f Enalisch Translation of the International Patent Applicaiton NO.
PCT/CH00/00307 in the name of Stratec Medical AG
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.
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 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.
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 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.
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.
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;
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.
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:
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 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 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.
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 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 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 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.