CROSS-REFERENCE TO RELATED APPLICATION

[0001] This application claims priority from U.S. Provisional Patent Application No.

62/566,991 filed on October 02, 2017, the entire disclosure of which is part of the disclosure of the present application and is hereby incorporated by reference in its entirety.

BACKGROUND AND FIELD OF THE INVENTION

[0002] This invention relates generally to multi-axis internal spinal fixation.

[0003] There are many systems available for internal fixation of the spine. A problem with all such systems, however, is the joint between the screws used to affix the system to the pedicle and the rods, cross-bars, and/or plates of the system. The problems at the site of this linkage may result from the geometry of the joint between the screw and the rod or plate. This difficult geometry results from several factors, including the different angles and placement of the vertebrae and their relative sizes, the shape of the vertebrae and the spacing between vertebrae, the placement of the screws, the lordosis of the spine, and the need to insert the screws into each vertebra at an angle. With regard to the angle of the pedicle screws, pedicle screws are angled inwardly and upwardly into the vertebra for maximum strength and, because the surfaces of the pedicles of each vertebrae are angled relative to each other, the screws rarely line up across the vertebral body into which they are screwed. Nor do they line up from one vertebra to the adjacent vertebra even if the adjacent vertebrae are the same size and shape (which they generally are not). Because the pedicle screws do not line up, the rod which runs along the longitudinal axis of the patient's spinal column, which provides the structural rigidity required to stabilize the spine, must either be bent to the location of each screw head or the stabilizer must be provided with adjustable structure which enables the screw head to be attached to the rod.

[0004] U.S. Pat. Nos. 6,355,038 and 6,669,697, the contents of which are incorporated by reference herein in its entirety, disclose a spinal stabilizer system comprising a rod, a screw, a cross-bar/plate having a hole therein, means for attaching the cross-bar to the rod, and a washer. The washer comprises a cylindrical body having one end angled with respect to the side walls of the cylindrical body and a longitudinal passage therethrough for receiving the screw for affixing the cross-bar to the vertebra of a patient. The washer also comprises means for resting on and rotatably engaging the margins of the hole in the cross-bar so that the body is capable of being rotated in the hole in the cross-bar to provide an infinite variety of angles and pedicle screw placements while maintaining an optimal interface between the head of the screw and the washer so as to effectively transfer the load from the spinal column to the cross-bar.

[0005] The spinal stabilizer system disclosed in U.S. Pat. Nos. 6,355,038 and 6,669,697 has several advantages. However, the inventor observed that the rods (or vertical plates) disclosed therein were subject to breakage when there was excess stress as in obesity, acute curvatures of the spine, and while reducing spondylolisthesis. Increasing the thickness of the vertical plates was proposed as a solution. However, an increase in the plate thickness adversely affected the bendability of the plates thereby making them unsuitable for their intended purpose.

[0006] Accordingly, there is a need for a spinal implant wherein the vertical plates can be bent and do not break under stress or tension.

SUMMARY OF THE INVENTION

[0007] According to an embodiment, a spondylolisthesis reduction kit is provided. The spondylolisthesis reduction kit contains: a plurality of horizontal plates; a plurality of vertical plates, and two sets of bolts. A first set of bolts is configured to couple one or more stacked pairs of vertical plates to a first horizontal plate. Each of the bolts in the first set of bolts includes: a square-shaped head, a non-threaded portion proximal to the square-shaped head, a first threaded portion proximal to the non-threaded portion, a second threaded portion, and a waist portion. The waist portion is configured to separate the first and second threaded portions. The second threaded portion is configured to be broken off. The combined length of the non-threaded portion and the first threaded portion is about 17.1 mm or longer (for example, when more than two vertical plates are stacked, the threaded portion can be longer than 17.1 mm).

[0008] The kit further includes a second set of bolts, wherein the second set of bolts is substantially shorter in length than the first set of bolts, the second set of bolts is configured to couple the one or more stacked pairs of vertical plates to at least a second horizontal plate, wherein each of the second set of bolts includes: a square- shaped head, a non-threaded portion proximal the square-shaped head, and a threaded portion proximal the non-threaded portion. The combined length of the non-threaded portion and the threaded portion of each of the second set of bolts is approximately 17.1 mm or longer. Each horizontal and vertical plate includes a through-hole for receiving one or more bolts from the first or second set of bolts.

[0009] According to another embodiment, a spinal implant kit is provided. The spinal implant kit contains : a plurality of horizontal plates ; a plurality of vertical plates ; and a set of bolts . Each of the bolts includes: a square- shaped head, a non-threaded portion proximal the square- shaped head, and a threaded portion proximal the non-threaded portion. Each horizontal and vertical plate includes a through -hole for receiving one or more bolts. The combined length of the non-threaded portion and the threaded portion is approximately 17.1 mm. The bolts are configured to couple one or more pairs of vertical plates to two or more horizontal plates. The spinal implant comprises a biocompatible material. In one embodiment, the biocompatible material comprises titanium.

[0010] In another embodiment, a method for extending an original spinal fusion is provided. The original spinal fusion comprises two or more horizontal plates and a first set of vertical plates coupled to the two or more horizontal plates. Extending the original spinal fusion involves: positioning a second set of vertical plates over the first set of vertical plates; affixing the second set of vertical plate to the first set of vertical plate and a last horizontal plate in the original spinal fusion; and coupling the second set of vertical plates to an additional horizontal plate or horizontal plates. The method further comprises providing a set of bolts. Each of the bolts possesses a pre-determined length for affixing the second set of vertical plates to the first set of vertical plates.

[0011] In yet another embodiment, a method of facilitating spondylolisthesis reduction is disclosed. The method involves providing a spinal implant kit containing a plurality of horizontal and vertical plates and two sets of bolts. Each of the plates includes a through-hole for receiving a bolt. The method further involves stacking a first vertical plate over a second vertical plate and a third vertical plate over a fourth vertical plate. Using a first set of bolts, the stacked vertical plates are secured to at least one horizontal plate. The horizontal plate can be positioned along a perpendicular axis to the stacked vertical plates. The method further involves using a second set of bolts to secure the stacked vertical plates to another horizontal plate, wherein this additional horizontal plate is positioned along a lower plane than the first horizontal plate for listhesis reduction. The second set of bolts is substantially longer than the first set of bolts. Each of the stacked vertical plates is configured to be bent to a desired degree of lumbar lordosis before affixing it to the horizontal plates. The method further comprises lifting a listhetic vertebrae upwards and back into normal alignment by forcing the stacked vertical plates down onto the listhetic vertebrae. Each of the second set of bolts includes a breakable portion. After alignment of the listhetic vertebrae, the breakable portion is detached. The vertical and horizontal plates and the first and second sets of bolts are each made of a biocompatible material.

BRIEF DESCRIPTION OF THE DRAWINGS

[0012] The features and advantages of certain embodiments will be more readily appreciated when considered in conjunction with the accompanying figures. The figures are not to be construed as limiting any of the preferred embodiments.

[0013] FIGs. 1A and IB illustrate a spinal implant in accordance with one embodiment of the invention.

[0014] FIG. 1C illustrates an embodiment of a square bolt in accordance with one embodiment of the invention.

[0015] FIG. 2A illustrates a spinal implant for reducing spondylolysthesis in accordance with another embodiment of the invention.

[0016] FIG. 2B illustrates an embodiment of a square bolt for reducing spondylolysthesis in accordance with one embodiment of the invention.

[0017] FIGs. 3A and 3B illustrate extension of an original spinal fusion in accordance with another embodiment of the invention.

DETAILED DESCRIPTION OF THE INVENTION

[0018] Contemplated embodiments disclosed herein address the deficiencies of the prior art that was discussed earlier. The embodiments of the invention also disclose methods for extending spinal fusion without removing the existing instrumentation. [0019] An embodiment of a spinal implant constructed in accordance with the present invention is shown in FIGS. 1A and IB. The embodiment, indicated generally at reference numeral 100, includes horizontal plates HOa-c ("110"). Each of the horizontal plates HOa-c includes a pair of oval through-holes 11 la-b, 11 lc-d, and 11 le-f ("111") respectively. The through-holes are intermediate the ends 120a-b, 120c-d and 120e-f ("120") of each horizontal plate HOa-c respectively. In an embodiment, a horizontal plate is bent at the ends 120a, 120b. The bent ends serve several advantages other than accommodating the shape of the vertebral body and is therefore particularly adapted for use in the spinal implant of the present invention.

[0020] The implant 100 further includes vertical plates 150a-d ("150"). Each of the vertical plates 150 is also provided with one or more oval through-holes 155a and 155b. The vertical plates 150 are oriented along the longitudinal axis of the spinal column on either side of the midline of the vertebrae (not shown).

[0021] Square bolts 160a-160f (together "160") are provided to secure the vertical plates to the horizontal plates. An exemplary square bolt of the invention is illustrated in FIG. 1C. The square bolt 160 includes a post 170 and a square-shaped head 172. The post 170 includes a threaded portion 174 and a non-threaded portion 176. Unlike the conventional bolts disclosed in the prior art which have a shorter length, typically around 12.1mm, the square bolts 160 are around 35%- 45% longer. In one embodiment, the length of the square bolt is around 17.1 mm. The square- shaped head 172 further includes an opposing pair of protrusions 178a,b ("178"). The protrusions 178 are dimensioned so that they can engage the outside edges of each horizontal plate 110. A nut 140 can be threaded onto the post 170 of square bolt 160 and tightened. In certain embodiments, the non-threaded portion 176 of the square bolt may include a belt-like protuberance 180 which can function to retain the square bolt in a groove of the through -holes l l la-f of the horizontal plates without the square bolt falling out of the horizontal plate HOa-c. The square bolt 160 is configured to be slidably moved within the through-holes l l la-f of the horizontal plates.

[0022] A method of facilitating spinal stabilization involves providing the spinal implant

100. In the operating theater, the vertical plates are secured to the horizontal plates. The vertical plate 150a is stacked over vertical plate 150b and vertical plate 150c is stacked over vertical plate 150d. The first pair of stacked vertical plates 150a-b is placed over the horizontal plates HOa-c proximal to the end 120a. The second pair of stacked plates 150c-d is placed over the horizontal plates HOa-c proximal to the end 120b. The first and second pair of stacked plates are positioned parallel to each other over the horizontal plates. The through-holes of the vertical plates are positioned above the through-holes of the horizontal plates forming a contiguous opening for the bolt 160. Each of the stacked vertical plates is configured to be individually bendable. In some embodiments, there maybe additional pairs of vertical plates next to 150a-b and 150c-d respectively.

[0023] The square bolts are configured to slide along the through-holes l l la-f of the horizontal plates to form a straight line to accommodate the straight vertical plates. Each of the stacked vertical plates can be bent to a desired degree of lumbar lordosis before affixing it to the horizontal plates.

[0024] A square bolt 160a is pushed upward from the base of a through -hole in the horizontal plate 110a. The non-threaded portion 176 of the square bolt is retained within the through-holes of the horizontal plate and the through-holes of a first pair of stacked vertical plates 150a-b. The threaded portion 174 of each square bolt passes upwardly through the through-holes of the horizontal and stacked vertical plates where it can be secured with the nut 28 and tightened. Similarly, the remaining square bolts 160b-f are pushed or pressed into the horizontal plates to securely couple the vertical stacked plates to the horizontal plates. The protrusions 178 of each square bolt is dimensioned so that they can engage the outside edges of each horizontal plate to prevent relative rotation between the square bolt 160 and the horizontal plate so that the nut 28 can be threaded onto the post 170 of square bolt 160 and tightened.

[0025] The square bolts have the extra length to accommodate two or more stacked plates.

The extra-long square bolts ensure that the stacked vertical plates are securely coupled to the horizontal plates. The stacking of the vertical plates facilitates strengthening of the spinal implant without compromising on its ability to maintain spinal curvature, through the bendability of an individual vertical plate.

[0026] The square bolts, horizontal plates and vertical plates can be comprised of a resilient, biocompatible material that allows passage of the square bolt upwardly through oval through-holes in the horizontal plate and stacked vertical plates but resists passage back in the other direction so that the square bolt does not fall out of the through-holes. In some embodiments, the square bolts, horizontal plates and vertical plates may be made of titanium.

[0027] Another embodiment of a spinal implant constructed in accordance with the present invention is shown in FIG. 2A. The second embodiment, indicated generally at reference numeral 200, can be used to reduce spondylolisthesis. The second embodiment 200 also includes horizontal plates 110 and vertical plates 150 as described with reference to FIGs. 1A and IB. The features of the horizontal and vertical plates are as disclosed earlier and, are therefore, not repeated herein for brevity.

[0028] A first set of square bolts 160a-d (together "160") is provided to secure the stacked vertical plates 150a-b and 150c-d to the horizontal plates 110a and 110b respectively. In some embodiments, the horizontal plate 110b may not be required while in other embodiments there can be more than two horizontal plates. Square bolt 160 is as described with reference to FIG. 1C and is therefore, not repeated herein for brevity.

[0029] A second set of square bolts 260a and 260b (together "260") is provided to secure the vertical plates to horizontal plate 110c for spondylolisthesis reduction. An exemplary square bolt 260 is illustrated in FIG. 2B. The square bolt 260 includes a post 270 and a square-shaped head 272. The post 270 includes a non-threaded portion 276, a first threaded portion 274a, a second threaded portion 274b and a waist portion 266 separating the first and second threaded portions. The second threaded portion 274b - that is the portion 274b above the waist portion 266 - is configured to be broken or snapped, when necessary. The combined length of the first threaded portion 274a and the non-threaded portion 276 is around 25%-35% greater than that of equivalent prior art bolts. In one embodiment, the combined length of the first threaded portion 274a and the non-threaded portion 276 is around 17.1 mm. The square-shaped head 272 further includes an opposing pair of protrusions 278a, b ("278"). The protrusions 278 are dimensioned so that they can engage the outside edges of each horizontal plate. A nut 28 can be threaded onto the post 270 of square bolt 260 and tightened. In certain embodiments, the non-threaded portion 276 of the square bolt may include a belt-like protuberance 280 which can function to retain the square bolt in a groove of the through -hole 11 If of the horizontal plate 110c without the square bolt 260 falling out of the horizontal plate 110c. The square bolt 260 is configured to be slidably moved within the through-hole 11 If of the horizontal plate 110c. [0030] A method of facilitating spondylolisthesis reduction involves providing the spinal implant 200. In the operating theater, vertical plate 150a is stacked over vertical plate 150b and vertical plate 150c is stacked over vertical plate 150d. The first pair of stacked vertical plates 150a- b is placed over the horizontal plates 1 lOa-b proximal to the end 120a. The second pair of stacked plates 150c-d is placed over the horizontal plates HOa-b proximal to the end 120b. The first and second pair of stacked plates are positioned parallel to each other over the horizontal plates. The through-holes of the vertical plates are positioned above the through-holes of the horizontal plates forming a contiguous opening for bolts 160. Each of the stacked vertical plates is configured to be individually bendable. In some embodiments, there can be more pairs of vertical plates along side 150a-b and 150c-d.

[0031] The square bolts are configured to slide along the through-holes l l la-f of the horizontal plates to form a straight line to accommodate the straight vertical plates. Each of the stacked vertical plates can be bent to a desired degree of lumbar lordosis before affixing it to the horizontal plates.

[0032] A square bolt 160a is pushed upward from the base of a through -hole in the horizontal plate 110a. The non-threaded portion 176 of the square bolt is retained within the through-holes of the horizontal plate and the through-holes of a first pair of stacked vertical plates 150a-b. The threaded portion 174 of each square bolt passes upwardly through the through-holes of the horizontal and stacked vertical plates where it can be secured with the nut 28 and tightened. Similarly, the remaining square bolts 160b-d are pushed or pressed into the horizontal plates 110a- b to securely couple the vertical stacked plates to horizontal plates.

[0033] Square bolts 260a and 260b are also pushed upward from the base of a through- hole in the horizontal plate 110c through the through-holes in the stacked vertical plates 150a-b and 150c-d where they can be secured with nuts 28 and tightened to facilitate spondylolisthesis reduction.

[0034] The method involves lifting the listhetic vertebrae upwards and back into normal alignment by forcing the stacked vertical plates 150a-d down onto the listhetic vertebrae using the square bolts 260a and 260b. After alignment, the second threaded portion 274b - that is the portion above the waist portion 274b - of square bolts 260a and 260b is then broken off. [0035] The square bolts 260a and 260b are substantially longer than conventional bolts to accommodate the heights of the stacked vertical plates. The extra-long square bolts ensure that the stacked vertical plates are securely coupled to the horizontal plates.

[0036] Immense tension is normally placed on a vertical level due to the spondylolisthesis.

The stacking of the vertical plates resists the tension on the vertical level and facilitates strengthening of the spinal implant without compromising on its ability to maintain spinal curvature.

[0037] The square bolts, horizontal plates and vertical plates can be comprised of a resilient, bio-inert/biocompatible material that allows passage of the square bolt upwardly through oval through-holes in the horizontal plate and stacked vertical plates but resists passage back in the other direction so that the square bolt does not fall out of the through -holes. In some embodiments, the plates may be made of titanium. Titanium has been observed to possess shape memory/recoil feature that facilitates gradually pulling the listhetic vertebral body back into normal alignment even if complete reduction is not achieved at the time of surgery.

[0038] In another embodiment, a method for extending spinal fusion by extension of instrumentation (spinal implant) is disclosed. The third embodiment is indicated generally by reference numeral 300.

[0039] During spinal fusion, a first spinal implant 300a is provided. The first spinal implant

300a includes horizontal plates 310a-c ("310") and vertical plates 350a-b ("350"). Horizontal plates 310 are similar to horizontal plates 110 and vertical plates 350 are similar to vertical plates 150 (with the exception that these are not stacked). The features of the horizontal and vertical plates are as disclosed earlier and, are therefore, not repeated herein for brevity. The first spinal implant 300a includes square bolts 360a-f (together "360"). The square bolts 360 are used to affix vertical plates 350a and 350b to the horizontal plates 310a-c. (In some embodiments, it can be just two plates and in others it can be more than three plates). Square bolt 360 is as described with reference to square bolt 160 FIG. 1C and is therefore, not repeated herein for brevity. The square bolts 360 are tightened with nuts 328.

[0040] In case of junctional stenosis, or other problems requiring extension of fusion, a second spinal implant 300b is provided. The second spinal implant 300b includes horizontal plates 310c-d and vertical plates 350c-d. However, it is understood that the second spinal implant may include only one level - that is just one horizontal plate 310c or it can include more than three levels - that is, it can further include plates 310f,g, h... (not shown). The square bolt 360e is used to stack and couple vertical plate 350a to vertical plate 350c and these stacked vertical plates to the last horizontal plate 310a of the original fusion 300a. The square bolt 360f is used to stack and couple vertical plates 350b to 350d and the stacked vertical plates to the last horizontal plate 310b of the original fusion 300a. Similarly, square bolts 360g-j are used to secure plates 310c and 310d to plates 310d and 310e. Square bolts 360g-j are similar to square bolt 160 as described with reference to FIG. 1C and their features are therefore, not repeated herein for brevity. The square bolts 360 are tightened with nuts 328. As seen in FIG. 3B, the square bolts 360 will stick out at all levels with the exception of square bolts 360e and 360f.

[0041] The method for extending fusion involves placing vertical plates 350c and 350d on top of vertical plates 350a and 350b respectively and tightening the bolts 360e and 360f with nuts without exposing or removing the previous instrumentation (such as, spinal implant 300a). The extra length of square bolts 360 facilitate, therefore, facilitate extension of vertical plates above (or below) an existing fusion making extension of instrumentation extremely easy. The extra long square bolts also facilitate angulation of segments of vertical plates in cases of major curvatures from scoliosis and can be extended in multiple segments with multiple junctions without compromising the stability.

[0042] In yet another embodiment, a kit containing one or more horizontal plates, vertical plates and square bolts (160, 360 and/or 260) is provided. The kit can also include one or more tightening nuts and other screws required for a spinal implant procedure.

[0043] For simplicity of explanation, the methodologies are described herein as a series of acts. It is to be understood and appreciated that the subject innovation is not limited by the acts illustrated and/or by the order of acts, for example acts can occur in various orders and/or concurrently, and with other acts not presented and described herein. Furthermore, not all acts can be required to implement the methodologies in accordance with the disclosed subject matter. The terms "a" or "an" as used herein are to describe elements and components of the invention. This is done merely for convenience and to give a general sense of the invention. The description herein should be read to include one or at least one and the singular also includes the plural unless indicated to the contrary. The term "comprises", "comprising", "includes", "including", "as", "having", or any other variation thereof, are intended to cover non-exclusive inclusions. For example, a process, method, article or apparatus that comprises a list of elements is not necessarily limited to only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus. What has been described above include mere examples of systems and methods. It is, of course, not possible to describe every conceivable combination of components or methods for purposes of describing this disclosure, but one of ordinary skill in the art can recognize that many further combinations and permutations of this disclosure are possible. Furthermore, to the extent that the terms "includes," "has," "possesses," and the like are used in the detailed description, claims, appendices and drawings such terms are intended to be inclusive in a manner similar to the term "comprising" as "comprising" is interpreted when employed as a transitional word in a claim.

[0045] All modifications which do not depart from the spirit of the present invention, are intended to fall within the scope of the following claims. The terms in the claims have their plain, ordinary meaning unless otherwise explicitly and clearly defined by the patentee. If there is any conflict in the usages of a word or term in this specification and one or more patent(s) or other documents that may be incorporated herein by reference, the definitions that are consistent with this specification should be adopted. The descriptions of the various embodiments have been presented for purposes of illustration, but are not intended to be exhaustive or limited to the embodiments disclosed. Many modifications and variations will be apparent to those of ordinary skill in the art without departing from the scope and spirit of the described embodiments, it is expressly intended that all combinations of those elements that perform substantially the same function in substantially the same way to achieve the same results are within the scope of the invention. Substitutions of elements or steps from one described embodiment to another are also fully intended and contemplated. The terminology used herein was chosen to best explain the principles of the embodiments, the practical application or technical improvement over technologies found in the marketplace, or to enable others of ordinary skill in the art to understand the embodiments disclosed herein.