Such fiducial markers can be temporarily inserted onto one or more vertebrae and can also be inserted into bone that is to be removed surgically. The role of the markers is to check local accuracy rather than being part of the overall navigation system. There are a number of surgical difficulties associated with the intra-operative use of fiducial markers including ease and accuracy of imaging the marker, ease of engagement with a navigating probe with the markers and ease of insertion of the markers into the vertebral bone.
Any discussion of documents, acts, materials, devices, articles or the like which has been included in the present specification is not to be taken as an admission that any or all of these matters form part of the prior art base or were common general knowledge in the field relevant to the present disclosure as it existed before the priority date of each claim of this application.
In one embodiment of both the above aspects, the fiducial marker comprises a fiducial screw.
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The fiducial marker may also comprise a pedicle screw. Alternatively, at least the upper surface and well features described may form part of another implant or a surgical tool. In the embodiment of both aspects wherein the fiducial marker comprises a pedicle screw, during insertion into a bone of a patient the pedicle screw may be registered on a navigation system and subsequently probed with the navigation probe to re-register its position throughout a surgical procedure.
The guide surface of the first aspect typically slopes from an outer edge of the head, inwardly and downwardly towards the shaft to an inner edge which defines the opening of the well. The head may include a depth from an upper edge of the upper surface to a lowest point on the lower surface. The depth of the head may vary depending upon the application of the screw including the type of surgery and depth of bone. In relation to the first aspect, the opening of the well of the head is typically defined by the inner edge of the guide surface and may be substantially centrally located on the head.
The well may include at least one sidewall extending from an uppermost edge towards the lower surface of the head.
The well further includes a closed base. A depth of the well is taken as the distance between the uppermost edge of the sidewall and the closed base. The diameter of the well may be between 0. In one embodiment the diameter is between 1. In a further embodiment, the diameter of the well is approximately 1.
The at least one sidewall and base of the well may define a number of shapes to receive a probe. In one embodiment, the well is substantially hemispherical in shape. This embodiment may be useful when receiving a substantially spherically ended probe. Alternatively, the at least one sidewall and base may define a substantially frustoconically shaped well.
In another embodiment, the well may be U-shaped. In one embodiment, the well is V-shaped, the one or more sidewalls meeting to form a pointed base. The base of the well may be substantially curved or, alternatively, the base may be substantially planar. The at least one sidewall of the well may comprise a continuous sidewall. The at least one sidewall may be substantially curved. Alternatively, the at least one sidewall may be substantially planar. The well may be defined by a plurality of sidewalls. For example, in one embodiment, the well may be defined by three or four sidewalls.
In a further embodiment, the well may be defined by five sidewalls; six sidewalls, seven sidewalls, eight sidewalls, nine sidewalls or ten or more sidewalls. In a preferred embodiment, the well is defined by six sidewalls to form a hexagonally shaped recess in the head. Each side wall may be substantially curved or alternatively, each sidewall may be substantially planar.
The shape defined by the well may substantially match with the shape of the guide surface of the upper surface. For example, if the well is a substantially hemispherical structure, the guide surface may define a similarly hemispherical structure. Where the well includes a plurality of sidewalls, the guide surface may include an equivalent number of faces on the upper surface. Alternatively, the shape defined by the sidewall s of the well may differ to the shape of the guide surface.
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The one or more sidewalls of the well may have a substantially steeper sloped pitch relative to the slope of an equivalent one or more faces of the guide surface. The pitch of the slope of the upper surface including the at least one sidewall of the well and the guide surface is taken to be the angle of the slope relative to an axis which is normal to the longitudinal axis of the shaft. The pitch of the slope of the guide surface may be constant along a length of the guide surface from the outer edge of the guide surface to the inner edge.
Alternatively, the pitch of the slope of the guide surface may vary along its length. Any variation in pitch of the guide surface slope is typically smooth and devoid of sharp transitions areas which may impede the smooth guidance of the probe. The head may further comprise at least one outer sidewall extending between the upper surface and the lower surface.
In one embodiment, the outer sidewall of the head may comprise a continuous cylindrical surface.
Alternatively, the outer sidewall may comprise a plurality of sidewalls. For example, the at least one sidewall may comprise three sidewalls, four sidewalls, five sidewalls, six sidewalls, seven sidewalls, eight sidewalls, nine sidewalls or ten or more sidewalls. In a preferred embodiment, the head includes six outer sidewalls. The at least one outer sidewall may be substantially planar. Alternatively the at least one outer sidewall may be substantially curved. The curvature of the at least one outer sidewall may be concave or convex. The at least one outer sidewall may comprise a ribbed or roughened surface.
Alternatively, the surface may be smooth.
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In one embodiment, wherein the outer sidewall includes a hexagonal structure with six sidewalls forming a driver feature, a socket driver may be used to engage the hexagonal structure of the head and insert the marker into the bone. By having such driver features of the fiducial marker comprising an outer surface of the head, the guide surface and the well of the head are unencumbered by any such features. This allows a probe to be touched down on the guide surface and into the well without any impediment.
The at least one outer sidewall of the marker of the first aspect may include a threaded region. In this embodiment, it is envisaged that the head of the fiducial marker may be threadingly advanced into a bone such that the head is substantially counter-sunk in said bone. The lower surface of the head typically includes a central portion substantially aligned longitudinally with the well of the head. The central portion typically includes the lowest point on the lower surface. Further, the shaft of the fiducial marker typically extends from the central portion of the lower surface. The lower surface may curve outwardly from the central portion to an outer portion which meets the at least one outer sidewall.
The curvature of the lower surface may vary depending upon the bone in which the marker is positioned. The rate of curvature of the lower surface may be constant or, alternatively the rate of curvature may vary along the lower surface from the central portion to the outer portion. A curved lower surface may allow the marker to be inserted into a bone at a number of angles other than at substantially right angles to the surface of the bone. Such curvature allows the head to sit on a bone despite having been introduced at an angle and such that the head does not present a significant prominence to cause a hazard in surgery or impede the use of other surgical equipment.
In one embodiment, a junction is formed between a lower edge of one or more outer sidewalls and the outer portion of the lower surface. The depth of the well is the depth measured from an uppermost edge of the well, which meets the inner edge of the guide surface, to its closed base. The base of the well typically substantially aligns with the junction formed between the lower edge of the one or more outer sidewalls and the outer portion of the lower surface.
The outer sidewalls may be visible to a CT or other scanner in use, the sidewall being distinct from the lower curved surface of the head. In the embodiment wherein the depth of the well is such that the base aligns with the junction between the outer sidewalls and the lower surface a ready visual comparison of the location of the navigation probe in relation to the fiducial marker on the navigation system's imaging screens is provided. If the probe is accurately shown on a screen it will appear to be centrally positioned on the head and at the same depth as the junction of the outer walls and the lower surface.
In one embodiment of the second aspect, the guide surface provides a convex surface to receive a complementary concave surface of the navigation probe. In one embodiment, the guide surface may be partially spherical. The guide surface may comprise a hemispherical surface. The guide surface may comprise only part of the upper surface.
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Typically, however, substantially all of upper surface comprises a convex surface to receive a complementary concave surface of the navigation probe. The upper surface may extend to a join with the lower surface. Alternatively, the head of the marker of this aspect may also include at least one outer sidewall extending between the upper surface and the lower surface.
At least a portion of the head of the fiducial marker of the second aspect may include an external thread. In this embodiment, the head of the fiducial marker may be at least partially countersunk into a target bone.
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The lower surface of the head of this aspect may extend from a join with the shaft of the fiducial marker to a join with the upper surface. The lower surface may be substantially planar such that the head sits flat on a bone in which the marker is inserted. The upper surface may include a drive portion to receive part of a suitable driver to allow the fiducial member to be driven into the bone. The drive portion may comprise a hexagonal socket to receive a hex key or Allen key. Alternatively, the drive portion may comprise crossed recesses to receive a driver member.
In a further embodiment of the second aspect, the guide surface may comprise a plurality of recesses in the upper surface. The plurality of recesses may receive complementary protrusions on part of the navigation probe. The guide surface may comprise one, two three, four or more recesses to receive complementary protrusions therein.
The following description relates to features of the fiducial markers of both the first and second aspects. The shaft of the marker is typically threaded along at least part of its length. The entire length of the shaft may be threaded. In a further embodiment the thread has a reduced depth adjacent to the lower surface of the head such as to increase grip and stability in the bone without compromising the ability to insert the marker. In a still further embodiment rather than a threaded shaft, the fiducial marker may include a surface texturing to secure the fiducial marker in bone.
In this embodiment a filler material such as polymethylmethacrylate for example or a bio-degradable filler or adhesive may be used to secure the fiducial marker to the bone. The fiducial marker may comprise a screw and be made from any suitable biocompatible material. The fiducial marker is typically of sufficient strength to be screwed into the bone and to be suitably imaged during a procedure. In one embodiment, the fiducial marker may be made from medical grade stainless steel. In a further embodiment, the fiducial marker may be made from titanium.
The head and shaft may be made from the same or from a plurality of different materials. In one embodiment, the fiducial marker may be made from a resorbable material. In one embodiment at least a portion of the well may be doped with such a material. Additionally, or alternatively, another portion of the fiducial marker may be doped including the one or more outer sidewalls of the marker. The fiducial marker may further include a region which is reflective of light or other electromagnetic energy. Alternatively, the fiducial marker may be connected to a reflective member such as one or more reflective balls.
In one embodiment, the fiducial marker may include a coating or patch which is reflective of light or other electromagnetic energy. Very well used, but complete and useable. May have flaws such as tears, pen marks or highlighting, large creases, stains, marks, a loose map, etc.
Extremely well used and has major flaws, which may be too numerous to mention. Item is complete unless noted. If you have any questions or comments regarding grading or anything else, please send e-mail to nobleknight nobleknight. Home Back to Results. Fair Very well used, but complete and useable.
Poor Extremely well used and has major flaws, which may be too numerous to mention. When only one condition is listed, then the box and contents are in the same condition. Columns Art of the Gamemaster: Numerology and Religion Things that go Bump in my Head: Cyber Settings The Stacked Deck: Powers of the Ancients Released: The Werewolf's Guide to Usenet.
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