U.S. patent application number 13/415223 was filed with the patent office on 2012-06-28 for non-invasive tracking of bones for surgery.
Invention is credited to Louis-Philippe Amiot, Francois Paradis, Eric Szmutny.
Application Number | 20120165707 13/415223 |
Document ID | / |
Family ID | 38956491 |
Filed Date | 2012-06-28 |
United States Patent
Application |
20120165707 |
Kind Code |
A1 |
Amiot; Louis-Philippe ; et
al. |
June 28, 2012 |
NON-INVASIVE TRACKING OF BONES FOR SURGERY
Abstract
The described method for determining at least orientation of a
pelvic bone in space and for tracking movement of the pelvic bone
using a computer assisted surgery (CAS) system includes removably
attaching, in a non-invasive manner, at least one reference marker,
in communication with the CAS system, to a skin surface covering
the pelvic bone. Registering at least orientation readings of the
reference marker is then performed with respect to a fixed
reference in a reference coordinate system, following which at
least an orientation of the pelvic bone in the reference coordinate
system is determined using the orientation readings of the
reference marker. These steps are repeated to update the
orientation readings while tracking the pelvic bone in space.
Inventors: |
Amiot; Louis-Philippe;
(Hampstead, CA) ; Szmutny; Eric; (Philipsburg,
CA) ; Paradis; Francois; (Boucherville, CA) |
Family ID: |
38956491 |
Appl. No.: |
13/415223 |
Filed: |
March 8, 2012 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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11878021 |
Jul 20, 2007 |
8152726 |
|
|
13415223 |
|
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60832151 |
Jul 21, 2006 |
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Current U.S.
Class: |
600/595 |
Current CPC
Class: |
A61B 90/36 20160201;
A61B 90/39 20160201; A61B 2034/2051 20160201; A61B 2034/2055
20160201; A61B 2090/3983 20160201; A61B 2017/00106 20130101; A61B
34/20 20160201; A61B 2090/378 20160201 |
Class at
Publication: |
600/595 |
International
Class: |
A61B 5/103 20060101
A61B005/103 |
Claims
1. A method for determining at least orientation of a pelvic bone
in space and for tracking movement of the pelvic bone using a
computer assisted surgery (CAS) system, the method comprising:
removably attaching, in a non-invasive manner, at least one
reference marker to a skin surface covering said pelvic bone, the
reference marker being in communication with the CAS system;
registering at least orientation readings of said reference marker
with respect to a fixed reference in a reference coordinate system;
determining at least an orientation of said pelvic bone in the
reference coordinate system using said at least orientation
readings of said reference marker; and repeating the steps of
registering and determining to update said at least orientation
readings while tracking the pelvic bone in space.
2. The method as defined in claim 1, wherein the step of removably
attaching further comprises using an adhesive to adhere the
reference marker to the skin surface covering the pelvic bone.
3. The method as defined in claim 2, further comprising mounting
the reference marker on a flexible support layer, and adhering the
flexible support layer to the skin surface covering the pelvic
bone.
4. The method as defined in claim 1, wherein each said reference
marker defines three axes which are determined and tracked by the
CAS system to produce said orientation readings.
5. The method as defined in claim 1, further comprising determining
both the orientation and position of said pelvic bone in space
using said CAS system.
6. The method as claimed in claim 5, further comprising registering
both orientation and position readings of said reference marker
with respect to the fixed reference in said reference coordinate
system, and using both the orientation and position readings to
determine the orientation and position of the pelvic bone in
space.
7. A system for determining at least an orientation of a pelvic
bone in space and tracking movement of the pelvic bone using a
computer assisted surgery (CAS) system, the system comprising: at
least one reference marker removably and non-invasively attachable
to a skin surface covering the pelvic bone, said reference marker
being in communication with the CAS system; a fixed reference
positioned in a reference coordinate system and used to identify at
least an orientation of said reference marker in said reference
coordinate system; and the computer assisted surgery (CAS) system
including: a sensing device adapted to register at least
orientation readings of said reference marker in the reference
coordinate system; and a processing unit receiving said orientation
readings from the sensing device and being operable to determine
and determining at least the orientation of said bone.
8. The system as defined in claim 7, wherein the reference marker
has an adhesive thereon for removably and non-invasively attaching
the reference marker directly to the skin surface covering the
pelvic bone.
9. The system as defined in claim 7, wherein said reference marker
is mounted on a flexible support layer, the flexible support layer
being secured to the skin surface covering the pelvic bone by an
adhesive.
10. A device for use with a computer assisted surgery (CAS) system
to determine at least orientation of pelvic bone in a reference
coordinate system and to track movement of the pelvic bone, the
device comprising at least one reference marker removably and
non-invasively attachable to a skin surface covering a pelvic bone,
the reference marker being in communication with the CAS system
such that the reference marker is detected and tracked in said
reference coordinate system by the CAS system with respect to a
fixed reference, said reference marker being adapted to provide at
least orientation readings thereof to the CAS system such as to
determine at least orientation of the pelvic bone in the reference
coordinate system and permit the CAS system to track movement of
the pelvic bone.
11. The device as defined in claim 10, wherein said reference
marker has an adhesive thereon for removably and non-invasively
attaching the reference marker directly to the skin surface
covering the pelvic bone.
12. The device as defined in claim 10, wherein said reference
marker is mounted on a flexible support layer, the flexible support
layer being secured to the skin surface covering the pelvic bone by
an adhesive.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] The present application is a Continuation of U.S. patent
application Ser. No. 11/878,021 filed Jul. 20, 2007, which claims
priority on U.S. Provisional Patent Application No. 60/832,151
filed on Jul. 21, 2006, the contents of which are incorporated
herein by reference.
TECHNICAL FIELD
[0002] The present invention relates to the field of
computer-assisted medical procedures, and more specifically, to
bone tracking and positioning in computer-assisted surgery (CAS)
systems.
BACKGROUND
[0003] Computer-assisted surgery (CAS) makes use of references
fixed to the patient using pins inserted into the bones of the
limbs or the pelvis. These pins, inserted into the bones before or
during the surgery, are of different diameter sizes and can cause
pain after the surgery. They are an extra step to the surgery,
exclusively because of the navigation system. Also, the insertions
of the pins into the bone may cause weaknesses of the bone that can
then more easily be fractured. Infections may also occur as for any
entry point at surgery.
[0004] Furthermore, the length of the pins is sometimes obtrusive
to the surgeon who may cut them to a length better adapted to his
movement during the surgery. The cut is also perceived as an extra
annoying step; its end may be sharp and hazardous to the personnel
working around the surgery table.
[0005] The pins are time-consuming and invasive. Therefore, there
is a need for an improvement in this area.
SUMMARY
[0006] In accordance with a first aspect of the present invention,
there is provided a method for determining at least orientation of
a pelvic bone in space and for tracking movement of the pelvic bone
using a computer assisted surgery (CAS) system, the method
comprising: removably attaching, in a non-invasive manner, at least
one reference marker to a skin surface covering said pelvic bone,
the reference marker being in communication with the CAS system;
registering at least orientation readings of said reference marker
with respect to a fixed reference in a reference coordinate system;
determining at least an orientation of said pelvic bone in the
reference coordinate system using said at least orientation
readings of said reference marker; and repeating the steps of
registering and determining to update said at least orientation
readings while tracking the pelvic bone in space.
[0007] In accordance with a second aspect of the present invention,
there is provided a system for determining at least an orientation
of a pelvic bone in space and tracking movement of the pelvic bone
using a computer assisted surgery (CAS) system, the system
comprising: at least one reference marker removably and
non-invasively attachable to a skin surface covering the pelvic
bone, said reference marker being in communication with the CAS
system; a fixed reference positioned in a reference coordinate
system and used to identify at least an orientation of said
reference marker in said reference coordinate system; and the
computer assisted surgery (CAS) system including: a sensing device
adapted to register at least orientation readings of said reference
marker in the reference coordinate system; and a processing unit
receiving said orientation readings from the sensing device and
being operable to determine and determining at least the
orientation of said bone.
[0008] In accordance with another aspect of the present invention,
there is provided a device for use with a computer assisted surgery
(CAS) system to determine at least orientation of pelvic bone in a
reference coordinate system and to track movement of the pelvic
bone, the device comprising at least one reference marker removably
and non-invasively attachable to a skin surface covering a pelvic
bone, the reference marker being in communication with the CAS
system such that the reference marker is detected and tracked in
said reference coordinate system by the CAS system with respect to
a fixed reference, said reference marker being adapted to provide
at least orientation readings thereof to the CAS system such as to
determine at least orientation of the pelvic bone in the reference
coordinate system and permit the CAS system to track movement of
the pelvic bone.
[0009] In this specification, the term "reference marker" is
intended to mean an active or passive marker, such as an emitter or
a reflector. The term "fixed reference" may also refer to any
active or passive device, with a known position in the reference
coordinate system.
BRIEF DESCRIPTION OF THE DRAWINGS
[0010] Further features and advantages of the present invention
will become apparent from the following detailed description, taken
in combination with the appended drawings, in which:
[0011] FIG. 1 is a front view of a pelvic bone with three base
units non-invasively attached on the skin surface;
[0012] FIG. 2 is a cross-sectional view of an elongated bone, such
as a femur, with three base units attached on the skin surface;
[0013] FIG. 3 is a front view of an elongated bone, such as a
femur, with multiple pairs of base units provided thereon;
[0014] FIG. 4 is a cross-sectional view of an elongated bone, such
as a femur, with a plurality of reference markers around the
bone;
[0015] FIG. 5 is a cross-sectional view of an elongated bone, such
as a femur, with a single pair of reference markers around the
bone;
[0016] FIG. 6 is an illustration showing a piece of fabric with
reference markers thereon attached to a leg;
[0017] FIG. 7 is a block diagram of an embodiment of a system of
the present invention used with a set of base units; and
[0018] FIG. 8 is a block diagram of an embodiment of a system of
the present invention used with a fabric having reference markers
attached thereto.
[0019] It will be noted that throughout the appended drawings, like
features are identified by like reference numerals.
DETAILED DESCRIPTION
[0020] FIG. 1 illustrates a pelvic bone 10 covered by the skin 12.
Three base units 14 are disposed on the pelvis 10 in a non-invasive
manner, either being attached directly to the skin 12, wherein the
base units 14 may be non-invasively attached for example using a
medical adhesive, i.e. non-toxic for the patient. Alternately, the
base units 14 can be provided on a piece of fabric, disposed
directly on the skin 12, that is worn by the patient during the
surgery. For example, this piece of fabric may include a pair of
snug-fitting shorts, corset or underwear (undergarment) having the
base units 14 attached thereto, which is worn by the patient.
[0021] One base unit 14 is attached to each crest of the hip
(anterior superior iliac spines), and a third base unit is attached
to the pubis area (pubic symphysis) of the pelvis. These locations
on the pelvis are chosen for having minimum distance between the
out-skin 12 and the bone 10. The base units 14 may be positioned at
other locations on the pelvic bone, without being restricted to
these locations in particular.
[0022] Reference markers 16 are present in/on each base unit. These
reference markers 16 may be active or passive, optical, RF,
(electro-)magnetic, or other. In FIG. 1, optical reflective
reference markers are illustrated. These three points define the
pelvic coordinate system. The position sensing system used with the
CAS system will register the position and orientation in space of
the pelvic bone with respect to either pre-operative images of the
patient, such as CT-scans, fluoroscopy, x-rays, etc, or with
respect to any type of intra-operative reconstruction of the bones
illustrated on an interactive display device. A fixed reference
present in the coordinate system and having a known position is
used to position and orient the pelvic bone in space.
[0023] In one embodiment of the present invention, the distance of
each base unit 14 on the out-skin 12 to the bone 10 is measured
using an ultrasound probe that is applied to each base unit 14. The
ultrasound, which is a transducer, emits an ultrasound wave and
measures the time it takes for the wave to echo off of a hard
surface (such as bone) and return to the transducer face. Using the
known speed of the ultrasound wave, the time measurement is
translated into a distance measurement between the base unit and
the bone located below the surface of the skin. In another
embodiment, an ultrasound device is integrated into each base unit
14. The measurement is done by either triggering it manually, or
automatically. In one embodiment, the measurement is repeated at
regular intervals. The measurements are constantly being
transferred to the CAS and the position and orientation of the bone
10 in space is updated. The measurement of the distance from the
base unit to the bone may also be done using alternative imaging
means, such as fluoroscopy. A metal reference is positioned on the
skin surface and used with a fluoroscopy system to identify the
bone surface. It is possible to make the measurement from the metal
reference to the bone surface on the fluoroscopic image
[0024] Once the distance between the base unit 14 and the bone 10
is known, an estimation of the possible displacement of the base
unit 14 on the outer-skin relative to the bone 10 can be done and
the bone can then be registered to the reference system. In the
case of the integrated ultrasound device within each base unit 14,
it becomes possible to measure in real-time variations in distance
between the base units 14 and the bone 10 during the surgery.
[0025] FIG. 2 is a cross-sectional view of a bone 18, such as a
femur, a tibia, or any other bone having an elongated form. The
base units 14 are positioned around the bone 18 on the out-skin 12.
Similarly to the case of the pelvis 10, the base units 14 may be
glued onto the skin 12 covering the bone 18, such as using an
adhesive tape or adhesive-backed fabric 23 or best 21 as described
further below, or a piece of fabric having the base units 14
attached thereto is placed on the body in a snug-fitting manner.
For a limb, a sleeve, sock, or belt may be used. The base units 14,
each having reference markers 16 are therefore distributed around
the bone. If the reference markers 16 are of the optical type, than
only the reference markers 16 in the line-of-sight of the position
sensing system will be registered. In the case of a limb, this may
mean that only half of the reference markers are visible. The other
half can be extrapolated using the readings obtained from the
visible markers. For other types of reference markers, such as RF
emitters, all reference markers on the bone will generate a reading
in order to register the position and orientation of the bone in
space.
[0026] When tracking the orientation and position of an elongated
bone, the problems encountered due to cutaneous movement can be
resolved by placing a single reference marker directly on the bone
at the beginning of the surgery. If that reference marker is an
ultrasound, the sound emitted by the reference marker can be
captured by the base units on the skin. Therefore, the invasive
pins are replaced by an ultrasound link, and the only invasive part
is the incision that would have been made in any case.
[0027] FIG. 3 is a front view of the bone shown in cross-section in
FIG. 2. The base units 14, including the reference markers (not
shown), are placed on the out-skin 12 of the bone 18. The distance
between the bone 18 and the out-skin 12 is measured using
ultrasound. The possible variation of distance between the base and
the bone during the surgery can be measured, either once at the
beginning or in real-time during the surgery.
[0028] The anatomical axis 20 of the bone 18 can also be
determined. The ultrasound probe is not necessary to determine the
anatomical axis 20. Pairs of reference markers on the out-skin 12
are positioned such that they are substantially facing each other,
as illustrated in FIG. 4. The mid-point between the measured
position of each marker in a pair will constitute a point on the
anatomical axis 20.
[0029] A minimum of one pair, i.e. two reference markers 16
face-to-face, is needed to determine the anatomical axis, as
illustrated in FIG. 5, if used in combination with a single
reference marker placed at a distal end of the bone. Alternatively,
two pairs of reference markers positioned face-to-face could also
be used to determine the anatomical axis 20 by providing at least
two points on the axis 20.
[0030] In one embodiment of the present invention, a belt having
ultrasound emitters thereon is attached around a leg of a patient,
as illustrated in FIG. 6. A fixed reference is provided in the
reference system, for example on a cutting block positioned on the
knee, or attached to the pelvis bone (not shown). The reference
markers on the belt 21 are referenced to the fixed reference, for
example by using a pointer and applying it to the reference markers
on the belt 21. This can also be done automatically without a
pointer. The ultrasound emitters measure the distance between the
skin and the bone, and the position and orientation of the bone in
space is determined.
[0031] In another embodiment, a belt 21 having reference markers
(not necessarily ultrasound emitters) is attached around a leg of
the patient. The reference markers are positioned such that there
are pairs of markers substantially facing each other. The
anatomical axis of the bone is determined by locating the middle
point between a pair of markers and forming a line from these
points along the bone. The position of the belt in space is
determined using the reference markers on the belt. At least one
pair of reference markers are needed to determine the anatomical
axis, if the reading from a single reference marker provides a
position from which more than one point on a line can be
determined.
[0032] FIG. 7 illustrates a system in accordance with one
embodiment of the present invention. A processing unit 30 and a
position sensing system 32 are coupled with a set of at least three
base units 14, each base unit 14 having a reference marker 16
thereon. The reference markers 16 on the base units 14 are used to
position the bone within a reference coordinate system. The
position sensing system, as is known in the art, will use either
active or passive devices as markers. The orientation and position
of the bone in space can be determined using the information
obtained from the reference markers 16 and using the known position
of the fixed reference 34 in the coordinate system. In addition, an
ultrasound device 36 is used to measure the distance between the
surface of the skin and the bone underneath the surface. By
updating this measurement, a more precise positioning of the bone
is obtained.
[0033] The base units may be provided with a non-toxic adhesive on
a surface and stuck directly onto the skin. Alternatively, a fabric
or tape strip mounted with the base units is adhered or otherwise
attached to the skin, as is described above. The ultrasound device
is either integrated into each base unit, or used externally to the
base units by applying it manually to each base unit, in the form
of a probe, for example.
[0034] An alternative embodiment of the system is illustrated in
FIG. 8. A processor 40 and a position sensing system 42 are coupled
to a fabric 23 which is removably and non-invasively attachable to
a bone and having a plurality of reference markers 16 distributed
thereon, and a fixed reference 44 positioned in the reference
coordinate system and used to identify a position and orientation
of the reference markers in the reference coordinate system.
[0035] The reference markers 16 on the fabric 23 may be distributed
on the fabric in a variety of ways. One such way is to have at
least two reference markers substantially facing each other when
the fabric is wrapped around a bone. One or more rows of pairs of
markers can be provided on the fabric, as is illustrated in FIG.
5.
[0036] The processor is preferably a general purpose computer
equipped with software that allows it to compute the location of a
bone surface from the information obtained by the reference markers
and ultrasound device. The results may be displayed on a screen or
monitor to be visualized by a user or operator. The information may
be used in conjunction with other known registration techniques to
assist in pre-operative or intra-operative procedures. The
components of the system may need to be calibrated using standard
procedures known to the person skilled in the art.
[0037] While illustrated in the block diagrams as groups of
discrete components communicating with each other via distinct data
signal connections, it will be understood by those skilled in the
art that the preferred embodiments are provided by a combination of
hardware and software components, with some components being
implemented by a given function or operation of a hardware or
software system, and many of the data paths illustrated being
implemented by data communication within a computer application or
operating system. The structure illustrated is thus provided for
efficiency of teaching the present preferred embodiment. The
embodiments of the invention described above are intended to be
exemplary only. The scope of the invention is therefore intended to
be limited solely by the scope of the appended claims.
* * * * *