Note: Descriptions are shown in the official language in which they were submitted.
f
CA 02444491 2002-11-18
Enalisch Translation of the International Patent Applicaiton NO.
PCT/CH00/00307 in the name of Stratec Medical AG
1$07/PCT
29.5.2000
Apparatus for positioning a surgical instrument
The invention relates to an apparatus for positioning and/or guiding surgical
instruments as claimed in the precharacterising part of claim 1.
1 o In surgical operations, a mechanical tool guidance by means of cutting
guide
heads or drill templates and saw guide slots is often indispensable for the
realisation of an exact osteotomy or resection of bone, as necessary, for
example, for the implantation of a joint endoprosthesis.
A device including a plurality of precision instruments for realising saw cuts
in
bone, particularly in the distal part of the femur adjoining the knee-joint,
is
known from US 4 524 766 PETERSEN. The different resection cuts to be made
on the femur and on the tibia are realised with this known device by means of
different precision instruments that are sequentially attached to the femur or
to
2 0 the tibia. As it is necessary to fix these precision instruments on one of
the
bones, to realise the planned saw cut, and to remove the precision instrument
again before fixing the next precision instrument on one of the bones for
executing a further saw cut, this leads to great number of operation steps,
2 5 The invention is intended to provide a remedy for this. It is accordingly
an object
of the invention to create an apparatus permitting to align and fix templates
for
tool guiding on a joint, in particular a knee joint, in a simple manner by
means of
precise drive elements. In order to confer increased stability, the invention
provides, if necessary, a rigid, mechanical connection between the two bones
30 adjoining the articulation. In addition, the invention is also intended to
be used
in combination with a surgical navigation system.
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According to the invention, this object is achieved by means of an apparatus
for
positioning and/or guiding surgical instruments which shows the features of
claim 1.
The apparatus according to the invention comprises essentially an external
fixator which consists of a rod-like, longitudinal carrier with a longitudinal
axis,
two jaws displaceable on said longitudinal carrier parallel to the
longitudinal
axis, and two transverse couplers arranged crosswise to the longitudinal axis
and fastenable to the longitudinal carrier by means of said jaws. Each jaw
1 o comprises a first joint by means of which the transverse coupler on one of
its
end portions is connected in such a way to the jaw that it is rotatable about
at
least two axes extending vertically to each other. On the other, free end
portion
of the transverse coupler, fasteners, in particular bone fixation devices, may
be
attached. By means of these fasteners provided on the transverse couplers, the
external fixator may, on the one hand, be fastened to one or both long bones
adjoining the articulation or, on the other, to a frame. Furthermore, the
apparatus comprises a slide member which may be mounted on the longitudinal
carrier, preferably between the jaws, in such a way as to be axially
displaceable
along the longitudinal axis and lockable in any desired position, a positioner
or
2o guide for positioning or guiding surgical instruments or tools being
attachable to
said slide member. The transverse couplers comprise at least one second joint,
equally rotatable about at least two axes, which makes the longitudinal
carrier
more freely movable and/or adjustable with respect to its fixation points,
which
are predefined by the fasteners.
An external fixation device including a longitudinal carrier telescopable on
both
sides and two jaws arranged between the longitudinal carrier and the bone
fixation devices is known from WO 99/59489 MARTINELLI and WO 99/59490
MARTINELLI. By means of the jaws, the bone fixation devices, particularly the
r o bone screws, may be pivoted about three axes relative to the longitudinal
carrier and may be attached thereto. For the positioning of surgical
instruments
or tools, however, the arrangement of only one joint between the bone fixation
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device and the longitudinal carrier will not provide sufficient degrees of
freedom
for the positioner which is equally connectible with the longitudinal carrier.
1n the preferred embodiment of the apparatus according to the invention, said
apparatus comprises a positioner which is telescopable perpendicularly to the
longitudinal axis and may be connected to the slide member so as to be
displaceable and fastenable on the longitudinal carrier parallel to the
longitudinal axis thereof. Preferably, the positioner consists of a transverse
rod
having a central axis, a free end portion for positioning and/or guiding
surgical
l0 instruments relative to a bone, and a fixed end portion which is attached
to the
slide member.
In another preferred embodiment, each transverse coupler comprises a
releasably lockable, third joint arranged between the front end portion and
the
rear end portion thereof, thus conferring to the longitudinal carrier
additional
degrees of freedom relative to its fixation points, which permits an exact
positioning and/or guiding of the positioner and/or guide.
According to another possible embodiment, the transverse couplers may be
a? o telescopable along telescopic axes extending perpendicularly to the
longitudinal
axis.
In another embodiment of the apparatus according to the invention, various
different tool-specific templates, in particular cutting heads permitting
osteotomy
2 5 or resection cuts to be realised by means of a surgical saw may be mounted
on
the positioner, so that for realising the resection cuts required, for
example, on
the femur and the tibia in the case of the implantation of an endoprosthesis
of
the knee-joint, two cutting heads may be used sequentially, one for guiding
the
cut to be made on the femur, the other for the cut realised on the tibia.
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Instead of mounting the templates sequentially, it is also possible, depending
on
the type of positioner or guide used, to have two or more templates mounted at
the same time.
In yet another embodiment of the apparatus according to the invention, the
slide
member comprises drive means for rotating the positioner about the central
axis. Thus it is possible, for example in the case of femoral and tibial
resections
required for the implantation of a knee endoprosthesis, to adjust the angle of
inclination of posteriorly and/or anteriorly skewed cut surfaces.
In a further embodiment of the apparatus according to the invention, a drive
element provided on the slide member serves for rotating the positioner about
an axis of rotation which extends perpendicularly to the longitudinal axis and
perpendicularly to the central axis, which makes it possible, for example, to
select adequate cut angles for the femoral and tibial resections that permit a
correction of varus/valgus deformities.
Preferably, the drive means as well as the drive element consist of set screws
by means of which the positioner is rotatable about two joints integrated into
the
2 o slide member.
In another embodiment of the apparatus according to the invention, the jaws
are respectively provided with a first joint which permits a rotation of the
transverse coupler about three axes extending vertically to one another. This
a 5 may be realised, for example, by the use of ball-and-socket joints. This
embodiment of the jaws allows the bone screws, if necessary, to be inserted
askew. By analogy to the first joints, also the second and third joints may
comprise several rotative degrees of freedom and may, for example, be shaped
in the form of ball-and-socket joints.
The transverse coupler and the joints provided thereon which assure a turnable
connection between the jaw and the transverse coupler and, depending on the
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embodiment of the transverse coupler, equally enable a turnable connection
between the transverse coupler and the bone fixation device, and which also
serve for realising an embodiment of the transverse coupler including two
articulated coupler portions, may be embodied in such a way that all joints
5 present on one transverse coupler may be releasably locked at the same time
using one single locking element. An embodiment of a stand of this type having
three hinges is disclosed in CH 608 874 MEIER.
The longitudinal carrier, in conjunction with the fixed fasteners, forms a
fixation
device for the two bones adjoining the articulation, making it possible to
lock the
joint and to fix the two bones in place relative to each other in such a way
as to
secure them against translational or rotational displacement.
Preferably, bone screws are used as bane fixation devices.
In another embodiment of the apparatus according to the invention, the
templates are provided with bores for receiving bone fixation devices, so that
first each template may itself be fixed on the corresponding bone. The
advantage thus achieved consists in the fact that once the template has been
'? 0 fixed the external fixator may be removed, so that the operating surgeon
is not
restricted in his movements by the longitudinal carrier and by the fasteners
when executing the resection cuts. In addition, in this case the cuts to be
performed may be executed at any desired joint position (extension, flexion)
offering optimum convenience for the surgeon.
~_ 5
In the case of the embodiments of the apparatus according to the invention
described hereinabove, the alignment of the templates is done manually.
In a further embodiment of the apparatus according to the invention, said
30 apparatus may be combined with a surgical navigation system and comprises
tracer elements to be attached to the bone fixation devices and to the
template.
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Preferably, each tracer element includes at least three non-linear,
electromagnetically or acoustically effective, active or passive markers.
Surgical navigation systems of this type including a computer and a position
detector for measuring the position of three-dimensionally movable, surgical
instruments and devices are disclosed, for example, in US 5 383 454
BUCHOLZ and in EP 0 359 773 SCHLONDORFF. Surgical navigation systems
are put on the market, for example, by the company MEDIVISION, Oberdorf,
Switzerland, under the trade name "Surgigate". Usually such systems equally
1 o comprise data memories for storing X-ray photographs or even entire
computer
tomograms (CTs) which are taken and stored in the data memory of the
computer prior to, or during surgery, either for diagnostic purposes or for
planning the intervention to be carried out. Frequently, optoelectronic
position
detectors are used which are capable of measuring the positions of optical
markers applied to said surgical instruments or devices within a three-
dimensional coordinate system in the operating theatre. Optoelectronic
position
detectors are commercially available, for example, under the trade name
Optotrak 3020 (manufactured by Northern Digital, Ontario, Canada).
0 Usually, LEDs (light emitting diodes) or IREDs (infrared light-emitting
diodes)
are used as optical markers.
Further advantageous embodiments of the invention will be characterised in the
dependent claims.
G S
The advantages achieved by the present invention consist essentially in the
fact
that the apparatus according to the invention makes it possible to reduce the
number of operation steps and thus to shorten the overall duration of the
surgical intervention. In particular, when utilised in prosthetic knee
surgery, the
30 invention offers the following advantages:
a) increased stability through the connection between the femur and the tibia;
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b) invasive operation steps such as the reaming of an intramedullary canal are
no longer necessary;
c) several templates may be aligned using only one instrument;
d) possibility of adjustment in view of a correction of varus/valgus
deformities;
e) possibility of adjustment for a posteriorly rising cut surface (posterior
slope).
If the apparatus according to the invention is used in combination with a
surgical navigation system, the following additional advantages may be
achieved:
l0
f) no alignment of the tibial axis on the second ray of the foot;
g) definition of the mechanical leg axes through digitization of the
anatomical
structures;
h) detection of the position of all templates; and
i) possibility of measuring the effects of different kinds of soft tissue
balancing.
If, in addition to this, preoperative X-ray photographs are made, the
following
further advantages may be achieved:
j) graphical determination of the tibial axis;
k) graphical determination of the centre of the hip (in the cases of a
destroyed
joint for which a measurement by pivoting is no longer practicable); and
I) evaluation of varus/valgus deformities (graphical assessment), possibility
of
planning a correction of abnormal leg positions.
2 '~
In the following, the invention and improvements of the invention will be
illustrated in greater detail with reference to the partially diagrammatic
representations of several embodiments.
In the drawings:
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Fig. 1 is a perspective view of one embodiment of the apparatus according to
the invention;
Fig. 2 is a partial view of an embodiment of the apparatus according to the
invention;
Fig. 3 is a perspective view of the embodiment of the apparatus according to
the invention shown in Fig. 2;
1 o Fig. 4 shows a detail of the embodiment of the apparatus according to the
invention shown in Figs. 2 and 3;
Fig. 5 is a view showing a transverse coupler as used in one embodiment of the
apparatus according to the invention; and
Fig. 6 is a perspective view of an embodiment of the apparatus according to
the
invention as used in combination with a surgical navigation system.
Fig. 1 shows an embodiment of the apparatus according to the invention which
2 o comprises a rod-like, longitudinal carrier 2 with a longitudinal axis 3, a
first end
portion 30, a second end portion 31, and a middle part 32, two transverse
couplers 5 extending perpendicularly to the longitudinal axis 3 and having
each
a rear end portion 34 and a front end portion 35, two jaws 4;14 displaceable
on
the longitudinal carrier 2 parallel to the central axis 3 and releasably
lockable
~~ 5 thereon for connecting the rear end portions 34 of the transverse
couplers 5 to
the longitudinal carrier 2, and a slide member 36 axially displaceable along
the
longitudinal axis 3 on the middle part 32 of the longitudinal carrier 2 and
lockable thereon. The transverse couplers 5 may be fixed on their front end
portions 35 to a bone, or to two bones, respectively, which adjoin an
o articulation, such as the femur 23 and the tibia 24 in the case of the knee-
joint,
or to a supporting frame, said supporting frame being attached either to the
operating table or to another supporting structure and/or appliance present in
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the operating theatre. Each jaw 4;14 comprises a releasably lockable, first
joint
8 by means of which the transverse coupler 5 connected to the respective jaw
4;14 is rotatable relative to the longitudinal carrier 2 about three axes
extending
perpendicularly to one another, one of said three axes being identical with
the
longitudinal axis 3. Each transverse coupler 5 further comprises a releasably
lockable, second joint 33 by means of which the bone fixation devices 17
shaped in the form of bone screws are hingedly connected to the front end
portions 35 of the transverse coupler 5. In this embodiment, the second joints
33 are realised in the form of ball-and-socket joints. The transverse couplers
5
1o are telescopable along an axis of telescopic extension 9;13 extending
perpendicularly to the longitudinal axis 3 and are releasably lockable at any
desired length by means of the clamping means 50. The first and second joints
8;33 are also releasably lockable by means of the clamping means 50.
Connected to the slide member 36, there is a positioner 6 which is provided
with
a transverse rod 41 having a central axis 11, a free end portion 42 for
positioning andlor guiding surgical instruments relative to a bone, and a
fixed
end portion 43, the transverse rod 41 being connected with its fixed end
portion
43 to the slide member 36. The transverse rod 41 is telescopable coaxiafly to
the central axis 11 and is also releasably lockable at any desired length by
means of a clamping means 50. Various different templates 7 used for guiding
surgical instruments and tools may be attached to the free end portion 42 of
the
positioner 6, a plurality of templates 7 being in certain cases attachable
simultaneously, depending on the design of said templates 7.
ae 5 The slide member 36 comprises a first screw-actuated appliance serving as
a
drive means 51 for rotating the transverse rod 41 about the central axis 11,
and
a second screw-actuated appliance serving as a drive element 10 for rotating
the transverse rod 41 about an axis of rotation 12 which extends
perpendicularly to the longitudinal axis 3 and perpendicularly to the central
axis
11.
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l~
The template 7 is provided with bores 16 for receiving bone screws, so that
the
template 7 may be screwed on the tibia 24 or on the femur 23.
Figs. 2, 3, and 4 show an embodiment of the apparatus according to the
invention including a longitudinal carrier 2 which comprises an external screw
thread 38 and several grooves 46 extending parallel to the longitudinal axis
3.
These grooves 46 engage with corresponding cams (not shown) formed in the
slide member 36 so as to secure said slide member 36 against rotation about
the longitudinal axis 3. The slide member 36 is provided with positioning
means
37 which are engageable and disengageable on the longitudinal carrier 2, so
that the slide member 36 is manually freely displaceable on the longitudinal
carrier 2 when the positioning means 37 are disengaged, and is displaceable on
the longitudinal carrier 2 in a controlled manner characterised by fine
adjustment and positive engagement when the positioning means 37 are
engaged. To this effect, the slide member 36 comprises a sleeve 39
displaceable on the longitudinal carrier 2 parallel to the longitudinal axis
3, the
positioning means 37, connected therewith and realised in the form of an
axially
separable, threaded sleeve, and operating levers 40 hingedly mounted in the
sleeve 39. By actuating the operating levers 40, the threaded sleeve may be
radially spread apart to such an extent that the internal screw thread of the
threaded sleeve is no longer in engagement with the external screw thread 38
of the longitudinal carrier 2. As the operating levers 40 are released again,
the
threaded sleeve, by the action of the resilient -means 47 which may, for
example, be realised in the form of a rubber ring, springs back radially to
its
a 5 initial position, so that the internal screw thread formed in the threaded
sleeve
re-engages with the external screw thread 38.
Fig. 5 shows a transverse coupler 5 of one embodiment of the apparatus
according to the invention. This transverse coupler 5 comprises a third joint
45
releasably lockable by means of a locking element 44. The transverse coupler 5
is hingedly connected to the jaw 4 by means of the first joint 8 realised in
the
form of a ball-and-socket joint, whereas the bone fixation device 17 is in
turn
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1l
hingedly connected to the transverse coupler 5 by means of the second joint 33
equally realised in the form of a ball-and-socket joint. The embodiment
involving
a simultaneous locking and/or releasing of all three joints 8;33;45 by means
of
the locking element 44 is described, for example, in CH 608 874 MEIER.
Fig. 6 shows the preferred embodiment of the apparatus according to the
invention in combination with a surgical navigation system. The surgical
navigation system comprises an integrated computer 15 including a data
memory 52, a keyboard 53, and a display screen 25 as well as a position
1 o detector 26 including three sensors 54. By means of the position detector
26,
the positions of the markers 19 are measured, so that it is possible, using
the
computer 15, to determine with respect to a space-based coordinate system 22
the position and orientation of a pointer 20, the bone fixation devices 17,
and
the template 7, in particular the cutting edge 21.
The utilisation of the apparatus according to the invention in combination
with a
surgical navigation system in order to realise, for example, the resection
cuts
required for the implantation of an endoprosthesis of the knee-joint includes
the
following steps:
- fixing one of the bone fixation devices 17 realised in the form of bone
screws
on the femur 23 and on the tibia 24, respectively;
- attaching a tracer element provided with three non-linear markers 19 on each
a 5 of the bone fixation devices 17;
- scanning the anatomy, in particular of the femoral condyles 23 and of the
facet
of the tibia by means of the pointer 20 and storing the scanned surfaces in
the
data memory 52 of the computer 15;
- planning the resection cuts to be made on the femur 23 and the tibia 24 by
means of the computer 15, the resection cuts being marked on the stored
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1. 2
surfaces as displayed on the display screen 25 and their position and
orientation being calculated within the space-based coordinate system 22;
- attaching the external fixator on the bone fixation devices 17 and mounting
the
positioner 6 equipped with the adequate templates) 7;
- computer-aided adjustment of the positioner 6 equipped with the templates)
7. The computer-aided adjustment is done by comparing the actual position of
the template 7 as measured by the position detector 26 with the position and
orientation in the space-based coordinate system as planned on the computer
15; and
- executing the resection cuts using the adequate surgical tool.
