Endplate preparation instrument

An instrument for preparation of vertebral endplates and a method of preparing a surface of a vertebral endplate are described. The instrument includes a body having a frame, an endplate preparation member supported by the body, and a pivot point. A tilt axis is perpendicular to and intersects a sweep axis at the pivot point. The endplate preparation member is coupled to the frame and controllably pivotable in an arc about the first tilt axis to change a tilt of the endplate preparation member. The endplate preparation member is also controllably pivotable in an arc about the sweep axis while maintaining the tilt of the endplate preparation member. By sweeping the endplate preparation member at incrementally larger tilt angles, recesses in a vertebral endplate surface are gradually formed, which may allow greater precision and control of a depth of the recesses and reduce stress on the vertebral endplate, as opposed to more aggressive techniques.

RELATED APPLICATIONS

This application is related to co-pending U.S. patent application Ser. No. 12/115,043 entitled “DISTRACTOR,” filed on May 5, 2008, which is herein incorporated by reference in its entirety.

FIELD OF INVENTION

The present invention relates to an instrument for preparing an endplate of a vertebra.

BACKGROUND

A spinal disc lies between endplates of adjacent vertebrae. The disc stabilizes the spine and assists in distributing forces between vertebral bodies. A spinal disc may be displaced or damaged due to trauma, disease or other degenerative processes that can occur over time. For example, a portion of the disk may weaken or tear which can result in the protrusion of the nucleus pulposus into a region of the spine (e.g., the vertebratal foramen) that includes spinal nerves. The protruding nucleus pulposus may press against spinal nerves causing pain, numbness, tingling, diminished strength and/or a loss of motion. Another common degenerative process is the loss of fluid from the disc. Such fluid loss can limit the ability of the disc to absorb stress and may reduce its height, which can lead to further instability of the spine, as well as decreasing mobility and causing pain.

To address the conditions described above, a displaced or damaged spinal disc may be surgically removed from the spine. Historically, after the disc is removed, a fusing implant is inserted into the disc space that allows the two adjacent vertebrae to fuse together. In other surgical procedures, the damaged disc is removed and replaced with an artificial disc. Specialized instruments have been provided to facilitate preparation of the site, which will receive the artificial disc.

SUMMARY

An aspect of the invention relates to a surgical instrument for preparing a surface of a vertebra. The instrument includes an elongated body having a frame, a first pivot point and a first endplate preparation member for preparing a surface of a vertebra. A first sweep axis and a first tilt axis that is substantially perpendicular to the first sweep axis pass through the first pivot point. The first endplate preparation member is supported by the body and controllably pivotable in an arc about the first tilt axis to change a tilt of the first endplate preparation member, and is controllably pivotable in an arc about the first sweep axis while maintaining a tilt of the first endplate preparation member.

Another aspect of the invention relates to a surgical instrument for preparing a surface of a vertebra having an elongated body with a frame, a first pivot point though which a first sweep axis passes, and a first endplate preparation member that is controllably pivotable in an arc about the first sweep axis. The first endplate preparation member is supported by the body and is controllably pivotable through a predetermined sweep range of greater than about 3 degrees and less that about 180 degrees. The first endplate preparation member is also able to be displaced along the first sweep axis changing a height of the first endplate preparation member.

Yet another aspect of the invention relates to a surgical instrument for preparing a surface of a vertebra including an elongated body having a frame and a first arm configured to cooperate with a first endplate preparation member. The first arm is controllably pivotable with respect to the frame about a first arm-sweep axis for controllably pivoting the first endplate preparation member about a first sweep axis that is substantially parallel to the first arm-sweep axis. The instrument is configured to controllably pivot the first endplate preparation member about a first tilt axis that is substantially parallel to and intersects the first sweep axis.

Another aspect of the invention relates to a preparation member unit for preparing a surface of a vertebra, The preparation member unit includes a first endplate preparation member having a portion configured to couple with an actuator of an instrument body and a mounting member configured to mount the preparation member unit to a frame portion of an instrument body. The preparation member unit also includes a first preparation member-mounting coupling that pivotably couples the endplate preparation member and the mounting member allowing the first endplate preparation member to pivot relative to the mounting member about a first sweep axis and about a first tilt axis that is perpendicular to, and intersects, the first sweep axis at a first pivot point.

Yet another aspect of the invention relates to an instrument body having a frame portion and an actuator coupled with the frame portion. The frame portion is configured to couple with a mounting member of a preparation member unit. The actuator is configured to cooperate with a first endplate preparation member of the preparation member unit. The actuator is also configured to controllably pivot the first endplate preparation member about a first sweep axis, and configured to pivot the first endplate preparation member about a first tilt axis that is substantially perpendicular to, and intersects, the first sweep axis.

Another aspect of the invention relates to an endplate preparation member for preparing a surface of a vertebra. The endplate preparation member includes a body portion with a first preparation surface, at least one endplate preparation element extending from the first preparation surface, and an extension of the body portion configured for engagement with a coupling in an instrument body. The body location also includes a pivot location being configured for movement about a tilt axis and about a sweep axis that is substantially perpendicular to the tilt axis and that passes through the pivot location.

Yet another aspect of the invention relates to a method of preparing a surface of a vertebral endplate. The method includes providing a vertebral endplate preparation instrument having a first endplate preparation member located at a distal portion of the instrument and inserting the distal portion of the instrument into a disc space adjacent to the vertebral endplate. The method also includes pivoting the first endplate preparation member relative to the vertebral endplate about a first tilt axis. The method further includes pivoting the first endplate preparation member relative to the vertebral endplate about a first sweep axis that is substantially perpendicular to the first tilt axis while the first endplate preparation member is in contact with the first vertebral endplate surface.

DETAILED DESCRIPTION

A vertebral endplate may be prepared to receive an implantable spinal disc and such preparation may include the formation of an endplate surface that is compatible with the contours and/or surface of the replacement disc. For example, the spinal disc may include certain projections intended for placement in complementary recesses to be formed in the vertebral endplate, and the instrument and methodology of the invention may be employed to achieve the same. An exemplary embodiment includes an instrument with a body having an elongated frame, a first pivot point, and a first endplate preparation member for preparing a surface of a vertebra. A first sweep axis and a first tilt axis that is substantially perpendicular to the first sweep axis intersect at the first pivot point. The first endplate preparation member is supported by the body and is controllably pivotable with respect to the frame about the first tilt axis to change a tilt of the first endplate preparation member, and controllably pivotable about the first sweep axis while maintaining the tilt. Teeth or other endplate preparation effectors may be incorporated in the first endplate preparation member, such that a sweeping motion of the first endplate preparation member will form recesses in the vertebral endplate.

The angular extent, or length, of a recess formed in a vertebral endplate may be controlled by limiting a total range of angular sweep of the first preparation member. For example, an inner frame width may limit the total range of angular sweep of the first preparation member. By allowing a user to controllably select a tilt angle of the first endplate preparation member with respect to the frame, depths of recesses formed in the vertebral endplate may be controlled.

A user may gradually form recesses in the vertebral endplate by initially “sweeping” the first endplate preparation member against the vertebral endplate at a small tilt angle, then “sweeping” against the vertebral endplate at incrementally larger tilt angles. Gradually forming recesses may allow greater control of the first endplate preparation member as the recesses are formed, which may result in greater control of a final depth of the recesses. Gradually forming recesses may also reduce a risk of damage to vertebrae during endplate preparation, as compared to more aggressive endplate preparation techniques. In addition, a user may receive tactile feedback regarding force applied to the vertebral endplate by the first preparation member during execution of a sweep through a first arm of the instrument.

Reducing a tilt angle of the first endplate preparation member may reduce the profile of the instrument, facilitating insertion and/or withdrawal of the working end of the instrument from the disc space. The instrument may include a tilt lock to maintain a selected tilt of the first endplate preparation member. The instrument may include a reduction actuator configured to place the first endplate preparation member in a reduced tilt configuration.

In some embodiments, an instrument with a first endplate preparation member and a second endplate preparation member is provided. The second endplate preparation member may be controllably pivotable about a second sweep axis that is substantially Is parallel to a first sweep axis, and controllably pivotable about a second tilt axis that is substantially perpendicular to the second sweep axis. Movement of the second endplate preparation member may be mechanically coupled to movement of the first endplate preparation member, or the second endplate preparation member and the first endplate preparation member may move independently.

Some embodiments of the invention provide an endplate preparation unit. Other embodiments of the invention provide an instrument body. The endplate preparation unit and the instrument body are configured to couple to each other, forming an endplate preparation instrument with the endplate preparation member at the tip of the device. A frame of the endplate preparation instrument may include a distal frame portion of the endplate preparation unit that mounts to a frame portion of the instrument body. The endplate preparation unit may include a distal frame portion, one or more endplate preparation members that are pivotably coupled to the distal frame portion so as to be moved in a sweeping and a tilting direction relative to respective sweeping and tilting axes of the distal frame portion, and where the distal frame portion is configured for connection to the frame portion of the instrument body.

The instrument body may include a frame portion configured to couple with the distal frame portion of the preparation member unit, and an actuator system for manipulating the sweep and tilt of the endplate preparation member. The actuator may be configured to controllably exert a force to pivot the endplate preparation member about a first sweep axis, and to controllably exert a force to pivot the endplate preparation member about a first tilt axis that is substantially perpendicular to the first sweep axis.

Another embodiment of the invention is an endplate preparation member that may be used with a preparation member unit and/or with an endplate preparation instrument. The endplate preparation member includes a first preparation surface and one or more primary cutting projections extending from the first preparation surface. The primary cutting projections are configured to form primary fixation recesses for receiving primary fixation elements of the implant. The endplate preparation member may also include dome-cutting projections configured to form a recess with a substantially domed shape for receiving an implant, such as an artificial disc. A configuration of the endplate preparation member may permit forming the overall dome shaped implant receiving recess and the primary fixation recesses simultaneously.

Other embodiments provide a method of endplate preparation using a vertebral endplate preparation instrument. Initially, an instrument is provided with a first endplate preparation member. A distal portion of the instrument is inserted into a disc space adjacent to a vertebral endplate. The instrument may be in a collapsed configuration as the distal portion is inserted into the disc space. The first endplate preparation member is pivoted relative to vertebral endplate about a first tilt axis until a first desired tilt angle is reached. The instrument may be set to controllably maintain the first desired tilt angle. Then, the first endplate preparation member is pivoted relative to the vertebral endplate about a first sweep axis, while the first endplate preparation member is in contact with a surface of the first vertebral endplate. After the disc is prepared, the distal portion of the instrument may be withdrawn from the disc space, while the instrument is in a reduced tilt collapsed configuration. The tilt of the endplate preparation member may be adjusted to increase the depth of the recesses formed in the bone surface.

Turning toFIGS. 1A and 1B, an exemplary endplate preparation instrument10including a body19with an elongated frame20, a first pivot point40, and a first endplate preparation member30for preparing a surface of a vertebra, is illustrated. The first endplate preparation member30is supported by the body19. As depicted, the first endplate preparation member30is pivotably coupled to the frame20. During preparation of a vertebral endplate, after a distal portion10bof the instrument in inserted into a disc space, the frame20may maintain a fixed position relative to a vertebra while the first endplate preparation member30moves with respect to the frame20and the vertebra.

The first pivot point40may be located at the distal portion10bof the instrument. As shown in the perspective view ofFIG. 1A, a first sweep axis42, and a first tilt axis44that is substantially perpendicular to the first sweep axis42, both pass through the first pivot point40. The first endplate preparation member30is controllably pivotable in an arc45about the first tilt axis44to change a tilt of the first endplate preparation member30, and controllably pivotable in an arc43about the first sweep axis44while maintaining the tilt of the first endplate preparation member30. The first endplate preparation member30may be controllably pivotable about the first tilt axis44and controllably pivot about the first sweep axis42simultaneously.

In some embodiments, this is accomplished through a first preparation member-frame coupling41that couples the first endplate preparation member30and the frame20, and that is configured to allow the first endplate preparation member30to controllably pivot relative to the frame20in an arc45about the first tilt axis44to change a tilt of the first endplate preparation member30. In some embodiments, the first preparation member-frame coupling41is releasable and in other embodiments the first preparation member-frame coupling may not be releasable. As used herein, changing the “tilt” of the first endplate preparation member30includes, but is not limited to, pivoting the first endplate preparation member30about the first tilt axis44. As shown in the side view ofFIG. 1B, the first preparation member-frame coupling41may also be configured to allow the first endplate preparation member30to controllably pivot relative to the frame20in an arc43about the first sweep axis42to change a “sweep position” of the first endplate preparation member30while maintaining the “tilt” of the first endplate preparation member30. As used herein, changing the “sweep position” of the first endplate preparation member30includes, but is not limited to, pivoting the first endplate preparation member30about the first sweep axis42.

In some embodiments, the instrument10may include a first arm50configured to cooperate with the first endplate preparation member30. The first arm50may be pivotably coupled with the frame20allowing the first arm50to controllably pivot with respect to the frame20in an arc47about a first arm-sweep axis46, which is substantially parallel to the first sweep axis42. Due to coupling between the first arm50and the first endplate preparation member30, moving a proximal first arm portion50aalong arc47with respect to the frame20changes a sweep position of the first endplate preparation member30. The proximal first arm portion50amay include a first grip52allowing a user to more easily grasp and control a position of the proximal first arm portion50a. The first arm50may form a portion of an actuator for controllably pivoting the first preparation member30about the first sweep axis42,

In some embodiments, the instrument is configured to controllably pivot the first endplate preparation member about the first tilt axis42. As depicted, the first arm50is pivotably coupled with the frame20of the instrument10all owing the first arm50to controllably pivot with respect to the frame20in an arc49about the first arm-tilt axis48, which is parallel to the first tilt axis44. Due to this coupling between the first arm50and the first endplate preparation member30, moving a proximal first arm portion50aalong arc49with respect to the frame20changes a tilt angle of the first endplate preparation member30. The first arm50may form a portion of an actuator for controllably pivoting the first preparation member30about the first sweep axis42and about the first tilt axis44.

Some embodiments of the endplate preparation instrument10may include a second pivot point70and a second endplate preparation member60for preparing a surface of a vertebra, as shown inFIGS. 1C and 1D. A second sweep axis72is substantially perpendicular to and intersects a second tilt axis74at the second pivot point70. The second endplate preparation member60is coupled with the frame20in a configuration that allows the second endplate preparation member60to controllably pivot with respect to the frame20along an arc73about a second sweep axis72. In the depicted embodiment, the second sweep axis72overlays the first sweep axis42; however, in other embodiments the second sweep axis72is substantially parallel to, but spatially displaced from, the first sweep axis42.

The second endplate preparation member60is controllably pivotable with respect to the frame20along an arc75about a second tilt axis74that is substantially parallel to the first tilt axis44. As depicted, a second preparation member-frame coupling71couples the second endplate preparation member60and the frame20, allowing the second endplate preparation member60to controllably pivot about the second sweep axis72and controllably pivot about the second tilt axis74. In the depicted embodiment, the second tilt axis74is spatially displaced from the first tilt axis44; however, in other embodiments the second tilt axis74may overlay the first tilt axis44.

Some embodiments of an endplate preparation instrument10may include a second arm80configured to cooperate with the second endplate preparation member60, as depicted. The second arm80may be pivotably coupled with the frame20allowing the second arm80to controllably pivot with respect to the frame20in an arc47about the first arm-sweep axis46, which is substantially parallel to the first sweep axis42and the second sweep axis72. Due to coupling between the second arm80and the second endplate preparation member60, moving a proximal second arm portion80aalong arc47with respect to the frame20changes a sweep position of the second endplate preparation member60. The proximal second arm portion80amay include a second grip82allowing a user to more easily grasp and hold the proximal second arm portion80a. The second arm80may form a portion of an actuator for controllably pivoting the second preparation member60with respect to the frame20about the second sweep axis72.

In the depicted embodiment, the first arm50and the second arm80pivot together about the arm-sweep axis46; however, in other embodiments the first arm50and the second arm80pivot in opposite directions along arc47. In still other embodiments, the first arm50and the second arm80pivot with respect to the arm-sweep axis46independently of each other, as the invention is not limited in this respect.

In some embodiments, the first arm50and the second arm80diverge from each other as they extend from the first arm sweep axis at the frame20toward the distal portion of the instrument10b. In some embodiments, the first arm50and the second arm80each bend so that the arms diverge laterally toward opposite sides of the frame20at the distal portion10bof the instrument.

A coupling between the second arm80and the frame20may be configured to allow the second arm80to pivot with respect to the frame20about an arm-tilt axis48along arc49. Due to coupling between the second arm80and the second endplate preparation member60, moving a proximal second arm portion80aalong arc49with respect to the frame20changes a tilt of the second endplate preparation member60.

Some embodiments of the invention permit control of a tilt of the first endplate preparation member30about the first tilt axis44, and permit control of a tilt of the second endplate preparation member60about the second tilt axis74. In the depicted embodiment, both the first arm50and the second arm80are may be used to control a tilt of the first endplate preparation member30and the second endplate preparation member. When the proximal first arm portion50aand the proximal second arm portion80aare pivoted closer to each other along arc49, a tilt of the first proximal head30is increased and a tilt of the second proximal head60is increased. At the same time, spacing Spbetween the first pivot point40and the second pivot point70may increase, as is discussed below with respect toFIGS. 5A and 5B.

As depicted, moving the proximal first arm portion50aand the proximal second arm portion80atoward each other symmetrically with respect to the frame20results in the first endplate preparation member30and the second endplate preparation member60tilting symmetrically with respect to the frame20. However, because the first arm50and the second arm80are both able to pivot with respect to the frame about tilt axis48, the first arm50and the second arm80can each pivot by a different angle with respect to the frame20resulting in a different tilt angle for the first endplate preparation member30than for the second endplate preparation member60. This “nonsymmetrical tilt” may allow the first endplate preparation member30and the second endplate preparation member60to conform or adjust to a disc space orientation that is not symmetrical with respect to the instrument frame20.

Embodiments may include a tilt select component for selecting a preparation member tilt from a predefined set of tilt values and may include a tilt lock component for maintaining a selected tilt. In the depicted embodiment, a ratchet component102on a proximal portion80aof the second arm and a complementary tooth component104on the proximal portion50aof the first arm provide a predefined set of tilt values based on a spacing of projections on the ratchet component102forming a tilt selection component101. The tilt selection component101allows an angle between the proximal portion50aof the first arm and the proximal portion of the second arm80ato be changed incrementally. The ratchet component102and the tooth component102may also maintain a selected tilt forming a tilt lock component105. In other embodiments, a tilt selection component may be separate from a tilt lock component, as the invention is not limited in this respect. A tilt lock component may maintain a force on one or both endplate surfaces as the first endplate preparation member30or both the first and the second endplate preparation members30,60execute a sweeping motion.

Some embodiments of the invention may include one or more biasing components to bias the proximal first arm portion50aand the proximal second arm portion80atoward separation, which corresponds to a low profile, decreased tilt instrument configuration. In some embodiments, biasing components106may include springs107,108, as depicted. Further details regarding a collapsed configuration, an expanded configuration are described below with respect toFIGS. 5A and 5B.

Some embodiments of the invention include additional elements that cooperate with coordinating elements on other instruments used during a surgical procedure. For example, a distal portion10bof the instrument may be inserted into a disc space through a channel520formed by a distractor510, as illustrated inFIGS. 1E and 1F. An alignment feature of the instrument10, such as a keel projection97, may cooperate with a coordinating alignment feature of the distractor510, such as an alignment slot512configured to receive the keel projection97, ensuring that the instrument10is properly aligned with the distractor510when it is inserted into the disc space. The instrument10may include at least one depth stop projection96that is engaged by a complementary depth stop feature514on a distractor to set a maximum insertion depth for insertion of the instrument10through the working channel520of the distractor510. Further explanation of using exemplary endplate preparation instruments with distractors may be found in related co-pending U.S. patent application Ser. No. 12/115,043 entitled “DISTRACTOR,” and filed on the same day as this application, and which is herein incorporated by reference in its entirety.

Exemplary embodiments may also include a frame handle22affixed to or integral with the frame20. The frame handle22may be used for positioning and stabilizing the instrument during insertion and/or may engage complementary stabilization features on another surgical instrument such as a distractor or an external frame. In some embodiments, an orientation of the frame handle22is adjustable relative to the frame20. For example, the frame handle22may pivot with respect to the frame20along arc23.

FIGS. 2A to 2Ddepict an enlarged distal portion10bof the instrument with the first endplate preparation member30at different sweep positions, in accordance with an embodiment of the invention.FIG. 2Ashows a side view of the enlarged distal portion10bof the instrument with the first endplate preparation member30in a central sweep position with respect to the frame20. The first endplate preparation member30is coupled with the first arm50by a first member-arm coupling91, which is configured to allow the first endplate preparation member30to pivot with respect to the first arm50about a first member-arm axis92that is substantially parallel to the first sweep axis42.FIGS. 2B and 2C, illustrate a sweeping motion of the first endplate preparation member30by showing side views of the distal portion of the instrument10bwith the first endplate preparation member30in one sweep position and in an opposite sweep position, respectively.

FIG. 2Dfurther illustrates a first preparation member-arm coupling91by showing an enlarged perspective view of a distal portion10bof the instrument. In one embodiment, the first member-arm coupling91includes an extension32of the first endplate preparation member30that extends through an arch54of the first arm50, as depicted. The interaction between the extension32of the endplate preparation member30and the arch54of the first arm acts as a pivotable coupling that allows the first preparation member30to pivot with respect to the first arm50.

FIG. 3provides a clear view of a backside of the first endplate preparation member30and the distal portion50bof the first arm by omitting the second endplate preparation member60and the second arm80. As shown inFIG. 3, the distal portion of the first arm50bmay extend behind the first endplate preparation member30past the first member-arm coupling91. The first preparation member30and the first arm50also contact each other where the first arm50presses against the backside of the first preparation member30. This contact allows the first arm to exert a force to tilt the first preparation member. Tilt of the first preparation member is described below in further detail with respect toFIGS. 5A and 5B.

An internal width Fwof the frame20may limit a total range of sweep αsof the first endplate preparation member30due to a portion of the frame20physically blocking a distal portion of the first arm50b. As depicted, the first endplate preparation member is able to sweep though about ±13 degrees or a total sweep range of about 26 degrees. In some embodiments, a sweep range may be smaller, for example about ±1 degree or about 2 degrees total. In other embodiments, a sweep range may larger, for example about ±90 degrees or about 180 degrees total. However, other sweep ranges may be employed, as will be apparent to one of skill in the art.

In some embodiments, the first preparation member-frame coupling41and the first member-arm coupling91may be configured to allow the preparation member to rotate about a first “twist” axis78within a total “twist” range of less than about 180 degrees as indicated by arrow79. The “twist” rotation may allow the first endplate preparation member30to adapt or conform to a rotational misalignment between the frame20and the disc space.

Some embodiments of the invention provide a first endplate preparation member30that is configured to be detached from an instrument. For example, in some embodiments, the first endplate preparation member30may be detachably connected with the frame20.FIGS. 4A-4Eshow different views of the first endplate preparation member30, in accordance with some embodiment of the invention. Although attributes and aspects of exemplary preparation members will be discussed with reference to the first endplate preparation member30, any attributes and properties described with respect to the first endplate preparation member30may be incorporated into the second endplate preparation member50or an additional preparation member, as the invention is not limited in this respect.

The first endplate preparation member30may have a proximal portion30p, a distal portion30d, a front side30fwith a first preparation surface31, a back side30band an edge30econnecting the front side30fand the back side30b. A proximal portion30pof the first endplate preparation member may include a pivot projection32that is configured to engage a feature of the first arm50, such as the coupling arch54, to form a portion of the first member-arm coupling91(see alsoFIG. 2D). The pivoting projection32may extend from the front side30fand/or the edge30eof the proximal portion30pof the first endplate preparation member30, in accordance with an embodiment of the invention. The pivoting projection32may be rounded facilitating more stable contact between the first endplate preparation member30and the coupling arch54as the first endplate preparation member30sweeps with respect to the frame20, and as the first endplate preparation member30tilts with respect to both the frame20and the first arm50(see alsoFIG. 2D). A rounded surface of the pivoting projection32may allow the first endplate preparation member30to rotate about the first twist axis78(see alsoFIG. 2D).

The first endplate preparation member30includes one or more endplate preparation elements extending from the first preparation surface31. The one or more endplate preparation elements may be configured to form one or more recesses or troughs, enlarge one or more recesses or troughs, shape one or more recesses or troughs, smooth one or more recesses or troughs and/or roughen one or more recesses and troughs in a vertebral endplate surface. The endplate preparation elements may include one or more primary cutting projections33a,33b,33cthat are configured to cut recesses or troughs into a vertebral surface. The recesses or troughs formed by the primary cutting projections33a,33b, and33cmay be primary fixation recesses configured to receive primary fixation features of an implant.

In some embodiments, the endplate preparation elements include dome-cutting projections37extending from the first preparation surface31configured to form, enlarge, shape and/or smooth a recess with a substantially domed shape, as shown inFIGS. 4A to 4D. In some embodiments, the dome-cutting projections37may be configured to enlarge, shape and/or smooth a pre-existing recess in a vertebral endplate. In some embodiments, at least some of the dome cutting projections37are elongated substantially radially outward from a first sweep axis42along the first preparation surface31as shown inFIGS. 4A and 4B. In some embodiments, each cutting projection37has a substantially curved profile, as shown inFIGS. 4A and 4D. A substantially curved profile of a dome cutting projection37may profile irregularities38configured to reduce a size of bone chips created by the dome cutting projection37during the endplate preparation process, as shown byFIG. 4D.

Although an exemplary embodiment of the first preparation member30is depicted with both primary cutting projections33a,33b, and33cand dome-cutting projections37, embodiments of the first preparation member may include primary cutting primary cutting projections33a,33b, and33c, but not dome-cutting projections37, may include dome-cutting projections37, but not primary cutting primary cutting projections33a,33b, or may include neither, as the invention is not limited in this respect. The first preparation member30may include other types of suitable endplate preparation elements, as will be appreciated by one of skill in the art.

In some embodiments, the first endplate preparation member30may include channels34connecting the front side30fand the backside30bof the first endplate preparation member30that facilitate removal of debris during the endplate preparation process.FIG. 4Eshows a region35on the back side30bof the first endplate preparation member30that is configured to cooperate with the first preparation member-frame coupling41(see alsoFIG. 1A). In some embodiments, a proximal portion30pof the first endplate preparation member30includes an extension portion36proximal to the pivoting projection32.

The first endplate preparation member30illustrated inFIGS. 4A to 4Emay be described as a rasp. However, other embodiments of the invention may include endplate preparation members in the form of rasps with other configurations, various types of cutting members, various types of grinders, combinations of cutting members and grinders, etc., as the invention is not limited in this respect.

FIGS. 5A and 5Bdepict cross-sectional views of a distal portion of instrument10illustrating a tilt α and a height h of the first endplate preparation member30and the second endplate preparation member60with respect to the frame20, in accordance with aspects of the invention.FIG. 5Adepicts a distal portion of the instrument10bin a configuration for insertion or withdrawal. In the collapsed configuration, a tilt α1of the first endplate preparation member30with respect to the frame20is relatively small and a separation h1between the first pivot point40and the frame20may be relatively small. For embodiments with a first endplate preparation member30and a second endplate preparation member60, a tilt α2of the second endplate preparation member60with respect to the frame20is relatively small in a collapsed configuration. A separation h2between the second pivot point71and the frame20may be relatively small in the collapsed configuration. For example, inFIG. 5Aboth the first endplate preparation member30and the second endplate preparation member60have zero tilt (α1=0 and α2=0).

FIG. 5Bdepicts the distal portion of the instrument10bin an expanded configuration. The angle α1between the first endplate preparation member30and the frame20is relatively larger in an expanded configuration. The separation h1between the first pivot point40and the frame20may be relatively larger in an expanded configuration than in a collapsed configuration. For embodiments having a first endplate preparation member30and a second endplate preparation member60, the tilt angle α2between the second pivot point70and the frame20is larger in the expanded configuration. The separation h2between the second pivot point70and the frame20may be larger in an expanded configuration. The first preparation member-frame coupling41may be configured to allow the first endplate preparation member30to controllably change a tilt angle α with respect to the frame20and to change a height h with respect to the frame20.

In some embodiments with both the first endplate preparation member30and the second endplate preparation member60, the first preparation member-frame coupling41includes a first end112aof a double-ended extendable pivot pin112and a first spherical retaining ring114attached to the first endplate preparation member30. The second preparation member-frame coupling71may include a second end112bof the double-ended extendable pivot pin12and a second spherical retaining ring116attached to the second endplate preparation member60.

In some embodiments, a portion of the pivot pin112may be attached to the frame20, as depicted. In some embodiments, the pivot pin112may connect the first endplate preparation member30and the second endplate preparation member60, as depicted. In some embodiments, the pivot pin112may connect the first endplate preparation member30and the second endplate preparation member50and be slidably coupled with the frame20, as the invention is not limited in this respect.

As described above with respect toFIGS. 1C and 1D, moving the proximal first arm portion50aand the proximal second arm portion80btoward each other, which causes the distal portion of the first arm50band a distal portion of the second arm80bto move further apart, changes a configuration of the instrument10from collapsed to expanded. As illustrated byFIG. 5B, the proximal portion of the instrument10bis expanded by the distal first arm portion50bexerting a force FE1on the back side30bof the first endplate preparation member and the distal second arm portion80bexerting a force FE2on a back side60bof the second endplate preparation member60. The force FE1exerted by the first arm50pivots the first endplate preparation member30about the first pivot point40away from the frame20. The first coupling arch54, through which the first endplate preparation member30extends, sets a maximum tilt angle when the first pivot projection32engages the first coupling arch54. As depicted, the tilt range as set by the maximum tilt angle is about 6 degrees for each of the first endplate preparation member30and the second endplate preparation member60for a total combined tilt range of about 12 degrees. In other embodiments, the tilt range may be smaller, for example, about 1 degree for each endplate preparation member for a total combined tilt range of about 2 degrees. However, other tilt ranges may be employed as will be apparent to one of skill in the art.

The force FE1exerted by the first arm50may also displace the first pivot point along the first sweep axis42, displacing the first endplate preparation member30away from the frame20. As depicted, the first pivot point40may be displaced when the extendable pivot pin112extends due to the force FE1.

Similarly, force FE2exerted by the second arm80may pivot the second endplate preparation member60about the second pivot point70away from the frame20. The second pivot point70may be displaced along the second sweep axis72, when the extendable pivot pin112extends.

Conversely, spreading the first handle52and the second handle82apart, which causes the distal portion of the first arm50band the distal portion of the second arm80bto move closer together, changes a configuration of the instrument10from extended to collapsed (see alsoFIGS. 1C and 1D). In some embodiments, a first reduction actuator122and/or a second reduction actuator124may be used to ensure that the first endplate preparation member30and/or the second endplate preparation member60remain in a collapsed configuration during insertion and withdrawal of the instrument10, as depicted inFIG. 5A. Part of the first reduction actuator122is indicated by a dotted line because it lies in a plane that is not visible in the cross-sectional views ofFIGS. 5A and 5B. The first reduction actuator122, which is pivotably attached to the distal first arm portion50b, exerts a force FC1on the extension portion36of the first endplate preparation member30to hold it against the distal portion of the first arm50b. The second reduction actuator124, which is pivotably attached to the distal second arm portion80b, exerts a force FC2on an extension portion66of the second endplate preparation member60to hold it against the distal portion of the second arm80b. Force FC2exerted by the second reduction actuator124on the second endplate preparation member60is due to a force FC3exerted by the first arm50on the second reduction actuator124, as shown inFIG. 5A. Similarly, force FC1exerted by the first reduction actuator122on the first endplate preparation member30is due to a force (not depicted) exerted by the second arm70on the first reduction actuator122.

The first reduction actuator122and the second reduction actuator124may allow a surgeon to ensure that the instrument is in a collapsed configuration. If the first endplate preparation member30and the second endplate preparation member60are not in a collapsed configuration, the first reduction actuator122and the second reduction actuator124prevent the first handle32and the second handle62from moving further apart.

Some embodiments of the invention may include a preparation member unit206, as shown inFIG. 6A. Other embodiments of the invention include an instrument body208. The preparation member unit206and the instrument body208are configured to couple to each other forming an endplate preparation instrument208. The preparation member unit206may include a first endplate preparation member210, a mounting member212configured to mount to a frame portion of the instrument body208, and a first pivotable preparation member-mounting coupling220that couples the mounting member212and the first endplate preparation member210. The first pivotable preparation member-mounting coupling220may be in the form of a pivot pin that extends through the mounting member212or a different type of coupling that is supported by the mounting member212, as the invention is not limited in this respect.

In some embodiments, the preparation member unit206may also include a second endplate preparation member215that is coupled to the mounting member212by a second pivotable preparation member-mounting coupling220. The first pivotable preparation member-mounting coupling220and the second pivotable preparation member-mounting coupling may be opposite ends of an extendable pivot pin disposed in the mounting member212, or may be separate coupling elements each supported by the mounting member212, as the invention is not limited in this respect.

In some embodiments, the mounting member214of the preparation member unit206may have channels212c, and the frame portion214of the instrument body208may have threaded channels214callowing the mounting member212to be attached to the frame portion214using threaded screws. The first pivotable coupling220connects the mounting member214and the first endplate preparation member210allowing the first endplate preparation member210to pivot relative to the mounting member220about a first sweep axis242and about a first tilt axis244substantially perpendicular to the first sweep axis242.

The preparation member unit206is detachable from the instrument body208and may be replaced with a different preparation member unit206. Multiple different preparation member units206may be compatible with the same instrument body208allowing a surgeon to select from different sizes of endplate preparation members210, endplate preparation members210with different preparation surface configurations, endplate preparation members210formed of materials with different material properties, etc.

The instrument body208includes a frame214configured to couple with the mounting member220of the preparation member unit210, and an actuator209coupled with the frame208and configured to cooperate with the first endplate preparation member210of the preparation member unit206. The actuator209is configured to controllably exert a force to pivot the first endplate preparation member210about a first sweep axis242, and configured to controllably exert a force to pivot the first endplate preparation member210about a first tilt axis244that is substantially perpendicular to, and intersects, the first sweep axis242. The actuator209may include a first arm and a second arm, as shown and described with respect toFIGS. 1A-2Dabove, may include a first arm and a tilt arm as described below with respect toFIGS. 7A-7D, or any other suitable configuration known in the art, as the invention is not limited in this regard.

Another embodiment of the invention including a preparation member unit226is depicted inFIG. 6B. The preparation member unit226is configured to mount to a frame portion234of an instrument body228forming an instrument. A frame of the total instrument includes a frame portion234of the instrument body228and a distal frame portion236of the preparation member unit226. A mounting member230of the preparation member unit226may include the distal frame portion236of the preparation member unit. In some embodiments, the distal portion of the frame236may be configured to attach to the frame portion234of the instrument body228using screws, with a quick release mounting, or using any other method known in the art, as the invention is not limited in this regard. Known quick release mountings include, but are not limited to: various types of snap fit mountings, and various types of cam release mountings.

As explained above with respect toFIG. 3, an inner frame width Fwmay define a total maximum sweep angle αsof a first endplate preparation member210. Different preparation member units226may be provided with different internal frame widths Fwallowing a surgeon to select a desired total maximum sweep angle αsas well as a desired size and configuration of first endplate preparation member210.

Although embodiments of an endplate preparation instrument depicted in the preceding figures showed two identical endplate preparation members, instruments with two differently sized endplate preparation members, instruments with two differently configured endplate preparation members, instruments with more than two endplate preparation members and instruments with one endplate preparation member also fall within the scope of the invention.

For example,FIGS. 7A to 7Ddepict an endplate preparation instrument310having only one endplate preparation member330, in accordance with another embodiment of the invention. Endplate preparation instrument310includes the endplate preparation member330, a body319with a frame320, a first (sweep) arm350, and a tilt arm380.FIG. 7Ashows a perspective view of the instrument310in a collapsed configuration with the endplate preparation member330in a central sweep position. A pivotable preparation member-frame coupling341allows the endplate preparation member330to pivot about a sweep axis342and to pivot about a tilt axis344that is substantially perpendicular to the sweep axis342. The first (sweep) arm350is used to control sweep of the endplate preparation member330and the tilt arm380is used to control tilt of the endplate preparation member330.

FIG. 7Bshows an enlarged perspective view of a distal portion310bof the instrument. In this embodiment, a member-sweep-arm coupling392couples the endplate preparation member330and the sweep arm350. The member-sweep-arm coupling392may include a rotatable coupling392aand a sliding-pivotable coupling392b, as shown inFIGS. 7B and 7D. A separate member-tilt-arm coupling394may slidably couple the endplate preparation member330and the tilt arm380, as shown inFIGS. 7B and 7D.

In some embodiments, the first arm350is rotatably coupled with frame320allowing the first arm350to rotate with respect to the frame320about an arm-sweep axis395that is parallel to the sweep axis342. In the depicted embodiment, the tilt arm380is rotatably coupled with frame20by the tilt-arm-frame coupling398allowing the tilt arm380to rotate about an arm-tilt axis397. However, the tilt-arm-frame coupling398does not allow the tilt arm380to rotate about the arm-sweep axis395. As shown inFIGS. 7C and 7D, although the endplate preparation member330has moved along arc343and the sweep arm350has rotated about axis395to change sweep position, the tilt arm380has not rotated about axis395. The tilt arm380maintains contact with the endplate preparation member330during sweeps through the slidable member-tilt-arm coupling394.

Endplate preparation instrument310may have a trigger-type tilt control388T includes the tilt arm380, and a trigger372coupled with a proximal portion380aof the tilt arm380. When the trigger372is depressed (arrow373), the proximal portion380aof the tilt arm rotates toward the frame320(arrow375) causing the distal portion30dof the tilt arm to rotate away from the frame20(arrow377), thereby increasing a tilt of the endplate preparation member330, as shown inFIG. 7C. The trigger-type tilt control388may include a biasing element (e.g. spring374) to bias the instrument310toward a collapsed configuration. In some embodiments, the trigger-type tilt control388may include a maximum tilt selection component and tilt lock component376. The instrument310may also include one or more alignment features378to aid in aligning the instrument for insertion into a disc space, as shown inFIGS. 7A and 7B.

Other exemplary embodiments include a method400of preparing a vertebral endplate, as illustrated in the flow chart ofFIG. 8. Solely for illustrative purposes, method400will be described with respect to the endplate preparation instrument10depicted inFIGS. 1A-1D. One of skill in the art will recognize that method400may be performed with other exemplary instruments, as the invention is not limited in this respect.

Initially, a vertebral endplate preparation instrument10having a first endplate preparation member30at a distal portion10bof the instrument is provided (step410). The instrument includes a frame20and a first endplate preparation member30disposed at a distal portion of the instrument20b. The instrument also includes a first pivot point40where a first sweep axis42intersects a first tilt axis44that is substantially perpendicular to the first sweep axis42at pivot point40.

The distal portion10bof the instrument is inserted into a disc space adjacent to a vertebral endplate (step420). In some embodiments, the instrument10is in a collapsed configuration when the distal portion10bof the instrument is inserted into the disc space (see alsoFIG. 5A). The first endplate preparation member30is pivoted relative to the vertebral endplate about a first tilt axis44(step430), (see alsoFIG. 5B). The first endplate preparation member30may be pivoted until a first desired tilt angle α1is reached. In some embodiments, the method also includes setting the instrument10to controllably maintain the tilt angle α1(step435). The instrument may be set using a ratchet mechanism, a tilt lock or any other suitable element or technique known to one of skill in the art.

The first endplate preparation member30is pivoted relative to the vertebral endplate about a first sweep axis42that is substantially perpendicular to the first tilt axis44while the endplate preparation member30is in contact with the first vertebral endplate surface (step440). In some embodiments, the first desired tilt angle α1is maintained while the first endplate preparation member30is pivoted about the first sweep axis42. In some embodiments, the instrument includes a frame20and the frame20is stationary with respect to the vertebral endplate while the first endplate preparation member30is pivoted with respect to the vertebral endplate. In some embodiments, a user of the instrument10has manual feedback regarding forces applied to the vertebral endplate during the sweeping motion by feeling a resistance to the sweeping motion.

In some embodiments, the first endplate preparation member30may be pivoted about the first tilt axis42until the first endplate preparation member30reaches a second desired tilt angle, which is larger than the first desired tilt angle (step450). The first endplate preparation member30may then pivot relative to the frame20about the first sweep axis42while maintaining the second desired tilt angle (step460). Incrementally increasing the tilt angle and sweeping the first endplate preparation member at each new tilt angle can gradually increase a depth of a feature in an endplate reducing stress on the vertebra as compared to more aggressive techniques. In some embodiments, the frame20of the instrument10can remains stationary with respect to the vertebra as the first endplate preparation member30is pivoted about the first tilt axis42and as the first endplate preparation member is pivoted about the first sweep axis.

In some embodiments, the instrument10also includes a second endplate preparation member60disposed at the distal portion10bof the instrument and a second pivot point70. A second sweep axis72and a second tilt axis74that is substantially perpendicular to the second sweep axis72, intersect at the second pivot point70. The method may also include pivoting the second endplate preparation member60relative to the vertebral endplate about the second tilt axis74to change a tilt angle of the second endplate preparation member60, and pivoting the second endplate preparation member30relative vertebral endplate about the second sweep axis72while maintaining the tilt angle. The second endplate preparation member60may be moved simultaneously with the first endplate preparation member30, or may move independently. If the second endplate preparation member60does not move at a same time as the first endplate preparation member30, the frame20of the instrument may remain in a same position for the sweeping motion of the first endplate preparation member30and the sweeping motion of the second endplate preparation member60.

According to some embodiments of the invention, the first endplate preparation member30is pivoted relative to a frame20of the instrument about the first tilt axis44until the distal portion10bof the instrument is in a collapsed configuration (step470). The distal portion10bof the instrument is then withdrawn from the disc space while maintaining the instrument10in a collapsed configuration (step480). Inserting and removing the distal portion10bof the instrument from the disc space with the instrument10in a collapsed configuration may reduce a risk that the first endplate preparation member30and/or the second endplate preparation member60damage one or both vertebral endplates during insertion or removal.