U.S. patent application number 11/183717 was filed with the patent office on 2005-11-10 for computer assisted intramedullary rod surgery system with enhanced features.
Invention is credited to Kienzle, Thomas C. III.
Application Number | 20050251113 11/183717 |
Document ID | / |
Family ID | 24742601 |
Filed Date | 2005-11-10 |
United States Patent
Application |
20050251113 |
Kind Code |
A1 |
Kienzle, Thomas C. III |
November 10, 2005 |
Computer assisted intramedullary rod surgery system with enhanced
features
Abstract
A computer assisted surgery system for positioning a surgical
implant within a patient's body that includes a localizing device
configured to measure a pose of the surgical implant, an imaging
device adapted for acquiring images of the surgical implant, and a
computer adapted for calculating an adjusted pose for the surgical
implant based on information developed from the images so as to
compensate for deformation of the surgical implant or inaccuracies
in localization.
Inventors: |
Kienzle, Thomas C. III;
(Lake Forest, IL) |
Correspondence
Address: |
MCANDREWS HELD & MALLOY, LTD
500 WEST MADISON STREET
SUITE 3400
CHICAGO
IL
60661
|
Family ID: |
24742601 |
Appl. No.: |
11/183717 |
Filed: |
July 18, 2005 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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11183717 |
Jul 18, 2005 |
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10756020 |
Jan 12, 2004 |
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6922581 |
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10756020 |
Jan 12, 2004 |
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09683107 |
Nov 19, 2001 |
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6718194 |
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60249697 |
Nov 17, 2000 |
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Current U.S.
Class: |
606/1 |
Current CPC
Class: |
A61B 2034/2065 20160201;
A61B 2034/2055 20160201; A61B 17/1725 20130101; A61B 34/20
20160201; A61B 34/10 20160201; A61B 2090/376 20160201; A61B 34/25
20160201; A61B 2034/107 20160201; A61B 17/1703 20130101 |
Class at
Publication: |
606/001 |
International
Class: |
A61F 002/38 |
Claims
1. A computer assisted surgery system for positioning a surgical
implant within a patient's body, said system comprising: a
localizing device configured to measure a pose of the surgical
implant; an imaging device adapted for acquiring images of the
surgical implant; and a computer adapted for calculating an
adjusted pose for the surgical implant based on information
developed from the images so as to compensate for deformation of
the surgical implant or inaccuracies in localization.
2. The system of claim 1, further comprising a display adapted for
displaying a graphic representation of the surgical implant based
on the adjusted pose of the surgical implant.
3. The system of claim 1, further comprising a surgical instrument
defining a trajectory and a display device, and wherein the
localizing device is further operative for measuring the pose of
the surgical instrument and the display device is adapted to
display a graphic representation of the trajectory relative to a
graphic representation of the surgical implant, based on the
measured pose of the surgical instrument and the adjusted pose of
the implant.
4. The system of claim 1, wherein the imaging device is an X-ray
imaging device.
5. The system of claim 1, wherein the information developed from
the images is an adjustment to be applied to the pose of the
surgical implant, said adjustment developed through image
processing techniques applied to the images of the implant.
6. The system of claim 1, wherein the localizing device is an
optical localizing device.
7. A method for positioning a surgical implant within a patient's
body, wherein the surgical implant has one or more holes, the
method comprising: calculating an adjusted pose for the surgical
implant based on information developed from acquired images of the
surgical implant so as to compensate for deformation of the
surgical implant or inaccuracies in localization.
8. The method of claim 7, further comprising displaying a graphic
representation of the surgical implant based on the adjusted pose
of the surgical implant.
9. The method of claim 7, further comprising: measuring a pose of a
surgical instrument; and displaying a graphic representation of a
trajectory of the surgical instrument relative to a graphic
representation of the surgical implant, based on the measured pose
of the surgical instrument and the adjusted pose of the
implant.
10. A computer program product for positioning a surgical implant
within a patient's body, wherein the surgical implant has one or
more holes, said computer program product comprising: instructions
for calculating an adjusted pose for the surgical implant based on
information developed from acquired images of the surgical implant
so as to compensate for deformation of the surgical implant or
inaccuracies in localization.
11. The computer program product of claim 10, further comprising
instructions for displaying a graphic representation of the
surgical implant based on the adjusted pose of the surgical
implant.
12. The computer program product of claim 10, further comprising
instructions for measuring a pose of a surgical instrument; and
instructions for displaying a graphic representation of a
trajectory of the surgical instrument relative to a graphic
representation of the surgical implant, based on the measured pose
of the surgical instrument and the adjusted pose of the implant.
Description
RELATED APPLICATIONS
[0001] This application is a continuation of U.S. application Ser.
No. 10/756,020, entitled "Computer Assisted Intramedullary Rod
Surgery System With Enhanced Features," which was filed Jan. 12,
2004 (the "'020 application"), which is in turn a continuation of
U.S. application Ser. No. 09/683,107, entitled "Computer Assisted
Intramedullary Rod Surgery System With Enhanced Features," which
was filed Nov. 19, 2001, now U.S. Pat. No. 6,718,194 (the "'194
patent"), which claims the benefit of U.S. Provisional Application
No. 60/249,697, which was filed Nov. 17, 2000 (the "'697
application"). The '020 application, the '194 patent, and the '697
application are hereby incorporated by reference in their
entireties.
BACKGROUND OF THE INVENTION
[0002] This invention relates to a computer assisted surgery system
for use in inserting interlocking screws in an intramedullary
rod.
[0003] A current surgical treatment for fractures of the shaft of
long bones (e.g., femur and tibia) is the insertion of an
intramedullary rod (IM rod). These devices are relatively rigid
devices inserted into one end of the bone and down the center canal
of the bone shaft, such that the fracture site is bridged.
Transverse holes in either end of the IM rod receive screws
inserted transversely through the bone in order to lock the two
bone fragments relative to one another. The insertion of the screws
farthest from the IM rod insertion hole is currently a difficult
and time consuming procedure requiring numerous x-ray images. An
intraoperative x-ray machine (C-arm) is repeatedly fired and
reoriented until it is exactly aligned with the transverse holes as
evidenced by x-ray images displaying the holes as "perfect
circles". To establish a starting point, the surgeon uses further
x-ray images to align the drill tip with the images of the holes.
The surgeon then uses the source-to-receiver axis of the C-arm as
an external reference frame along which the long axis of the drill
is oriented. Even after this, several attempts may be required to
drill the holes into the bone and through the transverse holes.
[0004] Several alternative approaches have been employed in an
attempt to speed this process. External jigs have been tried with
little success because inaccuracies in the jig, inaccuracy of the
mounting between jig and IM rod, and deformation of the IM rod
accumulate to cause the final jig hole positions to be unreliably
aligned with the IM rod holes. Radiolucent drills and drill guides
and laser sighting devices have been developed which, in the best
cases, improve the speed and accuracy of hole placement, but still
require a significant number of x-ray images to be obtained in
order to first achieve a C-arm orientation that produces "perfect
circles" in the images.
[0005] Image-guided approaches have been developed, but these too
require the "perfect circle" alignment of the C-arm. Most image
guided systems display the drill trajectory over "perfect circle"
images of the IM rod. One system assists the surgeon in correctly
orienting the C-arm to obtain "perfect circles": "Surgical
Navigation Based on Fluoroscopy Clinical Application for
Computer-Assisted Distal Locking of Intramedullary Implants", Suhm,
et. al., Computer Aided Surgery 5:391-400, 2000. Another difficulty
with existing image guided systems is that the surgeon must align
the drill guide while viewing an "end on" representation of the
drill guide, which can be quite challenging.
[0006] Several devices have been described (U.S. Pat. Nos.
5,411,503, 5,540,691, 6,074,394, 6,081,741) in which an emitter is
inserted into the IM rod, down to the level of the interlocking
holes, and transducers on the drill guide report the position of
the drill trajectory relative to the holes. These devices, however,
require equipment dedicated to this one surgical task, require the
extra step of inserting an emitter to the level of the hole, and
typically provide only rudimentary "end on" representations of the
drill trajectory.
[0007] U.S. Pat. No. 6,285,902, incorporated herein by reference,
entitled "Computer Assisted Targeting Device for Use in Orthopaedic
Surgery" describes a system in which, preferably, orthopaedic
surgical tools outfitted with infrared LEDs are tracked by an
optical localizing device. The poses of these tools are determined
and graphic representations of the tools are superimposed on
standard intraoperative x-ray images. This allows the surgeon to
view, in real time, the position of the tool or tools with respect
to an imaged body part or another tool or tools. In the preferred
embodiment, a drill guide outfitted with infrared LEDs is tracked
and the trajectory of its bore is displayed on the x-ray image of
the involved bone. This allows a surgeon to accurately predict the
trajectory of a guide pin that passes through the bore of the drill
guide. The guide pin, once inserted, is used as a reference for the
insertion of implantable cannulated screws.
[0008] An alternative embodiment of the previous invention,
described in the referenced patent, allows its use in the insertion
of distal interlocking screws in an intramedullary (IM) rod by
displaying the drill guide trajectory relative to a computer
generated representation of a cross-section of the IM rod. The
current invention is an enhancement to the previous invention that
adjusts the graphic representations of the IM rod based on
information developed from the x-ray images. This facilitates the
more accurate alignment of a drill through the holes and eliminates
the need to align the x-ray beam with the holes in the IM rod. This
can significantly reduce the amount of radiation involved in the
procedure and reduce the time required to insert the screws.
SUMMARY OF THE INVENTION
[0009] Accordingly, one objective of the present invention is to
provide a computer assisted surgery system for positioning an
instrument relative to a portion of a surgical implant. More
specifically, it assists a surgeon in drilling a hole through a
long bone and through transversely oriented holes in an
intramedullary rod (IM rod) during a fracture fixation procedure
regardless of deformation of the IM rod.
[0010] Another objective of the invention is to provide a technique
and apparatus for accurately displaying the trajectory of the drill
relative to the holes of the IM rod.
[0011] Still another objective of the invention is to provide a
technique and apparatus for using x-ray images of the IM rod to
accurately determine the locations of the holes.
[0012] These and other objects of the present invention are
achieved by the use of a computer assisted surgery system,
including a computer, a localizing device and a display monitor.
The system also includes a tracked adapter attached to the IM rod
and a drill guide, both of which have their poses determined by the
localizer. With the IM rod inserted in a long bone, and the tracked
adapter attached to the exposed end of the IM rod the pose of the
adapter and the IM rod are measured by the localizing device. Two
approximately orthogonal x-ray images are then obtained of the IM
rod in the vicinity of the holes. Image processing techniques are
used to accurately determine the location of the IM rod from the
x-ray images and an adjusted pose is calculated for the IM rod. A
graphic representation of the drill trajectory is displayed
superimposed over the images of the IM rod and over a graphic
representation of the IM rod, in order to assist the surgeon in
placing the drill in the proper position relative to the IM rod
holes.
BRIEF DESCRIPTION OF SEVERAL VIEWS OF THE DRAWINGS
[0013] FIG. 1 is a perspective view of an intramedullary rod
inserted into a femur, a tracked adapter attached to the
intramedullary rod, a drill guide, a partial C-arm, the computer
assisted surgery system with localizer camera and display screen
containing images and graphics.
[0014] FIG. 2 is a perspective view of the intramedullary rod with
attached tracked adapter.
[0015] FIG. 3 is an example of a screen display of two images and a
generated graphic with superimposed instrument representations.
[0016] FIG. 4 is a perspective view of an intramedullary rod
inserted into a femur, a tracked adapter attached to the
intramedullary rod, a drill guide, a partial C-arm, and a example
of a screen display of an image with superimposed graphics.
[0017] FIG. 5 is a diagrammatic illustration of the software
operation during pose adjustment.
DETAILED DESCRIPTION OF THE INVENTION
[0018] An embodiment of the image guided system of U.S. Pat. No.
6,285,902 teaches a system for placing distal interlocking screws
in an IM rod. As shown in FIG. 1, the system is based on a computer
(121) that receives input from an x-ray imaging device (110) and a
localizing device (120), and displays surgical instrument
representations (123) over x-ray images (125 and 126) in real time.
A tracked adapter (129) is attached to the exposed end of the
inserted IM rod (130) such that the pose of the rod can be tracked.
A drill guide (128) is also tracked, and a representation of its
trajectory (123) is overlaid on x-ray images (125 and 126) of the
IM rod (130). Additionally, the system displays, in a separate
window (127), the drill guide trajectory (123) relative to a
graphical representation (124) of a cross-section of the IM rod
(130) at the level of the transverse interlocking holes (131) by
projecting models of these instruments onto a picture plane (138).
During the procedure, the surgeon uses the AP image (126) of the IM
rod (130) to align the drill guide (128) in the coronal plane, and
the lateral image (125) and the cross sectional graphic (124) to
align the drill guide (128) in the axial plane.
[0019] The current invention improves upon the previous invention
by providing greater accuracy in generating the graphic
representations (124) of the IM rod (130) relative to the drill
guide (128), regardless of bending of the IM rod (130) or minor
errors in attaching the adapter (129) to the IM rod (130). This
improvement allows the surgeon to use these relative graphic
representations (124 and 123) alone to exactly align the drill
guide (128) in the axial plane. While the surgeon still uses the AP
view (126) to align the drill guide (128) in the coronal plane,
there is no longer a need to rely on the lateral view (125), thus
avoiding the difficulty of positioning a drill guide (128) using an
"end-on" representation, during the axial alignment of the
trajectory. It also eliminates the need for the surgeon to estimate
the required anteroposterior position of the drill guide tip based
on the distance between the IM rod and the femoral shaft cortex and
the amount of axial rotation of the IM rod. In the preferred
embodiment, the IM rod (130) is inserted in the long bone (133) in
the usual manner. While the invention will be preferably described
for drilling holes in the bone (133) for the interlocking holes
(131) in the end of the IM rod farthest from the exposed end, the
system may be alternately used for all interlocking screws and
associated implants. As shown in FIG. 2, a tracking device (129),
preferably comprising an adapter (136) to the IM rod (130) and an
array of three or more localizing emitters (137), is attached to
the exposed end of the IM rod (130). The exposed end of the IM rod
(130) is keyed to the adapter (136) such that the adapter (136) is
attached to the inserted rod in a unique manner and the
relationship is known within the limits of error of attachment
preferably to within a few degrees and a few millimeters. A
coordinate frame, A, is defined preferably at the interface between
the IM rod (130) and the tracking device (129) and is in a known
and fixed relationship to the localizing emitters (137). Computer
models of the features of the tracking adapter (129) and IM rod
relative to coordinate frame A and graphic representations of
features of the IM rod (130) relative to coordinate frame A are
stored in the computer's long term memory. A second coordinate
frame, Z, is defined relative to the localizing emitters (137) of
the tracking device (129) and is preferably located on the IM rod
(130) halfway between the transverse holes (131). It is oriented
with the z-axis coincident to the long axis of the IM rod (130) and
the x-axis parallel to the bore of the transverse holes (131).
Another coordinate frame, G, is selected relative the localizing
emitters (137) such that its x-axis and y-axis define a picture
plane (138) upon which instrument representations may be projected
to form an image for display. The z-axis of coordinate frame G is
preferably oriented such that it passes through the centers of both
distal transverse holes (131), thus causing representations of both
distal transverse holes (131) to project to the same location on
the picture plane (138). Alternatively, the picture plane (138) may
be selected in any pose that is near-orthogonal (e.g., within 20
degrees) to the long axis of the IM rod without departing from the
instant invention. Further, separate picture planes may be selected
for each transverse hole through which the system is to assist the
surgeon in inserting a screw.
[0020] With the tracking device (129) attached to the IM rod (130)
and its pose being read by the localizing device, a graphic
representation of the IM rod (130) is projected onto the picture
plane (138) defined by coordinate frame G. Because the picture
plane (138) is defined to be substantially perpendicular to the
long axis of the IM rod (130), the image projected on it will be an
"end-view" of the IM rod graphic representation. This end-view
image is projected onto the picture plane (138) and, as shown in
FIG. 3, is transformed into a graphic representation (124) of the
IM rod and displayed in a field (127) of the display screen. The
software can display different versions of an instrument
representation for different viewing angles. The end-view version
of the IM rod representation (124) is a pair of semicircles
representing the cross section of the IM rod (130) with a gap
between them representing the transverse holes (131). Virtual lines
are additionally displayed as dashed lines extending from the
straight portion of the semicircles to emphasize the orientation of
the transverse screw holes (131). The purpose of this
representation (124) is to provide the surgeon with improved
information regarding the orientation and location of the
transverse holes (131) in the axial plane.
[0021] Returning to FIG. 1, the C-arm (110) acquires x-ray images
(125 and 126) of the bone (133) that include the transverse holes
(131) of the inserted IM rod (130). These images (125 and 126) need
not be exactly anteroposterior or exactly lateral with respect to
the IM rod (130) (i.e., "perfect circles" need not be obtained).
The C-arm (110) need be oriented only to within about 30 degrees of
exactly AP or lateral, and the misalignment may be either axial or
oblique. The pose of the C-arm (110) and the pose of the tracking
device (129) and its related coordinate frame A are calculated by
the localizing device (120) when the image is acquired. If the
x-axis (134) or y-axis (135) of coordinate frame A is within,
preferably, 30 degrees of the source-receiver axis of the C-arm
(110), then the image is considered lateral or anteroposterier (AP)
respectively.
[0022] If the acquired image is determined to be an AP view then,
as shown in FIG. 3, the software will generate an AP version of the
graphic representation (145) of the IM rod which is intended to
highlight the transverse holes (131). This graphic representation
(145) is defined relative to coordinate frame A, and is overlaid
onto the AP image (126) of the IM rod (130). This AP version of the
IM rod representation (145) comprises lines along the sides of the
transverse holes' image (141), with dashed virtual lines extending
from either side to emphasize the orientation of the holes (141).
The drill guide representation (123) is displayed relative to the
IM rod representation (145) as both are overlaid on the AP image
(126) and improves the surgeon's ability to accurately align the
drill guide (128) with the IM rod transverse holes (131) in the
coronal plane.
[0023] If the acquired image is determined to be a lateral view
then the software will optionally generate a lateral version of the
graphic representation (144) of the transverse holes (131). This
graphic representation (144) comprises two circles representing the
openings of the two holes. It is overlaid on the transverse holes
(141) seen in the lateral image (125) to improve the surgeons
ability to identify the starting point for the drill. However, this
is of less importance when compared to the utility of the
cross-sectional graphic (127).
[0024] Alternatively, the graphic representation (124, 144 and 145)
of the IM rod (131) may take other forms including 3-D surface
models, bitmaps, or other wireframe models. Any version of the
graphic representations (124, 144 and 145), regardless of view
orientation, that provides the surgeon with sufficient information
to orient the drill guide (128) relative to the IM rod (130) in a
given plane may be used without departing from the instant
invention.
[0025] Additionally, as each image is acquired, adjustment of the
position of the graphic representation (124, 144, and 145) of the
IM rod (130) is performed to correct for any deviation due to
flexure of the IM rod (131) or inaccuracies in attachment of the
tracking device (129) or other conditions leading to inaccuracies
in localizing the IM rod (130). Turning to FIG. 4, the poses of the
IM rod tracking device (129) and the C-arm (110) are recorded at
the time of image acquisition. If the C-arm source-receiver axis
(150) is within, preferably, 30 degrees of the x-axis or y-axis of
coordinate frame Z then adjustment is to be performed along the
y-axis or x-axis, respectively. While the following adjustment
steps are illustrated in FIG. 4, they are preferably performed
without being displayed to the user. The adjustment is accomplished
by projecting this adjustment axis (151) of the Z coordinate frame,
onto the acquired image (125) using the conic projection model, and
then analyzing the image data along a specific segment (156) of
this projected line (155). Image processing techniques known to
those skilled in the art threshold the image data within the image
data segment (156) and find the center (158) of the radio-opaque IM
rod image (140). The difference between this image location (158)
and the projected origin (157) of coordinate frame Z is calculated
and the difference value stored. Alternatively, any image
processing techniques, or other means for directly measuring the
positional error of the IM rod (130) at or near the transverse
holes (131) may be used without departing from the instant
invention.
[0026] When the difference value for AP, lateral, or both images
have been processed, the corresponding Z frame x-axis and y-axis
components are calculated by techniques known in the art. These
difference components are then used to develop an adjustment
transformation. Returning to FIG. 3, this adjustment transformation
is applied to coordinate frame A, causing it to rotate such that
the IM rod's AP and lateral graphic representations (144 and 145)
defined relative to A, will align with the IM rod's x-ray images
(140). After the adjustment rotations, the positions of the cross
sectional representation (124), the AP representation (145), and
the optional lateral representation (144), which are displayed to
the user, more accurately represent the actual position of the IM
rod (130).
[0027] Alternately, the overlay of the graphic representations
(124, 144 and 145) may be corrected by the translation of
coordinate frame A instead of by rotation. Or, instead, the graphic
representations (124, 144 and 145) could be altered to effect the
correction. For example, if the total difference is attributed to
bending of the rod, the coordinate frame A could be left unchanged
and the graphic representations (123, 144 and 145) could be altered
to simulate the flexure of the IM rod (130). Any correction means
that uses the difference between the expected and actual positions
of the IM rod (130) to modify its graphic representation in such a
way to make it more accurate may be used without departing from the
instant invention.
[0028] In summary, the software steps required are shown in FIG. 5.
The image is acquired (160) and the poses of the C-arm and tracking
clamp determined (161). If the y-axis of the Z coordinate frame is
near-aligned with the C-arm (162) then project the Z frame x-axis
onto the image (163), isolate an appropriate segment of image data
along the projected line (164), apply a thresholding algorithm to
emphasize the IM rod (165), find the center of the IM rod in the
image data (166), and calculate the difference between the center
of the IM rod's image and the projected Z-frame's origin as modeled
(167). If the x-axis of the Z frame is near aligned with the C-arm
(168) then project the y-axis onto the image (169) and perform the
image processing steps above (164-167). Calculate an adjustment
transformation based on available x-axis and y-axis difference
values (170).
[0029] Returning to FIG. 1, once the corrected IM rod
representations (124 and 144 and 145 seen best in FIG. 3) are being
displayed, the surgeon prepares to drill the holes in the bone
(131). The drill guide (128) generates a trajectory (123) that
overlays both image fields (125 and 126) and projects onto the
graphics field (127) as well. As shown in FIG. 3, the surgeon
aligns the drill trajectory (123) to pass through the hole markers
of the AP IM rod representation (145) and through the hole path on
the cross sectional IM rod representation (124) in the graphics
field (127). Once the proper alignment is achieved, the drill is
advanced in the drill guide (128). The second hole is prepared in a
similar fashion and confirmatory x-rays are obtained prior to
inserting appropriately sized screws. Alternately, self-tapping
screws may be directly inserted with a suitable instrument.
[0030] While the above description relates to the placement of
interlocking screws in intramedullary rods placed in long bones,
persons skilled in the art will recognize the applicability of this
invention to other devices in other locations of the body such as
the insertion of screws into other implantable devices. Any
procedure wherein a first device is positioned relative to a second
device at a position that is not known with sufficient accuracy by
use of a localizing device can be performed in a more accurate
manner with this invention.
* * * * *