Note: Descriptions are shown in the official language in which they were submitted.
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SYSTEM AND METHOD FOR IDENTIFYING A LANDMARK
Background of the Invention
1. Field of the Invention
[0004]
Embodiments of the present invention generally relate to orthopaedic
implants and, more specifically, to identification of blind landmarks on
orthopaedic implants.
2. Related Art
[0005] The interlocking
femoral nail has significantly widened the scope for
intramedullary (IM) fixation of long bone fractures. Locking an IM nail makes
the construct
more stable longitudinally and stops rotation of the nail within the bone. A
typical IM nail
fixation surgery involves a combination of jigs, x-ray imaging, and manual
"eye-balling" to
locate and drill the distal screw holes.
[00061 In this surgical
procedure, an IM nail is hammered into the canal of a
fractured long bone in order to fixate the fractured ends together. Typically,
the proximal
locking is performed first and is usually carried out with a jig. Nail
deformation during
intramcdullary insertion, however, may make a jig inaccurate for the distal
screws. The
primary difficulty lies in the positioning of the distal locking screws and
alignment of the
drill for the drilling of the distal screw holes because it is the most time
consuming and
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challenging step of the overall implantation procedure. Consequently, the two
main reasons
for failure in distal locking are incorrect entry point on the bone and wrong
orientation of the
drill. If either of these two factors is wrong, then the drill will not go
through the nail hole.
[0007] An
inaccurate entry point also compounds the problem as the rounded end of
the drill bit often slips, and it is then difficult to place another drill
hole next to the earlier
one. Inaccurate distal locking may lead to premature failure with breakage of
the nail
through the nail hole, breakage of the screw, or the breaking of the drill bit
within the bone.
[0008]
Manual techniques are the most common and accepted techniques for
sighting the distal screw holes and predominate the orthopaedic industry. The
majority of
distal targeting techniques employ a bushing (cylindrical sleeve) that guides
the drill. The
mechanism of aligning the guide bushing and keeping it in place differs. There
are cases
where the surgeons use a half sleeve (bushing cut in half longitudinally) or a
full sleeve to
help steady the drill bit during drilling. In either situation, the surgeon
will incise the patient
and insert the drill through the incision. The manual techniques are based
primarily on the
surgeon's manual skill and make use of radiographic x-ray imaging and
mechanical jigs.
[0009]
Another method for achieving this on long nails is by using a technique
called "perfect circles" with the aid of a C-arm. This is where one orients
the patient and the
C-arm such that when viewing the implant fluoroscopically the hole with which
the screw is
to pass appears to be in the shape of a circle. If the C-arm is not
perpendicular to the hole
then it would appear oblong or even absent.
[0010]
There remains a need in the art for a system and method for targeting
landmarks of a medical implant. Further, there remains a need in the art for
accurately
positioning the distal locking screws and aligning the drill for the drilling
of the distal screw
holes.
Summary of the Invention
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[0011]
There is provided a system for identifying a landmark. The system comprises
a field generator for generating a magnetic field; an orthopaedic implant
located within the
magnetic field, the orthopaedic implant having at least one landmark; a
removable probe
with a first magnetic sensor spaced apart from the at least one landmark; a
landmark
identifier having a second magnetic sensor; and a processor for comparing
sensor data from
the first and second sensor and using the set distance to calculate the
position of the
landmark identifier relative to the at least one landmark.
[0012]
There is also provided a system for identifying a landmark, the system
comprising: a field generator for generating a magnetic field; an orthopaedic
implant located
within the magnetic field, the orthopaedic implant having at least one
landmark and a
longitudinal groove with a proximal end portion and a distal end portion; a
first magnetic
sensor mounted to the orthopaedic implant at the distal end portion of the
longitudinal
groove and spaced apart from the at least one landmark a set distance; a
landmark identifier
having a second magnetic sensor; and a processor for comparing sensor data
from the first
and second sensor and using the set distance to calculate the position of the
landmark
identifier relative to the at least one landmark.
[0013]
According to some embodiments, the landmark is selected from the group
consisting of a structure, a void, a boss, a channel, a detent, a flange, a
groove, a member, a
partition, a step, an aperture, a bore, a cavity, a dimple, a duct, a gap, a
notch, an orifice, a
passage, a slit, a hole, or a slot.
[0014] According to some embodiments, the orthopaedic implant is an
intramedullary nail.
[0015]
According to some embodiments, the orthopaedic implant has an outer
surface, an inner surface forming a cannulation, and a wall therebetween, and
the first
.. magnetic sensor is mounted within the wall.
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[0016] According to some embodiments, the orthopaedic implant further
includes a
pocket and the first sensor is located within the pocket.
[0017] According to some embodiments, the orthopaedic implant further
includes a
cover.
[0018] According to some embodiments, the orthopaedic implant further
includes a
second opening adapted to receive a cover.
[0019] According to some embodiments, the orthopaedic implant further
includes a
circumferential pocket.
[0020] According to some embodiments, the system includes a lead
connected to the
1 0 first magnetic sensor.
[0021] According to some embodiments, the system includes an
insertion handle
removably attached to the orthopaedic implant.
[0022] According to some embodiments, the system includes a monitor
electrically
connected to the processor.
[0023] According to some embodiments, the system includes a removable lead
connected to the first sensor.
[0024] According to some embodiments, the longitudinal groove is
along an outer
surface of the implant.
[0025] According to some embodiments, the orthopaedic implant further
includes a
cannulation, and the longitudinal groove is generally adjacent the
cannulation.
[0026] According to some embodiments, the landmark identifier
includes a drill
sleeve.
[0027] According to some embodiments, the landmark identifier further
includes a
serrated tip.
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[0028]
According to some embodiments, the landmark identifier further includes a
tube.
[0029]
According to some embodiments, the landmark identifier further includes a
marking sensor.
[0030] According to
some embodiments, the landmark identifier further includes a
handle.
[0031]
According to some embodiments, the processor provides feedback
information to a user.
[0032]
There is provided a system for identifying a landmark, the system
comprising: a field generator for generating a magnetic field; an orthopaedic
implant located
within the magnetic field, the orthopaedic implant having at least one
landmark; a magnet
mounted to the orthopaedic implant and spaced apart from the at least one
landmark a set
distance; a landmark identifier having a magnetic sensor; and a processor for
comparing
sensor data from the magnetic sensor and using the set distance to calculate
the position of
the landmark identifier relative to the at least one landmark.
[0033]
There is provided a method for identifying a landmark, the method
comprising: providing an orthopaedic implant assembly having an orthopaedic
implant with
a longitudinal groove and a removable lead having a magnetic sensor attached
thereto
situated within the longitudinal groove, the orthopaedic implant having a
proximal end
portion, a distal end portion, and at least one landmark on the distal end
portion; implanting
the orthopaedic implant assembly in a patient; first installing transfixion
elements in the
proximal end portion; identifying the at least one landmark using a landmark
identifier;
installing a transfixion element in the at least one landmark in the distal
end portion after
first installing transfixion elements in the proximal end portion; and
removing the
removable lead.
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[0034] There is provided a graphical user interface, comprising: a
first portion
indicating drill depth relative to an implant; and a second portion indicating
landmark
identifier position relative to a landmark located on the implant.
[0035] The invention has several advantages over prior devices and
techniques.
First, the invention operates independently of fluoroscopy and eliminates the
necessity of X-
ray devices for targeting of transfixion elements, thereby reducing the
exposure of users and
patients to radiation. Second, the invention allows a user to lock the driving-
end before
locking the non-driving end. In other words, the invention does not require
use of an implant
cannulation and allows for proximal locking prior to distal locking, in some
embodiments.
[0036] Further features, aspects, and advantages of the present invention,
as well as
the structure and operation of various embodiments of the present invention,
are described in
detail below with reference to the accompanying drawings.
Brief Description of the Drawings
[0037] The accompanying drawings, which are incorporated in and form
a part of the
specification, illustrate embodiments of the present invention and together
with the
description, serve to explain the principles of the invention. In the
drawings:
[0038] FIG. 1 illustrates a system for identifying a landmark in a
first embodiment;
[0039] FIG. 2 is a sectional view of an orthopaedic implant assembly
in a first
embodiment;
[0040] FIG. 3 illustrates a sensor mounting in a first embodiment;
[0041] FIG. 4 illustrates sensor mounting in a second embodiment;
[0042] FIG. 5 illustrates the sensor shown in FIG. 4;
[0043] FIG. 6 illustrates an orthopaedic implant assembly in a second
embodiment;
[0044] FIG. 7 is a front view of a removable lead;
[0045] FIG. 8 is a top view of the orthopaedic implant assembly shown in
FIG. 6;
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[0046] FIG. 9 illustrates a landmark identifier;
[0047] FIG. 10 is a sectional view illustrating point contacts in a
first embodiment;
[0048] FIG. 11 is a sectional view illustrating point contacts in a
second embodiment;
[0049] FIG. 12A is a sectional view illustrating a crimp electrical
connection;
[0050] FIG. 12B is a schematic view illustrating the electrical connection
in a first
alternative embodiment;
[0051] FIG. 12C is a schematic view illustrating a side view of the
electrical
connection shown in FIG. 12B;
[0052] FIG. 12D is a schematic view illustrating the electrical
connection in a second
.. alternative embodiment;
[0053] FIG. 13A is a partial perspective view illustrating
alternative mechanisms for
aligning the orthopaedic implant and the insertion handle in a first
embodiment;
[0054] FIG. 13B is a partial perspective view illustrating
alternative mechanisms for
aligning the orthopaedic implant and the electrical connection in a second
alternative
embodiment;
[0055] FIG. 14 illustrates connection of the insertion handle to the
orthopaedic
implant;
[0056] FIG. 15 illustrates the system for identifying a landmark in a
second
embodiment;
[0057] FIG. 16 is a schematic illustrating view selection criteria;
[0058] FIG. 17 is a flowchart illustrating the step of view
selection;
[0059] FIG. 18 is a schematic illustrating a first alternative method
of aligning the
landmark identifier;
[0060] FIG. 19 is a schematic illustrating a second alternative
method of aligning the
landmark identifier;
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[0061] FIG. 20 illustrates a monitor with exemplary views;
[0062] FIG. 21 illustrates an alternative embodiment of the landmark
identifier;
[0063] FIG. 22 illustrates a first alternative embodiment of the
insertion handle;
[0064] FIG. 23 illustrates the system for identifying a landmark in a
third embodiment;
[0065] FIG. 24 illustrates a second alternative embodiment of the insertion
handle;
[0066] FIG. 25 illustrates a system for identifying a landmark in a
third embodiment;
[0067] FIG. 26 illustrates a detailed cross-sectional view of the
intramedullary nail;
[0068] FIG. 27 illustrates a packaging embodiment;
[0069] FIG. 28 illustrates a method of connecting the system to a
network;
[0070] FIG. 29 illustrates a system for identifying a landmark in a fourth
embodiment;
[0071] FIG. 30 illustrates a first flowchart for using the system;
[0072] FIG. 31 illustrates a second flowchart for using the system;
[0073] FIG. 32 illustrates a second embodiment for tracking drill
depth;
[0074] FIGS. 33A and 33B illustrate a third embodiment for tracking drill
depth;
[0075] FIG. 34 illustrates a fourth embodiment for tracking drill
depth;
[0076] FIG. 35 illustrates an insertion handle.
[0077] FIG. 36 illustrates a top perspective view of an adjustable
stop;
[0078] FIG. 37 illustrates a bottom perspective view of the
adjustable stop shown in
FIG. 36;
[0079] FIG. 38 illustrates a third flowchart for system calibration.
Detailed Description of the Embodiments
[0080] Referring to the accompanying drawings in which like reference
numbers
indicate like elements, FIG. 1 illustrates a system 10 for identifying a
landmark in a first
embodiment. The system 10 includes a processor 12, a magnetic field generator
16, a
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landmark identifier 18, and an orthopaedic implant assembly 28. In some
embodiments, the
system 10 further includes a monitor 14 electrically connected to the
processor 12 and an
insertion handle 40 removably attached to the orthopaedic implant assembly 28.
The
processor 12 is depicted as a desktop computer in FIG. 1 but other types of
computing
devices may equally be used. As examples, the processor 12 may be a desktop
computer, a
laptop computer, a personal data assistant (PDA), a mobile handheld device, or
a dedicated
device. In the depicted embodiment, the magnetic field generator is a device
available from
Ascension Technology Corporation of 107 Catamount Drive, Milton Vermont,
U.S.A.;
Northern Digital Inc. of 103 Randall Drive, Waterloo, Ontario, Canada; or
Polhemus of 40
Hercules Drive, Colchester Vermont, U.S.A. Of course, other generators may be
used. As
examples, the field generator 16 may provide a pulsed direct current
electromagnetic field or
an alternating current electromagnetic field. In some embodiments, the system
10 further
includes a control unit (not shown) connected to the magnetic field generator
16. The
control unit controls the field generator, receives signals from small mobile
inductive
sensors, and communicates with the processor 12, either by wire or wirelessly.
In some
embodiments, the control unit may be incorporated into the processor 12 either
through
hardware or software.
[0081] The system 10 is a magnetic position tracking system. For
illustrative
purposes, the system 10 includes a magnetic field generator 16 comprised of
suitably
arranged electromagnetic inductive coils that serve as the spatial magnetic
reference frame
(i.e., X, Y, Z). The system 10 further includes small mobile inductive
sensors, which are
attached to the object being tracked. It should be understood that other
variants could be
easily accommodated. The position and angular orientation of the small mobile
inductive
sensors are determined from its magnetic coupling to the source field produced
by magnetic
field generator 16.
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[0082] It
is noted that the magnetic field generator 16 generates a sequence, or set, of
here six, different spatial magnetic field shapes, or distributions, each of
which is sensed by
the small mobile inductive sensors. Each sequence enables a sequence of
signals to be
produced by the small mobile inductive sensors. Processing of the sequence of
signals
enables determination of position and/or orientation of the small mobile
inductive sensors,
and hence the position of the object to which the small mobile inductive
sensor is mounted
relative the magnetic coordinate reference frame which is in fixed
relationship to the
magnetic field generator 16. The processor 12 or the control unit uses the
reference
coordinate system and the sensed data to create a transformation matrix
comprising position
and orientation information.
[0083] The
landmark identifier 18 is used to target a landmark, such as a landmark
on the orthopaedic implant assembly 28. The landmark identifier 18 includes
one or more
small mobile inductive sensors. In the depicted embodiment, the landmark
identifier 18 has
a second sensor 20. The landmark identifier 18 may be any number of devices.
As examples,
the landmark identifier may be a drill guide, a drill sleeve, a drill, a drill
nose, a drill barrel,
a drill chuck, or a fixation element. In the embodiment depicted in FIG. 1,
the landmark
identifier 18 is a drill sleeve. In some embodiments, the landmark identifier
may include one
or more of a serrated tip 22, a tube 24, and a handle 26. The tube 24 also may
be referred to
as a bushing, cylinder, guide, or drilling/screw placement guide. In the
depicted
embodiment, the second sensor 20 is oriented relative to an axis of the tube
24, which may
receive a drill. This offset of the sensor 20 from the tube 24 allows the
position and
orientation of the tube to be located in space in six dimensions (three
translational and three
angular) relative to the magnetic field generator 16 or another sensor in the
system. In some
embodiments, the processor 12 may need to be calibrated to adjust for the
offset distance of
the second sensor 20. In some embodiments, the landmark identifier 18 and the
field
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generator 16 may be combined into a single component. For example, the field
generator 16
may be incorporated within the handle 26.
[0084] The
orthopaedic implant assembly 28 includes an implant 30 and one or
more small mobile inductive sensors. In the depicted embodiment, the
orthopaedic implant
assembly 28 has a first sensor 32. In the embodiment depicted in FIG. 1, the
implant 30 is in
the form of intramedullary nail but other types of implants may be used. As
examples, the
implant may be an intramedullary nail, a bone plate, a hip prosthetic, or a
knee prosthetic.
The first sensor 32 is oriented and in a predetermined position relative to
one or more
landmarks on the implant 30. As examples, the landmark may be a structure, a
void, a boss,
a channel, a detent, a flange, a groove, a member, a partition, a step, an
aperture, a bore, a
cavity, a dimple, a duct, a gap, a notch, an orifice, a passage, a slit, a
hole, or a slot. In the
embodiment depicted in FIG. 1, the landmarks are transfixion holes 31. The
offset of the
first sensor 32 from the landmark allows the position of the landmark to be
located in space
in six dimensions (three translational and three angular) relative to the
magnetic field
generator 16 or another sensor in the system, such as the second sensor. In
some
embodiments, the processor may need to be calibrated to adjust for the offset
distance of the
first sensor 32.
[0085] The
first sensor 32 and the second sensor 20 are connected to the processor
12. This may be accomplished by wire or wirelessly. The first sensor 32 and
the second
sensor 20 may be a six degree of freedom sensor configured to describe the
location of each
sensor in three translational axes, generally called X, Y and Z and three
angular orientations,
generally called pitch, yaw and roll. By locating the sensor in these
reference frames, and
knowing the location and orientation of each sensor, the landmark identifier
18 may be
located relative to the landmark on the implant 30. In one particular
embodiment, the
information from the sensors allows for a surgeon to plan the surgical path
for fixation and
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properly align a drill with a blind fixation hole. In the depicted embodiment,
the sensors 32,
20 are six degrees of freedom sensor from Ascension Technology Corporation of
107
Catamount Drive, Milton Vermont, U.S.A.; Northern Digital Inc. of 103 Randall
Drive,
Waterloo, Ontario, Canada; or Polhemus of 40 Hercules Drive, Colchester
Vermont, U.S.A.
Of course, other sensors may be used.
[0086] The first sensor 32 may be attached to the implant 30. For
example, the first
sensor 32 may be attached to an outer surface 37. In the embodiment depicted
in FIG. 1, the
implant 30 further includes a groove 34 and a pocket 36 (best seen in FIG. 2).
The groove 34
and pocket 36 are located in a wall of the implant 30. In the depicted
embodiment, the first
sensor 32 is intended to be attached to the implant 30 and installed in a
patient for the
service life of the implant 30. Further, in some embodiments, the orthopaedic
implant
assembly 28 includes a cover 38 to cover the pocket 36 and/or the groove 34.
The cover 38
may be substantially flush with the external surface 37 of the implant 30.
Accordingly, in
some embodiments, the implant 30 includes a second opening 39 (best seen in
FIG. 2) to
receive the cover 38.
[0087] The first sensor 32 may be tethered to leads for communication
and power.
The leads, and the sensor, may be fixed to the implant 30. A lead 50 may be
used to connect
the first sensor 32 to the processor 12 or the control unit. The lead 50 may
be made from
biocompatible wire. As an example, the lead 50 may be made of DFT wire
available from
Fort Wayne Metals Research Products Corp., 9609 Indianapolis Road, Fort Wayne,
Indiana
46809. DFT is a registered trademark of Fort Wayne Metals Research Products
Corp. A first
connector 52 may be used to place the lead 50 relative to the implant 30. A
second
connector 54 may be used to connect the lead 50 to another device, such as the
processor 12,
the control unit, or the insertion handle 40.
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[0088] The
first sensor 32 may be fixed in the pocket 36 using a range of high
stiffness adhesives or polymers including epoxy resins, polyurethanes,
polymethyl
methacrylate, polyetheretherketone, UV curable adhesives, silicone, and
medical grade
cyanoacrylates. As an example, EPO-TEK 301 available from Epoxy Technology, 14
Fortune Drive, Billerica, Massachusetts 01821 may be used. The lead 50 may be
fixed in the
groove in a similar manner. These types of fixation methods do not adversely
affect the
performance of the electrical components. Thereafter, the cover 38 may be
placed on the
implant 30 and welded in-place. For example, the covers may be laser welded to
the
implant.
[0089] The monitor 14
may be configured to display the position and orientation of
the first sensor 32 and the second sensor 20 so that the display may show a
surgeon both
sensor positions and orientations relative to one another. The processor 12
may send
positional data, either by wire or wirelessly, to a user interface, which may
graphically
display the relative positions of the landmark identifier and the implant on
the monitor. The
view displayed on the monitor 14 may be oriented relative to the landmark
identifier so that
the surgeon may visualize the user interface as an extension of the landmark
identifier. The
user interface also may be oriented so that the surgeon may view the monitor
simultaneously
with the surgical field.
[0090] The
insertion handle 40 may be used for installation of the orthopaedic
implant assembly 28 and also may be used to route the leads from the first
sensor 32. For
example, the insertion handle 40 may route both communication and power leads
between
the implant 30 and the processor 12.
[0091] In
the embodiment depicted in FIG. 1, the landmark identifier 18 and the
insertion handle 40 each include a communications module 21, 25 for wirelessly
transmitting data from the sensor 20, 32 to the processor 12, but those
skilled in the art
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would understand that other methods, such as by wire, may be used. In the
depicted
embodiment, the second connector 54 plugs into the communications module 25.
Alternatively, and as is explained in greater detail below, the implant 30 and
the insertion
handle 40 may have mating electrical contacts that form a connection when the
components
are assembled such that the first sensor 32 is connected to the communications
module 25.
[0092] In
some embodiments, the implant 30 may include a communications circuit
and an antenna for wireless communication. Power for the first sensor 32
and/or the
communications circuit may be positioned within the insertion handle 40. For
example, a
battery may be placed within the insertion handle 40 for transferring power to
the first
sensor 32 and/or other electronics. Alternatively, the communications circuit,
the antenna,
and the battery may be located within the insertion handle 40 and each of
these may be
tethered to the first sensor 32. In yet another embodiment, the implant 30 may
include a coil
to inductively power the communications circuit and communicate data from the
first sensor
32. The power source may be a single source mode or may be a dual mode AC/DC.
[0093] In use, the
orthopaedic implant assembly 28 is installed in a patient. For
example, in the case of internal fixation, the intramedullary nail is placed
within an
intramedullary canal. Optionally, the user may use transfixion elements, such
as screws, to
first lock the proximal end of the intramedullary nail. An operator uses the
targeting device
18 and the first sensor 32 to identify the landmarks 31. For example, in the
case of
intramedullary nail fixation, a surgeon uses the targeting device 18 to
identify the blind
transfixion holes and drill through the holes for placement of a transfixion
element.
[0094] FIG.
2 further illustrates the implant 30 as shown in FIG. 1. The implant 30
includes the first sensor 32, the longitudinal groove 34, the pocket 36, the
cover 38, and the
second opening 39. As examples, the cover 38 may be comprised of gold or
titanium foil. In
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some embodiments, the implant 30 includes an inner surface 35 that forms a
cannulation 33.
The implant 30 includes the outer surface 37.
[0095] FIG.
3 illustrates a first embodiment of the first sensor 32. The first sensor 32
includes two coils cross-layed to one another and having an angle alpha.
[0096] FIGS. 4 and 5
illustrate a second embodiment of the first sensor 32. The first
sensor includes two coils generally orthogonal to one another in order to
establish the
orientation and position in the six degrees of freedom. A first coil may be
oriented along the
length of the implant 30. The second coil may be oriented either wrapped
around the
circumference of the implant, for example in a groove, or along the radius of
the implant 30.
In addition, while it is preferred to have the coils perpendicular to one
another, other
orientations may be used, although the mathematics may be more complex.
Further, the
coils may be oriented spirally around the implant 30. Such an orientation may
allow two
coils to be placed perpendicular to each other with both coils placed along
both the length of
the implant and along the circumference of the implant 30.
[0097] FIGS. 6-8
illustrate a second embodiment of the orthopaedic implant
assembly 60. The orthopaedic implant assembly 60 includes the implant 30. In
the
embodiment depicted in FIG. 6, the implant 30 includes landmarks in the form
of
transfixion holes 31. The implant 30 includes a longitudinal internal groove
66 and a
removable lead 64. In the embodiment depicted in FIG. 8, a diameter of the
longitudinal
groove 66 is shown as intersecting with the cannulation 33; however, in other
embodiments,
the diameter of the longitudinal internal groove is contained between the
outer surface 37
and the inner surface 35. The removable lead 64 includes the first sensor 32
at its distal end
portion 65. The first sensor 32 is located a known offset from the landmarks
31. The implant
in FIGS. 6-8 is comprised of biocompatible material, and may be a metal alloy
or a polymer.
The longitudinal groove 66 may be machined or molded in place.
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(0098) In use, the implant 30 with the removable lead is installed in a
patient. For
example, in the case of internal fixation, the intramedullary nail is placed
within an
intramedullary canal. Optionally, the user may use transfixion elements, such
as screws, to
first lock the proximal end of the intramedullary nail.. Because of the
location of the
longitudinal groove 66, the removable lead 64 does not interfere with first
locking the
proximal end of the intramedullary nail. An operator uses the targeting device
18 and the
first sensor 32 to identify the landmarks 31. For example, in the case of
intramedullary nail
fixation, a surgeon uses the targeting device 18 to identify the blind
transfixion holes and
drill through the holes for placement of a transfixion element. After the
implant 30 is
secured, the operator removes the removable lead 64 and it may be discarded.
(0099) FIG. 9 one particular embodiment of the landmark identifier 18 as
shown in
FIG.1. In the depicted embodiment, the landmark identifier 18 includes the
sensor 20, the
serrated tip 22, the tube 24. and the handle 26. A drill 90 has markings 92
that interact with
a marking sensor 19 adjacent the tube 24. The interaction is similar to a pair
of digital
measuring calipers in that the position between marking 92 and sensor 19
equate to a
distance. This distance can be used to determine the depth of the drill into
the bone and
ultimately the length of the bone screw that will be inserted into the drilled
hole. Distance,
or drill depth, readings are only obtainable when the sensors 92 and 19 are in
close
proximity to each other, i.e. the drill 90 is inside the tube 24. Exemplary
measurement
devices are shown in U.S. Pat. No. 6,675,491 issued on January 13, 2004 to
Sasaki et al. and
in U.S. Pat. No. 7,253,611 issued on August 7, 2007 to Me et al. In the
depicted
embodiment, the marking sensor 19 is connected to the communications module
21.
Alternatively, the marking sensor 19 may be connected by wire to the processor
12. In FIG.
9, the communications module 21 includes a third
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connector 23 for electrical connection to the processor 12. Additional
embodiments of the
landmark identifier are shown in FIGS. 32-34.
[00100] FIGS. 10-12 illustrate exemplary methods of electrically connecting
the
implant 30 to the insertion handle 40, which has corresponding electrical
contacts. In FIG.
10, biasing elements 72 bias contacts 70 toward the insertion handle 40. In
FIG. 11, the
implant 30 has elastomeric electrical contacts 74. In FIG. 12A, wires
extending between the
lead 50 and another component are crimped together at junction 76. In one
method, the
wires are tom free and separated at the junction 76 after installation of the
orthopaedic
implant assembly 28. In yet another method, the wires are cut above the
junction 76 after
installation of the orthopaedic implant assembly 28. In FIGS. 12 B and C, two
flex boards
53 are soldered together one or more pads 57 to connect a wiring harness 55 to
the sensor.
The wire harness 55 may be mounted to the insertion handle 40 or within a
cannulation of
the insertion handle 40. In the depicted embodiment, four pads 57 are soldered
together.
Locking tabs 59 are sandwiched between the implant 30 and the insertion handle
40 to
withstand abrasion and tension associated with the implant insertion. Once the
insertion
handle is removed, the wire harness 55 can be pulled such that all non-
biocompatible
materials are pulled with it. In FIG. 12D, rings 61, 63 are connected during
manufacturing.
After implantation, both rings 61, 63 are removed by pulling on a jacketed
wire 67.
[00101] Referring now to FIGS. 13A and B, the implant 30 and/or the insertion
handle 40 may includes one or more alignment features 44 and mating notch 80
or
alignment pin 46 and mating hole 82. The insertion handle may be configured to
align with
an upper surface of the implant. In one embodiment, the insertion handle may
have a key
configured to mate to a slot on the implant. Other alignment guides may be
used. In
addition, the guide may have an electrical connector configured to mate to an
electrical
connector on the implant. The connection between the guide and the implant may
be spring
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loaded to ensure electrical contact between the electrical connectors. In
order to avoid
shorting the connection between the guide and the implant, the electrical
connector may be
insulated. As another example of electrically connecting the insertion handle
to the implant,
the electrical connectors may include a post and slip rings. The rings may be
located on the
implant, and the posts located on the insertion handle. The posts are biased
to contact the
rings. In such an embodiment, the angular location of the insertion handle
relative to the
axis of the implant is not fixed. This would allow the insertion handle to be
positioned to the
implant irrespective of angular position.
[00102] In another embodiment shown in FIG. 13B, the implant 30 and/or the
insertion handle 40 may includes one or more alignment pin 47 and mating hole
83. The
alignment pins 47 may be spear tip pins designed to engage a single time and
when
removed, the pins grip portion of the implant to remove all non-biocompatible
materials
with them.
[00103] Any of the electrical connectors above may include a memory storage
device
(not shown) for storing offset values for sensor calibration.
[00104] Referring now to FIG. 14, the implant 30 and the insertion handle 40
may be
sized such that space remains available for the first connector 52 even when
the components
are assembled or mated.
[00105] As an example, the system for identifying a landmark may be used to
target
blind screw holes of an implanted intramedullary nail. The intramedullary nail
is implanted
in the patient. The electromagnetic field generator is activated. The
processor receives
signals from the sensor mounted to the intramedullary nail and from the sensor
mounted to
the landmark identifier, such as a drill sleeve. A computer program running on
the processor
uses the information of the at least two sensors and graphically display them
in relative
position on the monitor. A surgeon moves the landmark identifiers into
position using
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feedback provided by the processor. When the landmark identifier is in the
proper location,
the surgeon drill through bone and the intramedullary nail to create a screw
hole. In some
embodiments, the processor may provide feedback as to the depth of the drilled
hole. The
surgeon may then place a screw through the drilled hole to affix the blind
hole of the
intramedullary nail.
[00106] FIG. 15 illustrates a system 110 for identifying a landmark in a
second
embodiment. The system 110 includes a processor 112, a landmark identifier
118, and an
orthopaedic implant assembly 128. In some embodiments, the system 110 further
includes a
monitor 114 and an insertion handle 140.
[00107] The landmark identifier 118 is used to target a landmark. The landmark
identifier 118 includes a second sensor 120. In the embodiment depicted in
FIG. 15, the
landmark identifier 118 is a drill sleeve with a serrated tip 122, a tube 124,
and a handle
126. In the depicted embodiment, the second sensor 120 is oriented relative to
an axis of the
tube, which may receive a drill. This offset of the sensor from the tube
allows the position of
the tube to be located in space in six dimensions (three translational and
three angular)
relative to the transmitter or another sensor in the system. In some
embodiments, the
processor may need to be calibrated to adjust for the offset distance of the
second sensor
120.
[00108] The orthopaedic implant assembly 128 includes an implant 130 and a
magnet
132. The magnet may be a permanent magnet or an electromagnet. The magnet 132
is
oriented in a predetermined position relative to a landmark on the orthopaedic
implant 130.
This offset of the magnet from the landmark allows the position of the
landmark to be
located in space in six dimensions (three translational and three angular)
relative to the
transmitter or another sensor in the system, such as the second sensor. In
some
embodiments, the processor may need to be calibrated to adjust for the offset
distance of the
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magnet 132. In the embodiment depicted in FIG. 1, the implant 130 further
includes a
pocket 136 and a cover 138. In the case of an electromagnet, a lead 150
connects to the
magnet 132 and is contained within a groove 134.
[00109] As an example, the system for identifying a landmark may be used to
target
blind screw holes of an implanted intramedullary nail. The intramedullary nail
is implanted
in the patient. The processor receives signals from the sensor mounted to the
landmark
identifier, such as a drill sleeve. A computer program running on the
processor uses the
information of the sensor and graphically displays the sensor in relative
position to the
magnet on the monitor. A surgeon moves the landmark identifiers into position
using
feedback provided by the processor. When the landmark identifier is in the
proper location,
the surgeon drill through bone and the intramedullary nail to create a screw
hole. In some
embodiments, the processor may provide feedback as to the depth of the drilled
hole. The
surgeon may then place a screw through the drilled hole to affix the blind
hole of the
intramedullary nail.
[00110] FIG. 16 illustrates a method for selecting views corresponding to
landmark
identifier position. In some embodiments, the view displayed on the monitor is
dependent
upon the location of the landmark identifier relative to the implant. The
diameter of the
implant is broken into sectors or fields. In the embodiment depicted in FIG.
16, the diameter
is broken down into three fields: (A) 135 degrees to 225 degrees; (B) 0
degrees to 135
degrees; and (C) 225 degrees to 360 degrees. The initial view is based upon
landmark
identifier orientation relative to the implant. As the user moves landmark
identifier toward
or away from the implant, the monitor display zooms in or out on the selected
field.
[00111] FIG. 17 is a flowchart for view selection and display of one landmark.
The
process may be repeated for multiple landmarks. The processor 12 uses the
transformation
matrix in the following process steps. In step 200, landmark identifier
position is computed
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relative to the implant based upon the positions of the relevant sensors, and
the landmark
closest the landmark identifier is selected for display. In step 210, a global
view is defined
showing the whole implant with the selected landmark oriented for proper
viewing. A global
view is analogous to viewing the implant at a distance. In step 220, there is
a decision
whether there are multiple landmarks having the same orientation. If yes, then
in step 230,
the processor calculates which landmark is nearest to the landmark identifier
position and
selects it for viewing. If no, in step 240, a local view is defined and
centered upon the
selected landmark. A local view is analogous to viewing the implant in close
proximity. In
some embodiments, it may be desirable to hide the landmark identifier when the
local view
is defined. In steps 250, 260, and 270, the processor 12 identifies the
distance from
landmark identifier to the landmark and depending upon the decision made,
either hides or
renders the landmark identifier. In step 250, the distance from landmark
identifier to the
landmark and a comparison is made between the calculated distance D and set
variables
TGlobal and TLocal. If D> TGlobal, then the global view is selected in step
260 and the processor
proceeds to step 285. If D< TLocal, then the local view is selected and
centered upon the
landmark in step 270. Thereafter, the processor proceeds to step 275. In
optional step 275,
the landmark identifier is hidden. Otherwise, an intermediate camera position
is calculated
based upon the distance D to enable a smooth transition from global view to a
local view in
step 280. In step 285, the landmark identifier is shown. In step 290, the
scene with selected
camera position is rendered.
[00112] FIG. 18 is a schematic illustrating a first alternative method of
aligning the
landmark identifier. A computer program running on the processor may be used
to take the
information of the at least two sensors and graphically display them in
relative position (the
second sensor relative to the first sensor) on the monitor. This allows the
user to utilize the
system to guide the placement of the landmark identifier. In the case of
drilling a blind
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intramedullary nail hole, the system guides the user in placement of the drill
sleeve and
subsequently drilling accurately thru the hole in the intramedullary nail. The
graphical user
interface may include an alignment guide for each of the degrees of freedom. A
minimum
alignment level may be set such that the surgeon continues to orient the
landmark identifier
until each of the degrees of freedom meets the minimum alignment level for an
effective
placement of the landmark identifier. The example of FIG. 18 shows an instance
where the
placement in the Y-direction meets the minimum required tracking placement.
However, none
of the other translational or rotational degrees of freedom meet the minimum
requirements.
While the magnitudes of tracking are shown as bar graphs, other graphical
representations,
such as color coding, may be used.
[00113] FIG. 19 is a schematic illustrating a second alternative method of
aligning the
landmark identifier. In this embodiment, a graphical interface using a
plurality of LEDs to
position the drill may be placed upon the landmark identifier, such as a drill
sleeve. By using
the LEDs to trajectory track the drill, the surgeon may align the drill with
the blind fixation
hole. The trajectory may additionally use secondary displays to add more
information to the
system. For example, for affecting the magnitude of adjustment, the trajectory
may include
flashing LEDs so that high frequency flashing requires larger adjustments
while low frequency
flashing may require smaller adjustments. Similarly, colors may add
information regarding
adjustments to alignment.
[00114] FIG. 20 illustrates a monitor with exemplary views. A first portion
500
indicates the distance the drill is on each side of the implant. This may
provide the user with a
better understanding of drill depth and alert the user when to stop when
appropriate drill depth
has been achieved. The second portion 510 provides the user with alignment
information. As
an example, drill depth data may be obtained using the embodiment shown in
FIG. 9.
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[00115] FIG. 21 illustrates an alternative embodiment of the landmark
identifier. The
landmark identifier is configured to display, with LEDs, the position and
trajectory
information for proper alignment. The size of the LEDs may display additional
information
regarding the magnitude of required adjustment. The trajectory light may
display a simple
on/off toggle between an aligned trajectory and a mal-aligned trajectory. As
another example,
the trajectory LED may be color coded to suggest the magnitude of necessary
adjustment for
proper alignment.
[00116] FIG. 22 illustrates a first alternative embodiment of the insertion
handle 700.
The insertion handle 700 includes an arcuate slot 710. The arcuate slot limits
the movement of
.. the landmark identifier 18, 118 within the operating space. In the case of
identifying a blind
screw hole, the arcuate slot limits the movement of the drill sleeve for fine
adjustment of its
position. In some embodiments, the insertion handle 700 includes a carriage
712 that receives
the landmark identifier and rides in the slot 710.
[00117] FIG. 23 illustrates the system for identifying a landmark in a third
embodiment.
In this embodiment, the orthopaedic implant 800 is a bone plate and the
insertion handle 810 is
a guide affixed to the bone plate. In the depicted embodiment, the inductive
sensor is placed
on the surface of the orthopaedic implant 800 relative to one or more
landmarks. The guide
810 may allow a landmark identifier 818 to translate and/or rotate relative to
the guide to
properly align the landmark identifier with a landmark 802, such as a fastener
hole. In
addition, where multiple fixation holes are on the implant, then additional
guide holes 812 on
the guide 810 may help approximate the position of the additional fixation
holes.
[00118] FIG. 24 illustrates a second alternative embodiment of the insertion
handle.
The insertion handle 900 includes fine adjustment in landmark identifier 918
position through
the use of small servomotors 920, 922, 924. The servomotors 920, 922, 924 may
adjust the
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orientation and position of the landmark identifier 918. Control of the servos
may be automatic
or may be controlled by a surgeon.
[00119] FIG. 25 illustrates a bone 100 and a system 1010 for identifying a
landmark
in a third embodiment. The system 1010 includes a control unit 1012, a field
generator
1014, a landmark identifier 1016, an intramedullary nail 1024, and a probe
1029. The
landmark identifier 1016 also may be referred to as a targeter. The control
unit 1012 may be
included as part of the processor described above or may be a separate unit.
The
intramedullary nail 1024 is inserted into the bone 100, and the intramedullary
nail 1024 has
a hole or landmark 1028. In the depicted embodiment, the field generator 1014
is electrically
connected to the control unit 1012. In the depicted embodiment, an insertion
handle 1022 is
removably attached to the intramedullary nail 1024. The insertion handle 1022
and/or the
intramedullary nail 1024 may be cannulated. In some embodiments, the insertion
handle
1022 includes a third sensor 1032.
[00120] The landmark identifier 1016 includes a second sensor 1020. The
landmark
identifier 1016 may guide a drill bit 1018, and the drill bit 1018 may be
connected to a drill
(not shown). The second sensor 1020 may be connected to the control unit 1012,
either by
wire or wirelessly. In some embodiments, the field generator 1014 may be
directly mounted
on the landmark identifier 1016.
[00121] The probe 1029 includes a wire 1030, a tape 1034, and a stop 1036. In
the
depicted embodiment, the tape 1034 is a 0.125 inch wide by 0.060 inch thick
300 series
stainless steel fish tape available from Ideal Industries, Inc. of Sycamore,
Illinois. However,
those of ordinary skill in the art would understand that other materials and
other sizes may
be used. For example, any narrow band of polymer, composite material, or metal
may be
used as the tape 1034, but it may be preferred to use a non-ferrous metal. The
tape 1034 may
be coiled before placement into the intramedullary nail 1024. Coiling of the
tape 1034 may
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cause it to have a natural curvature. The tape 1034 may have, in some
embodiments, a
rectangular geometry that assists in orienting the tape as it is placed into a
cannulation of the
intramedullary nail 1024. An oval, square, or circular geometry also may be
used. In some
embodiments, the wire 1030 may be operatively connected to the tape 1034. For
example,
this may be accomplished through the use of an adhesive or fastener. The tape
1034 may
include graduations or detents to indicate a depth of the tape as it is
inserted into the
implant.
[00122] A first sensor 1026 is connected to the control unit 1012, either by
wire or
wirelessly. In the depicted embodiment, the first sensor 1026 is connected
through the use of
the wire 1030 and a connector 1038. In some embodiments, the connector 1038
may be
omitted. The first sensor 1026 may be connected to a distal end of the tape
1034, and the
stop 1036 may be connected to a proximal end of the tape 1034.
[00123] In some embodiments, the probe 1029 may include a sensor housing (not
shown) to house the first sensor 1026. The sensor housing may be attached to
the tape 1034.
The sensor housing may be made of a non-ferrous material, such as a polymer, a
composite,
or a metal. The sensor housing may include an appropriate strain relief to
shield the wire
1030 from stresses. The sensor housing may be constructed and arranged to be
large enough
to hold the first sensor 1026 but small enough to fit through the cannulation
of the insertion
handle or the implant. Further, the sensor housing may be constructed and
arranged to be
long enough to allow passage through intramedullary nail bends, intramedullary
nail bow,
and/or bends in relevant instrumentation. A geometry of the leading and
trailing faces of the
sensor housing may be designed such that the sensor housing does not catch or
snag on the
cannulation of the instrumentation or implant.
[00124] The stop 1036 may be used to control the placement of the sensor 1026.
If
the tape 1034 is a fixed length and the distance is known from the end of the
insertion
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handle to the hole 1028, repeatable placement of the first sensor 1026 may be
achieved. The
tape 1034 may be of sufficient length such that the sensor 1026 is aligned
with the hole
1028, adjacent the hole 1028, or offset from the hole 1028.
[00125] In some embodiments, the insertion handle 1022 may be omitted. In such
a
case, a different tape length may be selected such that the stop 1036 engages
a portion or
end of the nail 1024.
[00126] FIG. 26 illustrates a detailed view of the intramedullary nail 1024,
the sensor
1026, and the hole 1028. The sensor 1026 may be aligned with the hole 1028,
adjacent the
hole 1028, or offset from the hole 1028. In the depicted embodiment, the
sensor 1026 is
generally adjacent to the hole 1028.
[00127] In use, the intramedullary nail 1024 is placed into the bone 100. The
insertion
handle 1022 may be attached to the intramedullary nail 1024. The probe 1029 is
fed through
the cannulation of the insertion handle 1022 and into the cannulation of the
intramedullary
nail 1024 until the stop 1036 engages the insertion handle 1022. In one
particular
embodiment, the wire 1030 is connected to the control unit 1012, and the
sensors 1026,
1020, and 1032 are calibrated using the control unit 1012. In some
embodiments, the probe
1029 may be removed after calibration. If so, the third sensor 1032 and a
transformation
matrix may be used to identify the relative position of the second sensor 1020
and hence
landmark identifier 1016. Optionally, the user may use transfixion elements,
such as screws,
to first lock the proximal end of the intramedullary nail. An operator uses
the landmark
identifier 1016 and the first sensor 1026 to identify the landmarks 1028. For
example, in the
case of intramedullary nail fixation, a surgeon uses the landmark identifier
1016 to identify
the blind transfixion holes and drill through the holes for placement of a
transfixion element.
[00128] FIG. 27 illustrates a packaging embodiment. In general, intramedullary
nails
must be sterilized before implantation. If the sensor is installed in the
intramedullary nail
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prior to serialization, the sensor may lose its calibration during the
serialization process,
particularly if the sterilization process involves radiation. For example,
gamma radiation
may be used to sterilize hermetically sealed components, such as the sensor.
The
embodiment depicted in FIG. 27 illustrates a way to maintain the sterilization
of the
intramedullary nail while allowing for recalibration of the sensor. The
embodiment depicted
in FIG. 27 includes a first package 1040, a second package 1042, a first
connector 1044, a
second connector 1046, and a cable 1048. In the depicted embodiment, a sensor
(not shown)
and intramedullary nail 1024 are located within the first package 1040.
Alternatively, the
probe 1029 and the sensor are located within the first package 1040. In yet
another example,
only the sensor is located within the first package 1040. A memory device (not
shown) may
be connected to the sensor. The memory device may be used to store a
calibration
transformation matrix (xl,y1,z1,x2,y2,z2) as well as other data, such as
length and size of
the intramedullary nail or the probe. The memory device may be mounted to or
placed on
the intramedullary nail 1024 or the probe 1029. The first connector 1044 is
electrically
connected, but removably attached, to the second connector 1046. The first
connector 1044
is also electrically connected to the sensor or the memory device. The first
package 1040
maintains the sterilization of the device held within. The cable 1048 is
electrically connected
to the second connector 1046 and a storage device (not shown). The calibration
for the
sensor is downloaded from the storage device and transmitted through the
connectors 1044,
1046 to the sensor or the memory device. The calibration step may be performed
during
manufacturing of the system or immediately prior to implantation of the
implant.
[00129] FIG. 28 illustrates a method of connecting the system 1010 to a
network.
FIG. 28 illustrates a network 1060, a computing device 1050, the cable 1048,
the second
connector 1046, the first connector 1044, and the intramedullary nail 1024. In
the depicted
embodiment, a sensor (not shown) is located within the intramedullary nail
1024.
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Alternatively, the sensor may be attached to the probe 1029 or freestanding.
In some
embodiments, the intramedullary nail 1024 may be wrapped in packaging, such as
the first
package 1040 and/or second package 1042 but this is not always the case. A
memory device
(not shown) may be connected to the sensor. The memory device may be used to
store a
calibration transformation matrix (x 1 ,y1,z1,x2,y2,z2) as well as other data,
such as length
and size of the intramedullary nail or the probe. The memory device may be
mounted to or
placed on the intramedullary nail 1024 or the probe 1029. The network 1060
maybe a local
area network or a wide area network. The computing device 1054 is connected to
the
network 1060. In some embodiments, the network communication may be encrypted.
The
cable 1048 connects the computing device 1054 to the sensor or the memory
device through
the use the connectors 1044, 1046. In this way, the sensor calibration may be
downloaded
from the computing device 1054 and/or the network 1060. While the depicted
embodiment
illustrates the sensor within the intramedullary nail, this is not always the
case. The sensor
may be attached to the probe or freestanding. In some embodiments, the memory
device
may be located within the control unit, and the control unit is connected to
the network to
download the calibration data.
[00130] FIG. 29 illustrates a system 1110 for identifying a landmark in a
fourth
embodiment. The system 1110 includes a control unit 1112, a field generator
1114, a
landmark identifier 1116, an intramedullary nail 1124, a drop 1136, and a
probe 1129. The
control unit 1112 may be included as part of the processor described above or
may be a
separate unit. The intramedullary nail 1124 is inserted into the bone 100, and
the
intramedullary nail 1124 has a hole or landmark 1128. In the depicted
embodiment, the field
generator 1114 is connected to the control unit 1112, either by wire or
wirelessly. In the
depicted embodiment, an insertion handle 1122 is removably attached to the
intramedullary
.. nail 1124. The insertion handle 1122 and/or the intramedullary nail 1124
may be cannulated.
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In some embodiments, the insertion handle 1122 includes a third sensor 1144.
The drop
1136 may include a fourth sensor 1139.
[00131] The landmark identifier 1116 includes a second sensor 1120. The
landmark
identifier 1116 may guide a drill bit 1018, and the drill bit 1018 may be
connected to a drill
(not shown). The second sensor 1120 may be connected to the control unit 1112,
either by
wire or wirelessly. In some embodiments, the field generator 1114 may be
directly mounted
on the landmark identifier 1116.
[00132] The probe 1129 includes a wire 1130, a tape 1134, and a stop 1136. The
tape
1134 may have, in some embodiments, a rectangular geometry that assists in
orienting the
tape as it is placed into a cannulation of the intramedullary nail 1124. In
some embodiments,
the wire 1130 may be operatively connected to the tape 1134. For example, this
may be
accomplished through the use of an adhesive or fastener. A first sensor 1126
is connected to
the control unit 1112, either by wire or wirelessly. In the depicted
embodiment, the first
sensor 1126 is connected through the use of the wire 1130. In some
embodiments, a
detachable connector may be used. The first sensor 1126 may be connected to a
distal end of
the tape 1134, and the stop 1136 may be connected to a proximal end of the
tape 1134. The
stop 1136 may be used to control the placement of the sensor 1126. If the tape
1134 is a
fixed length and the distance is known from the end of the insertion handle to
the landmark
1128, repeatable placement of the first sensor 1126 may be achieved. The tape
1134 may be
of sufficient length such that the sensor 1126 is aligned with the landmark
1128, adjacent
the landmark 1128, or offset from the landmark 1128.
[00133] In use, the intramedullary nail 1124 is placed into the bone 100. The
insertion
handle 1122 may be attached to the intramedullary nail 1124. The probe 1129 is
fed through
the insertion handle 1122 and into the intramedullary nail 1124 until the stop
1136 engages
the insertion handle 1122. In one particular embodiment, the wire 1130 is
connected to the
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control unit 1112, and the sensors 1126, 1120, and 1132 are calibrated using
the control unit
1112. In some embodiments, the probe 1129 may be removed after calibration. If
so, the
third sensor 1132 and/or the fourth sensor 1139 and a transformation matrix
may be used to
identify the relative position of the second sensor 1120 and hence targeter
1116. Optionally,
the user may use transfixion elements, such as screws, to first lock the
proximal end of the
intramedullary nail. An operator uses the landmark identifier 1116 and the
first sensor 1126
to identify the landmarks 1128. For example, in the case of intramedullary
nail fixation, a
surgeon uses the landmark identifier 1116 to identify the blind transfixion
holes and drill
through the holes for placement of a transfixion element.
[00134] FIG. 30 illustrates a first method for using the system to identify a
landmark.
The method begins at step 1210. In step 1212, the sensor is placed in the
nail. In step 1214,
the insertion handle is connected to the nail, and the drop is attached to the
insertion handle.
In step 1216, the control unit is connected to the sensor. In step 1218, the
sensor is
calibrated. In step 1220, the sensor is aligned with the hole. In step 1222
the sensor position
is recorded through the use of the control unit. In step 1224, the sensor is
removed from the
nail. In step 1226, the nail is implanted into the bone. In step 1228, the
hole is drilled using
the targeter. The method stops in step 1230.
[00135] FIG. 31 illustrates a second method for using the system to identify a
landmark. In step 1310, the tracking system is turned on. In step 1312, the
intramedullary
nail is inserted into bone. In step 1314, the probe is inserted into the
intramedullary nail
canal at a predetermined location and orientation. In step 1316, there is a
decision whether
the intramedullary nail needs to be locked proximally before distally. If yes,
then in step
1326 the drop is attached to the nail. In step 1328, an offset is calculated
between the probe
and the drop. In other words, a transformation matrix is created.
Alternatively, the drop is
not connected to the intramedullary but instead a sensor mounted in the
insertion handle is
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used to calculate an offset. In step 1330, the probe is removed from the nail.
In step 1334,
the nail is locked proximally. This may be accomplished through the use of the
landmark
identifier, a mechanical jig, or by manual operation. In step 1336, the
landmark identifier is
used to target the drill. In step 1338, the hole is drilled for the distal
screw. In step 1340, the
intramedullary nail is locked distally. On the other hand, if the decision is
to lock distally
first, then in step 1318 the landmark identifier and probe are used to target
the drill bit. In
step 1320, the hole is drilled for the distal screw. In step 1322, the
intramedullary nail is
locked distally. In step 1324, the probe is removed from the intramedullary
nail. In step
1324, the intramedullary nail is locked proximally. This may be accomplished
through the
use of the landmark identifier, a mechanical jig, or by manual operation.
[00136] FIG. 32 illustrates a system for measuring depth of drill bit
placement. The
system 1400 includes a stator 1410 and a slider 1412. The stator 1410 and the
slider 1412
form a capacitive array that can sense relative motion. Moving the stator 1410
and the slider
1412 in a linear relation relative to one another causes a voltage fluctuation
that can be
interpreted and used to determine the distance traveled. In some embodiments,
an electronic
measuring circuit (not shown) and the slider 1412 may be housed inside the
landmark
identifier, and the drill bit may be specially constructed to have the stator
1410 along outer
surface so that the stator 1410 and the slider 1412 are in very close linear
proximity to each
other. The linear movement of the drill bit stator 1410 induces a voltage in
the receiving
slider 1412 which is interpreted by the electronic measuring circuit as a
distance
measurement. The distance measurement may be sent to the control unit and/or
displayed on
the monitor. Capacitive sensors are highly susceptible to moisture, and so
some
embodiments may be made to prevent liquids, such as bodily fluids, from
traveling between
the stator 1410 and the slider 1412. 0-rings or some other similar form of
wipes can be
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incorporated within the landmark identifier in order to keep the drill bit
substantially
moisture free.
[00137] FIGS. 33 A and 33B illustrate another system for measuring depth of
drill bit
placement. The system 1500 includes a reflective code wheel or strip 1510, a
lens 1512, and
an encoder 1514. The lens 1512 focuses light onto bar of the code strip 1510.
As the code
strip 1510 rotates, an alternating pattern of light and shadow cast by the
window and bar,
respectively, falls upon photodiodes of the encoder 1514. The encoder 1514
converts this
pattern into digital outputs representing the code strip linear motion. In the
depicted
embodiment, the encoder is an Avago Technologies AEDR-8300 Reflective Optical
Encoder available from Avago Technologies of 350 W Trimble Road, San Jose,
California.
Alternatively, the Avago Technologies ADNS-5000 One Chip USB LED-based
Navigation
System may be used. The encoder and its supporting electronics may be mounted
inside the
landmark identifier so that its input region is oriented toward a "window" in
the landmark
identifier cannulation. Markings, such as dark colored concentric rings or
bright reflective
rings, may be added to the drill bit in order to enhance the visibility of the
bit to the encoder.
These markings could also be used to denote the starting zero point for
measurement. As the
drill bit moves linearly within the landmark identifier, the encoder measures
the movement
of the drill bit. The distance measurement may be sent to the control unit
and/or displayed
on the monitor.
[00138] FIG. 34 illustrates yet another system for drill depth measurement.
The
system 1600 utilizes a Linear Variable Differential Transformer (LVDT) 1612.
An LVDT is
a type of electrical transformer used to measure linear displacement. The LVDT
1612
includes a plurality of solenoidal coils 1618 placed end-to-end around a tube
1610, which is
the landmark identifier in the depicted embodiment. In the embodiment depicted
in FIG. 34,
the center coil is the primary coil and the outer two coils are the
secondaries. A cylindrical
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ferromagnetic core 1610, such as the drill bit, slides along the axis of the
tube. An
alternating current 1614 is driven through the primary coil, causing a voltage
to be induced
in each secondary proportional to its mutual inductance with the primary. A
pickup sensor
1616 measures the magnitude of the output voltage, which is proportional to
the distance
moved by the core (up to its limit of travel). The phase of the voltage
indicates the direction
of the displacement. Because the sliding core does not touch the inside of the
tube, it can
move without friction, making the LVDT a highly reliable device. The absence
of any
sliding or rotating contacts allows the LVDT to be completely sealed against
the
environment. The distance measurement may be sent to the control unit and/or
displayed on
the monitor.
[00139] FIGS. 35-37 illustrate an insertion handle 1700 and an adjustable stop
1800.
The insertion handle 1700 a stem 1710 that connects to an implant, such as an
intramedullary nail (not shown), at an end portion 1712. The insertion handle
1700 may
include a quick connect 1716 for attachment to a drop, proximal targeting
device, or some
other instrument or apparatus. The insertion handle includes a top portion
1714, which may
include a hole and/or an alignment feature. The adjustable stop 1800 may
include a slot
1810, an alignment member 1812, and a fastener hole 1814.
[00140] In the embodiments depicted in FIGS. 35-37, the adjustable stop 1800
may
be removably attached to the top portion 1714. In some embodiments, the
adjustable stop
may be integrally formed with the insertion handle 1700. In yet other
embodiments, the
adjustable stop may be permanently attached to the insertion handle 1700. In
the depicted
embodiment, the alignment member 1812 fits within an alignment feature of the
top portion
to prevent rotation of the adjustable stop. A fastener (not shown) may be
placed through the
fastener hole 1814 to attach the adjustable stop to the insertion handle 1700.
The tape 1034,
1134 may be placed through the slot 1810, through the stem 1710, and into the
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intramedullary nail cannulation. The slot 1810 may have a shape to match the
geometry of
the tape to aid in its insertion or to prevent rotation of the tape. The tape
1034, 1134 may
include markings, graduations, or detents to indicate an appropriate depth for
the given nail
length. In some embodiments, the adjustable stop 1800 may include a locking
mechanism
(not shown) to temporarily lock the tape 1034, 1134 at a particular depth. In
it simplest
form, the locking mechanism may be a fastener that frictionally engages the
tape 1034,
1134.
[00141] FIG. 38 illustrates a method for calibrating the system for
identifying a
landmark. Calibration is necessary for accuracy. The method begins at step
1900, which may
include powering up the system. In step 1910, the probe and the landmark
identifier are
removed from packaging, if any, and scanned. In some embodiments, the drop is
also
scanned. Scanning may include reading a bar code using a bar code reader.
Scanning causes
the system to retrieve offset sensor values that correspond to the bar code
from a look up
table in step 1912. The look up table may be local or accessed over a network,
such as the
Internet. Alternatively, the probe and the landmark identifier may include a
serial number or
other unique identifier, and the unique identifier is used in conjunction with
the look up
table to retrieve offset sensor values. The offset sensor values are stored in
local memory of
the system in step 1914. In step 1916, the user places the probe relative to
the implant and
attempts to track a landmark using the landmark identifier in step 1916. In
step 1918, there
is a decision whether the calibration is correct. If so, the method ends in
step 1920.
Otherwise, new offset values are retrieved in step 1912.
[00142] In one particular embodiment, provided feedback information is
selected
from the group consisting of audible, visual, and tactile. The audible
feedback may be
output through a speaker, headphones, ear buds, or an ear piece. The audible
feedback signal
may be transmitted over wire or wireles sly using radio frequency or
terrestrial data
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transmission. The visual feedback may be output through a cathode ray tube, a
liquid crystal
display, or a plasma display. Visual feedback devices may include, as
examples, a television
monitor, a personal digital assistant, or a personal media player. The visual
feedback signal
may be transmitted over wire or wirelessly using radio frequency or
terrestrial data
transmission. The tactile feedback may be output through gloves, instruments,
or a floor
mat. The tactile feedback signal may be transmitted over wire or wirelessly
using radio
frequency or terrestrial data transmission.
[00143] The invention further includes a method for identifying a landmark.
The
method includes the steps of: providing an orthopaedic implant assembly having
an
orthopaedic implant with a longitudinal groove and a removable lead having a
magnetic
sensor attached thereto situated within the longitudinal groove, the
orthopaedic implant
having a proximal end portion, a distal end portion, and at least one landmark
on the distal
end portion; implanting the orthopaedic implant assembly in a patient; first
installing
transfixion elements in the proximal end portion; identifying the at least one
landmark using
a landmark identifier; installing a transfixion element in the at least one
landmark in the
distal end portion after first installing transfixion elements in the proximal
end portion; and
removing the removable lead. This method allows for proximal locking of the
implant prior
to distal locking. This is a significant advantage over the prior art as prior
devices required
distal locking prior to proximal locking.
[00144] System calibration may be accomplished during manufacturing, after
distribution, or immediately preceding implant implantation. The calibration
step is
analogous to registration in computer assisted surgery. Calibration may be
needed for
different reasons. For example, sensor calibration may be needed to correct
for
manufacturing tolerances. The system may be designed based upon a computer-
aided-design
model, and calibration is used to accurately place the sensors relative to one
another. The
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processor or the control unit may include software to generate X, Y, Z, pitch,
yaw, and roll
offset values to locate the sensors in a global coordinate system or simply
placement relative
to one another. In one embodiment, the system is manufactured and calibrated
during
manufacturing and assigned a unique identifier, such as a serial number, color
code, bar
code, or RFID tag. If the system needs to be re-calibrated, the unique
identifier may be used
to retrieve the offset values, either locally or over a network. Further, the
unique identifier
may be used to retrieve other data, such as the size of the intramedullary
nail or the length of
the intramedullary nail and/or the probe.
[00145] In view of the foregoing, it will be seen that the several advantages
of the
invention are achieved and attained.
[00146] The embodiments were chosen and described in order to best explain the
principles of the invention and its practical application to thereby enable
others skilled in the
art to best utilize the invention in various embodiments and with various
modifications as are
suited to the particular use contemplated.
[00147] As various modifications could be made in the constructions and
methods
herein described and illustrated without departing from the scope of the
invention, it is
intended that all matter contained in the foregoing description or shown in
the accompanying
drawings shall be interpreted as illustrative rather than limiting. For
example, while FIG. 1
illustrates a pocket for affixing the first sensor to the implant, other
structure and/or methods
may be used to affix these items together. Thus, the breadth and scope of the
present invention
should not be limited by any of the above-described exemplary embodiments, but
should be
defined only in accordance with the following claims appended hereto and their
equivalents.
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