Patent Application
20100274299
The present invention relates to an instrument for preparing a surface of a vertebra, such as a vertebral endplate.
A spinal disc lies between surfaces of adjacent vertebrae, known as endplates. 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. For example, a portion of the disc may weaken or tear which can result in a protrusion into a region of the spine (e.g., the vertebratal foramen) that includes spinal nerves. The protruding portion 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 these conditions, a displaced or damaged spinal disc may be surgically removed from the spine and replaced with a spinal disc implant. Specialized instruments have been provided to facilitate preparation of the site which wilt receive the spinal disc implant.
In one aspect, a surgical instrument is provided for preparing the surface of a vertebra. The instrument has a working end including a working tool configured for insertion between adjacent vertebra, the working tool having working implements for preparing the vertebral surface. The working tool is moveable in a direction that may be side-to-side, top-to-bottom, or along a path that includes both side-to-side and top-to-bottom aspects. The instrument includes a rotary to linear translation system for moving the working tool.
In another aspect, a vertebral surface preparation unit for use in a surgical instrument is provided. The unit includes a frame removable from and reattachable to the surgical instrument body. A working tool is configured for insertion between adjacent vertebra, and is mounted to the frame. The working tool is moveable in a direction that may be side-to-side, top-to-bottom, or along a path that may include both side-to-side and top-to-bottom aspects. The working tool includes at least a first surface with one or more working implements for preparing the vertebral surface. The working tool includes an anterior end, and an aspect of a rotary to linear translation system is accessible at the anterior end.
In another aspect, a vertebral surface preparation unit for use in a surgical instrument is provided. The unit includes a U-shaped frame including a pair of resilient, inwardly compressible legs that are adapted to releasably engage with a compatible frame mount on a surgical instrument body. A working tool, configured for insertion between adjacent vertebra, is mounted to the frame. The working tool is moveable in a direction that may be side-to-side, top-to-bottom, or along a path that may include both side-to-side and top-to-bottom aspects. The working tool including at least a first surface with one or more working implements for preparing the vertebral surface.
In a still further aspect, a surgical instrument for preparing the surface of a vertebra is provided. The instrument includes an elongated tube and a rotatable drive shaft internal to the elongated tube. A distal end of the drive shaft includes a cam pin. A working tool, configured for insertion between adjacent vertebrae, has at least one surface with working implements for preparing a vertebral surface. The working tool includes an anterior end and a cam follower slot accessible at the anterior end that is couplable with the cam pin. A frame mounts the working tool about a pivot pin. A mount is supported by the tube and is engageable with the frame, with the cam pin and the cam follower slot being couplable when the mount and the frame are engaged.
In the drawings, each identical or nearly identical component that is illustrated in various figures may be represented by a like numeral. For purposes of clarity, not every component may be labeled in every drawing. In the drawings:
a is a view of a surgical instrument for preparing a vertebral surface;
b is a view of the surgical instrument of
c-1e are views of the surgical instrument of
a is a view of a vertebral surface preparation unit;
b is a view of the frame portion of the unit of
c is a view of the anterior end of the working tool aspect of the unit of
d is a view of the posterior end of the working tool aspect of the unit of
e is a side view of the working tool aspect of the unit of
a-3b are views of a surgical instrument for preparing a vertebral surface mounted through an associated vertebrae distractor; and
a-4c are views of a surgical instrument for preparing a vertebral surface, with the instrument arranged to move in a top-to-bottom direction against the vertebral surface.
A vertebral surface, such as an endplate, may be prepared to receive a spinal disc implant and such preparation may include the formation of an endplate surface that is compatible with the adjacent contours and/or surface of the replacement disc. The spinal disc implant may include certain projections and/or other features to resist shear or rotation of the prosthetic device, to facilitate osseointegration of the implant, and/or for other purposes, and an endplate may be prepared to accommodate such projections and/or other features. An instrument suitable for such preparation of a vertebral surface is now described. Although discussed in connection with preparing an endplate or other vertebral surface, the instrument is not so limited and other applications are contemplated.
Turning to
A functional handle 16 at a proximal end of the instrument may be coupled, directly or indirectly, to the shaft, so that rotation of the handle, turns the shaft and, in turn, drives the cam and cam follower system. The handle may be integrally connected, or releasably joined, to the shaft. The instrument may include an elongated outer tube 26 with the shaft extending through and being rotatable within the outer tube. A collar 28 may be threaded to the outer tube, centering and assembling the shaft within the outer tube. Unthreading the collar allows removal of the cam shaft, for example when sterilizing the instrument. A side-arm handle 24 may be provided to facilitate positioning of the instrument and may be removeable, such as from an underlying post, if desired, to avoid encumbering the field of view. One or more alignment fins 30 may be provided on the outer tube to cooperate with complementary alignment features in an associated device, such as a vertebrae distractor. Depth stop rods 32 may be provided for use with an instrument positioning system in such an associated device.
As observed earlier, in certain embodiments the working tool may be configured to sweep from side-to-side. The limit, or angle of sweep, of the working tool may characterized by reference to a sweep axis and may be the same (i.e., symmetric) along each side of the working tool. Alternatively, the working tool may be arranged so that different sweep angles (i.e., asymmetric) are provided at each side. A sweep axis may be provided at a centerline of the working tool, along a distal end. Alternatively, the sweep axis may be provided off-center and, or alternatively, closer to the proximal end of the working tool. In the latter scenario, for example, a greater arc of sweep results at the distal end of the working tool. The invention is not limited to a particular location of a sweep axis and other arrangements are contemplated including, for example, locating a sweep axis at the center of the working tool. Representative sweep angles include: ±11.5° (total sweep angle of 23°), ±10.5° (total sweep angle of 21°), and ±9.5° (total sweep angle of 19°). The invention is not limited to the particular sweep angles noted, and other sweep angles are contemplated.
In one embodiment, a pivot pin 34 is provided at the sweep axis and the working tool moves about the pivot pin. The pivot pin may be a separate component or may be integrally formed with the working tool. A frame 36 may be provided which supports the pivot pin, and the working tool may include a hole, recess or other arrangement for cooperating with the pivot pin. The frame may be of a planar form, and have a generally U-shape. In the embodiment shown, the frame is formed of metal (although the invention is not so limited) and includes a pair of legs 38 that are each characterized by a thin proximal segment 40 that may have a slight, outwardly bowed shape, an outwardly diverging intermediate segment 42 that may include a wide shoulder, a first converging segment 44 and then a second, more acutely, converging segment 46. The first and second converging segments of each leg together define an opening having a compound shape including a distal triangular shape and a proximal quadrilateral shape (see dashed lines in
Recesses 50 may be arranged in the sides of the working tool to receive a portion of the frame legs, such as the first and second converging segments, and may be of a sufficient depth so that the side of the working tool projects outwardly beyond the juxtaposed portion of a leg when the working tool is at its farthest extent of sweep. A standoff 80, exposed by the recesses, separates the top and bottom portions of the working tool and may have a compound shape including a proximal, generally quadrilateral shape 90, and a distal generally triangular configuration 92. The standoff is smaller than the opening between the first converging segments, ensuring freedom of movement of the working tool. Interior faces of the working tool that have been exposed by the recesses may include a bottomed out hole for receiving the pivot pin. Neither the frame, the recesses, the standoff, nor the pivot pin connection are limited to the particular configurations just described.
The proximal end 60 of the working tool, also referred to as an anterior end in connection with an instrument for preparing a vertebral surface for implantation of a spinal disc, includes an elongated slot 62 that extends in a side-to-side direction. The elongated slot provides access to a cam follower slot 22 that may extend, as shown, in a first surface (e.g., top) to second surface (e.g., bottom) direction, so that the cam follower slot extends in a direction substantially perpendicular to the elongated slot. The cam follower slot is provided in the floor of the elongated slot and, as such, the elongated slot may be characterized as a counter-bore with respect to the cam follower slot. The invention is not limited to the particular shapes of the elongated slot and the cam follower slot, and other shapes for one or both may be employed. Although shown as extending linearly, either slot may be curved or have other non-linear orientation. The elongated slot and cam follower slot need not be substantially normal to each other, and other relative axial directions also are contemplated. The elongated slot is sized to receive an end of the elongated shaft, while the cam follower slot is sized to receive the cam pin at the end of the shaft. When the cam pin is mated with the cam follower, rotation of the cam by the shaft will cause the working tool to sweep reciprocally from side-to-side. Alternatively, the cam follower slot may be arranged to move the working tool in a top-to-bottom direction, or along a path that combines both side-to-side and top-to-bottom aspects. In certain embodiments, the cam follower slot may be characterized as extending in a direction transversely to the desired direction of movement of the working tool. The cam follower slot may be aligned with the axis, or may be offset therefrom. A wall may separate the elongated slot from the frame receiving recesses. Alternatively, the recesses and elongated slot could be continuous so long as the recesses are sufficiently narrower than the elongated slot at their junction, forming a reduced dimension which would act to stop movement of the working tool relative to the shaft. In certain embodiments, the elongated slot may be eliminated and the cam follower slot provided at the anterior end face. The instrument is not limited to the drive system described and other cam and cam follower arrangements are contemplated. Further, other rotary-to-linear translation systems may be employed including, without limitation, rack and pinion systems, eccentric cam systems, and shaft and bevel gear systems. Although described in connection with a manual arrangement for driving the rotary-to-linear translation system, a mechanical drive system or a power drive system may, alternatively, be used as would be apparent to one of skill in the art. Further, it also is contemplated that the drive system could be arranged to provide movement of the working tool in a distal-proximal direction.
The frame may be permanently attached to the instrument or, preferably, may be removeable, such that the frame and working tool may constitute a separate unit. The removeable frame and working tool embodiments allow a different size or type of working tool to be employed with the same instrument body, or the same working tool to be removed, perhaps for cleaning or for some other reason, and then reconnected if desired. As shown, a mount 70 may be provided on the outer tube which may include an opening for receiving the proximal segment of the frame legs. The thinner proximal segment is resilient and may be compressed by hand into a slender profile that is insertable into the mount. The intermediate and distal segments (first and second converging segments) may have a more robust configuration, as shown, to ensure adequate support for the working tool. The proximal segment of the legs may include a cam feature 71, such as the wedge shape shown, to facilitate reduction of the legs as the frame is inserted into the mount. The legs may include a latch 72, such as a shoulder located at the end of the cam, as illustrated, which springs back and engages the mount upon clearing the mount end. The legs may also include a second latch, such as an opposed shoulder 74 that locks against the other end of the mount. To release the frame and working tool unit from the instrument, the legs are compressed until the latches 72 are narrower than the mount, and then the reduced frame may be withdrawn. The arrangements for engaging the frame and mount are not limited to the embodiment just described, as should be apparent to one of skill in the art, and other approaches are contemplated including, without limitation, push-button detents, snap-lock structures, and male/female locking systems. The mount may be in the form of a bracket, as illustrated, or may be embodied in other forms that are suitable for supporting the frame. The mount may be integrally formed with the outer tube or may be a separate component that is then associated with the outer tube.
The working tool, preferably formed of metal, is configured for insertion between adjacent vertebrae and includes at least one surface that is arranged with working implements 90 for preparing the vertebral endplate surface. As observed earlier, certain spinal implants may include fixation features for securing the implant either temporarily or permanently and, for example, may provide increased resistance to shear and rotation. The working implements may prepare the endplate surface for receipt and/or engagement with the fixation features or otherwise prepare the endplate surface for insertion of the spinal implant and/or to facilitate osseointegration therewith, or for other purposes as may be desired. The working implements may include one or more projections extending from the surface of the working tool and may be in the form, without limitation, of the following: rasp, cutter, file, grinder, chisel, shaver, reamer, awl, probe or borer. The working implements may be provided on a single surface, on two surfaces, which may include a first surface 92 and a second surface 94, or on more than two surfaces. The instrument is not limited to the number of surfaces bearing working implements. The type and pattern of working implements may be the same on the first and second surfaces or may be arranged differently. Further a combination of different working implements may be provided on a working tool surface. The working implements may be arranged on a top and/or a bottom surface of the working tool and, further or alternatively, may include working implements on a side surface and/or front and back end faces. The surface of the working tool also may include channels for removing debris formed by the working implements. In the embodiment shown, the height of each working surface increases from an outer portion towards the center, providing a dome-like shape. The overall thickness of the working tool may be greater at the proximal end as compared to the distal end, and such thickness may gradually decline from the proximal end towards the distal end. The shapes and dimensions of the working tool are not limited to the embodiments shown or described, and other arrangements are contemplated as should be apparent to one of skill in the art. Each of the surfaces illustrated in
As shown in
An endplate preparation instrument 200 arranged for movement of a working tool 202 in a top-to-bottom direction is illustrated in
The basic components of instrument 200 may be similar to the instrument 100 described in connection with
The working tool shown is pivotable in the top and bottom directions about a sweep axis, and includes working implements for acting against the vertebral endplate surface. The working tool may include a pivot pin 204 that cooperates with a complementary feature in a frame 206. An anterior end 208 of the working tool may include a cam follower slot. The cam follower slot extends from side-to-side; that is, in a direction transverse to the desired direction of movement of the working tool. Other arrangements of the cam follower slot are contemplated. A cam pin at the end of the drive shaft mates with the cam follower slot and rotation of the drive shaft moves the working tool in an upward/downward direction against the endplate surface. Although not illustrated, nor necessary for instrument 200, an elongated slot may be provided in a counter-bore relationship to the cam follower slot, elongated in the desired direction of movement of the working tool; so in a top-to-bottom direction and normal to the direction of the cam follower slot. The elongated slot is adapted to receive the distal end of the shaft.
Having thus described several aspects of at least one embodiment of this invention, it is to be appreciated various alterations, modifications, and improvements will readily occur to those skilled in the art. Such alterations, modifications, and improvements are intended to be part of this disclosure, and are intended to be within the spirit and scope of the invention. Accordingly, the foregoing description and drawings are by way of example only.
