Note: Descriptions are shown in the official language in which they were submitted.
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UNIVERSAL POSITIONING BLOCK ASSEMBLY
TECHNICAL FIELD
[0001] The present invention relates generally to a surgical tool for use
in bone surgery, and particularly to a multiple degree-of-freedom positioning
block assembly for joint replacement surgery. More specifically, the present
invention is directed to a universal positioning block assembly for use with a
computer assisted surgery (CAS) system in total knee replacement surgery.
More specifically, the present invention provides for a positioning block
assembly which when fixed to a bone element of a joint, will assist a surgeon
by providing the location of a surgical tool guide block, which surgical tool
guide block is used by the surgeon so as to perform the cutting of the bone
element.
BACKGROUND
[0002] Although emphasis is put on total joint replacement surgery, it is
to be understood that the following invention may also apply to other related
bone surgeries such as for example, unicondylar osteotomy,
unicompartmental joint replacement, etc.
[0003] Total jpint replacement surgery requires the removal of the joint
structure and the replacement thereof with an artificial joint. Generally
speaking, each of the two opposite bones leading into the joint structure need
to be completely cut at a point removed from the joint so as b allow the
removal of the joint. In order for such a surgery to be as successful as
possible, and to minimize any post-operative difficulties, a surgeon needs to
severe the bone as accurately as possible, taking into account the normal
variation in body physiology from one patient to the next.
[0004] Accuracy of cuts and drilled holes is important in joint
replacement surgery such as in knee arthroplasty, wherein installation of the
implants such that the kinematics of the natural knee are duplicated as much
as possible, is important to the success of the total knee replacement. To
achieve this, the use of CAS systems for orthopedic operations in general,
and for total knee replacement surgery in particular, is becoming increasingly
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more commonplace with advancements in CAS equipment that ensure
improved accuracy, near fail safe operation and increased ease of use.
[0005] Known optical, radio frequency and magnetic based CAS
systems employ passive and active trackable elements affixed to objects,
such as surgical tools and patient bone references, in order to permit the
determination of position and orientation of the objects in three-dimensional
space. Preoperatively taken images, computer generated models created
from preoperative patient scans or intra operative landmark digitization are
used to provide accurate patient anatomical information to which the rea{-time
position of the same anatomical elements can be registered or calibrated,
thereby permitting subsequent tracking of the anatomical elements and
display of these elements relative to the surgical tools used during the
surgery.
[0006] Total knee replacement surgery, for example, may require
several precise cuts to be made in the femur and tibia to completely remove
the knee joint, such that the implant may fit correctly and best replicates
the
geometry of a natural healthy knee. Alternatively a single cut to the femur
and
the tibia may do. To perform these steps, in both conventional and CAS total
knee replacement, it is well known to use a too{ or implement known as a
surgical tool guide block which provides a drill and/or cutting guide to
assist
the surgeon to perform the steps required to prepare the femur and tibia for
receiving the implant. Thus in traditional, known CAS surgery, the surgical
tool
guide block would be drilled to that part of the bone to be severed, while in
other bone CAS systems, the surgical tool guide block would also be screwed
into that part of the bone to be severed, and its position would be determined
through known computer assisted surgery.
[0007] Present CAS systems using tracked CAS positioning blocks
permit improved visualization of the surgical tool guide block relative to the
bone elements of the femur, requiring fewer fixed anatomical reference
surfaces. However, to best permit the fixation of the surgical tool guide
block
in a determined position, presently a surgeon must use a positioning block
which requires controllable adjustment of several degrees of freedom. While
certain flexibility is provided by total knee replacement positioning blocks
of
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the prior art, there nevertheless remains a need for a positioning block
permitting additional controllable flexibility of movement, and being adapted
for use with a CAS system. One such system is described in ORTHOsoft Inc.
U.S. patent application No. 10/357,493 entitled "UNIVERSAL POSITIONING
BLOCK", by Couture et al.
[0008] Once the positioning block has been positioned so as to have its
reference surface located in a position corresponding to the predetermined
emplacement of the bone cutting guide, Iocaing pegs are secured to the bone
so that the bone cutting guide may be properly placed once the positioning
block is removed. However, this two step process may lead to some
imprecision in the final cutting plane. Furthermore, the positioning block
being
transiatable along a proximal-distal axis corresponding to the longitudinal
axis
of a polyaxial screw positioned at the distal end of the bone, the proximal
translation is limited by the distance of the head of the polyaxial screw with
regards to the distal end of the bone.
SUMMARY
[0009] Accordingly, it is an object of the present invention to provide a
positioning block assembly for bone surgery allowing improved precision in
the positioning of a surgical tool guide block.
[0010] There is therefore provided, in accordance with the one aspect
of the present invention, a positioning block assembly for use in bone
surgery,
to be releasably affixed to a bone element to undergo surgery, the position
block assembly permitting up to six degrees-of-freedom movement relative to
the bone element to which it is to be releasably affixed. The positioning
block
assembly comprises: a main block element being removably attachable to the
bone element such that the main block element is rotatable in a flexion-
extension rotation plane and translatable along a medio-lateral axis relative
to
the bone element; a slider element being slidably engaged with the main block
element such that it is translatable along an antero-posterior axis and
rotatable in a varus-vaigus rotation plane relative to the block element and a
holder element being slidably engaged with the slider element such that it is
translatable relative to the slider element along a proximal-distal axis and
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rotatable in a medio-lateral rotation plane, the holder element being
configured and disposed to releasably engage a surgical tool guide element.
[0011] In accordance with another aspect of the present invention,
there is provided a computer assisted bone surgery system comprising: a
positioning block assembly being releasably affixed to a bone element; means
for determining the position and orientation of the positioning block relative
to
the bone element; a guide element being releasably engaged the positioning
block assembly; means for identifying a desired position of the positioning
block assembly relative to the bone element, such that the guide element is
located in a selected position relative to the bone element, such that a cut
can
be made in the bone element at the selected position and a display capable of
indicating when the desired location of the positioning block assembly is
reached.
[0012] In accordance with a further aspect of the present invention,
there is provided a method of installing a guide element on a bone element,
the guide element being releasably engaged to a positioni ng block assembly,
the method comprising: fastening the positioning block assembly to the bone
element; determining a desired position of the guide element engaged to the
positioning block assembly relative to the bone element; adjusting at least
one
of the position and orientation of the positioning block assembly until the
guide
element is in the desired position and securing the guide element on the bone
element at the predetermined location.
BRIEF DESCRIPTION OF THE FIGURES
[0013] Embodiments of the invention will now be described by way of
examples only with reference to the accompanying drawings, in which:
[0014] FIG. 1 is a perspective view of a universal positioning block
assembly operatively engaged with a surgical tool guide block, mounted to a
femur.
[0015] FIG. 2 is a top view of the universal positioning block assembly
of FIG. I.
[0016] FIG. 3 is a perspective view of a bone anchor mounted to a
femur.
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[0017] FIG. 4 is a perspective view of an altemate embodiment of the
bone anchor mounted to a femur.
[0018] FIG. 5 is a perspective view of a bone anchor assembled with a
main block and an antero-posterior slider, mounted to a femur.
[0019] FIG. 6 is a perspective view of an altemative embodiment of
FIG. 5.
[0020] FIG. 7 is a cross-sectional view of the main block.
[0021] FIG. 8 is a cross-sectional view of an alternate embodiment of
the main block.
[0022] FIG. 9 is a perspective view of a bone anchor assembled with a
main block, an antero-posterior slider, a guide block holder and a tracker
member, mounted to a femur.
[0023] FIG. 10 is a perspective view of the guide block holder.
[0024] FIG. 11 is a bottom view of the guide block holder of FIG. 10.
[0025] FIG. 12 is a perspective view of an alternate embodiment of a
guide block holder.
[0026] FIG. 13 is a bottom view of the guide block holder of FIG. 12.
[0027] FIG. 14 is a schematic flow chart of the method used to install
the universal positioning block of the present invention to a bone element.
DETAILED DESCRIPTION
[0028] Throughout this application, a particular embodiment of the
present invention will be referred to as a universal positioning block
assembly
or simply positioning block assembly, and is for use in bone surgery, such as
for example, total or partial joint replacement surgery of the knee, elbow,
hip,
shoulder or other joint, unicondylar osteotomy, unicompartmental knee
replacement, total knee arthroplasty, high tibial osteotomy, etc. Furthermore,
the positioning block assembly may be used as in conjunction with a computer
assisted surgical (CAS) system or may be used on its own. The positioning
block assembly comprises a guide block holder that is releasabily, operatively
engageable with a surgical tool guide block and is adapted to accurately
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position and align the surgical tool guide block. The surgical tool guide
block is
adapted for guiding a surgical tool and it is to be understood that such a
surgical tool as defined herein includes all surgical instruments necessary
for
bone surgery and joint replacement surgery, for example those which can
remove bone from a bone element, such as drills, rasps and saws and that
such a surgical tool guide block is similarly adapted for any surgical
instrument necessary for joint replacement surgery, for example those which
can remove bone from a bone element. It may be further understood that the
surgical tool guide block may also be a surgical device.
[0029] The universal positioning block assembly may be trackable by a
computer assisted surgical (CAS) system which provides means for
determining the position, orientation and movement of the positioning block
assembly in a three dimensional space, and permits the positioning block
assembly to be visualized, for example using a display, relative to the
patient
anatomy. The CAS system further provides means for determining a desired
position of the positioning block assembly relative to a bone element, whether
from a real patient, a cadaver or a model. The CAS system further provides
means for indicating where to fasten the surgical tool guide block on such a
bone element such that it can be affixed into the desired position.
Additionally,
the present positioning block assembly may be used with both CT-based and
image-less CAS systems or fluoroscopic systems. The CAS system may, in
other words, use either computer generated anatomical models created from
pre-operatively taken scans, such as CT scans, or use intra-operatively
generated bone surface models created by digitizing a plurality of points and
anatomic landmarks on the surface of the bone element, to relate the position
of the positioning block assembly to the bone elements of the patient.
[0030] Referring to FIGS 1 and 2, the universal positioning block
assembly 100 comprises generally a main block 20, a guide block holder 40
for holding a surgical tool guide block 70 and a tracker member 50 connected
to the guide block holder 40. It is to be understood that the tracker member
50
may be omitted if the positioning block assembly 100 is not to be used with a
CAS system. Referring to Fig. 3, a bone anchor 10 is used to mount the
universal positioning block assembly 100 to a femur 4. The bone anchor 10
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may generally comprise opposed first 11 and second ends 13, a body 12
which may have a cross-shaped cross-section to prevent rotation about its
longitudinal axis and a head 14, which may be generally cylindrical in shape.
It
~i.
is to be understood that other body 12 cross-section geometries that prevent
rotation may also be used. The bone anchor 10 may be impact engaged into a
distal end of the femur 4, for example, in the intercondylar notch, between
the
two distal condyies 2 in such a way that the head 14 has a longitudinal axis
generally parallel to the medio-lateral axis and is generally perpendicular to
the flexion-extension rotation plane. In an alternative embodiment, the body
12 of the bone anchor 10 may be in the shape of a screw and would be
screwed into the femur 4. In an further alternative embodiment, shown in FIG.
4, a bone anchor 10' may generally comprise opposed first 11' and second
ends 13', a body 12' having a generally funnel or triangular shaped body 12'
and a head 14', which may be generally cylindrical in shape. The bone anchor
10' is attached to a distal end of the femur 4 over the intercondylar notch,
by
screwing a cortical screw 15' in each of the two distal condyles 2 in such a
way that the head 14' has a longitudinal axis generally parallel to the medio-
lateral axis and is generally perpendicular to the flexion-extension rotation
plane. It is further understood that additional configurations and
dispositions of
the bone anchor 10 may be contemplated to be within the ambit of the present
invention. In particular, as long as a bone anchor 10 is provided so that once
anchored into the, for example, head of the femur, a head 14 is disposed
generally parallel to the medio-lateral axis and is generally perpendicular to
the flexion-extension rotation plane.
[0031] Refening to Fig. 5, the main block 20 is shown as being
provided with an aperture 22, for receiving the head 14 of the bone anchor 10
and an aperture 26 for receiving the body 32 of an antero-posterior slider 30
therein. The main block 20 is engaged to the bone anchor 10 by sliding the
main block 20 onto the bone anchor 10 such that the head 14 of the bone
anchor 10 slides within its correspondingly sized and configured main block
aperture 22. Thus positioned, the main block 20 may be translated along the
medio-lateral axis and rotated in the flexion-extension rotation plane. A
medio-
lateral translation/flexion-extension angle friction locking screw 24 engages
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the head 14 of the bone anchor 10 to retain a selected position relative to
the
bone anchor 10.
[0032] The antero-posterior slider 30 may generally comprise opposed
first 31 and second ends 33, the body 32, which may be generally cylindrical
in shape and has a longitudinal axis that generally corresponds to the antero-
posterior axis and is generally perpendicular to the varus-valgus rotation
plane, and a head 34, which may be generally cylindrical in shape. The
antero-posterior slider 30 is engaged to the main block 20 by sliding the body
32 of the antero-posterior slider 30 within a correspondingly sized and
configured main block aperture 26. Thus positioned, the antero-posterior
slider 30 may be translated along the anterior-posterior axis and rotated in
the
varus-vaigus plane. An antero-posterior translation/varus-vaigus angle
friction
locking screw 28 engages the body 32 of the antero-posterior slider 30 to
retain a selected position relative to the main block 20. In an alternative
embodiment, shown in FIG. 6, the antero-posterior slider head 34 has a
flattened top part 36 or may have a flattened lateral side.
[0033] In FIG. 7, there is shown a cross-section of the main block 20
that illustrates the medio-Iateral translation/flexion-extension angle
friction
locking screw 24 engaging the head 14 of the bone anchor 10 to retain a
selected position relative to the bone anchor 10. In an altemate embodiment
shown in FIG. 8, the friction locking screw 24 may be replaced by an endless
screw 24', which engages a bone anchor head 14' having a series of
indentations 16' which are reciprocal to the threads of the medio-lateral
translation/flexion-extension angle endless screw 24'. Similarly, the anterior-
posterior translation/varus-valgus angle friction locking screw 28 may be
replaced by an endless screw, which engages a antero-posterior sliderbody
having a series of indentations which are reciprocal to the threads of the
anterior-posterior translation/varus-valgus angle endless screw.
[0034] Referring to FIG. 9, the guide block holder 40, having opposed
proximal 41 and distal 43 ends, is engaged to the antero-posterior slider 30
by
sliding the guide block holder 40 onto the antero-posterior slider 30 such
that
the head 34 of the antero-posterior slider 30 slides within a corresponding
shaped and configured aperture 42 in the guide block holder 40. Thus
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positioned, the guide block holder 40 may be translated generally in the
direction of the proximal-distal axis, without being interfered with by the
distal
end of the femur 4, and rotated in the medio-lateral rotation plane. A
proximal-
distal translatiorymedio-lateral rotation friction locking screw 44 engages
the
head 34 of the antero-posterior slider 30 to retain a selected position
relative
to the antero-posterior slider 30. In an alternative embodiment (not shown),
in
a similar fashion as for the previous friction locking screws 24 and 28,
friction
locking screw 44 may be replaced by an endless screw, which engages an
antero-posterior slider head having a series of indentations which are
reciprocal to the threads of the proximaWistal tra nsiation/med io- lateral
rotation endless screw. Referring back to FIG. 6, it is to be understood that
if
this alternative embodiment of the antero-posterior slider 30 is used, the
guide
block holder 40 may not be rotated in the medio-lateral rotation plane, thus
providing one less degree-of-freedom.
[0035] As shown in FIGS 1 and 2, a conventional surgical tool guide
block 70 having, for example, a number of drill guide holes 74 and a cutting
guide slot 72, may be releasably engaged directly to universal positioning
block assembly 100, via the guide block holder 40, which has a connector in
the form of lip component 46 at its proximal end 41, as best seen in FIGS 9,
and 11, that is sized and configured so that it may be inserted into a cutting
guide slot 72 of the surgical tool guide block 70 or alternatively into
another
recess. One or more cutting guide locking screws 48, having a first 45 and
second end 49, are provided to engage the surgical tool guide block 70, such
that it may be held firmly in between the lip component 46 and the first end
45
of the cutting guide locking screws 48. The lip component 46 is preferably of
a
thickness such that it may be inserted, for example, in a snugly fitting
relationship into any type of surgical tool guide block 70 cutting guide slot
72,
the cutting guide locking screws 48 bring operative in securing the surgical
tool guide block 70 to the guide block holder 40 regardless of the difference
between the thickness of the lip component 46 and the width of the cutting
guide slot 72.
[0036] In an alternate embodiment, illustrated in FIGS 12 and 13, the
cutting guide holder lip component 46' is actuated, having a fixed first
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connector part 46a' and a displaceable second connector part 46b', which
may be displaced by rotating adjustment screw 47'. By rotating the adjustment
screw 47', the displaceable second connector part 46b' may be displaced so
as to become either in or out of horizontal alignment with the fixed first
connector part 46a'. Thus, to secure the surgical tool guide block 70 to the
guide block holder 40, the horizontally aligned fixed first connector part
46a'
and displaceable second connector part 46b' are inserted into the cutting
guide slot 72 and the adjustment screw 47' rotated so that the fixed first
connector part 46a' and the displaceable second connector part 46b' are
horizontally displaced with respect to one another and are each biased
against an opposite interior wall of the cutting guide slot 72.
[0037] Referring back to FIG. 9, the tracker member 50 comprises at
least three detectable elements 52, engaged to the tracker member 50 via
mounting posts 54. The detectable elements 52 may be, for example,
spherical passive markers locatable by a camera-based, optical tracking CAS
system. However, it is to be understood that active optical markers may
equivalently be used as the detectable elements and that CAS systems using
any other type of tracking elements, such as for example electromagnetically
and acoustically detectable elements, may also similarly be employed. The
tracker member 50 is connected, via the tracker stem 56, to distal end 43 of
the guide block holder 40 although it may be affixed elsewhere to guide block
holder 40. Thus, the guide block holder 40 being operatively engaged to the
surgical tool guide block 70, as shown in FIG. 1, the tracker member 50 tracks
the precise position of the cutting plane of the surgical tool guide block 70
by
tracking the position of the lip component 46.
[0038] Referring back to FIGS 1 and 2, showing the universal
positioning block assembly 100 mounted to the distal end of a femur 4 by the
bone anchor 10, and to FIG. 14 showing method steps involved with installing
the positioning block assembly 100 and positioning the surgical tool guide
block 70 on a femur 4. The degree of mobility of the positioning block
assembly 100 permits significant simplification of the surgical procedures
employed in certain surgeries, such as total knee replacement surgery. The
sequence of steps composing the method involved with installing the
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positioning block assembly 100 and positioning the surgical tool guide bbck
70 on a femur 4 is described in the sequence of blocks 202 to 208. Generally,
the first step, at block 202, comprises fastening the positioning block
assembly 100 to the femur 4. As shown in FIG. 3, this is preferably done using
the bone anchor 10, which is first aligned with the entrance point of the
mechanical axis at the distal end of the femur 4 and introduced therein. Then,
the main block 20, as best seen in FIG. 5, is slid unto the head 14 of the
bone
anchor 10 via main block aperture 22. Following which, the antero-posterior
slider 30, as best seen in FIG. 7, is slid into main block aperture 26.
Finally, as
best seen in FIG. 1, the guide block holder 40, with- a surgical tool guide
block
70 engaged thereto and with the tracker member 50 connected to it, is
engaged to the antero-posterior slider 30 by sliding the guide block holder 40
onto the antero-posterior slider 30 such that the head 34 of the antero-
posterior slider 30 slides within the corresponding aperture 42 in the guide
block holder 40.
[0039] The next step, at block 204, consist in determining a desired
position of the surgical tool guide block 70, either by the CAS system itself,
by
the surgeon using the CAS system as a guide or independently by the
surgeon, in order to determine what final position the universal positioning
block assembly 100 should be moved into. It is to be understood that if the
universal positioning block assembly 100 is to be used with a CAS system, a
tracker element has to have been previously attached to the femur 4 so that
the CAS system may determine the position of the universal positioning block
assembly 100 relative to the femur 4. This final positioning of the
positioning
block assembly 100 has for effect the positioning of the surgical tool guide
block 70 such that a drilled hole or a saw cut may be made in the femur 4 at a
predetermined location that is required for the installation of an implant.
[0040] The step described at block 206 comprises adjusting the
position and orientation of the universal positioning block assembly 100 until
the surgical tool guide block 70 is located in the desired position that was
previously determined at block 204. This may involve rotatably adjusting and
translating the positioning block assembly 100 relative to the femur 4, using
the CAS system, for example through a display generated by the CAS
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system, to aid in the correct orientation in each rotational axis of rotation
and
translation axis. Up to three rotational and three translational degrees of
freedom are thereby possible, and the entire positioning block assembly 100,
and thus surgical tool guide block 70, may be oriented in a desired plane, for
example parallel to the distal cut to be made in the femur 4. The three
possible rotations are in the flexion-extension plane, having for center of
rotation the head 14 of the bone anchor 10, in the varus-vaigus plane, having
for center of rotation the body 32 of the antero-posterior slider 30 and in
the
medio-lateral plane, having for center of rotation the head 34 of the antero-
posterior slider 30. As for the three possible translations, they are in the
medio-lateral axis, along the head 14 of the bone anchor 10, the anterior-
posterior axis, along the body 32 of the antero-posterior slider 30, and the
proximal-distal axis, along the head 34 aF the antero-posterior slider 30. As
seen previously, the surgical tool guide block 70 is engaged to the guide
block
holder 40 which in turn is engaged to the tracker member 50 via the mounting
posts 56. Thus, the position of the tracker member 50 is fixed relative to the
surgical tool guide block 70, which permits the exact placement of the
surgical
tool guide block 70 by rotatably adjusting and translating the positioning
block
assembly 100 relative to the femur 4 using the CAS system.
[0041] Once the desired position and orientation of the universal
positioning block assembly 100, and consequently of the positioning of the
surgical tool guide block 70, is achieved, the step of block 208 is performed.
This step comprises attaching the surgical tool guide block 70 to the femur 4
by drilling pin holes into the femur 4 using the necessary guide holes 74 in
the
surgical tool guide block 70, best seen in FIG. 2, and then inserting pins
through the guide holes 74 and into the femur 4, securing the surgical tool
guide block 70 to the femur 4. The entire positioning block assembly 100 may
then be removed, and the femur 4 cut may be made to resect the chosen
amount from the distal end of the femur 4.
[0042] The six degree-of-freedom adjustment that is possible by the
universal positioning block assembly 100, as well as its guide block holder 40
design, permits it to be universally used in total knee replacement surgery,
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regardless of the type of implant line being used and of the surgical steps to
be performed.
[0043] Although the universal positioning block assembly 100 has been
described above with emphasis on the preparation of a femur for receiving the
femoral portion of a knee replacement implant, the positioning block assembly
100 may also be used for the preparation of the tibia for the corresponding
tibial portion of a knee replacement implant. The steps required to prepare
the
tibia, include: defining the tibial mechanical axis; using the positioning
block
assembly 100 to determine a desired rotational and translational alignment of
a tibial proximal cutting guide and fastening it in place to the anterior
surface
of the proximal end of the tibia using the bone anchor 10; adjusting the
universal positioning assembly 100 to ensure a desired posterior slop and
level of tibial resection; inserting pins through the guide holes of the
tibial
cutting guide; removing the positionina assembly 100 and resecting the
chosen amount of tibial bone. The positioning assembly 100 may further still
be used for total replacement surgery of joints other than the knee, for
example elbow replacement surgery or other related bone surgeries such as
for example, unicondylar osteotomy, unicompartmental joint replacement, etc.
[0044] Although the present invention has been described by way of
particular embodiments and examples thereof, it should be noted that it will
be
apparent to persons skilled in the art that modifications may be applied to
the
present particular embodiment without departing from the scope of the
present invention.
