Patent Application
20110046740
The present invention relates to a spinal implant, a surgical instrument set and a method for introducing the spinal implant between adjacent vertebrae of a patient, and more particularly to a spinal implant comprising two or more cages to be surgically implanted as support between adjacent vertebrae.
The spine is made up of many individual bones called vertebrae. Between the adjacent vertebrae is tissue known as a disc, which serve as a cushion and allow the spine to bend. The spinal disc may however be displaced or damaged due to trauma, disease, aging, degenerative defects or improper body posture, which may lead to chronic back pain. The current treatment to remedy these conditions is to place a fusion cage between the adjacent vertebrae to prevent collapse of the disc space and promote fusion of the vertebrae.
In this art, various designs of fusion cages have been developed, such as cylindrical, threaded, C-shaped, banana-shaped, and hollow structures with multiple side holes, constructed from a variety of materials such as titanium alloys, porous tantalum, other metals, bones, polymers or ceramic materials. Optionally, one or two cages may be implanted between adjacent vertebral bodies. In the lumber region, for example, two cylindrical threaded cages can be positioned on either side of the midline to seek for more balance and stability. However, there are many practical problems with the use of two or more cages, including that a very large retraction is necessary, difficulty in achieving symmetric positioning with these cages, high costs and long operative and recovery time.
Recoules-Arche described in the European Patent Application No. 1 897 518 a spinal implant and instrument of an instrument set which comprises a first cage and a second cage and an instrument with a distal end configured to push the cage which is first inserted into the disc space laterally in its proper anatomical location, said distal end of the instrument having a tip which is curved and has a curved inner side configured to contact an outer curved side of the first cage, allowing the insertion of two cages through a relatively small incision. Biyani provided in the U.S. Patent Application Publication No. 2007/0260314 a banana-shaped cage having first and second spacer members for insertion between adjacent vertebrae with a hinge between the spacers. A mechanism is located between the first and second spacer members that pivotally moves the first and second spacer members relative to each other at an angle which facilitates the insertion of the cage around the spinal cord; and after insertion, the mechanism is operable to position the first and second spacer members in the desired position between the two adjacent vertebrae.
It is desirable to provide a spinal implant with multiple cages that could be safely inserted with one relatively small incision and achieve ideally symmetric balance and stability of adjacent vertebrae.
In one aspect, the present invention provides a spinal implant comprising:
(i) two or more cages; and
(ii) a support which is returnable from a constrained linear shape to an expanded shape and affixed to each of the two or more cages, said implant having a first configuration to arrange the cages in order when the support is in the constrained linear shape, and a second configuration that gives a transformed arrangement of the cages to define a plane by the cages and the support when the support is in the expanded shape.
In another aspect, the present invention provides a surgical instrument set, comprising:
(a) an implant which comprises
(b) an introducing means for creating a pathway between the adjacent vertebrae of the patient and introducing the implant into the disc space between the adjacent vertebrae of the patient.
In yet another aspect, the present invention provides a method for implanting an implant into a disc space between adjacent vertebrae of a patient wherein said implant comprises:
(i) two or more cages; and
(ii) a support which is returnable from a constrained linear shape to an expanded shape and affixed to each of the two or more cages, said implant having a first configuration to arrange the cages in order when the support is in the constrained linear shape, and a second configuration that gives a transformed arrangement of the cages to define a plane by the cages and the support when the support is in the expanded shape;
said method comprising the steps of:
(a) introducing the implant through a pathway to the disc space wherein the support is kept in the constrained linear shape and the implant stays in the first configuration to arrange the cages in order during the introduction of the implant; and
(b) deploying the implant when it is disposed in the disc space, whereby the support returns to the expanded shape and the implant turns to the second configuration to define a plane by the cages and the support.
The present invention will become apparent to those skilled in the art with the benefit of the following detailed description and upon reference to the accompanying drawings in which:
The present invention will now be described in detail with reference to a few embodiments thereof as illustrated in the accompanying drawings. In the following description, numerous specific details are set forth in order to provide a thorough understanding of the present invention. It will be apparent, however, to one skilled in the art, that the present invention may be practiced without some or all of these specific details. These examples are offered for the purpose of illustration and are not to be construed in any way as limiting the scope of the present invention.
Unless defined otherwise, all technical and scientific terms used herein have the same meanings as is commonly understood by one of skill in the art to which this invention belongs.
As used herein, the articles “a” and “an” refer to one or more than one (i.e., at least one) of the grammatical object of the article. By way of example, “an element” means one element or more than one element.
The main idea of the present invention is to connect multiple cages with a support which is returnable from a constrained linear shape to an expanded shape so as to provide a spinal implant which has multiple cages which may be arranged in two configurations due to the two different shapes of the support. The present invention therefore provides a spinal implant, a surgical instrument set and a method for implanting a spinal implant into a disc space between adjacent vertebrae of a patient. According to the invention, at lease the following advantages are obtained: (i) multiple cages can be inserted into a disc space through one single incision; (ii) the incision thus caused can be minimal because the implant is kept in a first configuration to arrange the cages in order (when the support is in the constrained linear shape) before and during the insertion into the disc space; (iii) the implant provides ideally symmetric balance and stability of adjacent vertebrae because it can turn to a second configuration that gives a transformed arrangement of the cages to define a plane by the cages (when the support is in the expanded shape) if the implant is disposed in the disc space; and (iv) the configurations defined by the cages and the support are automatically changed when the implant is located in the disc space, and thus no further tool is required for adjusting the arrangement or positions of these cages.
In one aspect, the present invention provides an implant for stabilizing adjacent vertebrae of a patient, comprising:
(i) two or more cages; and
(ii) a support which is returnable from a constrained linear shape to an expanded shape and affixed to each of the two or more cages, said implant having a first configuration to arrange the cages in order when the support is in the constrained linear shape, and a second configuration that gives a transformed arrangement of the cages to define a plane by the cages and the support when the support is in the expanded shape.
As used herein, the term “support” refers to a means for connecting and supporting the two or more cages according to the invention, having the ability to return from a constrained linear shape to an expanded shape. Specifically, the support stays in a constrained shape in one condition and changes to an expanded shape in another condition. Generally, the support is deformed under constraint and return to its pre-determined shape when the constraint is removed. In some certain cases, however, the return from a constrained shape to an expanded shape of the support is triggered by an alternation of temperature, light, or an electric or magnetic field, depending on the nature of the material of which the support is composed. For example, the support may stay in a constrained linear shape at a low temperature and return to a pre-determined shape at a high temperature after removal of the constraint.
The support of the invention may be made of any material that gives the implant the above-described flexible property. In one embodiment, the support is composed of a spring metal. In another embodiment, the support is composed of a superelastic material. As used herein, the term “superelastic material” (also called “pseudoelastic material” or “shape memory material”) refers to a material which is deformed reversibly under a relatively high strain, which includes but is not limited to, a shape memory alloy, a shape memory polymer (SMP) and a shape memory metal-polymer composite. Some examples of the shape memory alloys include but are not limited to Ni—Ti, Au—Cd, Ag—Cd, Cu—Zn, Cu—Zn—Al, Cu—Zn—Sn, Cu—Zn—Si, Cu—Sn, Cu—Zn—Ga, Au—Cu—Zn, Ni—Al, Fe—Pt, Ti—Ni—Pd, Ti—Nb, U—Nb and Fe—Mn—Si alloys and etc. In one certain embodiment of the invention, the shape memory alloy is a nickel-titanium (NI-TI) alloy. Any SMP is applicable in the invention, such as a thermally induced SMP, a light-induced SMP or an electro-active SMP. Examples of SMPs include polyurethanes, polyurethanes with ionic or mesogenic components, or crosslinked polyurethanes, linear, amorphous polynorbornenes, or organic-inorganic hybrid polymers consisting of polynorbornen units.
The support used in the invention may be made in any form, single or multiple, as long as it is proper to connect the cages and provide flexible configuration of the implant as above described. For example, the support may be single or multiple, in the form of a strip, sheet, membrane, rod, band, string or wire.
In addition, the cages used in the invention can be of any shape and structure known in the art, including but are not limited to round, square, cylindrical, rectangle, hallow, open box and threaded, additionally with slots and holes in the side or teeth on the upper and lower surfaces. The cages can be made of a variety of materials such as metals, polymers, bone grafts or combinations thereof. The bone graft may be autogenic bone, allogenic bone, xenogenic bone or combinations thereof. The term “autogenic bone” as used herein refers to a bone graft obtained from another location of a patient. The term “allogenic bone” as used herein refers to a bone graft derived from the same species as the patient. The term “xenogenic bone” as used herein refers to a bone derived from a species other than that of the patient. The most common polymer in current use for cages is polyetheretherketone (PEEK). Examples of metals for cages include titanium, titanium alloys such as Ti-6A1-4V, chrome alloys such as CrCo or Cr—Co—Mo and stainless steel.
According to the invention, the support is affixed to each of the two or more cages as described above. A variety of conventional methods may be used for affixation. Certain examples of the affixation are described below.
According to the invention, the implant exhibits two configurations, and the shape (or state) of the support determines what configuration the implant is in. When the support is in a constrained linear shape, the implant of the invention is in a first configuration to arrange the cages in order; and when the support is in an expanded shape, the implant of the invention is in a second configuration that gives a transformed arrangement of the cages to define a plane by the cages and the support. It can be understood that the plane defined by the cages and the support when the implant is in the second configuration has a broad area, which is substantially larger and wider than that by the first configuration of the implant wherein the cages are arranged in order. Such first configuration facilitates the introduction of the implant into a disc space between the adjacent vertebrae, while the second configuration provides a better symmetric balance and stability of the adjacent vertebrae.
Specifically, when the implant is in the first configuration, the cages are arranged, for example, in a straight line, and the incision caused during insertion into the disc space can be minimal; on the other hand; when the implant is in the second configuration, the cages are arranged expandedly, and a plane will be defined by the cages and the support so that the plane defined by the cages and the support accordingly is, for example, angular such as triangle-like, square-like, rectangle-like, trapezoid-like, or polygon-like (e.g., pentagon-like, hexagon-line, heptagon-like, or octagon-like), circular, oval, or semicircular in shape. In particular, it is noted that the shape of the second configuration is given to match the anatomy of the disc space to provide better balance and stability of adjacent vertebrate, and of course is not limited to those as above listed. One skilled in the art can design the support to have a proper expanded shape to allow the cages to be properly disposed in the disc space based on the anatomy of the disc space between the adjacent vertebrae so as to create sufficient contact region with adjacent vertebrate, thus provide better balance and stability of the adjacent vertebrae.
In use, the implant of the invention can stay in the first configuration before being inserted to the disc space, and change to the second configuration when the implant is disposed in the disc space. Generally, the implant is kept under constraint to be in the first configuration before being inserted to the disc space, and turns to be in the second configuration by removal of the constraint when the implant is disposed in the disc space. In some certain cases, however, the change of the first configuration to the second configuration of the implant is triggered by an alternation of temperature, light, or an electric or magnetic field, depending on the nature of the material of which the support is composed. For example, the implant can be kept cool to stay in the first configuration and expand to the second configuration when the implant is disposed in the disc space and warmed by the body heat.
Referring to
Referring to
According to the invention, the cages may be affixed to the support by a variety of methods such as commonly used methods or the standard methods for affixation. In one embodiment of the invention as shown in
In use, the implant may be introduced in a disc space through an introducing means, such as a tube.
In another aspect, the present invention provides a surgical instrument set, which comprises:
(a) an implant comprises
(b) an introducing means for creating a pathway between the adjacent vertebrae of the patient and introducing the implant into the disc space between the adjacent vertebrae of the patient.
The term “introducing means” as used herein refers to a means for creating a pathway to the disc space in a patient and for introducing the implant into the disc space of the patient. In one example of the invention, the introducing means comprises a tube for carrying the implant, and an insertion tool for pushing the implant out of the tube and to dispose the implant into a disc space between the adjacent vertebrae. In another embodiment of the invention, the introducing means comprises a simple piston pump consisting of a tube and a plunger that fits in the tube; wherein the plunger can be pulled and pushed along inside the tube to allow the implant to be pushed out to dispose into the space disc between the adjacent vertebrae through the open end of the tube, or to allow the tube to be pulled out of the adjacent vertebrae.
Referring to
In yet another aspect, the present invention provides a method for implanting an implant into a disc space between adjacent vertebrae of a patient wherein said implant comprises:
(i) two or more cages; and
(ii) a support which is returnable from a constrained linear shape to an expanded shape and affixed to each of the two or more cages, said implant having a first configuration to arrange the cages in order when the support is in the constrained linear shape, and a second configuration that gives a transformed arrangement of the cages to define a plane by the cages and the support when the support is in the expanded shape;
said method comprising the steps of:
(a) introducing the implant through a pathway to the disc space wherein the support is kept in the constrained linear shape and the implant stays in the first configuration to arrange the cages in order during the introduction of the implant; and
(b) deploying the implant when it is disposed in the disc space, whereby the support returns to the expanded shape and the implant turns to the second configuration to define a plane by the cages and the support.
The implant as used herein is as defined above. In one embodiment of the method of the invention, the implant is kept in the first configuration under constraint in Step (a), and the implant is deployed in Step (b) by removal of the constraint. For example, the implant before being introduced to the disc space is placed inside an introducing tube to stay in the first long configuration, and the implant is deployed in Step (b) by being pushed out of the introducing tube. In Step (b), it is also possible to deploy the implant by an alternation of temperature, light, an electric or magnetic filed or pH surrounding the implant depending on nature of the material of which the support is composed as described above.
According to the method of the invention, it is feasible to introduce two or more cages into a disc space in a safe, easy and effective way. The incision thus caused is single and minimal because the cages are kept in order and the implant is in the first configuration during the introduction; and the symmetric stability of adjacent vertebrae is provided when the implant is disposed in the disc space because it then changes to the second configuration to define a plane by the cages and the support. Especially, the implant automatically changes to the second configuration when it is disposed in the disc space and thus no further adjustment is needed.
The present invention has been described in an illustrative manner. This description is to be construed as illustrative only and is for the purpose of teaching those skilled in the art the general manner of carrying out the invention. Many modifications and variations of the present invention are possible in light of the above teachings. It is, therefore, to be understood that within the scope of the appended claims, the invention may be practiced otherwise than as specifically describes.
