CORTICAL, ANTI-MIGRATION, FACET DOWEL FOR FUSION OF FACET JOINTS IN THE SPINE AND DEVICES FOR SETTING THE SAME IN PLACE
A novel allograft is provided for insertion into a prepared site between adjacent spinal facets. The allograft or facet dowel is typically comprised of three portions, a partially spherical body defining a spherical segment, a nose portion, and a tail portion, all aligned along a longitudinal axis. In addition, a set of instruments is provided for the excavation of an allograft placement site between the two facets. The set of instruments includes a T-spade drill which will, in conjunction with a normal drill, excavate a site for the emplacement of the allograft. A novel method of using the instruments and the allograft is also provided.
This application is a divisional of U.S. patent application Ser. No. 13/051,488, filed Mar. 18, 2011, which claims the benefit of U.S. Patent Application No. 61/315,071, filed Mar. 18, 2010. U.S. patent application Ser. No. 13/051,488 is herein incorporated by reference.
FIELD OF THE INVENTIONFacet dowel allografts and devices for emplacement of the same, more specifically, for emplacement of a facet dowel allograft for fusion of facet joints in the open surgery of the spine.
BACKGROUND OF THE INVENTIONMillions of Americans suffer from lower back pain. For facet joint disorders, often the source of lower back pain, the most commonly used procedure for alleviating the pain is facet fusion.
It is one objective in a facet spinal fusion procedure to reduce a patient's post-operative pain, blood loss, and rehab time. An important consideration in achieving these foregoing objectives is an allograft that ensures vertebrae stability and is resistant to graft migration.
OBJECTS OF THE INVENTIONIt is an one of the objects of this invention to provide for a facet dowel allograft that is stable and helps prevent allograft migration after implanting.
It is another object of the present invention to provide for a set of instruments that will help prepare the adjacent facets for receipt of the novel dowel and to emplace the novel dowel in an open surgical operation between the adjacent facets.
SUMMARY OF THE INVENTIONA novel allograft is provided for insertion into a prepared site between adjacent facets, the allograft or facet dowel typically comprised of three portions, a partially spherical body defining a spherical segment, a nose portion, and a tail portion, all aligned along a longitudinal axis. In addition, a set of instruments is provided for the excavation of an allograft and placement site between the two facets. The set of instruments includes a T-spade drill which will, in conjunction with a normal drill, excavate a site for the emplacement of the allograft. A novel method of using the instruments and the allograft is also provided.
The novel facet dowel is typically comprised of 100% cortical bone, but may, in an alternate embodiment, be comprised of cancellus bone. The facet dowel typically is comprised of three portions in an integrated body having a long axis: a partially spherical body defining a spherical segment, a nose portion along the long axis thereof and a tail portion extending along the long axis thereof.
Dimensions in the drawings are in inches and millimeters. The dimensions illustrated on all the sheets are in mm (inches bracketed) nominal, approximate, and may vary.
Nose portion 14 is seen to include a least some tapered walls 14a, which define a rounded, cap-like or core-like structure, which may have a tip portion 14b. Nose portion is typically partly cylindrical with a larger diameter DN where it joins body portion 12 and a smaller diameter DNT at a tip portion 14b thereof.
Tail portion 16 may be at least party cylindrical and may have a diameter of DT. DT is usually equal to or approximately equal to DN. DN and DT are typically smaller than diameter DS, which is the diameter of the body portion or spherical segment 12 of the implant or allograft 10.
After the allograft site is selected and drilled out in ways known in the art, the prep-drill is removed from the working channel 1 and a T-spade drill 3 is inserted. It is a function of T spade drill 3 to remove bone adjacent the inter-facet gap for receipt of allograft 10 therein.
When the T spade drill is moved to an extended position from that shown in FIGS. 10D1-10D3, it may be rotated typically 180-360° in the inter-facet location that was previously drilled with the prep-drill to excavate space for the spherical segment of allograft 10. By such rotation, bone is removed from the vertebrae located above and below to define a volume that is spherical with a shape substantially identical to body 12, the volume with a diameter about equal to Ds (see
Turning now to the details of tip portion 3a, tip portion 3a is seen to have a nose portion 3e, which nose portion may have a perimeter 3f and which nose portion joins a body or flat portion 3g. The body or flat portion 3g joins the near end of body 3b, which body may include a tapered portion 3h. The diameter of the nose portion 3e, which is typically tapered, is about equal to the diameter of the working portion 3a of the drill, here about 4.09 mm (may be slightly more or slightly less). The diameter of the flat portion 3g is approximately equal to or slightly greater or slightly less than the diameter of the spherical or segmented portion 12 (DN). This thickness of the flat portion is typically about 1.52 mm or about equal to or slightly more or less than an inter-facet gap at the drill site. The thickness can be seen in
Turning now to removed end 3c, it is seen to include a stop portion 3i which will limit the limit the longitudinal extension of the T-spade drill through the working channel as seen in
Tip 1a is seen to comprise the pair of legs 1d and 1e, which are spaced apart, as best seen in
Legs 1d/1e of the working channel extend about 8 mm beyond the end walls 1i of the working channel 1 and the drill stop 2d puts the tip 2a of the drill 2 about 3 mm beyond the ends of the legs, about the same distance for the T-spade 3. That is to say, the nose of the drill 2 and the nose of the T-spade extend about 3 mm beyond the ends of the legs of the working channel when the either the drill or T-spade stop hits the end walls of the working channel. It may be seen with respect to
With the working channel in place as seen in
Channel set 8 is seen to have a cylindrical, hollow channel 8a therein. Channel set 8 is further seen to have a nose portion 8b extending from a body portion 8c, both portions 8a and 8b being cylindrical and having inner walls which define hollow channel 8a. Body 8c is seen to have forward stop 8d between nose portion 8b and body portion 8c.
A brief summary of the steps used to implant the allograft to assist in the fusion, which implanted allograft is illustrated in
FIG. 10D3 illustrates the excavated space and the T-spade drill in the aligned position, which will allow the withdrawal of the instrument from the working channel.
Next, the allograft 10 is loaded into inserter 4 and moved to the insertion site, which has been drilled and excavated. The inserter is then placed into the working channel, with the allograft on the tip until the inserter is flush with the channel instrument (see
In
After the site is located and prepared by the joint finder in ways known in the art, then the working channel 1 is slipped over the joint finder as is illustrated in
FIGS. 10D-10D3 illustrate the shaping step wherein the T-spade drill 3 is inserted into the working channel and extended with orientation boss 3j through longitudinal slot 1e, which orientation of the boss in the slot will place the flat portion of parallel to the faces of the interior and superior facets, which are adjacent the inter-facet space. Moreover, it is seen that orientation slot 1e on the working channel is located aligned the legs 1e of the working channel 1, which legs define the plane in which the flat portion 3g of the T-spade drill 3 is placed when the T-spade drill 3 is urged up to the annular ring. Rotation of 180° in either direction will then allow the spherical leading edge defining the outer perimeter of the flat portion 3g to shape the vertebrae bone above and below the drilled out channel in such a way as to provide a fit for the allograft as best seen in the detailed portion of
At this point, as illustrated in
Although the invention has been described in connection with the preferred embodiment, it is not intended to limit the invention's particular form set forth, but on the contrary, it is intended to cover such alterations, modifications, and equivalences that may be included in the spirit and scope of the invention as defined by the appended claims. For example, gas is considered to be a fluid, the device may operate with either a liquid or a gas.
Claims
1. A drill for use in conjunction open spinal facet implant surgery wherein the facet implant comprises a substantially rigid spherical segment having a diameter Ds; a tail segment comprising a cylindrical shape joined at a first end and integral to the spherical segment and having a removed end, the tail segment having a longitudinal axis, a diameter Dt, and a length Lt; and a nose segment comprising a cylindrical shape and a removed end, the nose segment integral with the spherical segment at a near end and having a length Ln, a longitudinal axis coincident with the longitudinal axis of the tail segment, and a diameter Dn, the drill comprising:
- a nose portion comprising a cylindrical shape;
- a tail portion comprising a cylindrical shape, wherein the diameters of the nose portion and the tail portion are approximately the same as the diameter of the nose segment of the facet implant; and
- a body portion having a thickness substantially less than the diameter of the nose portion, and having a width about the same as the diameter of the spherical segment of the facet implant.
2. The drill of claim 1, wherein the cylindrical shape of the nose portion of the drill has a diameter of approximately 4 mm.
3. The drill of claim 1, wherein the thickness of the body portion of the drill is approximately 1.5 mm.
4. The drill of claim 1, wherein the width of the body portion of the drill is approximately 6 mm.
5. The drill of claim 1, wherein the length of the body portion of the drill is approximately 4.5 mm.
6. The drill of claim 1, wherein the cylindrical shape of the nose portion of the drill has a diameter of approximately 4 mm, the thickness of the body portion of the drill is approximately 1.5 mm, the width of the body portion of the drill is approximately 6 mm, the length of the body portion of the drill is approximately 4.5 mm, and the cylindrical shape of the tail portion of the drill has a diameter of approximately 4 mm.
7. The drill of claim 1, further comprising an elongated shaft coupled to the tail portion of the drill at a first end of the shaft, the elongated shaft sized to place the body portion of the drill between opposing spinal facets while extending outside of an associated facet joint and to provide torque to rotate the body portion to remove bone from opposing spinal facets.
8. The drill of claim 7, further comprising:
- a working channel through which the shaft extends, the shaft having a second end that extends from the working channel remotely from the drill, wherein the first end of the shaft tapers to the tail portion; and
- a T-handle at the second end of the shaft, the T-handle sized to allow a user to apply torque to the shaft.
9. A drill for use in conjunction with open spinal facet implant surgery, the drill comprising:
- a nose portion having a thickness wider than a pre-surgery distance between opposing spinal facets;
- a tail portion having a thickness approximately the same as the nose portion; and
- a body portion having a thickness substantially less than the thickness of the nose portion and having a width substantively greater than the thickness of the nose portion.
10. The drill of claim 9, wherein the thickness of the nose portion is approximately 4 mm.
11. The drill of claim 9, wherein the nose portion comprises a cylindrical shape.
12. The drill of claim 11, wherein the cylindrical shape of the nose portion has a diameter of approximately 4 mm.
13. The drill of claim 9, wherein the thickness of the body portion is approximately 1.5 mm.
14. The drill of claim 9, wherein the width of the body portion is approximately 6 mm.
15. The drill of claim 9, wherein the tail portion is cylindrical in shape.
16. The drill of claim 15, wherein the cylindrical shape of the tail portion has a diameter of approximately 4 mm.
17. The drill of claim 9, wherein the length of the body portion is approximately 4.5 mm.
18. The drill of claim 9, wherein the thickness of the nose portion is approximately 4 mm, the thickness of the body portion is approximately 1.5 mm, the width of the body portion is approximately 6 mm, the length of the body portion is approximately 4.5 mm, and the thickness of the tail portion is approximately 4 mm.
19. The drill of claim 9, further comprising an elongated shaft coupled to the tail portion at a first end of the shaft, the elongated shaft sized to place the body portion between opposing spinal facets while extending outside of an associated facet joint and to provide torque to rotate the body portion to remove bone from opposing spinal facets.
20. The drill of claim 19, further comprising:
- a working channel through which the shaft extends, the shaft having a second end that extends from the working channel remotely from the drill, wherein the first end of the shaft tapers to the tail portion; and
- a T-handle at the second end of the shaft, the T-handle sized to allow a user to apply torque to the shaft.
Type: Application
Filed: Oct 29, 2014
Publication Date: Mar 19, 2015
Inventor: M. David Dennis (San Antonio, TX)
Application Number: 14/527,197
International Classification: A61B 17/16 (20060101); A61B 17/70 (20060101);