WO2005046451A2

WO2005046451A2 - Apparatus and methods for use in mounting a surgical trajectory guide

Info

Publication number: WO2005046451A2
Application number: PCT/US2004/037660
Authority: WO
Inventors: Gene H. Barnett
Original assignee: The Cleveland Clinic Foundation
Priority date: 2003-11-10
Filing date: 2004-11-10
Publication date: 2005-05-26
Also published as: WO2005046451A3

Abstract

An apparatus (10) and methods for mounting a surgical trajectory guide (12) having a plurality of mounting apertures (14) above a patient’s scalp includes a plurality of bone pillars (20) that correspond in quantity to the plurality of mounting apertures (14) in the trajectory guide (12). Each of the bone pillars (20) has oppositely disposed distal (22) and proximal ends (24) and a cylindrical main body section (26) extending between the ends. The distal end (22) of each of the bone pillars (20) includes a self-tapping threaded surface portion (28) for screwing into and through a patient’s scalp. The proximal end (24) of each of the bone pillars (20) includes a threaded receptacle (42) for receiving a threaded fastener (16) and a driving surface (40) for engagement by a rotatable member (60) to rotate each of the bone pillars (20).

Description

APPARATUS AND METHODS FOR USE IN MOUNTING A SURGICAL TRAJECTORY GUIDE

Related Applications This application claims the benefit of U.S. Provisional Patent

Application Serial No. 60/518,711 , filed November 10, 2003, the subject matter of which is incorporated herein by reference.

Field of the Invention The present invention relates generally to surgical trajectory guides, and more specifically relates to an apparatus and methods for use in mounting a surgical trajectory guide.

Background of the Invention It can be appreciated that methods of improving the accuracy of the trajectory of invasive surgical tools, such as drills, are generally important and useful for surgical methods in order to minimize the number and size of incisions needed to reach an anatomic target, thereby reducing operative time, surgical complications, pain, and morbidity. Trajectory precision is an important determinant of surgical outcome, because a trajectory even slightly imprecise in angle or depth may cause serious damage to surrounding tissues, organs, and vessels. Recently, trajectory guides have come into general use as an improvement upon the traditional method of estimating the proper trajectory by hand and eye. A trajectory guide, primarily containing a longitudinal lumen, is affixed to a rigid spot on the patient's anatomy. Once the guide is affixed, the longitudinal lumen precisely constrains the trajectory of the surgical tool that is typically perpendicular to the patient's body surface. Occasionally, the trajectory guide may be intentionally angled for precise usage of a surgical drill or other instrument. The fixation of the trajectory guide to the patient's body surface may be achieved by a variety of methods. In the earliest versions of such devices, a stereotactic frame was affixed to the patient's anatomy at several points, and a surgeon could attach the trajectory guide to the frame at a predetermined location and orientation. However, the bulk, discomfort, and added tissue stress caused by the stereotactic frame rendered this device an inefficient method of fixation. A more recent implementation is disclosed in U.S. Patent No. 6,206,885 (hereinafter "the '885 patent"). The apparatus described in this patent is available under the commercial name "Navigus Trajectory

Guide" from Image-Guided Neurologies, and is widely used for the purpose of providing a trajectory guide for penetrating the skull with a neurosurgical drill. This surgical trajectory guide physically restricts the application of a surgical instrument, such as a drill, to the most direct trajectory for accessing brain structures. One common usage of this device is the introduction of a catheter for monitoring, flushing, shunting, or removing cerebrospinal fluid. The apparatus of the '885 patent includes a solid body with a flat base, out of which rises a tall stem element that encloses a narrow- diameter longitudinal lumen. This lumen is the physical guide for the trajectory of surgical instruments. The apparatus is affixed to the patient's skull or scalp by screwing the flat base securely into the skin or bone. A surgical instrument, such as a drill or catheter, may then be inserted in the top of the stem and guided downward. The stem restricts the trajectory of the instrument to a substantially perpendicular approach. One important feature of the apparatus of the '885 patent, which is suggested both in the preferred embodiment and in the commercialized product, is the presence of a groove along the longitudinal length of the apparatus. The purpose of the groove is to enable the physician to see the progress of the surgical tool within the lumen and the contact of the instrument with the patient's head structures. The fixation of the apparatus of the '885 patent is achieved either by screwing the base into the skin of the scalp, or by incising the skin down to the skull and screwing the apparatus onto the skull. Both options present substantial drawbacks. Screwing the apparatus into the skin causes twisting flesh wounds that often lead to tissue necropsy and substantial patient pain. Moreover, the softness of the skin reduces the degree of immobilization, and consequently reduces the stability and accuracy of the trajectory guide. The skull serves as a more stable surface of fixation, but screwing the trajectory guide directly onto the skull requires a considerable scalp incision. While many neurosurgical procedures require such an incision in the course of surgery, recent developments in this surgical field increasingly utilize minimally-invasive methods that require small incisions through which catheter-based surgical tools are percutaneously introduced. The diminished trauma to tissue substantially reduces pain, recovery time, and complications. However, such improvements are not compatible with the large incision required to access the skull in order to affix a trajectory guide. A similar apparatus is disclosed in U.S. Patent No. 6,206,890 (hereinafter "the '890 patent"). In this patent, a trajectory-constraining lumen is enclosed in a tube attached to a triangular base and a ball joint.

The ball joint is attached to a lower triangular base that is affixed to the patient's anatomy. The surgeon may swivel the tube, the triangular base, and the ball joint around the lower triangular base in order to achieve the desired angle of approach, and the ball joint may then be immobilized in order to fix the trajectory. Catheters and catheter-like instruments may then be introduced through the lumen in the tube, which extends into the ball joint and through the lower triangular base, in order to achieve a satisfactory trajectory. However, the large footprint of the lower triangular base renders this apparatus subject to the same options of fixation to either the skin or the skull, and the aforementioned problems associated with each option. Furthermore, the lower triangular base obstructs the visibility of surgical instrument action against the skin, thereby complicating surgery. The present invention substantially departs from the aforementioned conventional concepts and designs, and provides a method and apparatus for enhancing the precision of a surgical trajectory guide in order to achieve an optimal surgical trajectory and to reduce tissue trauma, surgical duration, pain, surgical complications, and morbidity.

Summary of the Invention The present invention is an apparatus for use in mounting a surgical trajectory guide having a plurality of mounting apertures. The apparatus comprises a plurality of bone pillars that correspond in quantity to the plurality of mounting apertures in the trajectory guide. Each of the plurality of bone pillars has oppositely disposed distal and proximal ends and a cylindrical main body section extending between the ends. The distal end of each of the plurality of bone pillars includes a self-tapping threaded surface portion for screwing into and through a patient's scalp. The proximal end of each of the plurality of bone pillars includes a threaded receptacle for receiving a threaded fastener and a driving surface for engagement by a rotatable member to rotate each of the bone pillars. The bone pillars are operable to mount the trajectory guide above the patient's scalp. In accordance with one aspect of the invention, the apparatus can further comprise a jig having a base frame and a plurality of tubular posts extending from the base frame. The plurality of tubular posts corresponds in quantity and location to the plurality of mounting apertures in the trajectory guide.

In accordance with another aspect of the invention, the apparatus can further comprise a plurality of extension pillars that correspond in quantity to the plurality of bone pillars. Each of the plurality of extension pillars has oppositely disposed distal and proximal ends and a cylindrical main body portion extending between the ends. The distal end of each of the plurality of extension pillars includes a threaded projection for screwing into the threaded receptacle on the proximal end of each of the plurality of bone pillars. The proximal end of each of the plurality of extension pillars includes a threaded receptacle for receiving a threaded fastener. The plurality of extension pillars attach to the plurality of bone pillars to mount the trajectory guide farther above the patient's scalp. The present invention further provides a method for mounting a surgical trajectory guide above a patient's scalp. The trajectory guide has a plurality of mounting apertures. According to the inventive method, a plurality of bone pillars that correspond in quantity to the plurality of mounting apertures in the trajectory guide are provided. Each of the bone pillars has oppositely disposed distal and proximal ends. The distal end of each of the plurality of bone pillars includes a self-tapping threaded surface portion. The proximal end of each of the plurality of bone pillars includes a threaded receptacle. The plurality of bone pillars are implanted into the patient's scalp by screwing the self-tapping threaded surface portion of each of the bone pillars into the scalp at locations that correspond to the spacing of the mounting apertures in the trajectory guide. The trajectory guide is positioned over the bone pillars so that the plurality of mounting apertures aligns with the plurality of bone pillars. The trajectory guide is then secured to the bone pillars using a plurality of threaded fasteners so that the trajectory guide is positioned above the patient's scalp. In accordance with other aspects of the inventive method, prior to the step of screwing the bone pillars into the patient's scalp, a jig having a plurality of tubular posts that correspond in quantity and location to the plurality of mounting apertures in the trajectory guide is provided. The jig is oriented on the patient's scalp. The plurality of bone pillars is inserted into the plurality of tubular posts in the jig. The plurality of bone pillars is screwed into the patient's scalp and the jig is then removed from the plurality of bone pillars. In accordance with further aspects of the inventive method, a plurality of extension pillars that correspond in quantity to the plurality of bone pillars is provided. Each of the extension pillars has oppositely disposed distal and proximal ends. The distal end of each of the plurality of bone pillars includes a threaded projection. The threaded projection on each of the extension pillars screws into the threaded receptacle in each of the bone pillars. The trajectory guide is positioned over the extension pillars so that the plurality of mounting apertures aligns with the plurality of extension pillars. The trajectory guide is secured to the extension pillars using a plurality of threaded fasteners so that the trajectory guide is positioned above the patient's scalp.

Brief Description of the Drawings Further features of the present invention will become apparent to those skilled in the art to which the present invention relates from reading the following description of the invention with reference to the accompanying drawings in which: Fig. 1 is an exploded perspective view of components of an apparatus for use in mounting a surgical trajectory guide in accordance with a first embodiment of the present invention; Fig. 2 is a perspective view of one of the components of Fig. 1 ; Fig. 3 is a perspective view of a tool for use with the apparatus of

Fig. 1 ; Fig. 4 is a perspective view of another tool for use with the apparatus of Fig. 1 ; Fig. 5 is a sectional view of the apparatus of Fig. 1 affixed to a patient's skull; Fig. 6 is a sectional view illustrating use of the apparatus of Fig. 1 to mount a surgical trajectory guide to a patient's skull; Fig. 7 is a perspective view of a component of an apparatus for use in mounting a surgical trajectory guide in accordance with a second embodiment of the present invention; Fig. 8 is a sectional view illustrating use of the apparatus of Fig. 1 along with the component of Fig. 7 to mount a surgical trajectory guide to a patient's skull; Fig. 9 is a perspective view of a component of an apparatus for use in mounting a surgical trajectory guide in accordance with a third embodiment of the present invention; Fig. 10 is a perspective view of a tool for use with the apparatus of Fig. 9; and Fig. 11 is an exploded perspective view of components of an apparatus for use in mounting a surgical trajectory guide in accordance with a fourth embodiment of the present invention.

Detailed Description of Embodiments The present invention relates generally to surgical trajectory guides, and more specifically relates to an apparatus and methods for use in mounting a surgical trajectory guide. In accordance with a first embodiment of the present invention, Fig. 1 illustrates an apparatus 10 for use in mounting a known surgical trajectory guide 12 (Fig. 6) having a plurality of mounting apertures 14. The apparatus 10 comprises a plurality of bone pillars 20 (Fig. 2) having a central axis A. The quantity of bone pillars 20 corresponds to the number of mounting apertures 14 in the trajectory guide 12. The bone pillars 20 are made of a medical grade metal, such as stainless steel or other suitable biocompatible material, and are 10-30 mm long. Each of the bone pillars 20 has oppositely disposed distal and proximal ends 22 and 24 and a main body section 26 extending between the ends. The main body section 26 has a cylindrical shape with an outer diameter D1 that is 1-5 mm. The distal end 22 of each of the bone pillars 20 includes a self- tapping threaded surface portion 28 and a conical surface portion 30 that extends between the threaded surface portion and the main body section 26. As shown in Fig. 2, the conical surface portion 30 tapers radially outward from the threaded surface portion 28 to the main body section 26. The proximal end 24 of each of the bone pillars 20 includes a reverse-cone end surface 40 that tapers radially inward to a threaded receptacle 42 that extends along the axis A. The proximal end 24 further includes a driving surface in the form of a wedge-shaped flange 46 that projects from the end surface 40. The apparatus 10 may further comprise a jig 50 (Fig. 1 ). The jig 50 may be made of plastic, metal, or any other suitable material. The jig 50 has a base frame 52 and a plurality of tubular posts 54 that project in parallel from the base frame. The frame 52 may have a variety of different shapes and may be solid (as shown) or truss-like. The tubular posts 54 correspond in quantity and location to the plurality of mounting apertures 14 in the trajectory guide 12. Further, the tubular posts 54 have a cylindrical inner surface with an inner diameter D2 that is slightly greater than the outer diameter D1 of the bone pillars 20. Figs. 3 and 4 illustrate tools that may be used in connection with the apparatus 10. An insertion tool 60 is shown in Fig. 3 and a removal tool 70 is shown in Fig. 4. The insertion tool 60 resembles a screwdriver and has a tip portion 62 that is designed to mate with the proximal end 24 of the bone pillars 20. The tip portion 62 of the insertion tool 60 includes a screw portion 64 and a conical portion 66. The removal tool 70 resembles a screwdriver and has a tip portion 72 that includes an alignment pin 74 and a conical portion 76. The tip portion 72 of the removal tool 70 further includes a wedge surface 78 that is complimentary to the wedge-shaped flange 46 on the proximal end 24 of the bone pillars 20. To use the apparatus 10 to mount the trajectory guide 12 above patient's scalp, a jig is selected so that it matches the chosen surgical trajectory guide. It is anticipated that a surgical kit for the apparatus 10 will include several jigs, each of which has a set of tubular posts 54 that matches the spatial layout of the mounting apertures 14 in the commonly- used surgical trajectory guides. As shown in Fig. 5, the jig 50 is positioned at the appropriate location on the patient's scalp 80. A bone pillar 20 is then inserted into each of the tubular posts 54 in the jig 50. Next, the insertion tool 60 is then used to implant each of the bone pillars 20 into the skull 82. The screw portion 64 of the insertion tool 60 is screwed into the threaded receptacle 42 on the proximal end 24 of the bone pillars 20 until the conical portion 66 of the insertion tool abuts the reverse-cone end surface 40 on the bone pillars. From this point on, further rotation of the insertion tool 60 causes rotation of the bone pillar 20 and screws the self-tapping threaded surface portion 28 of the bone pillars into the scalp 80. The conical surface portion 30 on the bone pillars 20 helps the bone pillars to penetrate through the scalp 80 and into the outer table 84, yet also helps to prevent the bone pillars from penetrating beyond an intended depth. When the bone pillars 20 are implanted to a desired depth, the insertion tool 60 used to rotate each of the bone pillars is disengaged and removed. It should be noted that it may be necessary to hold the implanted bone pillars 20 to prevent rotation when disengaging the screw portion 64 of the insertion tool 60 from the threaded receptacle 42 in the bone pillars. As may be seen in Fig. 5, during the implantation of the bone pillars 20, the tubular posts 54 in the jig 50 ensure that the bone pillars are implanted at the proper angles and in parallel with each other. Following implantation of all of the bone pillars 20, the jig 50 is removed from its position over the bone pillars. Next, the surgical trajectory guide 12 is positioned over the bone pillars 20, as shown in Fig. 6, so that the mounting apertures 14 in the trajectory guide align with the bone pillars. The trajectory guide 12 is then secured to the proximal ends 24 of the bone pillars 20 using a plurality of mounting screws 16 that have a typical machine screw configuration. The mounting screws 16 extend through the mounting apertures 14 in the trajectory guide 12 and into the threaded receptacles 42 on the proximal ends 24 of the bone pillars 20. Thus, as shown in Fig. 6, the apparatus 10 provides for a secure and stable attachment of the trajectory guide 12 to the skull 82 in a percutaneous procedure that elevates the trajectory guide above the scalp 80.

It should be noted that it is contemplated that the bone pillars 20 could be implanted into the skull 82 without using the jig 50. Such an alternative method would involve placing the trajectory guide 12 on the scalp 80 and using it as a template to mark the locations on the scalp in which to implant the bone pillars 20. Following the completion of the surgical procedure for which the trajectory guide 12 was required, the trajectory guide and the bone pillars 20 are removed from the skull 82. The trajectory guide 12 is detached from the bone pillars 20 by unscrewing the mounting screws 16 and lifting the trajectory guide off the bone pillars. The bone pillars 20 are then removed from the skull 82 using the removal tool 70. More specifically, the alignment pin 74 on the tip portion 76 of the removal tool 70 is inserted into the threaded receptacle 42 in each of the bone pillars 20 and the wedge surface 78 on the removal tool is engaged with the wedge- shaped flange 46 on each of the bone pillars. With the wedge surface 78 on the removal tool 70 engaging the wedge-shaped flange 46 on the bone pillar, counter-clockwise rotation of the removal tool causes the self-tapping threaded surface portion 28 of the bone pillar to unscrew from the skull 82.

Each of the bone pillars 20 is unscrewed and removed from the skull 82 in this manner using the removal tool 70. Figs. 7 and 8 illustrate an apparatus 110 for use in mounting a trajectory guide in accordance with a second embodiment of the present invention. In the second embodiment of Figs. 7 and 8, structures that are identical to structures described in the first embodiment of Figs. 1-6 utilize the same reference numbers. According to the second embodiment, the apparatus 110 further comprises a plurality of extension pillars 120 that attach to the plurality of bone pillars 20 to mount the trajectory guide 12 farther above the patient's scalp 80. The quantity of extension pillars 20 corresponds to the number of mounting apertures 14 in the trajectory guide 12. The extension pillars 120 are made of a medical grade metal, such as stainless steel or other suitable biocompatible material, and are 10-30 mm long. Each of the extension pillars 120 has oppositely disposed distal and proximal ends 122 and 124 and a main body section 126 extending between the ends. The main body section 126 has a cylindrical shape with an outer diameter D3 that is equal to the diameter D1 of the bone pillars 20. The distal end 122 of each of the extension pillars 120 includes a threaded projection 128 and a conical surface portion 130 that extends between the threaded surface portion and the main body section 126. As shown in Fig. 7, the conical surface portion 130 tapers radially outward from the threaded surface portion 128 to the main body section 26. The distal end 122 of each of the extension pillars 120 further includes a driver surface in the form of a wedge-shaped flange 134 that is complimentary to the wedge-shaped flange 46 on the bone pillars 20. The proximal end 124 of each of the extension pillars 120 includes a reverse-cone end surface 140 that tapers radially inward to a threaded receptacle 142 that extends along the axis A. The proximal end 124 further includes a driving surface in the form of a wedge-shaped flange 146 that projects from the end surface 140. Use of the apparatus 110 to mount the trajectory guide 12 above the patient's scalp 80 involves most of the procedure described above for the apparatus 10, except that the extension pillars 120 are secured between the bone pillars 20 and the trajectory guide to further elevate the trajectory guide above the scalp. It is contemplated that extension pillars 120 of various lengths will be available for selection based on the needs of a specific procedure. As shown in Fig. 8, after the bone pillars 20 are implanted as previously described regarding the first embodiment, the extension pillars 120 are attached to the bone pillars by screwing the threaded projections 128 on the extension pillar into the threaded receptacles 42 in the bone pillars. The insertion tool 60 can be used to screw the extension pillars 120 into the bone pillars 20 in a similar manner to that described above. Specifically, the screw portion 64 of the insertion tool 60 is screwed into the threaded receptacle 142 on the proximal end 124 of the extension pillars 120 until the conical portion 66 of the insertion tool abuts the reverse-cone end surface 140 on the extension pillars. From this point on, further rotation of the insertion tool 60 causes rotation of the extension pillar 120 and screws the threaded projection 128 of the extension pillars into the threaded receptacle 42 in the bone pillars 20. When the extension pillars 120 are tightly secured to the bone pillars 20, the insertion tool 60 used to rotate each of the extension pillars is disengaged and removed. It should be noted that it may be necessary to hold the extension pillars 120 to prevent rotation when disengaging the screw portion 64 of the insertion tool 60 from the threaded receptacle 142 in the extension pillars. Next, the surgical trajectory guide 12 is positioned over the extension pillars 120, as shown in Fig. 8, so that the mounting apertures 14 in the trajectory guide align with the extension pillars. The trajectory guide 12 is then secured to the proximal ends 124 of the extension pillars 120 using the mounting screws 16. The mounting screws 16 extend through the mounting apertures 14 in the trajectory guide 12 and into the threaded receptacles 142 on the proximal ends 124 of the extension pillars 120. Thus, as shown in Fig. 8, the apparatus 110 provides for a secure and stable attachment of the trajectory guide 12 to the skull 82 in a percutaneous procedure that elevates the trajectory guide further above the scalp 80. Following the completion of the surgical procedure for which the trajectory guide 12 was required, the extension pillars 120 and the bone pillars 20 may be removed from the skull 82. The trajectory guide 12 is first detached from the extension pillars 120 by unscrewing the mounting screws 16 and lifting the trajectory guide off the extension pillars. The extension pillars 120 and the bone pillars 20 are then removed from the skull 82 as an assembly using the removal tool 70. Removal of the extension pillars 120 and the bone pillars 20 as an assembly is enabled by the abutting wedge-shaped flanges 46 and 134 on the bone pillars and the extension pillars, respectively, which allow rotation of the extension pillars to be transmitted to the bone pillars. Hence, when the wedge surface 78 on the removal tool 70 is engaged with the wedge-shaped flange 146 on each of the extension pillars, counter-clockwise rotation of the removal tool causes the self-tapping threaded surface portion 28 of the bone pillar 20 to unscrew from the skull 82. Each assembly of extension pillars 120 and bone pillars 20 is unscrewed and removed from the skull 82 in this manner using the removal tool 70. It should be understood, however, that the bone extensions 120 and the bone pillars 20 could be removed as individual components, rather than as assemblies, using the removal tool 70. Fig. 9 illustrates an apparatus 210 for use in mounting a trajectory guide in accordance with a third embodiment of the present invention. In the third embodiment of Fig. 9, structures that are identical to structures described in the first embodiment of Figs. 1-6 utilize the same reference numbers. According to the third embodiment, the apparatus 210 comprises a plurality of bone pillars 220 that are similar to the bone pillars 20, except that the driving surface on the proximal end 24 of each of the bone pillars comprises a hexagonal recess 246. The apparatus 210 is used to mount the trajectory guide 12 above the scalp 80 in an identical fashion to that which is described above, except that a single driving tool 270 (Fig. 10) is used for both insertion and removal of the bone pillars 220. The driving tool 270 includes an alignment pin 272 and a hexagonal outer surface 274 that engages the hexagonal recess 246 in the bone pillars to allow for rotation of the bone pillars. Fig. 11 illustrates an apparatus 310 for use in mounting a trajectory guide in accordance with a fourth embodiment of the present invention. In the fourth embodiment of Fig. 11 , structures that are identical to structures described in the earlier embodiments utilize the same reference numbers. According to the fourth embodiment, the apparatus 310 comprises a plurality of bone pillars 320 and the plurality of extension pillars 120. The bone pillars 320 are identical to the bone pillars 20 described in the first embodiment, except that the self-tapping threaded surface portion comprises left-hand threads 328 that penetrate upon being rotated counterclockwise. The apparatus 310 is used to mount the trajectory guide 12 above the scalp 80 in a similar fashion to that which was described above in the second embodiment of Figs. 7 and 8, but with a few notable differences. First, the tool 70 of Fig. 4 is used to implant the bone pillars 320. More specifically, the alignment pin 74 on the tip portion 76 of the tool 70 is inserted into the threaded receptacle 42 in each of the bone pillars 320 and the wedge surface 78 on the removal tool is engaged with the wedge- shaped flange 46 on each of the bone pillars. With the wedge surface 78 on the tool 70 engaging the wedge-shaped flange 46 on the bone pillar 320, counter-clockwise rotation of the removal tool causes the self- tapping threaded surface portion 28 of the bone pillar to screw into the skull 82. Each of the bone pillars 320 is thus implanted in this manner using the tool 70. The extension pillars 120 are then attached to the bone pillars 320 as described above with regard to the second embodiment of Figs. 7 and 8. Finally, the trajectory guide 12 is attached to the extension pillars 120, as previously described, with the mounting screws 16. A second difference between the second embodiment of Figs. 7 and 8 and the fourth embodiment of Fig. 11 is how the extension pillars 120 and the bone pillars 320 are removed. The extension pillars 120 and the bone pillars 320 are removed as an assembly using the tool 60 of Fig. 3. The screw portion 64 of the tool 60 is screwed into the threaded receptacle 142 on the proximal end 124 of the extension pillars 120 until the conical portion 66 of the insertion tool abuts the reverse-cone end surface 140 on the extension pillars. From this point on, further clockwise rotation of the tool 60 causes clockwise rotation of the extension pillar 120 and the bone pillar 320, which unscrews the left-handed threads on the bone pillars from the skull 82. Each of the assemblies of extension pillars 120 and bone pillars 320 is thus removed in this manner using the tool 60. A benefit of the apparatus according to the present invention is the rigid fixation of a surgical trajectory guide to the patient's skull, which improves the precision of trajectory guidance. This technique provides better stability, more precise trajectory guidance, and less trauma than devices that screw into skin tissue, and also avoid the large incision and bulky stereotactic frame that are required of other trajectory guide devices that screw into the skull. Another benefit of the present system is its ability to adapt easily in height to patient's cranial anatomy. A further benefit of the present invention is the ability to adapt the configuration of the pillars in order to match one of many kinds of currently available surgical trajectory guides simply by changing the jig and the number of pillars used for fixation. A further benefit of the present invention is the added visibility for the surgical tools and surgical site associated with raising the surgical trajectory guide above the incision site, without compromising the rigid fixation of the trajectory guide to the cranial surface or the precision of trajectory guidance. A further benefit of the present invention is the ability to manufacture the apparatus from inexpensive materials and construction methods, thereby rendering the apparatus affordable and disposable. From the above description of the invention, those skilled in the art will perceive improvements, changes, and modification. For example, it is contemplated that the present invention could be adapted for use in mounting a trajectory guide to other areas of the body besides the skull. Moreover, the foregoing is considered as illustrative only of the principles of the invention. Since numerous modifications and changes will be readily appreciated by one skilled in the art, it is not desired to limit the invention to the exact construction and operation shown and described, and accordingly, all suitable modifications and equivalents are intended to fall within the scope of the invention.

Claims

Claims Having described the invention, I claim:

1. Apparatus for use in mounting a surgical trajectory guide having a plurality of mounting apertures, said apparatus comprising a plurality of bone pillars that correspond in quantity to the plurality of mounting apertures in the trajectory guide, each of said plurality of bone pillars having oppositely disposed distal and proximal ends and a cylindrical main body section extending between said ends, said distal end of each of said plurality of bone pillars including a self-tapping threaded surface portion for screwing into and through a patient's scalp, said proximal end of each of said plurality of bone pillars including a threaded receptacle for receiving a threaded fastener and a driving surface for engagement by a rotatable member to rotate each of said bone pillars, wherein said plurality of bone pillars are operable to mount the trajectory guide above the patient's scalp.

2. The apparatus of claim 1 wherein each of said plurality of bone pillars includes a conical surface portion that extends between said threaded portion and said main body section.

3. The apparatus of claim 1 wherein said proximal end of each of said plurality of bone pillars further includes a reverse-cone end surface.

4. The apparatus of claim 3 wherein said driving surface on said proximal end of each of said plurality of bone pillars comprises a wedge- shaped flange projecting from said conical end surface, said wedge-shaped flange engageable by a complimentary wedge surface on the rotatable member for rotating each of said bone pillars.

5. The apparatus of claim 4 wherein said self-tapping threaded surface portion on said distal end comprises left-hand threads and said threaded receptacle in said proximal end comprises right-hand threads.

6. The apparatus of claim 1 wherein said driving surface on said proximal end of each of said plurality of bone pillars comprises a hexagonal recess that is engageable by a complimentary hexagonal outer surface on the rotatable member for rotating each of said bone pillars.

7. The apparatus of claim 1 further comprising a jig having a base frame and a plurality of tubular posts extending from said base frame, said plurality of tubular posts corresponding in quantity and location to the plurality of mounting apertures in the trajectory guide.

8. The apparatus of claim 7 wherein each of said plurality of tubular posts has a cylindrical inner surface with an inner diameter that is slightly larger than the outer diameter of said cylindrical main body section of each of said plurality of bone pillars.

9. The apparatus of claim 1 further comprising a plurality of extension pillars that correspond in quantity to the plurality of bone pillars, each of said plurality of extension pillars having oppositely disposed distal and proximal ends and a cylindrical main body portion extending between said ends, said distal end of each of said plurality of extension pillars including a threaded projection for screwing into said threaded receptacle on said proximal end of each of said plurality of bone pillars, said proximal end of each of said plurality of extension pillars including a threaded receptacle for receiving a threaded fastener, wherein said plurality of extension pillars attach to said plurality of bone pillars to mount the trajectory guide farther above the patient's scalp.

10. The apparatus of claim 9 wherein said distal end of each of said plurality of extension pillars includes a driver surface for engaging said driving surface on said proximal end of said plurality of bone pillars.

11. The apparatus of claim 10 wherein said proximal end of each of said plurality of extension pillars includes a driving surface for engagement by a rotatable member to rotate each of said extension pillars.

12. The apparatus of claim 11 wherein each of said plurality of extension pillars includes a conical surface portion that extends between said threaded projection and said main body portion.

13. The apparatus of claim 11 wherein said driving surface on said proximal end of each of said plurality of bone pillars comprises a wedge-shaped flange projecting from said conical end surface, said driver surface on each of said plurality of extension pillars comprising a complimentary wedge surface.

14. The apparatus of claim 11 wherein said self-tapping threaded surface portion on said distal end of each of said plurality of bone pillars comprises left-hand threads and said threaded projection on said distal end of said plurality of bone extensions comprises right-hand threads that screw into said threaded receptacle in said proximal end of each of said plurality of bone pillars. >

15. The apparatus of claim 9 further comprising a jig having a base frame and a plurality of tubular posts extending from said base frame, said plurality of tubular posts corresponding in quantity and location to the plurality of mounting apertures in the trajectory guide.

16. The apparatus of claim 15 wherein each of said plurality of tubular posts has a cylindrical inner surface with an inner diameter that is slightly larger than the outer diameter of said cylindrical main body portion of each of said plurality of extension pillars.

17. A method for mounting a surgical trajectory guide above a patient's scalp, the trajectory guide having a plurality of mounting apertures, said method comprising the steps of: providing a plurality of bone pillars that correspond in quantity to the plurality of mounting apertures in the trajectory guide, each of the bone pillars having oppositely disposed distal and proximal ends, the distal end of each of the plurality of bone pillars including a self-tapping threaded surface portion, the proximal end of each of the plurality of bone pillars including a threaded receptacle; implanting the plurality of bone pillars into the patient's scalp by screwing the self-tapping threaded surface portion of each of the bone pillars into the scalp at locations that correspond to the spacing of the mounting apertures in the trajectory guide; positioning the trajectory guide over the bone pillars so that the plurality of mounting apertures align with the plurality of bone pillars; and securing the trajectory guide to the bone pillars using a plurality of threaded fasteners so that the trajectory guide is positioned above the patient's scalp.

18. The method of claim 17, wherein prior to said step of screwing the bone pillars into the patient's scalp, said method further comprises the steps of: providing a jig having a plurality of tubular posts that correspond in quantity and location to the plurality of mounting apertures in the trajectory guide; orienting the jig on the patient's scalp; inserting the plurality of bone pillars into the plurality of tubular posts in the jig; screwing the plurality of bone pillars into the patient's scalp; and removing the jig from the plurality of bone pillars.

19. The method of claim 17 further comprising the steps of: providing a plurality of extension pillars that correspond in quantity to the plurality of bone pillars, each of the extension pillars having oppositely disposed distal and proximal ends, the distal end of each of the plurality of bone pillars including a threaded projection; screwing the threaded projection on each of the extension pillars into the threaded receptacle in each of the bone pillars; positioning the trajectory guide over the extension pillars so that the plurality of mounting apertures align with the plurality of extension pillars; and -21- securing the trajectory guide to the extension pillars using a plurality of threaded fasteners so that the trajectory guide is positioned above the patient's scalp.