a substantially "C"-shaped
ferrite core near the portion of the patient.
30. The method of claim 27, wherein the moving step includes
positioning the primary coil such that the primary coil is coplanar
with at least a portion of the orthopaedic device.
31. The method of claim 27, wherein the moving step includes
positioning the primary coil such that the primary coil is
inductively coupled with a secondary coil of the orthopaedic
device.
32. The method of claim 27, wherein the moving step includes moving
the primary coil until the amount of power used by the primary coil
is at or above a predetermined threshold value.
33. The method of claim 27, wherein the determining step includes
determining the location of the orthopaedic device when the amount
of power used by the primary coil is at or above a predetermined
threshold value.
34. The method of claim 27, further comprising tuning a resonant
frequency of the primary coil to match a resonant frequency of a
secondary coil of the orthopaedic device.
35. The method of claim 27, further comprising receiving a wireless
data signal from the orthopaedic device.
Description
CROSS-REFERENCE TO RELATED U.S. PATENT APPLICATION
[0001] Cross-reference is made to U.S. Utility Patent Application
Ser. No. ______ entitled "Apparatus, System, and Method for
Transcutaneously Transferring Energy" which was filed Jun. 30, 2005
by Jason T. Sherman, the entirety of which is expressly
incorporated herein by reference.
TECHNICAL FIELD
[0002] The present disclosure relates generally to transcutaneous
energy transfer devices and methods, and more particularly to
devices and methods for transcutaneously transferring energy to an
implantable medical device.
BACKGROUND
[0003] Transcutaneous energy transfer (TET) devices are used to
transfer energy across a boundary such as skin and other tissue of
a patient. For example, a TET device may be used to transfer energy
from a source external to a patient's body to a device implanted in
the patient's body to power and/or recharge the device. Because the
implanted device receives power transcutaneously, the implanted
device typically does not require an implanted power source, such
as a battery, to operate. As such, the patient is relieved from
continual surgical operations to replace and/or recharge the
implanted battery or other power sources.
SUMMARY
[0004] According to one aspect, an apparatus for transcutaneously
transferring an amount of energy to an implantable orthopaedic
device is disclosed. The apparatus may include a primary coil. The
primary coil may have an aperture configured to receive a portion
of a patient's body such as a leg, an arm, or the torso of the
patient. The aperture may have, for example, an inner diameter of
six inches or greater. Alternatively, the primary coil may be wound
around a portion of a substantially "C"-shaped core. The "C"-shaped
core may be, for example, a ferrite core. The core may include an
elongated middle portion, which may be sized based on a length of
the secondary coil of the implantable orthopaedic device. The core
may also include two end portions extending substantially
orthogonally from opposite distal ends of the elongated middle
portion. In some embodiments, the primary coil may be coupled with
a limb brace such as a leg or knee brace.
[0005] The primary coil may have a resonant frequency matched to a
resonant frequency of a secondary coil of the implantable
orthopaedic device. The resonant frequencies may be matched by use
of a capacitive device such as a capacitor. In some embodiments,
the resonant frequency of the primary coil is adjustable to match
the resonant frequency of additional secondary coils.
[0006] The implantable orthopaedic device may include an electrical
circuit configured to receive power from the secondary coil. For
example, the electrical circuit may include a transmitter
configured to transmit data in response to a power signal received
from the secondary coil.
[0007] The apparatus may further include a power circuit which may
supply a power signal to the primary coil to generate an
alternating magnetic field. The power circuit may include a
wireless receiver configured to receive data signals from the
implantable orthopaedic device, a measuring device configured to
measure an amount of power used by the primary coil, and/or a
display configured to display the amount of power to a caregiver or
user of the apparatus. In some embodiments, the power circuit
includes a direct current power source and a converter configured
to convert the direct current power source to an alternative
current power signal. In such embodiments, the primary coil and the
power circuit may be included in a portable housing.
[0008] According to another aspect, a method for determining a
location of an orthopaedic device implanted in a patient's body is
disclosed. The method may include moving or sweeping a primary coil
over the patient's body or portion thereof. The amount of power
used by the primary coil may be measured while the primary coil is
being moved. The location may then be determined based on the
amount of power used by the primary coil. That is, the location of
the implanted orthopaedic device may be determined based on when
the amount of power used by the primary coil is at or above a
predetermined threshold value (e.g., a user defined maximum value).
The method may further include tuning a resonant frequency of the
primary coil to match a resonant frequency of a secondary coil of
the implanted orthopaedic device. The method may also include
receiving a wireless data signal from the implanted orthopaedic
device.
[0009] The above and other features of the present disclosure,
which alone or in any combination may comprise patentable subject
matter, will become apparent from the following description and the
attached drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0010] The detailed description particularly refers to the
following figures, in which:
[0011] FIG. 1 is a diagrammatic view of a transcutaneous energy
transfer system;
[0012] FIG. 2 is a perspective view of one embodiment of the
primary coil of the transcutaneous energy transfer system of FIG.
1;
[0013] FIG. 3 is a cross-sectional view taken generally along
section lines 3-3 of FIG. 2 (note the patient's limb is not shown
for clarity of description);
[0014] FIG. 4 is a perspective view of a leg brace having the
primary coil of FIG. 2 coupled therewith;
[0015] FIG. 5 is a perspective view of another embodiment of the
primary coil of the transcutaneous energy transfer system of FIG.
1;
[0016] FIG. 6 is a cross-sectional view taken generally along
section lines 6-6 of FIG. 5;
[0017] FIG. 7 is an elevational view showing the primary coil of
FIG. 5 being used to transfer energy to an implanted orthopaedic
device;
[0018] FIG. 8 is an elevational view of a tibial tray;
[0019] FIG. 9 is an exploded elevational view of the secondary coil
and bobbin assembly of the tibial tray of FIG. 8;
[0020] FIG. 10 is a cross-sectional view taken generally along the
section lines 6-6 of FIG. 5;
[0021] FIG. 11 is a block diagram of one embodiment of a
transcutaneous energy transfer system;
[0022] FIG. 12 is a block diagram of another embodiment of a
transcutaneous energy transfer system;
[0023] FIG. 13 is a simplified flow chart of an algorithm for
transcutaneously transferring an amount of energy; and
[0024] FIG. 14 is a simplified flow chart of an algorithm for
determining a location of an implanted orthopaedic device in the
body of a patient.
DETAILED DESCRIPTION OF THE DRAWINGS
[0025] While the concepts of the present disclosure are susceptible
to various modifications and alternative forms, specific exemplary
embodiments thereof have been shown by way of example in the
drawings and will herein be described in detail. It should be
understood, however, that there is no intent to limit the concepts
of the present disclosure to the particular forms disclosed, but on
the contrary, the intention is to cover all modifications,
equivalents, and alternatives falling within the spirit and scope
of the invention as defined by the appended claims.
[0026] Referring to FIG. 1, a system 10 for transcutaneously
transferring an amount of energy includes a primary coil 12 and an
implantable orthopaedic device 14. The implantable orthopaedic
device 14 includes a secondary coil 16. Illustratively, the
orthopaedic device 14 is implanted in a leg 18 of a patient 20.
However, in other embodiments, the device 14 may be implanted in
any location of the patient 20. As such, the device 14 may be any
type of implantable orthopaedic device such as, for example, a
tibial tray implant, a bone distractor, or the like. Based on the
particular application, the device 14 may include other electronic
circuitry and/or devices such as sensors, processors, transmitters,
electrical motors, actuators, or the like.
[0027] The primary coil 12 is coupled with a power circuit 22 via a
number of interconnects 24. The power circuit 22 provides an
alternating current power signal to the primary coil 12 to energize
the primary coil 12. In response to the power signal, the primary
coil 12 generates an alternating magnetic field. While the primary
coil 12 is positioned near the implanted orthopaedic device 14 such
that the primary coil 12 and the secondary coil 16 are inductively
coupled, the alternating magnetic field generated by the primary
coil 12 induces a current in the secondary coil 16. In this way,
energy is transferred from the primary coil 12 to the secondary
coil 16. It should be appreciated that the primary coil 12 may be
positioned such that the coil 12 inductively couples with the
secondary coil 16 while not coming into contact with the skin of
the patient 20.
[0028] To improve the efficiency of the energy transfer between the
coils 12, 16, the resonant frequency of the primary coil 12 is
matched to the resonant frequency of the secondary coil 16 of the
orthopaedic device 14. As used herein in reference to resonant
frequencies, the terms "match", "matched", and "matches" are
intended to mean that the resonant frequencies are the same as or
within a predetermined tolerance range of each other. For example,
the resonant frequency of the primary coil 12 would match the
resonant frequency of the secondary coil if the current induced in
the secondary coil 16 is sufficient to power an electrical circuit
or device coupled therewith. Conversely, the resonant frequencies
of the coils 12, 16 would not match if the current induced in the
secondary coil 16 is insufficient to power the electrical circuit
or device. The resonant frequency of the primary coil 12 and the
secondary coil 16 may be configured using a capacitive device, such
as a capacitor, as discussed in more detail below in regard to
FIGS. 11 and 12. The resonant frequency of the primary coil 12 and
the secondary coil 16 may be matched to any frequency. However, in
some embodiments, the resonant frequency of the coils 12, 16 is
configured to a frequency such that patient exposure to magnetic
fields is reduced. For example, in some embodiments the resonant
frequencies of the coils 12, 16 are matched to a resonant frequency
of about 9 kilohertz or lower. In one particular embodiment, the
resonant frequencies of the coils 12, 16 are matched to a resonant
frequency of about 5 kilohertz. The frequency of the power signal
produced by the power circuit 22 is also matched to the resonant
frequency of the primary coil 12. In some embodiments, the resonant
frequency of the primary coil 12 and the power circuit 22 may be
adjustable to match the resonant frequencies of other secondary
coils of other implantable orthopaedic devices. In this way,
different orthopaedic devices (i.e. the secondary coils of the
orthopaedic devices) may have different resonant frequencies to
allow selective energy transfer to one implanted orthopaedic device
while reducing the amount of energy inadvertently transferred to
other implanted orthopaedic devices (i.e., the resonant frequencies
of the other implanted orthopaedic devices do not match the
resonant frequency of the primary coil 12). The resonant frequency
of the primary coil may, however, be adjusted to match the resonant
frequency of the other implantable devices to transfer energy to
such devices.
[0029] Referring now to FIG. 2, in one embodiment, the primary coil
12 is embodied as a primary coil 26 having an aperture 28
configured to receive a portion of the patient's 20 body.
Illustratively, the aperture 28 is configured to receive a leg 18
of the patient 20. However, in other embodiments, the aperture 28
may be configured to receive any portion of the patient's 20 body
including, for example, an arm, a finger, the head, or the torso of
the patient 20. That is, the primary coil 12 has an inner diameter
30, as illustrated in FIG. 3, of sufficient length to allow the
portion of the patient's 20 body to be received by the aperture 28
while allowing the primary coil 26 to be spaced away from the skin
of the patient 20 (i.e., an air gap is present between the primary
coil 26 and the skin of the patient 20). In one embodiment, the
aperture 28 of the primary coil 26 may have an inner diameter 30
greater than about six inches. In one particular embodiment, the
aperture 28 has an inner diameter 30 of about 8.5 inches.
[0030] Illustratively, the primary coil 26 is toroidal in shape,
but primary coils having other shapes capable of including the
aperture 28 may be used. For example, primary coils having square
or rectangular shapes may be used. The primary coil 26 is wound
around a bobbin 32 as illustrated in FIG. 2. The bobbin 32 may be
formed from any nonmagnetic and nonconductive material such as, for
example, a plastic material. The bobbin 32 provides a support
structure for the primary coil 26 and may, similar the primary coil
26, have a toroidal shape or other shape capable of defining an
aperture configured to receive a portion of the patient 20. The
primary coil 26 is formed from individual turns. The number of
turns which form the primary coil 26 may vary depending upon the
particular application and required magnetic intensity. The
individual turns are wound around the bobbin 32 and positioned in a
coil track 34. The coil track 34 has a height 36 configured to
accommodate the number of turns. That is, the height 36 may be
increased to accommodate additional individual turns. In one
particular embodiment, the height 36 of the coil track 34 has a
track height 34 of about 1.5 inches. To improve conductivity (i.e.,
reduce the effects of the "skin effect") of the primary coil 26 at
operating frequencies, the coil 26 may be formed from Litz wire
(i.e., wire formed from a number of individual strands of wire).
Depending on the desired resonant frequency of the primary coil 26,
the Litz wire may have a strand count greater than about fifty
strands. In one particular application, the primary coil 26 is
formed from Litz wire having a strand count of about 100 strands.
In addition, in some embodiments, the primary coil 26 may be formed
from a number of individual, parallel coils to reduce the voltage
requirements of each individual coil.
[0031] In use, a portion of the patient 20, such as the leg 18, is
positioned in the aperture 28 of the primary coil 26. The primary
coil 26 is positioned such that the coil 26 is substantially
coplanar with the orthopaedic device 14 and circumferentially
surrounds the portion of the patient 20. For example, the primary
coil 26 may be positioned such that the coil 26 and the secondary
coil 16 of the device 14 may be inductively coupled. To do so, a
caregiver (e.g., a physician, a nurse, or the like) may grasp a
portion of the bobbin 32 to move the primary coil 26 to the desired
location. In some embodiments, a handle 38 may be coupled with a
portion of the bobbin 32 to facilitate the positioning of the
primary coil 26. Once the primary coil 26 is located in the desired
position, an alternating current power signal may be applied to the
primary coil 26. In response to the power signal, the primary coil
26 generates an alternating magnetic field. The power signal and
primary coil 26 are configured such that the alternating magnetic
field generated by the coil 26 extends into the portion (e.g., the
leg 18) of the patient 20. The magnetic field is received by the
secondary coil 16 of the orthopaedic device 14. As discussed above,
the alternating magnetic field produces a current in the secondary
coil 26 which may be used to power electrical circuitry and/or
devices coupled with the coil 26.
[0032] Referring now to FIG. 4, in some embodiments, the primary
coil 26 may be included in a limb brace 40 to provide better
stability for the coil 26 during operation of the system 10. The
limb brace 40 may be any type of limb brace configured to couple to
any limb of the patient 20. Illustratively, the limb brace 40 is a
leg brace, commonly referred to as a knee brace, configured to
couple to the leg 18 of the patient 20. The limb brace 40 includes
a brace structure 42. The brace structure 42 includes coupling
means, such as straps, snaps, hook and loop fasteners, or the like,
to secure the structure 42 to the leg 18 or other limb of the
patient 20. The primary coil 26 is coupled with the bracing
structure 42 via, for example, mounting posts or the like. The
primary coil 26 may be permanently mounted to the bracing structure
42 such that the primary coil 26 is positioned in a similar
location every time the limb brace 40 is worn by the patient 20.
Alternatively, the primary coil 26 may be movable about the bracing
structure 42 to allow the coil 26 to transfer energy to implantable
orthopaedic devices located in regions in addition to the knee area
of the patient 20. Regardless, because the primary coil 26 is
coupled with the limb brace 40, the caregiver is not required to
constantly hold the primary coil 26 in the desired position.
Additionally, the primary coil 26 may be used to transfer energy
while the patient 20 is performing an exercise such as walking or
jogging. In other embodiments, the primary coil 26 may be coupled
with a stand or other structure to stabilize the primary coil 26
and allow the primary coil 26 to be inserted over the portion of
the patient 20 without the aid of the caregiver.
[0033] Referring now to FIGS. 5 and 6, in another embodiment, the
primary coil 12 may be embodied as a primary coil 46 wound around a
portion of a substantially "C"-shaped core 48. The core may be made
from any ferrous material such as iron, ferrite, or the like. In
the illustrative embodiment, the core 48 is formed from a unitary
core having an elongated middle portion 50, a first end portion 52,
and a second end portion 54. In some embodiments, the elongated
middle portion 50 has a length based on the length of the secondary
coil 16. The first and second end portions 52, 54 extend
substantially orthogonally from the middle portion 50 at opposite
distal ends and are coplanar with each other. However, in other
embodiments, the substantially "C"-shaped core 48 may be formed
from a middle portion and two end portions coupled with the middle
portion using a suitable adhesive. Additionally, although the
illustrative core 48 has a circular shaped cross-section, cores
having other geometric cross sections, such as square or
rectangular, may be used in other embodiments. Regardless, the
"C"-shaped core 48 is configured such that the magnetic field
generated by the primary coil 46 is increased in the direction of
the end portions 52, 54. That is, the magnetic field extends
further away from the primary coil 46 ins the direction of the end
portions 52, 54.
[0034] Similar to the primary coil 26, the primary coil 46 is
formed from individual turns, which may, in some embodiments, be
formed from Litz wire. The individual turns which form the primary
coil 46 are wound around the elongated middle portion 50 of the
core 48. In some embodiments, an insulator film (not shown) is
wrapped around the core 48 prior to the primary coil 46 being wound
thereon to insulate the turns of the coil 46 from the core 48.
Alternatively, in some embodiments, a bobbin (not shown) having an
aperture configured to receive the core 48 is used. In such
embodiments, the primary coil 46 is wound around the bobbin, which
forms an insulative barrier between the coil 46 and the core 48.
Additionally, in some embodiments, a sleeve 56 may be positioned
around the outside of the primary coil 46 to protect the coil 46.
The sleeve 56 may be formed from any nonmagnetic and nonconductive
material such as plastic or the like.
[0035] Referring now to FIG. 7, in use, the primary coil 46 is
positioned near the portion of the patient's 20 body wherein the
orthopaedic device 14 is implanted. The primary coil 46 is
positioned such that the coil 46 is substantially coplanar with the
implanted orthopaedic device 14. For example, the primary coil 46
may be positioned such that the coil 46 and the secondary coil 16
of the device 14 may be inductively coupled. To do so, a caregiver
may grasp the sleeve 50 to move the primary coil 46 to the desired
location. In some embodiments, the primary coil 46 and the core 48
are housed in a portable housing having a handle or the like to
facilitate the positioning of the primary coil 46. Once the primary
coil 26 is located in the desired position, an alternating current
power signal may be applied to the primary coil 46. In response to
the power signal, the primary coil 46 generates an alternating
magnetic field. The power signal and primary coil 46 are configured
such that the alternating magnetic field generated by the coil 26
extends into the leg 18 or other portion of the patient 20. The
magnetic field is received by the secondary coil 16 of the
implanted orthopaedic device 14. As discussed above in regard to
FIG. 1, the alternating magnetic field produces a current in the
secondary coil 26 which may be used to power electrical circuitry
and/or devices coupled with the coil 26.
[0036] Referring now to FIG. 8, in one embodiment, the implantable
orthopaedic device 14 includes a tibial tray 60. The tibial tray 60
is configured to be coupled with a tibia of the patient 20 during a
surgical procedure such as a total knee anthroplasty procedure. The
tibial tray 60 includes a platform 62 for supporting a bearing
insert 64. The insert 64 provides a bearing surface for a femur or
femur implant to articulate. The tibial tray 60 also includes a
stem portion 66 for securing the tray 60 to the tibia of the
patient 60. The stem portion 66 is configured to be inserted into a
resected end portion of the tibia and may be secured in place by
use of bone cement, although cementless configurations may also be
used. The tibial tray 60 also includes a bobbin assembly 68 secured
to a distal end of the stem portion 66. As illustrated in FIG. 9,
the bobbin assembly 68 includes a screw head 70 having a
hemispherical shape and a bobbin 72 extending axially from the
screw head 70 in the direction of an axis 74. The bobbin assembly
68 also includes a thread portion 76 that extends axially from the
bobbin 72 in the direction of an axis 74. The bobbin assembly 68
may be formed from any nonmagnetic material such as a plastic
material.
[0037] The secondary coil 16 is wound around the bobbin 72 of the
bobbin assembly 68. Illustratively, solid wire is used to form the
primary coil 16, but in other embodiments, Litz wire may be used.
Similar to the primary coil 12, the secondary coil 16 is formed
from a number of individual turns. The individual turns of the
secondary coil 16 are wound around the bobbin 72 in a coil track
82. The dimensions of the bobbin 72 are based upon the particular
application and implantable orthopaedic device 14 being used. For
example, as illustrated in FIG. 10, the bobbin 72 may have an outer
diameter 80 and a coil track width 84 sized based on the number of
individual turns of the secondary coil 16. That is, the outer
diameter 80 and/or the coil track width 84 may be increased to
accommodate additional individual turns. To protect the secondary
coil 16, a sleeve 78 is configured to slide over the secondary coil
16 when the bobbin assembly 68 is secured to the stem portion 66
(via the thread portion 76). The sleeve 78 may also be formed from
any type of nonmagnetic material such as a plastic or rubber
material.
[0038] As discussed in more detail below in regard to FIG. 11, the
implantable orthopaedic device 14 may also include additional
electronic circuitry and/or devices. The secondary coil 16 provides
power to such electronic circuitry and devices. In some
embodiments, the additional electronic circuitry is coupled with
the insert 64 (e.g., embedded in the insert 64). In other
embodiments, the electronic circuitry may be coupled with the
tibial tray 60. Regardless, wires or other interconnects from the
secondary coil 16 may be routed up through the stem portion 66 of
the tibial tray 60 and coupled with the electronic circuitry and/or
devices.
[0039] Referring now to FIG. 11, in one embodiment, the power
circuit 22 of the system 10 includes a waveform generator 90, an
amplifier 92, and a meter 94. The waveform generator 90 is coupled
with the amplifier 92 via a number of interconnects 96. The
interconnects 96 may be embodied as any type of interconnects
capable of providing electrical connection between the generator 90
and the amplifier 92 such as, for example, wires, cables, PCB
traces, or the like. The waveform generator 90 may be any type of
waveform generator that is capable of producing an output signal
having a frequency that matches the resonant frequency of the
primary coil 12, 26, 46. For example, the waveform generator 90 may
be formed from discrete and/or integrated circuitry. Alternatively,
the waveform generator 90 may be formed from a stand-alone waveform
generation device. For example, in one embodiment, the waveform
generator 90 is embodied as a PCI-5401 Single Channel Arbitrary
Function Generator for PCI commercially available from National
Instruments of Austin, Tex.
[0040] The amplifier 92 is configured to amplify the output signal
received from the generator 90 and produce an amplified output
signal having a predetermined amplitude. The predetermined
amplitude of the amplified output signal may be determined based on
the particular primary coil 12, 26, 46 used and/or the application
of the system 10. For example, in embodiments including primary
coil 26, an amplified output signal having a higher amplitude may
be used due to the increased distance between the coil 26 and the
secondary coil 16. Comparatively, in embodiments including primary
coil 46, an amplified output signal having a lower amplitude may be
used due to the increased inductive coupling efficiency provided by
the core 48. The amplifier 92 may be any type of amplifier capable
of amplifying the output signal of the waveform generator to the
predetermined amplitude. For example, the amplifier 92 may be
formed from discrete and/or integrated circuitry. Alternatively,
the amplifier 92 may be formed from a stand-alone amplification
device. For example, in one embodiment, the amplifier 92 is
embodied as a model AR-700A1 Amplifier commercially available from
Amplifier Research of Souderton, Pa.
[0041] The meter 94 is coupled with the amplifier 92 via a number
of interconnects 98 and to the primary coil 12, 26, 46 via the
interconnects 24. The interconnects 98 may be embodied as any type
of interconnects capable of providing electrical connection between
the meter 94 and the amplifier 92 such as, for example, wires,
cables, PCB traces, or the like. The meter 94 is configured to
measure the amount of power supplied to (i.e., used by) the primary
coil 12, 26, 46. In some embodiments, the meter 94 is coupled in
parallel with the outputs of the amplifier 94 (i.e., the amplifier
92 is coupled directly to the primary coil 12, 26, 46 and to the
meter 94). In other embodiments, the meter 94 may have a
pass-through input-output configuration. Regardless, the meter 94
has a large input impedance such that the effects of the meter 94
on the amplified power signal are reduced. The meter 94 may be any
type of meter capable of measuring the power supplied to the
primary coil 12, 26, 46. For example, the amplifier 92 may be
formed from discrete and/or integrated circuitry. Alternatively,
the amplifier 92 may be formed from a stand-alone amplification
device. For example, in one embodiment, the meter 94 is embodied as
Model 2330 Sampling Watt Meter commercially available from
Clarke-Hess Communication Research Corporation of Long Island City,
N.Y.
[0042] In some embodiments, the power circuit 22 may also include a
control circuit 100, a display 102, and a receiver 104. The control
circuit 100 may be communicatively coupled with the meter 94 via a
number of interconnects 106, with the display 102 via a number of
interconnects 108, and with the receiver 104 via a number of
interconnects 110. The control circuit 100 may be embodied as any
type of control circuit capable of performing the functions
described herein including, but not limited to, discrete circuitry
and/or integrated circuitry such as a processor, microcontroller,
or an application specific integrated circuit (ASIC). The receiver
104 is configured to wirelessly receive data from the implantable
orthopaedic device 14 and transmit the data to the control circuit
100. The control circuit 100 may display the data, or computed data
based thereon, on the display 102. Additionally, the control
circuit 100 may display power usage data received from the meter 94
on the display 102. The display 102 may be embodied as any type of
display capable displaying data to the caregiver including, for
example, a segmented light emitting diode (LED) display, a liquid
crystal display (LCD), or the like.
[0043] The power circuit 22 is coupled with the primary coil 12,
26, 46 via the interconnects 24. In embodiments including the
primary coil 46, the primary coil 46 includes the substantially
"C"-shaped core 48. A tuning capacitor 112 is coupled in parallel
with the primary coil 12, 26, 46 (i.e., the capacitor 112 and the
primary coil 12, 26, 46 form a parallel resonance circuit). The
tuning capacitor 112 is used to configure the resonant frequency of
the primary coil 12, 26, 46. That is, the capacitance value of the
tuning capacitor 112 is selected such that the resulting resonant
frequency of the primary coil 12, 26, 46 matches the resonant
frequency of the secondary coil 16. In addition, in some
embodiments, the turning capacitor 112 is selected such that the
quality factor (Q) of the resulting resonance curve is high. In
such embodiments, the resonant frequency of the primary coil 12,
26, 46 matches a narrower bandwidth of frequencies.
[0044] In some embodiments, the tuning capacitor 112 is physically
coupled to a portion (e.g., bobbin 32) of the primary coil 12, 26,
46 such that the tuning capacitor 112 moves with the primary coil
12, 26, 46. In other embodiments, the tuning capacitor 112 may be
included in the power circuit 22. Alternatively, the tuning
capacitor 112 may be separate from both the power circuit 22 and
the primary coil 12, 26, 46. Additionally, in some embodiments, the
tuning capacitor 112 is embodied as a capacitive device having a
variable capacitance value. In such embodiments, the resonant
frequency of the primary coil 12, 26, 46 may be adjusted to match
the resonant frequency of other secondary coils by adjusting the
capacitance value of the capacitor 112 and reconfiguring the
resonant frequency of the power signal. The degree to which the
resonant frequency of the primary coil 12, 26, 46 can be tuned is
dependant up the granularity of the capacitance values obtainable
with the variable capacitive device (i.e., the selection of
available capacitance values). However, fine tuning of the resonant
frequency may be accomplished by configuring the frequency of the
power signal via the waveform generator 90. In one embodiment, the
tuning capacitor 112 is embodied as a CS-301 Capacitance
Substituter commercially available from IET Labs, Incorporated of
Westbury, N.Y.
[0045] The implantable orthopaedic device 14 includes the secondary
coil 16, a tuning capacitor 116 coupled in series with the
secondary coil 16, and an implanted electrical device 118 coupled
in parallel with the secondary coil 16 and the tuning capacitor
116. The capacitor 116 and the secondary coil 16 form a series
resonance circuit. The tuning capacitor 116 is used to configure
the resonant frequency of the secondary coil 116. That is, the
capacitance value of the tuning capacitor 116 is selected such that
the resulting resonant frequency of the secondary coil 16 is equal
to a predetermined frequency. In addition, in some embodiments, the
turning capacitor 116 is selected such that the quality factor (Q)
of the resulting resonance curve is low. In such embodiments, the
resonant frequency of the secondary coil 16 matches a broader
bandwidth of frequencies.
[0046] The implanted electrical device 118 may be embodied as any
electrical circuit(s), electrical device(s), or combination
thereof, capable of being housed in or on the implantable
orthopaedic device 14 and powered by the current produced by the
secondary coil 16. For example, the implanted electrical device 118
may include, but is not limited to, sensors such as magnetic
sensors, load sensors, chemical sensors, biological sensors, and/or
temperature sensors; processors or other circuits; electrical
motors; actuators; and the like. In one embodiment, the implanted
electrical device 118 is embodied as an anisotropic magneto
resistive sensor (AMR sensor). In one particular embodiment, the
implanted electrical device 118 is embodied as an HMC1023 3-axis
Magnetic Sensor commercially available from Honeywell
International, Incorporated of Morristown, N.J. It should be
appreciated that the implanted electrical device 118 receives power
only while the primary coil 12, 26, 48 is energized via the power
signal to produce the alternating magnetic field and the secondary
coil 16 is exposed to the alternating magnetic field such that a
current is induced in the secondary coil 16.
[0047] In some embodiments, the implantable orthopaedic device 14
may also include a transmitter 120. The transmitter 120 is coupled
in communication with the implanted electrical device 118 via a
number of interconnects 122 and receives power from the secondary
coil 16 in a manner similar to the device 118. The transmitter 120
is configured to transmit data received from the implanted
electrical device 118 to the receiver 104 of the power circuit 22
via a wireless communication link 124. For example, in embodiments
wherein the implanted electrical device 118 is a pressure sensor,
the transmitter 120 is configured to transmit pressure data
received from the device 118 to the receiver 104. In response, the
control circuit may be configured to display the pressure data to
the caregiver on the display 102. The transmitter 120 may transmit
the data to the receiver 104 using any suitable wireless
communication protocol such as, for example, Bluetooth, wireless
USB, Wi-Fi, WiMax, Zigbee, or the like.
[0048] The implantable orthopaedic device 14 may also include an
energy storage device 126. The energy storage device 126 may be
embodied as any device capable of storing an amount of energy for
later use by the implanted electrical device 118. For example, the
energy storage device 126 may be embodied as a rechargeable battery
such as a nickel cadmium battery or a storage capacitor and
associated circuitry. Regardless, the energy storage device 126 is
configured to be charged (i.e., energy is stored in the device 126)
while the orthopaedic device 14 is being powered by the cooperation
of the power circuit 22, the primary 12, 26, 46, and the secondary
coil 16. Once the device 14 is no longer receiving power from the
secondary coil 16, the energy storage device 126 begins providing
power to the implanted electrical device 118. Once the energy
storage device 126 becomes drained of energy, the device 126 may be
recharged via the power circuit 22 and the primary coil 12, 26, 46.
In this way, the device 118 may be powered over long periods of
time.
[0049] Referring now to FIG. 12, in one embodiment, the power
circuit 22 and primary coil 12, 26, 46 are positioned in a portable
housing 130. In some embodiments, the portable housing 130 is
embodied as a hand-held housing, which facilitates the positioning
of the power circuit 22 and primary coil 12, 26, 46 by the
caregiver. In such embodiments the caregiver may quickly reposition
the primary coil 12, 26, 46, move or sweep the primary coil 12, 26,
46 over a portion of the patient 20 and transport the power circuit
22 and the primary coil 12, 26, 46 to a new location. To further
facilitate portability, in such embodiments, the power circuit 22
includes a direct current (DC) power source 132, such as
rechargeable or replaceable batteries. Accordingly, the housing 130
may be moved about the patient 20 without the need of an AC cord or
ACpower outlet.
[0050] The power circuit 22 also includes a converter 134 coupled
with the power source 132 via a number of interconnects 136. The
converter 134 is configured to convert the DC power signal received
from the DC power source 132 to an AC power signal. The converter
134 may be embodied as any circuit or device capable of converting
the DC power signal to a AC power signal including, for example,
discrete circuitry, integrated circuitry, or a combination thereof.
A frequency multiplier 138 is coupled with the converter 134 via a
number of interconnects 140. The frequency multiplier 138 is
configured to convert the AC power signal received from the
converter 134 to an AC power signal having a predetermined
frequency. That is, the frequency multiplier 138 produces an AC
power signal having a frequency that matches the resonant frequency
of the primary coil 12, 26, 46. The frequency multiplier 138 may be
embodied as any circuit or device capable of multiplying the
frequency of the AC power signal by a predetermined amount.
[0051] The power circuit 22 also includes an amplifier 142 coupled
with the frequency multiplier 138 via a number of interconnects
144. The amplifier 142 is configured to amplify the output signal
received from the frequency multiplier 138 and produce an amplified
output signal having a predetermined amplitude. The predetermined
amplitude of the amplified output signal may be determined based on
the particular primary coil 12, 26, 46 used and the application of
the system 10. The amplifier 142 may be embodied as any type of
amplifier capable of amplifying the output signal of the frequency
multiplier 138 to the predetermined amplitude. For example, the
amplifier 142 may be formed from discrete and/or integrated
circuitry.
[0052] A measuring circuit 146 is coupled with the amplifier 142
via a number of interconnects 148 and to the primary coil 12, 26,
46 via the interconnects 24. The measuring circuit 146 is
configured to measure the amount of power supplied to the primary
coil 12, 26, 46. In some embodiments, the meter 94 is coupled in
parallel with the outputs of the amplifier 144 (i.e., the amplifier
142 is coupled directly to the primary coil 12, 26, 46 and to the
measuring circuit 146). In other embodiments, the measuring circuit
146 may have a pass-through input-output configuration. Regardless,
the measuring circuit 146 has a large input impedance such that the
effects of the measuring circuit 146 on the amplified power signal
are reduced. The measuring circuit 146 may be any type of measuring
circuit capable of measuring the power supplied to the primary coil
12, 26, 46. For example, the measuring circuit 146 may be formed
from discrete and/or integrated circuitry.
[0053] A control circuit 150 is communicatively coupled with the
measuring circuit 146 via a number of interconnects 152, with a
display 154 via a number of interconnects 156, and with a receiver
158 via a number of interconnects 160. The control circuit 150 may
be similar to the control circuit 100 described above in regard to
FIG. 11. The control circuit 150 may be embodied as any type of
control circuit capable of performing the functions described
herein including, but not limited to, discrete circuitry and/or
integrated circuitry such as a processor, microcontroller, or an
application specific integrated circuit (ASIC). The receiver 158 is
configured to wirelessly receive data from the implantable
orthopaedic device 14 and transmit the data to the control circuit
150. The control circuit 150 may display the data, or computed data
based thereon, on the display 154. Additionally, the control
circuit 150 may display power usage data received from the
measuring circuit 146 on the display 154. The display 154 may be
embodied as any type of display capable displaying data to the
caregiver including, for example, a segmented light emitting diode
(LED) display, a liquid crystal display (LCD), or the like.
[0054] In addition to the power circuit 22, the primary coil 12,
26, 46 (and the core 48 in some embodiments) and the tuning
capacitor 112 are positioned in the portable housing 130. As
discussed above in regard to FIG. 11, the tuning capacitor 112 is
used to configure the resonant frequency of the primary coil 12,
26, 46 and, in some embodiments, is selected such that the quality
factor (Q) of the resulting resonance curve is high. The tuning
capacitor 112 may be physically coupled to a portion (e.g., bobbin
32) of the primary coil 12, 26, 46 or may be separate from the
primary coil 12, 26, 46. Regardless, the tuning capacitor 112 is
coupled in parallel with the primary coil 12, 26, 46 to form a
parallel resonance circuit.
[0055] Although illustrated and described above as separate
components, it should be appreciated that any two or more of the
power source 132, the converter 134, the frequency multiplier 138,
the amplifier 142, the measuring circuit 146, the control circuit
150, the display 154, and the receiver 158 may be included as a
single component capable of performing the functions of the
individual components. For example, in some embodiments, the
converter 134 and the frequency multiplier 138 may be embodied as a
single circuit, integrated or discrete, that is capable of
converting the DC power signal from the power source 132 to an AC
power signal having a frequency that matches the resonant frequency
of the associated primary coil 12, 26, 46. As such, the
interconnects 136, 140, 144, 148, 152, 156, 160 may be embodied as
any type of interconnects capable of providing electrical
connection between the various components of the power circuit 22
such as, for example, wires, cables, PCB traces, internal
integrated circuit connections, or the like.
[0056] Referring now to FIG. 13, an algorithm 200 for
transcutaneously transferring an amount of energy to the
implantable orthopaedic device 14 begins with a process step 202.
In step 202, the resonant frequency of the primary coil 12, 26, 46
is configured to match the resonant frequency of the secondary coil
16 in the implantable device 14. For example, the tuning capacitor
112 may be selected or replaced such that the resulting resonant
frequency of the primary coil 12, 26, 46 matches the resonant
frequency of the secondary coil 16. In embodiments, wherein the
tuning capacitor 112 is embodied as a variable capacitor, the
capacitance of the tuning capacitor 112 may be adjusted to match
the frequencies of the primary coil 12, 26, 46 and the secondary
coil 16. As discussed above in regard to FIGS. 11 and 12, the
turning capacitor 112 may be selected such that the quality factor
(Q) of the resulting resonance curve is high. That is, the resonant
frequency of the primary coil 12, 26, 46 matches a narrower
bandwidth of frequencies.
[0057] In some embodiments, the resonant frequency of the secondary
coil 16 of the implantable orthopaedic device 14 is predetermined
based on the type of orthopaedic device 14. For example, all knee
implants may be configured to a resonant frequency of about 5
kilohertz while all hip implants may be configured to a resonant
frequency of about 4 kilohertz. In such embodiments, the resonant
frequency of the secondary coil 16 may already be configured to the
predetermined frequency. In addition, in embodiments wherein the
orthopaedic device 14 has been previously implanted in the patient
20, the resonant frequency of the secondary coil is also
predetermined (i.e., pre-configured prior to the surgical
procedure). However, in other embodiments or applications, such as
when the orthopaedic device 14 has not yet been implanted into the
patient 20, the resonant frequency of the secondary coil 16 may be
configured. To do so, as discussed above in regard to FIG. 11, the
capacitance value of the tuning capacitor 116 is selected such that
the resulting resonant frequency of the secondary coil 16 matches a
predetermined frequency (e.g., 5 kilohertz). Additionally, the
turning capacitor 116 may be selected such that the quality factor
(Q) of the resulting resonance curve is low. That is, the resonant
frequency of the secondary coil 16 matches a broad bandwidth of
frequencies.
[0058] Once the resonant frequency of the primary coil 12, 26, 46
(and, in some embodiments, the secondary coil 16) has been
configured, the algorithm 200 advances to process step 204. In
process step 204, the power signal is configured. That is, the
frequency of the power signal is configured to match the resonant
frequency of the primary coil 12, 26, 46. To do so, the waveform
generator 90 or the frequency multiplier 138 may be configured to
produce an output signal having a frequency that matches the
resonant frequency of the primary coil 12, 26, 46. For example, if
the resonant frequency of the primary coil 12, 26, 46 is configured
to 6 kilohertz, the waveform generator or the frequency multiplier
138 is configured to produce an output signal having a frequency of
about 6 kilohertz.
[0059] Once the resonant frequency of the power signal has been
matched to the resonant frequency of the primary coil 12, 26, 46,
the primary coil 12, 26, 46 is positioned in process step 206. To
do so, in embodiments including the primary coil 26, the portion of
the patient 20 (e.g., leg 18) wherein the implantable orthopaedic
device 14 is located is positioned in the aperture 28 such that the
primary coil 26 circumferentially surrounds the portion of the
patient 20. The primary coil 26 is then positioned such that the
primary coil 26 is substantially coplanar with the implanted
orthopaedic device 14. Because the aperture 28 has a diameter 30
greater than the width of the portion of the patient 20, the
primary coil 26 may be positioned such that coil 26 is spaced away
from the skin of the patient 20 to reduce the likelihood of
damaging the skin of the patient 20. To position the primary coil
26 in the desired location, the caregiver may grasp the bobbin 32
or handle 38 to move the coil 26.
[0060] Alternatively, in embodiments including the primary coil 46,
the primary coil 46 may be positioned near the portion of the
patient 20 (e.g., leg 18) wherein the implantable orthopaedic
device 14 is located. The primary coil 46 is positioned such that
the primary coil 46 is substantially coplanar with the orthopaedic
device 14. The primary coil 46 may also be spaced away from the
skin of the patient 20 to reduce the likelihood of damaging the
skin of the patient 20. To position the primary coil 46 in the
desired location, the caregiver may grasp the sleeve 56 or a
portion of the core 48 to move the coil 46.
[0061] In embodiments wherein the power circuit 22 and the primary
coil 12, 26, 46 are positioned in a portable housing 130, the
caregiver may position the primary coil 12, 26, 46 may positioning
the portable housing 130 such that the housing 130 (i.e., the
primary coil 12, 26, 46 located within the housing 130) is near and
substantially coplanar with the implantable orthopaedic device 14.
To do so, the caregiver may grasp the housing 130, or a handle
coupled therewith, to move the housing 130 and the primary coil 12,
26, 46 to the desired location.
[0062] Once the primary coil 12, 26, 46 has been positioned at the
desired location, the primary coil 12, 26, 46 is energized via a
power signal from the power circuit 22 in process step 208. In
response, the primary coil 12, 26, 46 generates an alternating
magnetic field. The alternating magnetic field is received by the
secondary coil 16 (i.e., the secondary coil 16 is exposed to the
magnetic field) and the primary coil 12, 26, 46 and the secondary
coil 16 become inductively coupled. Because the secondary coil 16
is exposed to an alternating magnetic field, a current is induced
in the secondary coil 16. In this way, the secondary coil 16
provides power to the implanted electrical device(s) and other
circuitry of the implantable orthopaedic device 14. Because the
resonant frequencies of the power signal, the primary coil 12, 26,
46, and the secondary coil 16 are matched; the transfer efficiency
of energy from the primary coil 12, 26, 46 to the secondary coil 16
is increased. In embodiments including the display 102 or display
154, the power supplied to the primary coil 12, 26, 46 may be
displayed to the caregiver.
[0063] Additionally, in some embodiments, the algorithm 200 may
include a process step 210 in which data is received from the
implantable orthopaedic device 14. The received data may be any
type of data obtained by or produced by the implanted electrical
device 118. For example, in embodiments wherein the implanted
electrical device 118 is embodied as a sensor, sensory data may be
received by the receiver 104 from the transmitter 120 of the
orthopaedic device 14. In some embodiments, the implanted
electrical device 118 is configured to measure or determine the
data while receiving power from the secondary coil 16. In other
embodiments, such as in embodiments including the energy storage
device 126, the implanted electrical device 118 may be configured
to continually or periodically measure or determine the data.
Regardless, the data so determined is transmitted to the power
circuit 22 via the wireless link 124.
[0064] Once the data is received by the power circuit 22 (via the
receiver 104, 158), the data may be displayed to the caregiver via
the associated display 102, 154 in process step 212. To do so, the
control circuit 100, 150 may control the display 102, 154 to
display the data. In addition, the control circuit 100, 150 may be
configured to process the data to determine additional data based
on the data received from the orthopaedic device 14.
[0065] Referring now to FIG. 14, an algorithm 220 for determining a
location of an orthopaedic device implanted in a patient's body
begins with a process step 222. In the process step 222, the
primary coil 12, 26, 46 is positioned in a new location. That is,
in the first iteration of the algorithm 220, the primary coil 12,
26, 46 is positioned in an initial location near the portion of the
patient 20 wherein the orthopaedic device 14 is implanted. To do
so, in embodiments including the primary coil 26, the portion of
the patient 20 (e.g., leg 18) wherein the implanted orthopaedic
device 14 is located is positioned in the aperture 28 such that the
primary coil 26 circumferentially surrounds the portion of the
patient 20. Alternatively, in embodiments including the primary
coil 46, the primary coil 46 is positioned near the portion of the
patient 20 (e.g., leg 18) wherein the orthopaedic device 14 is
implanted. Because the exact location of the orthopaedic device 14
may not be known, the primary coil 12, 26, 46 may not be
substantially coplanar with the orthopaedic device 14 during the
first iteration of the algorithm 220 (i.e., while the primary coil
12, 26, 46 is at the initial location).
[0066] Once the primary coil 12, 26, 46 is positioned in the
initial location in step 222, the power usage of the primary coil
12, 26, 46 is determined in process step 224. To do so, the meter
94 or measuring circuit 146 determines the power supplied to the
primary coil 12, 26, 46. In some embodiments, the power supplied to
the primary coil 12, 26, 46 may also be displayed to the caregiver
via the display 102, 154. The power usage of the primary coil 12,
26, 46 varies according to the inductive coupling of the primary
coil 12, 26, 46 and the secondary coil 16. That is, as the
secondary coil 16 draws power from the alternating magnetic field,
the primary coil 12, 26, 46 uses an increased amount of power to
maintain the alternating magnetic field. Accordingly, the power
usage of the primary coil 12, 26, 46 increases as the primary coil
12, 26, 46 becomes more coplanar, and more inductively coupled,
with the secondary coil 16.
[0067] In process step 226, the algorithm 220 determines if the
power usage at the present location of the primary coil 12, 26, 46
is at or above a predetermined threshold value (e.g., a user
defined maximum value). To do so, the control circuit 100, 150 may
be configured to store previously measured power usage amounts in a
memory device. The power usage of the primary coil 12, 26, 46 at
the present location may then be compared to the stored power usage
amounts. If the power usage of the primary coil 12, 26, 46 at the
present location is not at or above the predetermined threshold
value, the algorithm 220 loops back to the process step 222 in
which the primary coil 12, 26, 46 is positioned in a new location.
It should be appreciated that the process steps 222, 224, 226 may
be repeated until a location is found at which the power supplied
to the primary coil 12, 26, 46 is at or above the predetermined
threshold. For example, a caregiver may move or sweep the primary
coil 12, 26, 46 over the location of the patient 20 wherein the
orthopaedic device 14 is implanted. As the caregiver sweeps the
primary coil 12, 26, 46 over the patient 20, the power usage of the
primary coil 12, 26, 46 varies. A location at which the power
supplied to the primary coil 12, 26, 46 is at or above the
predetermined threshold value may be determined by monitoring the
display 102, 104. Alternatively, in some embodiments, the power
circuit 22 may include an audible or visual indicator that is
activated when the primary coil 12, 26, 46 sweeps over a location
at which the power supplied to the primary coil 12, 26, 46 is at or
above a predetermined threshold value.
[0068] The location(s) at which the power usage of primary coil 12,
26, 46 is at or above the predetermined threshold value correlates
to a location at which the primary coil 12, 26, 46 is substantially
coplanar with the secondary coil 16 of the implanted orthopaedic
device 14. Accordingly, once such a location is found, the location
of the implanted orthopaedic device 14 is recorded in process step
228. The location of the device 14 may be recorded by, for example,
establishing a mark on the skin of the patient 20, recording
coordinate data identifying the location of the device 14, or the
like.
[0069] While the disclosure has been illustrated and described in
detail in the drawings and foregoing description, such an
illustration and description is to be considered as exemplary and
not restrictive in character, it being understood that only
illustrative embodiments have been shown and described and that all
changes and modifications that come within the spirit of the
disclosure are desired to be protected.
[0070] There are a plurality of advantages of the present
disclosure arising from the various features of the systems and
methods described herein. It will be noted that alternative
embodiments of the systems and methods of the present disclosure
may not include all of the features described yet still benefit
from at least some of the advantages of such features. Those of
ordinary skill in the art may readily devise their own
implementations of the systems and methods that incorporate one or
more of the features of the present invention and fall within the
spirit and scope of the present disclosure as defined by the
appended claims.
* * * * *