Patent Description:
The present invention relates to a surgical tool and methodology for guiding surgical instruments, and more particularly, to a drilling platform tool that provides a well-defined drilling or cutting path.

Many surgeries require that the surgeon perform drilling and/or cutting through bone or other body parts. For example, some patients may have hearing loss in one or both ears that is too severe to be helped by hearing aids, and can benefit from a cochlear implant. To insert the cochlear implant, the surgeon typically has to perform surgical operations that require drilling into the middle ear.

A normal ear transmits sounds as shown in <FIG> through the outer ear <NUM> to the tympanic membrane (eardrum) <NUM>, which moves the bones of the middle ear <NUM> (malleus, incus, and stapes), which in turn vibrate the oval window and round window openings of the cochlea <NUM>. The cochlea <NUM> is a long narrow duct wound spirally about its axis for approximately two and a half turns. The cochlea <NUM> includes an upper channel known as the scala vestibuli and a lower channel known as the scala tympani, which are connected by the cochlear duct. The scala tympani forms an upright spiraling cone with a center called the modiolar where the spiral ganglion cells of the acoustic nerve <NUM> reside. In response to received sounds transmitted by the middle ear <NUM>, the fluid-filled cochlea <NUM> functions as a transducer to generate electric pulses that are transmitted to the cochlear nerve <NUM>, and ultimately to the brain.

Hearing is impaired when there are problems in the ability to transduce external sounds into meaningful action potentials along the neural substrate of the cochlea. In such cases a cochlear implant is an auditory prosthesis which uses an implanted stimulation electrode to bypass the acoustic transducing mechanism of the ear and instead stimulate auditory nerve tissue directly with small currents delivered by multiple electrode contacts distributed along the electrode.

<FIG> also shows some components of a typical cochlear implant system which includes an external microphone that provides an audio signal input to an external signal processing stage <NUM> where various signal processing schemes can be implemented. The processed signal is then converted into a digital data format, such as a sequence of data frames, for transmission into the implant stimulator <NUM>. Besides extracting the audio information, the implant stimulator <NUM> also performs additional signal processing such as error correction, pulse formation, etc., and produces a stimulation pattern (based on the extracted audio information) that is sent through connected wires <NUM> to an electrode array <NUM> inserted into the cochlea. Typically, this electrode array <NUM> includes multiple electrode contacts on its surface that provide selective stimulation of the cochlea <NUM>. Stimulation is either carried out against an external reference electrode contact (i.e., a remote ground contact) outside the cochlea or against another electrode contact of the array within the cochlea <NUM>.

The insertion of the electrode array <NUM> often includes making an incision behind the ear, and using a drill to then enter the middle ear. The electrode array <NUM> is placed through an opening created in the cochlea <NUM>, and the implant stimulator <NUM> is then placed into a pocket under the skin on the skull behind the ear.

Various prior art devices have been proposed that assist the surgeon in making such precise surgical drill holes or other cuts. <CIT> discloses various surgical guide tools that include a guide platform having legs of adjustable lengths that rest on a body part. However, the assembly and adjustment of the positioning of the legs on the body part can be time-consuming and expensive. To avoid disadvantages of having adjustable legs, <CIT>) proposes a positioning aid with legs that cannot be changed in length. The guide plate in <CIT> is manufactured for each patient according to produced pre-operative images, whereas the other components of the system may be reusable. In <CIT>, the calculated optimal drilling trajectory is enabled by providing a guide plate having a center and an axis perpendicular to the surface of the plate and through which a trajectory may be drilled off-center and under a certain angle to the axis. This may not be optimal, as the surgeon may thus have to move a drill oriented at an angle other than perpendicular from the surface of the plate. <CIT> discloses a catheter guiding device with a bolt including a shaft configured to be inserted within a hole drilled in a bone and a passageway extending longitudinally therethrough along a bolt axis and a guide member received within the passageway of the bolt and extending longitudinally along a guide axis. The guide member includes a guide channel extending therethrough along the guide axis, wherein, in a first configuration, the guide member is arrangeable to a desired position relative to the bolt to align the guide axis with a target area and, in a second configuration, the guide member is fixed in the desired position relative to the bolt such that the guide axis is at a desired angle relative to the bolt axis within a permitted range of angulations. <CIT> relates to a positioning aid for surgical procedures, comprising a support system and a guide. The support system consists of a support plate, which is provided with a recess, and supports. The support plate can be secured to a cranial bone via the supports over an operating field for the surgical procedure. The guide comprises a guide plate which can be connected to the support plate in a play-free manner and which comprises a guide opening. The guide opening is arranged and oriented in the guide plate, which consists of a blank, in an individualized manner according to coordinates ascertained in advance. The central longitudinal axis of the guide opening matches a trajectory for accessing the operating field for the surgical procedure when the support system and the guide are assembled and the support system is secured to the cranial bone.

In accordance with an embodiment of the invention, a surgical guide tool according to claim <NUM> and a method according to claim for are provided. A surgical guide tool disclosed herein includes a non patient-specific platform including one or more supports for attaching to a body part of a subject. A non patient-specific block has a top planar surface and a bottom planar surface, and includes a guide aperture extending from the top planar surface to the bottom planar surface for guiding a surgical instrument in making at least one of a cut and a drill hole. An intermediate module is removably positioned between the platform and the block. The intermediate module has patient-specific dimensions such that the guide aperture has a desired alignment relative to the body part when the surgical guide tool is attached to the body part of the patient and the intermediate module is positioned between the platform and the block.

In accordance with related guide tools disclosed herein, the guide aperture may be a borehole defining an axis through the block. The axis may be perpendicular to both the top and bottom planar surfaces of the block.

In accordance with further related guide tools disclosed herein, the intermediate module may have a top module surface for positioning adjacent the block, and a bottom module surface for positioning adjacent the platform, the intermediate module having a varying height between the top surface and the bottom surface such that the guide aperture has a desired alignment relative to the body part when the surgical guide tool is attached to the body part of the patient. The top module surface and the bottom module surface may be planar and non-parallel.

In accordance with still further related guide tools disclosed herein, the supports of the platform may include legs that are fixed and immobile relative to the platform, the legs having non-adjustable dimensions. Both the intermediate module and the platform may be configured so that they do not block the aperture in the block when the intermediate module is positioned between the platform and the block. The block may be braced to the platform such that there is no freedom of play in one or more dimensions. The surgical tool may further include a clamp, for clamping the platform, block and/or intermediate module to each other. The platform, block and/or intermediate module may include one of an elevation, a recess, a pin, and/or a pin receptacle, to ensure proper positioning relative to each other.

Further disclosed herein is a method including providing a non patient-specific platform for attaching to a body part of a subject. A non patient-specific block is provided having a top planar surface and a bottom planar surface, the block including a guide aperture extending from the top planar surface to the bottom planar surface for guiding a surgical instrument. Electronic image data is obtained of an anatomical area of the subject. A trajectory for at least one of a cut and a drill hole is determined based, at least in part, on the electronic image data. An intermediate module is provided that is configured to be removably positioned between the platform and the block, the intermediate module having patient-specific dimensions such that the guide aperture in the block is configured to guide the surgical instrument in making the at least one of a cut and drill hole along the determined trajectory when the platform is attached to the body part of the patient and the intermediate module is sandwiched between the platform and the block.

In accordance with related methods described herein, obtaining the electronic image data may include one of pre-operatively, intraoperatively, optically, an MRI, a CT and a spiral CT, or combinations thereof.

In accordance with further related methods described herein, the method may further include mounting the platform on the body part, with the intermediate module sandwiched between the platform and the block, and using the guide aperture to make at least one of a cut and a drill hole into the body part. The body part may be the skull, wherein the platform is mounted on the skull, and wherein the guide aperture is used in guiding a surgical instrument to drill a hole through the skull into the middle ear, the method further including inserting an electrode array of a cochlear implant into the hole.

In accordance with still further related methods described herein, the intermediate module may have a top module surface for positioning adjacent the block, and a bottom module surface for positioning adjacent the platform, the intermediate module having a varying height between the top surface and the bottom surface such that the guide aperture has the desired alignment relative to the body part when the surgical guide tool is attached to the body part of the patient and the intermediate module is positioned between the platform and the block. The top module surface and the bottom module surface may be planar and non-parallel.

In accordance with yet further related methods described herein, the guide aperture may be a borehole defining an axis through the block. The axis may be perpendicular to both the top and bottom planar surfaces of the block. The platform may include legs for attaching to the body part, the legs being fixed and immobile relative to the platform, the legs having fixed dimensions that cannot be varied. Both the intermediate module and the platform do not block the aperture in the block when the intermediate module is sandwiched between the platform and the block. Providing the intermediate module may include cutting, drilling, milling, and/or laser sintering a blank of material.

In accordance with the invention, a surgical guide tool includes a non patient-specific platform including one or more supports for attaching to a body part of a subject. A patient-specific block has a top surface and a bottom surface, the block including a guide aperture extending from the top surface to the bottom surface for guiding a surgical instrument in a making at least one of a cut and a drill hole. The block has patient-specific dimensions such that the guide aperture has a desired alignment relative to the body part when the surgical guide tool is attached to the body part of the patient and the block is braced against the platform. The top surface and the bottom surface of the block are planar and non-parallel. The guide aperture is a borehole defining an axis through the block, and the axis is perpendicular to the top surface of the block.

In accordance with related embodiments, supports of the platform include non patient-specific legs that are fixed and immobile relative to the platform, the legs having non-adjustable dimensions. When the block is braced to the platform there may be no freedom of play in one or more dimensions. The surgical tool may include a clamp for clamping the block to the platform. The block and/or platform may include an elevation, a recess, a pin, and/or a pin receptacle, to ensure proper positioning of the block relative to the platform.

In accordance with the invention, a method includes providing a non patient-specific platform for attaching to a body part of a subject. Electronic image data is obtained of an anatomical area of the subject. A trajectory for making at least one of a cut and a drill hole is determined based, at least in part, on the electronic image data. A patient-specific block is provided having a top surface and a bottom surface, the block including a guide aperture extending from the top surface to the bottom surface for guiding a surgical instrument in making at least one of a cut and a drill hole. The top surface and the bottom surface of the block are planar and non-parallel. The guide aperture is a borehole defining an axis through the block, and the axis is perpendicular to the top surface of the block.

In accordance with related embodiments of the invention, obtaining the electronic image data may include one of pre-operatively, intraoperatively, optically, an MRI, a CT and a spiral CT, or combinations thereof.

A method is described hereafter, which may further include mounting the platform on the body part, with the block braced against the platform. The guide aperture is used to make at least one of a cut and a drill hole into the body part. The body part may be the skull, wherein the platform is mounted on the skull, and wherein the guide aperture is used in guiding a surgical instrument to drill a hole through the skull into the middle ear, the method further including inserting an electrode array of a cochlear implant into the hole.

In accordance with still further embodiments of the invention, the block may be braced to the platform such that there is no freedom of play in one or more dimensions. The guide aperture may be a bore hole defining an axis through the block. There may be a non patient-specific, predefined arrangement between the axis and the top surface of the block. Illustratively, there may be a non patient-specific, predefined angle between the axis of the guide aperture and the top surface of the block, wherein the height between the top surface and the bottom surface of the block varies such that the angle is at the desired alignment relative to the body part when the surgical guide tool is attached to the body part of the patient and the block is braced against the platform. The axis may be perpendicular to the top surface of the block. The platform may include non patient-specific legs for attaching to the body part, the legs being fixed and immobile relative to the platform, the legs having fixed dimensions that cannot be varied. Providing the block may include cutting, drilling, milling, and/or laser sintering a blank of material. The block may be clamped to the platform. The block and/or platform may include one of an elevation, a recess, a pin, and a pin receptacle, or combinations thereof, to ensure proper positioning of the block relative to the platform.

In accordance with embodiments related to the above-described embodiments, the surgical guide tool may include a guiding element that may be attached or integral with the block. The guiding element may have guiding walls, with, for example, rollers operatively coupled to the guiding walls. When making the drill hole or cut, the surgical instrument contacts the rollers to ensure that the surgical instrument moves through the guide aperture without tilt.

In illustrative embodiments of the invention, a surgical guide tool and methodology for guiding a surgical instrument in making a cut and/or drill holes in a body of a subject is provided. In an exemplary embodiment, the surgical guide tool may be used when drilling into the skull of a patient, and more particularly, to drill a hole in the middle ear facilitating insertion of an electrode array of a cochlear implant. Note however, that the provided surgical tool and methodology is not limited to the skull, and may also be applied to other parts of the body. Details hereto are described below.

<FIG> shows a composite view of a surgical guide tool <NUM>, in accordance with an embodiment of the invention. <FIG> shows an exploded view of the surgical guide tool <NUM> depicted in <FIG>.

The surgical guide tool <NUM> includes a non patient-specific platform <NUM> having a plate <NUM>. One or more supports <NUM> may be fixed to the plate <NUM>, the support(s) <NUM> for attaching to a body part <NUM> of a subject. The support(s) <NUM> may include, without limitation, one or more legs <NUM>. The legs <NUM> may have fixed dimensions and shape that cannot be varied. The leg <NUM> may be integral with the plate <NUM>, or attached at one end to the plate <NUM> with, for example, screws or welds, such that they are fixed and immobile relative to the platform <NUM>. The other end of each leg <NUM> serves to rest on the body part, and may include various attachment mechanisms <NUM> known in the art, such as screws or pins, for fixing the legs, and hence the platform <NUM>, to the body part <NUM>.

<FIG> shows a top view of the platform <NUM>, and <FIG> shows a side view of the platform <NUM>, in accordance with an embodiment of the invention. The platform <NUM> may include an opening <NUM>. The opening <NUM> is a cavity which leads from one side to the other of the plate <NUM> and may be surrounded in whole or in part by plate <NUM>. For example, the plate <NUM> may have, without limitation, the shape of an L as shown in <FIG>. In other embodiments, the plate <NUM> may be circular or rectangular in form, or have other forms which support the surgical process described further below. Plate <NUM> has a top surface <NUM>, upon which, for example, a block may sit on, described in more detail below.

Referring back to <FIG> and <FIG>, the surgical guide tool <NUM> further includes a non patient-specific block <NUM> having a top planar surface <NUM> and a bottom planar surface <NUM>. The bottom surface <NUM> of the block <NUM> is closer to the body part <NUM> when the surgical guide tool <NUM> is fixed to the body part <NUM>, as shown in <FIG> and <FIG>. The block <NUM> includes a guide aperture <NUM> extending from the top planar surface <NUM> to the bottom planar surface <NUM> for guiding a surgical instrument in making at least one of a cut and a drill hole.

In illustrative embodiments of the invention, the block <NUM> may serve as a drilling table, with the guide aperture <NUM> being a borehole <NUM> that defines an axis <NUM> through the block <NUM>. There may be a non patient-specific, predefined arrangement between the axis <NUM> and the top surface <NUM> of the block <NUM>. For example, and without limitation, the axis <NUM> may be perpendicular to both the top and bottom planar surfaces <NUM>, <NUM> of the block <NUM>. This may be advantageous for a surgeon, as it may often be easier to keep and move a drill oriented perpendicular to a surface than under other angles. However, the axis <NUM> may also be non-perpendicular to the top and bottom planar surfaces <NUM>, <NUM> of the block <NUM>. In contrast to conventional drilling tables, such as, for example, the one described in <CIT>, not only the non patient-specific platform <NUM>, but also the non patient-specific block <NUM> may be manufactured independent of the body part <NUM> (e.g. the patient's skull) and may be reusable for many patients.

As shown in <FIG> and <FIG>, the surgical guide tool <NUM> also includes an intermediate module <NUM> removably sandwiched between the platform <NUM> and the block <NUM>. The intermediate module <NUM> has patient-specific dimensions, customized to the patient, such that the guide aperture <NUM> has a desired alignment relative to the body part <NUM> when the surgical guide tool <NUM> is attached to the body part <NUM> of the patient and the intermediate module <NUM> is positioned between the platform <NUM> and the block <NUM>. Thus, regardless of the alignment of the guide aperture <NUM> in the reusable, non patient-specific block <NUM>, the patient-specific intermediate module <NUM> will ensure that the guide aperture <NUM> has the proper alignment to make the cut or drill hole.

<FIG> shows a top view of the intermediate module <NUM>, while <FIG> shows a side view of the intermediate module <NUM>, in accordance with an embodiment of the invention. The intermediate module <NUM> includes a top module surface <NUM> for positioning proximate and/or adjacent the block <NUM>, and a bottom module surface <NUM> for positioning proximate and/or adjacent the platform <NUM>. In various embodiments, the top module surface <NUM> and the bottom module surface <NUM> are planar and non-parallel. The height between the top module surface <NUM> and the bottom module surface <NUM> may vary over the area of the intermediate module <NUM>, such that the guide aperture <NUM> has a desired alignment relative to the body part <NUM> when the surgical guide tool <NUM> is attached to the body part <NUM> of the patient. For example, if the intermediate module <NUM> is L formed, at least some of the heights <NUM>, <NUM>, and <NUM> may be different (see <FIG>).

From a top view, intermediate module <NUM> may have a different form as the plate <NUM>, or they may have similar forms, as exemplarily shown in <FIG>, top view. In any case, the intermediate module <NUM> has an opening <NUM> which borders should not cover opening <NUM> of plate <NUM> when the platform <NUM> and intermediate module <NUM> are adjacent each other.

While the basic form of plate <NUM> and intermediate module <NUM> may be similar, their lateral dimension may vary. This is exemplarily indicated by lengths x' of plate <NUM> (see <FIG>) and x" of intermediate module <NUM> (see <FIG>). x' may be substantially equal to x", however in various embodiments x" may also be larger than x' for reason outlined further below. Similarly, the lengths perpendicular to x' or x" may vary.

Intermediate module <NUM> may be manufactured interoperatively during a medical procedure as a disposable module, or may be manufactured preoperatively. As the dimensions of the intermediate module <NUM> are patient-specific, it is manufactured for each patient individually and may be used just once, whereupon it may be disposed. In contrast, the platform <NUM> and block <NUM> are non patient-specific, and may be used repeatedly with various patients.

<FIG> is a flowchart illustrating a methodology that includes manufacturing an intermediate module, in accordance with an embodiment of the invention, and further includes performing a medical procedure, which is not covered by the appended claims. The non patient-specific platform and block are provided, steps <NUM> and <NUM>. A surgeon may choose from a set of platforms/plates and blocks which best suit the anatomy of the patient's body part and anatomical area of interest (for example, and without limitation, the skull). The platform may include marker elements utilized during subsequent imaging of the patient's body part and anatomical area of interest. The marker elements may be visible on the acquired image of the patient and may be advantageous in determining the position and orientation of the platform relative to the patient's area of interest.

Electronic image data of the patient's anatomical area of interest is obtained, step <NUM>. Obtaining the electronic image data may be done intraoperatively, or alternatively, pre-operatively. Obtaining the electronic image data may include an MRI, a CT and/or a spiral CT. The electronic image data may also be obtained optically.

Based on the electronic image data, a trajectory to be cut or drilled is determined, step <NUM>. For example, a specialized software module running on a processor may analyze the electronic image data and calculate parameters for a trajectory to be drilled. Illustratively, when inserting an electrode array of a cochlear implant, this may be the optimal trajectory from the patient's skull bone behind the ear into the middle ear. Important trajectory parameters of the trajectory may include, without limitation, its trajectory <NUM> (shown in <FIG>) and the point where the axis crosses the surface of the skull.

Per these trajectory parameters, a suitable intermediate module together with its characteristic module parameters can be determined and manufactured, step <NUM>. If the intermediate module is L shaped as shown in <FIG>, then characteristic module parameters may include, without limitation, heights <NUM>, <NUM>, and <NUM>, as well as lateral offsets y and z between the platform <NUM> and intermediate module <NUM>, as exemplary shown in <FIG>. In various embodiments, the characteristic module parameters may also include lateral offsets between intermediate module and block. Referring to <FIG>, these offsets may be used to ensure that in the composite surgical guide tool <NUM>, the axis <NUM> of bore hole <NUM> in the block <NUM> coincides with the determined trajectory <NUM>.

A wide variety of mechanical processes may be used in manufacturing the intermediate module. These mechanical processes may include, without limitation, cutting, drilling, milling, etc. from a blank of suitable material. In other embodiments, the intermediate module may be molded.

Once the intermediate module is provided, the platform may be mounted on the body part, with the intermediate module sandwiched between the platform and the block, step <NUM>. Illustratively, as shown in <FIG>, a drilling platform <NUM> may be mounted on patient's skull bone <NUM> upon which the intermediate module <NUM> and then the drilling table <NUM> sits. In the composite state, with the surgical guide tool <NUM> mounted on the body part to perform a drilling procedure, the longitudinal axis <NUM> of the bore hole <NUM> coincides with the longitudinal axis of the desired and predetermined trajectory <NUM> into the skull bone <NUM>.

The surgeon or robot may then insert a surgical instrument through the guide aperture to make the cut or drill hole, step <NUM>. The intermediate module ensures that the trajectory or the surgical instrument follows the desired trajectory. Additionally, as described above, in various embodiments of the invention the longitudinal axis of the guide aperture in the non patient-specific block may be perpendicular to the surface of drilling table. This may be beneficial for the surgeon, as it may be easier to keep and move a drill oriented perpendicular to the surface of the block than under another angle.

In various embodiments, there may be a position defining element on surface <NUM> of platform table <NUM> and/or plate <NUM>, as shown in <FIG>. This position defining element may be, for example, a longitudinal or punctate or conical elevation. In <FIG>, this is shown as longitudinal elevations in both dimensions of the plane <NUM>. An according recess may be milled in the bottom surface <NUM> of intermediate module <NUM> during manufacturing. Alternatively, the elevation is in bottom surface <NUM> and the recess may be on the platform <NUM> or plate <NUM>. There may be similar elevations and recesses on/in surfaces <NUM> of intermediate module <NUM>, and surface <NUM> of block <NUM>.

An alternative solution of, or in combination with, providing elevations and recesses may be cylindrical pins extending out of platform table <NUM> and/or plate <NUM>, and/or recesses made by drilling during the medical procedure as described above. In some cases, it may be required that intermediate module <NUM> is larger than plate <NUM> and/or block <NUM> in either or both dimensions of the respective surface planes such that possible shifts y and z can be realized. At least two cylindrical pins/recesses would be beneficial on each of the surfaces. In embodiments wherein the intermediate module <NUM> is manufactured intraoperatively during the medical process, it may be advantageous that the intermediate module <NUM> receives the recesses whereas the elevations (pins) are provided to platform <NUM>/plate <NUM>, and or block <NUM>.

One purpose of these complementary constructional elements of elevations (pins) and recesses is so that the platform <NUM>/the plate <NUM>, the block <NUM>, and the intermediate module <NUM> fit to each other free of play in the predetermined positions calculated, without limitation, by the processor software, to guarantee the coincidence of trajectory <NUM> and axis <NUM>. In further embodiments clamps (not shown) may be used to keep all three components <NUM>, <NUM>, and <NUM> together.

In further embodiments of the invention, the surgical guidance tool described herein may be realized without an intermediate module, as shown in <FIG> (top view) and <FIG> (side view). To do so, various portions of the block <NUM> may be patient-specific to guarantee coincidence of the determined trajectory with axis <NUM> of guide aperture <NUM>.

The patient-specific block <NUM> has planar and non-parallel top and bottom surfaces with at least some of the heights <NUM>, <NUM>, <NUM>, and <NUM><NUM> assuming different values. The heights <NUM>, <NUM>, <NUM> and <NUM> are patient-specific to ensure that the non-patient specific, predefined arrangement between the axis <NUM> of the guide aperture <NUM> and the top surface of the block <NUM> provides the proper predetermined angle/trajectory. Similar to above-described embodiments, the axis <NUM> may be perpendicular to the top planar surface <NUM> of the block <NUM>. However, in other embodiments, the axis <NUM> may be non-perpendicular to the top planar surface <NUM>. The bore hole <NUM> may be in or off the center of block <NUM>.

There might be a trade-off between size of bore hole <NUM>/<NUM> and precise alignment of axis <NUM>/<NUM> with trajectory <NUM> during the trajectory e.g. into patient's skull. On one hand, bore hole <NUM>/<NUM> must match exactly the dimension of that part of the bore apparatus, which is moved through block <NUM> by the surgeon's (or a robot's) force during drilling in order to avoid an unintended angle between axis <NUM>/<NUM> and trajectory <NUM>. On the other hand, the more precise the outer diameter of that part of the bore apparatus matches the inner diameter of bore hole <NUM>/<NUM> the higher may become the friction between these two parts. However, higher friction may increase the danger of unintended tilt of the bore apparatus during insertion such that axis <NUM>/<NUM> and trajectory <NUM> are not any more perfectly aligned. To avoid this, there may be a guiding element that may, for example, be attached to surface <NUM> of block <NUM> (alternatively, this guiding element may be integral part of block <NUM>), which keeps the bore apparatus in an orientation such that axis <NUM>/<NUM> and trajectory <NUM> are perfectly aligned during drilling.

<FIG> shows a guiding element, in accordance with an embodiment of the invention. The guiding element may include guiding walls <NUM>, with, for example, guiding rollers <NUM> operatively coupled to the guiding walls <NUM> which ensure that portion <NUM> of the bore apparatus moves without lateral tilt and such that axis <NUM>/<NUM> and trajectory <NUM> are always perfectly aligned during drilling. The rollers may have various shape, and generally be, without limitation, wheel shaped, circular, cylindrical or spherical in nature. Such guiding element of a bore apparatus can be advantageously utilized in connection with the systems shown, for example, in <FIG>, compared to the invention disclosed in <CIT>, because the entire block <NUM> may be manufactured non patient-specific. Therefore, the angle of axis <NUM> relative to surface <NUM> of block <NUM> is independent of the patient and the guiding element can be oriented accordingly. And although, in the embodiment of <FIG>, the block <NUM> is patient-specific, the angle between surface <NUM> and axis <NUM> is non patient-specific and therefore again the guiding element can easily be oriented accordingly.

Claim 1:
A surgical guide tool (<NUM>) comprising:
a non patient-specific platform (<NUM>) including one or more supports (<NUM>) for attaching to a body part (<NUM>) of a subject;
a patient-specific block (<NUM>) having a top surface (<NUM>) and a bottom surface, the block (<NUM>) including a guide aperture (<NUM>) extending from the top surface (<NUM>) to the bottom surface for guiding a surgical instrument in a making at least one of a cut and a drill hole, the block (<NUM>) having patient-specific dimensions such that the guide aperture (<NUM>) has a desired alignment relative to the body part (<NUM>) when the surgical guide tool (<NUM>) is attached to the body part (<NUM>) of the patient and the block (<NUM>) is braced against the platform (<NUM>), wherein the top surface (<NUM>) and the bottom surface of the block (<NUM>) are planar and non-parallel, wherein
the guide aperture (<NUM>) is a bore hole defining an axis (<NUM>) through the block (<NUM>), and wherein the axis (<NUM>) is perpendicular to the top surface (<NUM>) of the block (<NUM>).