U.S. patent number RE46,582 [Application Number 14/844,768] was granted by the patent office on 2017-10-24 for orthopaedic implant with sensors.
This patent grant is currently assigned to DEPUY SYNTHES PRODUCTS, INC.. The grantee listed for this patent is DePuy Synthes Products, Inc.. Invention is credited to Geoffrey Flexner, Charles E. Geltz, James M. Green, Harry T. Hall, Chad Morgan.
United States Patent |
RE46,582 |
Morgan , et al. |
October 24, 2017 |
**Please see images for:
( Certificate of Correction ) ** |
Orthopaedic implant with sensors
Abstract
A monitoring system includes: (1) an implant having at least one
sensor and configured for at least partial insertion into a
patient, a first one of sensors being in contact with a perimeter
of a hole in a body portion of the implant for accepting a
fastener; (2) a microchip associated with the implant and the
sensor, the microchip configured to receive at least a first signal
from the sensor; (3) a transmitter associated with the microchip
for transmitting a second signal, representative of the first
signal; (4) a receiver located outside of the patient, the receiver
configured receive the transmitted second signal; and (5) a display
device associated with the receiver, the display device configured
to provide an audible or visual representation of the second signal
to a user.
Inventors: |
Morgan; Chad (West Grove,
PA), Hall; Harry T. (Downingtown, PA), Green; James
M. (Portland, OR), Flexner; Geoffrey (Chester Springs,
PA), Geltz; Charles E. (Drexel Hill, PA) |
Applicant: |
Name |
City |
State |
Country |
Type |
DePuy Synthes Products, Inc. |
Raynham |
MA |
US |
|
|
Assignee: |
DEPUY SYNTHES PRODUCTS, INC.
(Raynham, MA)
|
Family
ID: |
35503608 |
Appl.
No.: |
14/844,768 |
Filed: |
September 3, 2015 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
|
|
11147750 |
Dec 27, 2011 |
8083741 |
|
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60578107 |
Jun 7, 2004 |
|
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Reissue of: |
13298808 |
Nov 17, 2011 |
8551092 |
Oct 8, 2013 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
A61B
5/14539 (20130101); A61B 5/411 (20130101); A61N
1/205 (20130101); A61B 17/68 (20130101); A61B
5/4839 (20130101); A61B 5/076 (20130101); A61B
17/80 (20130101); A61B 90/06 (20160201); A61B
5/4504 (20130101); A61B 17/7037 (20130101); A61F
2002/4666 (20130101); A61B 17/663 (20130101); A61F
2/442 (20130101); A61B 2017/00084 (20130101); A61B
2560/0219 (20130101); A61F 2002/30677 (20130101); A61F
2310/0097 (20130101); A61B 17/60 (20130101); A61B
5/01 (20130101); A61B 17/7225 (20130101); A61F
2002/4672 (20130101); A61B 17/72 (20130101); A61F
2250/0002 (20130101); A61F 2002/3067 (20130101); A61B
17/64 (20130101); A61B 2090/064 (20160201); A61B
17/7001 (20130101); A61B 2017/00734 (20130101); A61F
2002/2821 (20130101); A61B 17/70 (20130101); A61B
17/86 (20130101) |
Current International
Class: |
A61B
17/56 (20060101); A61B 17/68 (20060101) |
Field of
Search: |
;606/53,60,57,90,105,282 |
References Cited
[Referenced By]
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2006/098759 |
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Sep 2006 |
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WO |
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Primary Examiner: Flanagan; Beverly M
Attorney, Agent or Firm: Fay Kaplun & Marcin, LLP
Parent Case Text
RELATED APPLICATION DATA
The present application is .Iadd.a Reissue Application of the U.S.
patent application Ser. No. 13/298,808 filed on Nov. 17, 2017, now
U.S. Pat. No. 8,551,092; which is.Iaddend. a Continuation
application of U.S. patent application Ser. No. 11/147,750 filed on
Jun. 7, 2005, now U.S. Pat. No. 8,083,741, which claims priority to
U.S. Provisional Patent Application Ser. No. 60/578,107, filed Jun.
7, 2004, the entire contents of which are expressly incorporated
herein by reference thereto.
Claims
What is claimed is:
1. A method of mending a broken bone, comprising: affixing a bone
fixation implant to first and second portions of the broken bone
using a plurality of fasteners, the implant including a microchip
and a plurality of sensors arranged on the implant and connected to
the microchip, a first one of the sensors being in contact with a
perimeter of a hole in a body portion of the implant for accepting
a fastener; collecting data from the sensors by the microchip; and
transmitting the data from the microchip to an external receiving
device.
2. The method of claim 1, wherein at least one of the sensors is a
thermocouple.
3. The method of claim 1, wherein at least one of the sensors is a
pressure transducer.
4. The method of claim 1, wherein at least one of the sensors is a
strain gauge.
5. The method of claim 1, wherein at least one of the sensors is a
digital imaging element.
6. A monitoring system comprising: an implant having at least one
sensor and configured for at least partial insertion into a
patient, a first one of sensors being in contact with a perimeter
of a hole in a body portion of the implant for accepting a
fastener; a microchip associated with the implant and the sensor,
the microchip configured to receive at least a first signal from
the sensor; a transmitter associated with the microchip for
transmitting a second signal, representative of the first signal; a
receiver located outside of the patient, the receiver configured
receive the transmitted second signal; and a display device
associated with the receiver, the display device configured to
provide an audible or visual representation of the second signal to
a user.
7. The monitoring system of claim 6, wherein the microchip further
comprises a data logger.
8. The monitoring system of claim 6, wherein the display device is
further configured to continuously record the transmitted second
signal.
9. The monitoring system of claim 6, wherein the implant is a bone
plate.
10. The monitoring system of claim 6, wherein the at least one
sensor is configured and adapted to receive a strain from at least
a portion of the implant.
11. The monitoring system of claim 6 wherein the at least one
sensor is configured and adapted to receive a pressure applied to
at least a portion of the implant.
12. The monitoring system of claim 6 wherein the at least one
sensor is configured and adapted to receive a temperature of at
least a portion of the implant.
13. The monitoring system of claim 6, wherein the implant further
comprises a compartment for holding a therapeutic agent for release
in response to a signal received by the microchip.
.Iadd.14. The method of claim 1, wherein the bone fixation implant
is a bone plate..Iaddend.
.Iadd.15. A method of orthopaedic surgery, comprising: attaching an
orthopaedic device to a bone using a plurality of fasteners, the
orthopedic device including a microchip and a plurality of sensors
operably connected to the orthopaedic device to monitor the
orthopaedic device, the plurality of sensors being connected to the
microchip, intraoperatively adjusting the orthopaedic device, and
intraoperatively receiving data from the sensors via the microchip,
the data corresponding to an adjustment of the orthopaedic device
to achieve a desired spatial relationship of bone segments to one
another..Iaddend.
.Iadd.16. The method of orthopaedic surgery of claim 15, further
comprising the step of: intraoperatively adjusting the orthopaedic
device based on the data from the sensors..Iaddend.
.Iadd.17. The method of orthopaedic surgery of claim 15, wherein
the bone segments are vertebrae and the orthopaedic device is a
spinal fixation implant comprising a spinal fusion rod
assembly..Iaddend.
.Iadd.18. The method of orthopaedic surgery of claim 15, wherein
the data is wirelessly transmitted to an external computing
device..Iaddend.
.Iadd.19. A method of orthopaedic surgery, comprising: attaching a
first rod of an orthopaedic device along a first side of a first
portion of a bone via a first transverse member extending from the
first rod, the first rod having a first sensor operably connected
thereto; attaching a second rod of the orthopaedic device along a
second side of a second portion of the bone via a second transverse
member extending from the second rod, the second rod having a
second sensor operably connected thereto; receiving data via a
microchip connected to the first and second sensors; and providing
the data to a user to facilitate intraoperative adjustments to the
orthopaedic device by the user..Iaddend.
.Iadd.20. The method of claim 19, wherein the first portion of bone
is a vertebra and the orthopaedic device is a spinal fusion rod
assembly..Iaddend.
.Iadd.21. The method of claim 19, wherein the data is configured to
facilitate intraoperative adjustments to the orthopaedic device to
achieve one of a desired stress, strain and pressure applied to the
first portion of bone via the orthopaedic device..Iaddend.
.Iadd.22. The method of claim 19, wherein the data includes one of
a stress, strain and pressure applied to the orthopaedic
device..Iaddend.
.Iadd.23. A method of orthopaedic surgery, comprising: attaching a
spinal fixation member to a bone via a transverse member extending
therefrom, the spinal fixation member including a sensor operably
connected thereto to monitor the spinal fixation member; and
intraoperatively receiving data from the sensor via a microchip
connected to the sensor, the data corresponding to a desired
intraoperative adjustment of the spinal fixation
member..Iaddend.
.Iadd.24. The method of claim 23, wherein the spinal fixation
member is a spinal fusion rod assembly..Iaddend.
.Iadd.25. The method of claim 23, wherein the spinal fixation
member includes two rods configured to be attached to opposing
sides of the bone..Iaddend.
.Iadd.26. The method of claim 23, wherein the sensor detects one of
stress, strain and pressure applied to the bone..Iaddend.
Description
FIELD OF THE INVENTION
The present invention relates to orthopaedic implants, such as bone
plates, for use in repairing fractured bones or for addressing
other orthopedic conditions. More particularly, the present
invention relates to an orthopaedic implant having sensors and/or a
microchip for measuring and transmitting data concerning the
implant and/or the surrounding tissue to doctors and/or
patients.
BACKGROUND OF THE INVENTION
Bone plates have been used for many years in the field of
orthopedics for the repair of broken bones and are well known in
the art. One example of such a bone plate is shown and described in
U.S. Pat. No. 6,623,486 to Weaver, et al. which is hereby
incorporated by reference. Such bone plates function well in most
instances, and fracture healing occurs more predictably than if no
plate were used. In some instances, however, improper installation,
implant failure, infection or other conditions such as patient
non-compliance with prescribed post-operative treatment may
contribute to compromised healing of the fracture, as well as
increased risk to the health of the patient. Health care
professionals currently use non-invasive methods such as x-rays to
examine fracture healing progress and assess condition of implanted
bone plates. However, x-rays may be inadequate for accurate
diagnoses. They are costly, and repeated x-rays may be detrimental
to the patient's and health care workers' health. In some cases,
non-unions of fractures may go clinically undetected until implant
failure. Moreover, x-rays may not be used to adequately diagnose
soft tissue conditions or stress on the implant. In some instances,
invasive procedures are required to diagnose implant failure or
infections early enough that appropriate remedial measures may be
implemented.
Therefore there is a need for an orthopaedic implant that can
provide precise and accurate information to doctors and patients
concerning the status of the implant, progress of fracture healing,
and the surrounding tissue without the need for x-rays or invasive
procedures.
SUMMARY OF THE INVENTION
The present invention comprises an orthopaedic implant, e.g., a
bone plate, intramedullary nail, etc., for fixation of bone having
one or more microchips (i.e., integrated circuits) and various
sensors for the gathering of information relating to the implant
and its environment.
An implant is provided comprising a body portion configured to
contact patient tissue, one or more microchips, and a plurality of
sensors arranged on the implant body and connected to said
microchip wherein at least one sensor is configured to receive
physical stimulus from a portion of the implant or the patient's
tissue. The microchip may further comprise a data logger and a
power source, such as a battery.
The implant may be a bone plate, bone screw, intramedullary nail,
spinal fixation element (pedicle screw, pedicle hook, fixation
plate, fixation rod, etc.), intervertebral implant (artificial
spinal disc or fusion spacer), distractor, external fixation system
or other orthopaedic implant. The implant may have a coating, which
may include a polymer or a porous metal, and may act as a carrier
or substrate for a pharmaceutically active agent or other
therapeutic substance. The implant may also include a compartment
for storing a therapeutic agent, such as an antibiotic, a growth
factor, a chemotherapeutic agent, etc. The therapeutic agent may be
released in response to a signal received by the microchip.
One or more sensors on the implant may be configured and adapted to
receive a strain from at least a portion of the implant. The
sensors may be configured and adapted to receive a pressure applied
to at least a portion of the implant, and/or to receive a
temperature of at least a portion of the implant. The sensors may
also be configured to capture digital images (video and/or
photographs) of the surrounding patient tissue. The sensors may
also be configured and adapted to emit an electric current for
stimulating bone growth.
The patient tissue may comprise first and second bone portions of a
fracture, the implant may further comprise an element configured to
apply a micro-motion to the first and second bone ends to
facilitate fusion of the fractured portions.
The implant may further comprise a counter for counting a number of
loading cycles applied to the implant.
In another embodiment, an implant for the fixation of bone
comprises a plurality of holes for accepting fasteners, an onboard
microchip comprising a data logger, signal conditioner,
multiplexer, and transmitter, and a plurality of sensors connected
to the microchip and arranged at various points on said implant,
wherein said sensors are configured to receive at least one
physical stimulus at a portion of the implant.
One of said sensors may be selected from at least one of the group
consisting of a pressure transducer, a thermocouple, a strain gauge
and a cycle counter.
In another embodiment, the present invention relates to a method of
mending a broken hone, comprising providing a bone fixation implant
with a microchip, arranging a plurality of sensors on said implant,
connecting said plurality of sensors to said microchip, affixing
the implant to first and second portions of the broken bone using a
plurality of fasteners, providing data from said sensors to said
microchip, and transmitting said data from said microchip to an
external receiving device.
In another embodiment, a monitoring system is provided comprising
an implant having at least one sensor and configured for at least
partial insertion into a patient, a microchip associated with the
implant and the sensor, the microchip configured to receive at
least a first signal from the sensor, a transmitter associated with
the microchip for transmitting a second signal, representative of
the first signal, a receiver located outside of the patient, the
receiver configured receive the transmitted second signal, and a
display device associated with the receiver, the display device
configured to provide an audible or visual representation of the
second signal to a user. The display device may be further
configured to continuously record the transmitted second
signal.
The implant may be coated. Such a coating may include a polymer or
porous metal, such as magnesium, that can be a carrier or substrate
for a pharmaceutically active agent or synthetic agent.
BRIEF DESCRIPTION OF THE DRAWINGS
To facilitate an understanding of and for the purpose of
illustrating the present invention, exemplary and preferred
features and embodiments are disclosed in the accompanying
drawings, it being understood, however, that the invention is not
limited to the precise arrangements and instrumentalities shown,
and wherein similar reference characters denote similar elements
throughout the several views, and wherein:
FIG. 1 is a perspective view of a first embodiment of a bone plate
according to the present invention;
FIG. 2 is a side view of a second embodiment of a bone plate
according to the present invention attached to a bone;
FIG. 3 is a perspective view of the underside of an embodiment of a
bone plate according to the present invention;
FIG. 4 is a block diagram of an embodiment of the various microchip
components;
FIG. 5 is a cross-section of a bone plate according to the present
invention as attached to a bone;
FIG. 6 is perspective view of an intramedullary nail according to a
preferred embodiment of the present invention;
FIG. 7 is a perspective view of a pedicle screw according to
another preferred embodiment of the present invention;
FIG. 8 is a perspective view of a pedicle hook according to yet
another preferred embodiment of the present invention;
FIG. 9 is a side view of an intervertebral implant according to
still another preferred embodiment of the present invention;
FIG. 10 is a perspective view of a maxillofacial distractor
according to a preferred embodiment of the present invention;
and
FIG. 11 is a side view of an external bone fixation system
according to a preferred embodiment of the present invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
Reference is now made to FIGS. 1-2, which show a bone plate 10
according to a first preferred embodiment of the present invention.
The bone plate 10 shown in FIG. 1 comprises upper surface 15 and
lower surface 20, with the lower surface 20 configured to contact
the bone. The plate may further have a number of holes 30
configured and adapted to receive fasteners, such as, for example,
screws, that will affix the bone plate to the bone. One or more
microchips 40 may be located on the plate top surface 15, bottom
surface 20, the side wall of the bone plate, or as with the
illustrated embodiment, may be placed within a compartment 45 in
the bone plate for recording information gathered by numerous
sensors 50 which may be located at various locations anywhere on
the top, bottom or sides of the plate, or may surround or be
located within the plate holes. The sensors may be located on the
surface of the plate, or they may be embedded therein. A small
cover 60 may be provided to conceal and protect microchip 40 within
the bone plate. The cover 60 may seal the microchip from exposure
to the environment within which the bone plate is placed.
Alternatively, microchip 40 may not be covered and may be openly
exposed. While reference is made to a plate having the
configuration illustrated in FIG. 1, it will be noted that one or
more microchips 40 and sensors 50 may be used in conjunction with
any appropriate fixation device known in the art, e.g.,
intramedullary nails, screws for external or internal fixation,
spinal fixation elements (pedicle screws, hooks, fixation rods,
etc.), intervertebral implants (artificial spinal disks and
spacers), distractors for lengthening bones and correcting
deformities, etc. Furthermore, it should be emphasized that
multiple microchips 40 and/or multiple sensors 50 may be provided
for a single fixation device to monitor different segments of the
fixation device or to monitor different types of sensors (e.g.
strain, pressure, temperature, cycle count) provided with the
plate. Moreover, microchips 40 located in one implant 10 can send
and receive data to and from other implants. For example, a bone
plate 10 located at one fracture site can send data to another
plate 10 located at a different fracture site in the same or a
different bone. Similarly, pedicle screws at one location can
receive data from other pedicle screws, hooks or fixation rods. The
implants of the present invention may also be used at an impending
pathological fracture site, where information concerning increasing
strain on the implant would indicate that the affected bone is
weakening.
Similarly, such implants could also be employed at locations where
osteotomies or resections have been performed to monitor bone
strength.
In addition, the holes 30 in the bone plate 10 may be threaded to
receive screws with threaded heads, as described in U.S. Pat. No.
5,709,686 to Talos, which is hereby incorporated by reference. The
threaded connection between the screw and the plate may serve to
lock the screw and plate together so that the screw will not back
out of the plate even if the screw shank loses purchase with the
surrounding bone, which can occur in patients having substandard
bone structure resulting from osteoporosis or other factors.
Standard compression screws having no such plate-locking feature
may tend to pull out of substandard bone when subjected to the
bending forces generated in the plate during post-installation
loading. Further, standard compression screws are designed to
engage the screw holes of the plate in a manner that forces the
fractured bone ends together to aid healing. Thus, where a plate
having only compression screws is installed across a fracture site,
the bone portions may move slightly in the period following
fixation. As a result, the measured strain in the plate during that
period may not be truly representative of the true load-bearing
capacity of the bone (i.e. it may be unnaturally high). Thus, a
strain reading from a sensor on a plate using only compression
screws may not provide the surgeon with reliable information
regarding early healing of the bone (i.e. in the days or first week
following implantation) from which he or she may make a diagnosis
regarding whether the fracture is healing properly. Only after the
fractured bone portions have settled will strain readings become
sufficiently accurate that a proper diagnosis may be made. By
contrast, where locking screws (i.e. those having heads that
threadably engage the plate holes) are used, there is no period of
settling, and thus the strain values observed in the plate will
immediately upon implantation be representative of the load carried
by the plate (and correspondingly the load carried by the bone). As
such, the surgeon may use these early measured strain readings to
develop an accurate, early assessment of the fracture healing rate
and the potential for not uniting. An early diagnosis of delayed
union is advantageous because it allows the surgeon to take
remedial steps as soon as a possible non-union is suspected, thus
prompting intervention.
FIG. 2 shows an alternate embodiment of the invention installed on
a bone. FIG. 2 shows a bone plate 10 attached to a bone 80 by
several screws 90. Bone plate 10 may have curved, flared, or bent
sections. The microchip cover 60 protects and covers one or more
microchips 40. The various sensors 50 that wrap around different
parts of the bone plate can also be seen.
FIG. 3 shows the underside of an embodiment of the bone plate 10,
showing holes 30 and sensors 50. On the surface of the bone plate
that attaches to the bone there may also be one or more electrodes
70 for the stimulation of bone growth. There may also be a small
opening 65 for the various sensor electrodes to enter the bone
plate and connect with the microchip contained therein. Opening 65
may also hold a pharmaceutically active agent, such as a bolus of
antibiotics, chemotherapy agents, pain medication and/or other
therapeutic agents. The agent may be released by the implant in
response to a signal conveyed by the treating physician or the
patient, or may be dispensed automatically by the implant when an
elevated temperature or other data signaling a need for the agent
is recorded by one or more of sensors 50. In one embodiment, the
agent may include growth factors, such as Bone Morphogenetic
Proteins (BMPs) or Vascular Endothelial Growth Factor (VEGFs). In
other pathologic applications, the agent may include angiogenesis
inhibitors, e.g., fibulin-5, which act to deprive tumors of
nutrients and oxygen. In other reconstructive applications, the
pharmaceutically active agent may include drugs with the ability to
stimulate hair growth in areas of the scalp, such as
Minoxidil.RTM.. Sensors 50 may comprise pressure sensors disposed
along the underside of the plate, and may be used to measure
compression of the plate to the underlying bone (further described
in relation to FIG. 5 below). l
As seen in FIG. 4, the implant may contain a microchip 100 which
may include a data logger 140, signal conditioner 110, multiplexer
120, and transmitter 130. The microchip may be connected to one or
more sensors 50 attached at different locations along the implant.
The sensors may be used to monitor loading of the implant by
measuring strain at the individual locations and count the cycles
of loading and unloading. Alternatively, the sensors may be
configured to measure conditions immediately surrounding the
implants; such as temperature, pH, etc. Sensors 50 and/or microchip
40 may also include digital photographic capabilities, such as a
CMOS chip, which can capture and transmit images or video of
patient tissue in the vicinity of the implant.
FIG. 5 is a cross-section of one embodiment of a bone plate 10
according to the present invention as attached to the bone 80. This
figure shows how the bone plate 10 is semi-curved but has a
different curvature from the bone 80 so that the bone plate only
contacts the bone along the edges, or rails, of the bone plate.
This type of contact is useful in minimizing the disruption of
blood flow to the bone as described in U.S. Pat. No. 6,309,393 to
Tepic, which is hereby incorporated by reference. Thus, sensors 50
disposed between the edges or rails of the plate and the bone
surface may detect the compression force between the bone and the
plate at those sensor locations. Resulting initial force
measurements may be used to provide a baseline for the engagement
of the plate with the bone immediately following implantation.
Subsequent measurements may then he compared to the baseline
measurements to determine whether the plate remains sufficiently
engaged with the bone, or whether remedial action is required (e.g.
the plate or screw(s) need to be replaced). The ideal fixation case
is one in which the compression force between plate and bone
remains constant from the time the implant is installed to the time
it is removed. Where multiple individual sensors are disposed along
the plate rails, subsequent readings associated with each sensor
can be used to individually identify the condition of each screw in
the plate, and may also be used to assess the overall integrity of
the connection between the bone and the plate.
Thus, the various sensors arranged on the implant may include
thermocouples, pressure transducers, force probes, counters, strain
gauges, and digital imaging devices. At least one sensor may be
used to count the number of loading cycles the implant experiences,
including axial, bending and torsional loads. The information
gathered from these sensors may be used to diagnose conditions
associated with the implant and/or the tissue surrounding the
implant.
For example, it may be important to monitor strain at various
locations on the implant, since such strain may be directly related
to forces applied to and experienced by the implant. Monitoring the
force applied to the implant, e.g., a bone plate, over time may
allow the doctor to determine whether the bone is healing at the
appropriate rate. As a bone heals, the amount of load carried by
the bone will increase, and a proportionally lower load will be
carried by the implant, and thus a lower strain will be measured by
a strain gauge mounted to the plate. If the measured plate loading
does not decrease at the expected rate, the doctor may take
remedial action. Similarly, early detection of an overloading
condition in the plate may allow the doctor to correct or replace
an over-stressed or fatigued plate or fastener. It has been
observed that non-unions are clinically diagnosed six months after
the fracture event. If the strain gauge does not detect transfer of
loading conditions, it may indicate delayed union and could signal
potential damage to the implant or the end of its useful life.
One or more sensors may also be used to monitor the number of
loading cycles, e.g., axial, bending, torsional, etc., experienced
by the implant. One cycle may be defined as an application of
stress to the implant followed by the release of that stress. For
example, if the implant is installed along the femur of a patient,
one cycle could be one step in which the patient puts pressure on
the implant as his or her foot hits the ground followed by a
release of that stress when the patient lifts his or her foot from
the ground. The life of an implant is usually determined by how
many cycles it experiences until bone healing occurs or until the
implant fails. A doctor can determine when an implant needs to be
replaced by using a counter programmed to log the amount of cycles
the implant has been through. In addition, such a counter may be
useful in determining the cause of an implant failure, such as due
to over-activity of the patient or clinical non-union of the
fracture.
It may also be desirable to obtain temperature readings at various
locations along the implant to determine whether the tissue
surrounding the implant is infected following implantation. Normal
healthy human tissue has a temperature in the range of from about
36 degrees Celsius to about 37.5 degrees C. It has been observed
that infected tissue may evidence an increase in temperature to a
range above about 38 degrees C. Thus, if such a temperature
increase is detected by one or more of the temperature sensors on
the implant, the doctor may choose to initiate a regimen of
antibiotics, or may take other more invasive actions to eliminate
the infection. In one embodiment, as discussed above, the treating
physician may send a signal to the implant to release a bolus of
antibiotics stored in a compartment within the implant in order to
treat an infection, or, alternatively, the implant itself may be
configured to automatically release antibiotics if a certain
threshold temperature is reached. Abnormally high tissue
temperatures in the vicinity of the implant may also signal that
the patient is experiencing an adverse reaction to the material of
the implant. For example, if the implant is made of or contains a
material to which the patient is allergic (e.g. nickel), the
patient's body may react to the implant in a manner similar to that
of an infection. Thus, patient rejection of the implant may
likewise be determined through temperature measurement. Digital
photographic elements within sensors 50 in the implant may also be
used to view images of patient tissue for signs of infection and/or
implant rejection.
Since body temperatures may be influenced by factors such as
exercise, temperature readings would likely take place in the
doctor's office or other controlled setting, rather than being
constantly monitored or monitored by the patient. The temperature
sensors preferably will be located anywhere on the surface of the
plate, except between the plate and the bone. Monitoring of
temperatures through sensors mounted on a bone plate thus may aid
the doctor in making an important early diagnosis of infection,
increasing the chance that the infection may be effectively
contained. In still other embodiments, sensors 50 on implant 10 may
detect chemical agents/reagents formed by and in the patient's
surrounding tissues.
Reference is now made to FIG. 4 which is a block diagram of a
microchip contained on the implant of the present invention. In one
embodiment, the microchip 100 may contain a data logging device 140
for storing information recorded by the sensors. The microchip may
also contain a signal conditioner 110 for powering the sensor and
preparing the signal received by the sensor, a mutiplexer 120 for
combining information received from numerous sensors, and a
transmitter 130 or transmitting the information received from the
sensor or sensors. As information is received by one or more
sensors 50, it is passed through the signal conditioner 110 to the
multiplexer 120 and on to both the data logging device 140 which
may store information in storage 150 provided on microchip 100 and
the wireless transmitter 130 which transmits the information to a
receiving device 160 which may be connected to a computer 170.
Device 160 can both send data to and receive data from microchip
100. In addition, in an alternate embodiment, wireless transmitter
130 may be replaced with a hard wired connection.
In one embodiment the receiving device is a wireless hand-held
computer, such as a Pocket PC.RTM., Palm Pilot.RTM.,
Blackberry.RTM. device or cellular telephone, that may be used to
request information from the implant, store information sent by the
implant, and send information to the implant. For example, the
surgeon may pass the handheld device over the portion of the
patient's body containing the implant, and the device may upload
strain, temperature, pH, and/or pressure data from one or more
sensors located on the implant. Thereafter, software associated
with the microchip 100, sensors 50 and/or handheld device 160 may
manipulate the uploaded data to provide a visual readout to the
surgeon. Such a readout may comprise discrete force, temperature
and pressure and stress cycle values taken from the individual
sensors. The readout may also comprise a graph of the values
obtained from the same patient over time. It may also provide an
alarm feature that would signal a dangerous condition such as
substantial implant overloading, substantial loss of compression
between implant and bone, a high temperature condition indicative
of infection, and/or an abnormally low or high cyclic loading count
indicating the patient is either not participating in the
proscribed recuperative therapy or is exerting him or herself more
than a prescribed amount. In one embodiment, the software may
display an image of the particular implant with measured force,
pressure and temperature readings displayed at or near the actual
location of the sensors on the implant. Further, instead of a
discrete numerical readout associated with each sensor, the image
may simply be color-coded to indicate satisfactory or
unsatisfactory (i.e. alarm) conditions. Thus, in an exemplary
embodiment, portions of the plate that are experiencing expected
values of strain, pressure, pH, time, cycle count and temperature
would appear in blue, whereas portions of the plate experiencing
much higher than expected values would appear in red. Threshold
normal and high strain, temperature, pressure and cycle values may
be programmed into the microchip on the implant, or may be selected
by the surgeon using the handheld device or from another computer
associated with the implant. The surgeon may then use a stylus to
select desired portions of the implant on the screen, and specific
loading, pressure, cycle count, time, and/or temperature data would
be displayed for the affected (i.e. red) area of the implant. In
other embodiments, the receiving device may include external
diagnostic equipment such as a CT scanner, which can send and
receive data to and from the implants 10, and/or other handheld
devices 160. The method of communication between implants 10 and/or
devices 160 may include infrared communication.
In one embodiment, the microchip 100 and data logging device 140
may contain implant-specific information supplied by the
manufacturer such as implant type, sensor type, implant/sensor
manufacturing date, location, lot, etc. Calibration data for each
sensor may also be contained therein. Further, the microchip 100
and data logging device 140 may contain all of the historical
readings from all of the sensors associated with the implant. The
microchip 100 may also be programmed to perform manipulation of the
data received from the sensors. Thus, in one embodiment the
handheld device may perform minimal manipulation of data and may
instead simply display data that has already been manipulated by
the microchip 100 and stored by the data logging device 140.
Alternatively, the handheld device may be used to perform some data
manipulation.
Thereafter, the doctor may transmit the information from the
handheld device to a desktop computer or web server for long term
storage or for further manipulation as desired. In one embodiment,
data may be transmitted anonymously to the manufacturer
confidentially via the internet or other secure transmission method
(to protect patient privacy). The manufacturer may then use such
data to assist in designing future implants. The implants 10 and
sending/receiving device 160 may also be configured for satellite
communication.
In one embodiment, the microchip may be programmed to turn on and
off at predetermined intervals in order to transmit information
only at certain times of the day. Such an arrangement may be
advantageous where the microchip is powered by a battery, and may
thus may act to conserve battery power. Alternately, the microchip
may be configured to continuously transmit data throughout the life
of the implant. This may be useful when a computer is used to
continuously gather the information so that graphs may be made of
different variables, such as temperature, strain, load and fatigue,
and how these variables may change throughout the day, including
how the patient's activities may affect the variables and whether
and how such variables may affect the implant.
As earlier noted, the information stored in the data logging device
140 may be sent to a receiver 160 outside the body using a wireless
(i.e., radio frequency (RF), infrared, etc.) transmitter 130. The
wireless receiver may be connected to a handheld device or a
personal computer 170 so that the patient and/or surgeon may view
information transmitted from the bone plate or may send the
information over the Internet to a recipient for analysis. In an
alternative embodiment, data stored by implant 10 may be
transmitted to a receiver 160 outside the body using a hard wired
connection.
Alternately, the patient in whom the implant is installed may have
a receiver in their home or office. The microchip may be configured
to transmit a signal wirelessly to the receiver station if a
certain condition occurs. For example, if the microchip senses an
increase in temperature over a predetermined temperature, it may
send an alarm signal to the base station, which may then issue an
alarm signal audible to the user. Similar alarms based on
over-strain, under-pressure, or over-cycling conditions may
likewise be implemented. Alarm signals received by a wireless base
station may also be sent automatically by the base station over the
Internet to a doctor who may contact the patient with immediate
instructions.
In one embodiment, the microchip may be powered using the principle
of induction. In this embodiment, one coil of wire is attached to
the microchip within the implant and one coil of wire is embedded
in a reader device located outside the patient. Excitation in the
coil located outside the patient will produce an excitation in the
coil within the implant. A remote energy source, such as an
ultrasound device, may be used to excite the induction coils. This
arrangement may operate like a transformer to power the microchip,
thus obviating the need for battery power.
In an alternate embodiment, the implant may use a piezoelectric
crystal which will use the loading and unloading cycle of the bone
plate to generate a voltage which may be used to power the bone
plate.
In yet another alternate embodiment, the microchip may use
piezoelectric technology to create micro-motion within the implant.
This micro-motion may be transmitted to the bone to facilitate
healing of the bone. Alternatively, the micro-motion inherent in a
healing bone may be used to power the microchip. Thus, a
piezoelectric crystal may be used to receive the micro-motion and
convert the motion to a charge that may power the device.
Referring again to FIG. 2, a specific positioning of the sensors on
bone plate 10 is illustrated. In this embodiment, the sensors 50
are positioned around the screw holes to provide information to the
doctor or patient concerning the location of the screws and the
stress placed on the bone plate by each screw. However, one skilled
in the art would recognize that sensors of such small size may be
located on any part of the bone plate and thus may be used to
provide information regarding physical characteristics of the bone
plate sections and/or the environment associated with individual
bone plate sections.
In another embodiment, the microchip may be used to send electric
current through electrodes 70 located on different locations of the
bone plate in order to electronically stimulate growth of the bone.
Such stimulation may speed bone growth and recovery, and such
phenomenon are well known in the art. One example of electrical
current used to stimulate bone growth in implants and increase
infection resistance of any antibacterial agents used with the bone
plate is described in U.S. Pat. No. 6,663,634 to Ahrens et al.,
which is hereby incorporated by reference.
In a further embodiment, at least a portion of the bone plate may
be coated, where the coating may include a polymer or porous metal,
such as magnesium, that can act as a carrier or a substrate for a
pharmaceutically active agent or synthetic agent. Such agents can
include antibiotics, microbicides, growth factors (BMPs and/or
VEGFs), angiogenesis inhibitors (fibulin-5) or chemotherapeutic
agents. The coating may be biodegradable in the patient. A
non-limiting exemplary coating is described in detail in U.S.
patent application Ser. No. 09/801,752 to Schmidmaier et al., filed
on Mar. 9, 2001, which is hereby incorporated by reference.
In one embodiment, the microchip may transmit information
wirelessly by radio frequency (RF) as known in the art. The bone
plate may also be encoded with information such as when the plate
was installed and who installed it so that doctors can access this
information from the plate by using radio frequency identification
(RFID).
Although the present invention has been shown and described in
connection with an implanted bone plate, one skilled in the art
would recognize that the present invention can also be practiced
with other types of orthopaedic implants, such as bone screws,
intramedullary rods, spinal fixation elements and implants (e.g.,
pedicle screws, hooks, etc.), external fixators and distractors.
One example of such a bone screw is shown and described in U.S.
Pat. No. 6,306,140 to Siddiqui which is hereby incorporated by
reference. Siddiqui describes a bone screw inserted into bone which
is suitable for stabilizing a fractured bone. The bone screw has
threads and provides compression to stabilize different regions of
bone. A microchip may be installed within the bone screw with one
or more sensors located at different locations on the bone screw to
monitor stress, strain, temperature and pressure. FIG. 7 shows a
pedicle screw 210, having threads 212 and an upper portion 214 for
connection to a fixation rod 216. Pedicle screw 210 includes one or
more microchips 40 and sensors 50. which function as described
above with reference to implant 10.
An embodiment of a bone pin which may be used in connection with
the present invention is shown and described in U.S. Pat. No.
6,663,634 to Ahrens et al. Ahrens discloses a bone pin for
insertion into bone that is coated with an antibacterial agent. The
bone pin as disclosed in Ahrens may be adapted to practice the
present invention by installing a microchip within the bone pin and
one or more sensors located on the bone pin.
As shown in FIG. 6, the present invention may also be practiced in
a similar manner in connection with an intramedullary nail 200
having one or more openings 202, 204 for receiving locking elements
and/or cross members. Intramedullary nail includes one or more
microchips 40 and sensors 50 for collecting and transmitting data
concerning the implant and/or the surrounding patient tissue. A
cross-member (not shown) used with an intramedullary nail 200,
which may pass through an upper opening 202 and penetrate the
femoral head when repairing femoral fractures, may also include one
or more microchips 40 and sensors 50. Another example of an
intramedullary nail is shown and described in U.S. Pat. No.
6,607,531 to Frigg which is hereby incorporated by reference.
As discussed above, the present invention may also be practiced in
connection with spinal fixation devices such as pedicle screws 210
(FIG. 7), pedicle hooks 220 (FIG. 8), and fixation rods 216, 222
(FIGS. 7 & 8) for insertion into and/or attachment to the
spinal column. In accordance with the present invention, the
pedicle screw 210, pedicle hook 220 and/or fixation rod 216, 222
may contain one or more microchips 40 and one or more sensors 50
for the collection and transmission of strain, temperature,
pressure and cycle data as previously described. Other pedicle
screws and spinal fixation devices are shown and described in U.S.
Pat. No. 6,325,802 to Frigg and U.S. Pat. No. 6,610,063 to Kumar et
al., both of which are hereby incorporated by reference.
The present invention may also be practiced in connection with
intervertebral implants, such as artificial spinal discs or spacers
used in both fusion and non-fusion procedures for replacing damaged
spinal discs. FIG. 9 shows an artificial spinal disc 230 inserted
between two adjacent vertebrae 232 in the spinal column. Artificial
disc 230 includes one or more microchips 40 and sensors 50, which
function in the manner described above to collect and transmit
implant/patient information.
As shown in FIG. 10, another embodiment of the present invention
may be a distractor, such as a maxillofacial distractor. Distractor
240 is secured to bone segments 244 using bone screws 242, and
includes one or more microchips 40 and sensors 50. In this
embodiment, distractor 240 can provide live feedback to the
physician or patient during adjustment of the distractor. In
addition, microchip 40 may also be used to automatically drive the
adjustment of the distractor (e.g., via motor, solenoid, etc.)
based on the data recorded by microchip 40 and sensors 50 on
distractor 240.
Similarly, as shown in FIG. 11, the present invention may take the
form of an external fixation apparatus, e.g., spatial ring, wrist
fixator, or other bone fixation system. External fixator 250 is
attached to bone segments 252 using rods 254. One or more
microchips 40 and sensors 50 can record and transmit data
concerning the fixation system to physicians and patients. As with
distractor 240 discussed above, external fixator 250 can provide
live feedback to the physician or patient during adjustment of the
apparatus and microchip 40 may be used to automatically drive the
adjustment of the fixator based on the implant and patient data
recorded.
Another embodiment of the invention would provide for a centralized
web server maintained by the manufacturer of the implants. The web
server would be in communication with the various doctors that
install and service the implants. When a doctor uses a computer or
wireless device to collect information from the implant, the doctor
may then transmit this information to the centralized web server.
The manufacturer may then use this information to determine the
average useful life of the particular implant model, and may also
compile the data to determine what the common causes of failure for
the implant model. The manufacturer also may also use this data to
determine whether trends in implant success or failure may be used
to educate surgeons on the most effective installation technique
for a particular implant. This information may assist the
manufacturer in designing new and improved implants, and in
refining installation techniques.
While the present invention has been described with reference to
the preferred embodiments, those skilled in the art will recognize
that numerous variations and modifications will be made without
departing from the scope of the present invention. This is
especially true with regard to the specific shape and configuration
of the implant and sensors. For example, sensors for measuring
strain, temperature, compression and/or load cycling may be used in
virtually any known orthopedic fixation application. Non-limiting
examples of such applications are: plates used in maxillofacial
fixation applications, footplates used with facial distraction
systems, cranial flap clamps, pins used with external fixation
devices, spinal fusion plates, spinal fusion rod assemblies,
etc.
Accordingly, it should be clearly understood that the embodiments
of the invention described above are not intended as limitations on
the scope of the invention, which is defined only by the following
claims.
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