Patent Application
20080306598
n/a
The present invention relates to a method and system for replacing diseased and/or damaged intervertebral discs, and in particular, provides an artificial intervertebral disc prosthesis.
Disease, advancing age, and trauma can lead to changes in various bones, discs, joints, and ligaments of the body. Some changes and trauma often manifest themselves in the form of damage or degeneration to a spinal disc or portion thereof. Such conditions often lead to chronic back pain, which can range from mild discomfort to severe, debilitating conditions. Treatment for degeneration and/or disease may include spinal fusion of two adjacent vertebral bodies, which are joined together after removing the intervening intervertebral disc. Typically, a prosthetic device is positioned between the two adjacent vertebral bodies in place of the removed disc to subsequently fill the space left by the removed disc, which may allow bone to grow between the two vertebral bodies.
The success or failure of a spinal fusion procedure can often depend upon the particular characteristics of the prosthesis that is placed between the adjacent vertebral bodies. In addition to having sufficient structural integrity to withstand the repeated and varying loads experienced in the spine from day to day, the prosthesis must be biocompatible, and further, the prosthesis should permit the ingrowth of bone to complete the fusion. Furthermore, the prosthesis should have characteristics that permit the prosthesis to remain fixed in the desired position, and to further resist movement or subsidence into the surrounding vertebrae due to shifting, rotation, or slippage of the prosthesis.
Despite known prostheses for the fusion of adjacent vertebral bodies, there remains a need for additional prostheses that have desirable geometries and characteristics for achieving secure and effective implantation within a patient's spine.
The present invention provides an intervertebral prosthesis having desirable geometries and characteristics for achieving secure and effective implantation within a patient's spine. In particular, a spinal prosthesis is provided generally defining a first wall, a second wall, and sidewalls extending from the first wall to the second wall. The spinal prosthesis may further define an upper surface and a lower surface, each of which may extend across a substantial portion of the body of the prosthesis. The spinal prosthesis may include somewhat of an “X” shaped cross section to provide improved resistance against compression forces experienced once implanted. In addition, an aperture may extend through a portion of the prosthesis from the upper surface to the lower surface, where the aperture may provide a path for bone growth and/or may allow for the addition of therapeutic materials within a portion of the prosthesis upon implantation. The surfaces and walls of the prosthesis may define a geometric profile of the spinal prosthesis.
The spinal prosthesis may further define one or more passages providing for an affixation element, such as a screw or nail, to be inserted therethrough. The passages may each include a first portion for receiving a head or tip of an affixation element, and a second portion of a smaller diameter or dimension than the first portion for accommodating a threaded or smaller portion of the affixation element. Moreover, each passage may be situated with a substantial amount of the second portion of the passage located above or below a midline of the prosthesis in order to minimize the amount of tissue from the surrounding area required for removal in order to guide a fixation element into the one or more passages at the desired angle upon implantation. The one or more passages of the prosthesis may further be angled to provide for increased pull strength to securely anchor the prosthesis and to further resist movement of an inserted affixation element when implanted.
One or more openings may also be provided on the spinal prosthesis for coupling the prosthesis to a surgical tool to aid in the placement and manipulation of the prosthesis during a particular procedure. In addition, the upper and lower surfaces and/or a portion of the first and second walls of the prosthesis may include a depression or surface void of any teeth for the insertion of the prosthesis where a distraction tool is situated about the surgical site.
The present invention may further include one or more sizing elements similarly shaped to the spinal prosthesis for determining the suitable dimensions of the spinal prosthesis to be used. In particular, the sizing elements may each include a sizing element body defining a first wall, a second wall, a pair of sidewalls, and upper and lower surfaces. The sizing element bodies may accordingly define a geometric profile substantially similar to the geometric profile of the spinal prosthesis, as described above. The sizing elements may have varying dimensions corresponding to the available dimensions of a particular implant, such that the sizing elements can temporarily be placed within the implant site to verify that a particular width, height, or the like, will provide the desired anatomical result upon implantation of a spinal prosthesis having similar dimensions.
The present invention also provides a spinal prosthesis including a prosthesis body defining a first wall, a second wall, a pair of sidewalls, an upper surface, and a lower surface; wherein the prosthesis body defines a midline extending from the first wall to the second wall and centered between the upper surface and lower surface; and a tissue scaffold element coupled to the prosthesis body. Each sidewall may define a serpentine curvature extending in a direction between the first and second walls, e.g., the sidewall curvature may include a convex portion and a concave portion.
The spinal prosthesis may further include a passage for receiving an affixation element, wherein the passage defines a first portion and a second portion, the second portion having a width less than the first portion, and wherein a substantial part of the second portion of the passage is located on one side of the midline. The passage may define a longitudinal axis, and wherein the longitudinal axis intersects the midline at an angle greater than approximately 35 degrees and less than approximately 45 degrees. The prosthesis body further may also define a centerline centered between the sidewalls extending from the first wall to the second wall, wherein the longitudinal axis of the passage intersects the centerline at an angle greater than approximately 10 degrees and less than approximately 20 degrees.
A more complete understanding of the present invention, and the attendant advantages and features thereof, will be more readily understood by reference to the following detailed description when considered in conjunction with the accompanying drawings wherein:
The present invention provides a system and method for repairing a diseased and/or damaged intervertebral disc or a portion thereof. Now referring to
As shown in
The spinal prosthesis 10 may further define one or more passages providing for an affixation element, such as a screw or nail (not shown), to be inserted therethrough. Although not illustrated, the passages may be threaded or include a contoured or textured surface for securely receiving an affixation element. In particular, the spinal prosthesis 10 may include a first and second passage 30,30′ extending from a portion of the upper surface 18 proximate to the first wall 12, through the lower surface 20 and towards the second wall 14. In addition, the prosthesis may include a third passage 30″ extending from a portion of the lower surface 20 proximate to the first wall 12, and through the upper surface 18 towards the second wall 14. The passages may each include a first portion 32 for receiving a head or tip of an affixation element, and a second portion 34 of a smaller diameter or dimension than the first portion for accommodating a threaded or smaller portion of the affixation element. Moreover, each passage may be situated with a substantial amount of the second portion 34 of the passage located above or below a midline 24 of the prosthesis in order to minimize the amount of tissue from the surrounding area required for removal in order to guide a fixation element into the one or more passages at the desired angle upon implantation. In particular, the first and second passages 30,30′ may have a substantial part of their respective second portions located below the midline 24 as they extend downward towards the lower surface 20 in a direction towards the second wall 14, while the third passage 30″ may include a substantial part of the second portion located above the midline 24 towards the upper surface 18.
The one or more passages of the prosthesis may further be angled to provide for increased pull strength to securely anchor the prosthesis and to further resist movement of an inserted affixation element when implanted. For example, the first, second, and/or third passages may be oriented between the upper and lower surfaces of the prosthesis such that a longitudinal axis 36 extending through each of the respective passages is at an angle with the midline 24 of the prosthesis between approximately 35 degrees and approximately 45 degrees, as shown in
Now referring to
The upper and lower surfaces and/or a portion of the first and second walls of the prosthesis may include a depression or surface 40 void of any teeth 28 for the insertion of the prosthesis where a distraction tool is situated about the surgical site. In a typical procedure, a spinal distraction tool is used to separate two intervertebral discs for the subsequent placement of a prosthesis. By providing a smooth and/or recessed portion on the prosthesis, the prosthesis may be maneuvered around a distraction tool already in place about the surgical site. As a result, the interference with the tool and surrounding tissue is minimized while the prosthesis 10 is maneuvered into a desired position. The smooth and/or recessed portion 40 of the prosthesis may be centered along the centerline 26 of the prosthesis, and may include dimensions adapted for receiving and/or being positionable about a spinal distraction tool.
The spinal prostheses described herein may be constructed from a myriad of biocompatible materials providing desired mechanical behavior throughout the movement and resultant forces experienced in a spinal column. Moreover, the prostheses may include therapeutic substances disposed about the prosthesis, as well as imaging elements, such as radiopaque markers, embedded in portions of the prosthesis to aid in the positioning and/or monitoring of an implanted prosthesis.
Now referring to
Now referring to
In addition, the spinal prosthesis 110 may include a plurality of protrusions or teeth 128 on a portion of the first and second surfaces to resist movement of the prosthesis once implanted into the desired position. The teeth may be sized or dimensioned to provide sufficient friction against movement of the implant upon implantation while reducing the likelihood that the teeth extend too far into the endplates of the surrounding vertebral bodies as to cause tissue damage. Each tooth or protrusion may generally define a base and a peak, and may further extend along a portion of the width of the prosthesis between the sidewalls 116, 116′. The teeth may be oriented substantially parallel to the first and second walls such that the peak and base of each tooth or protrusion is substantially transverse to the sidewall 116, 116′. Alternatively, the teeth may be oriented in an angular, nonparallel and/or non-transverse fashion (not shown) to both the first and second walls, as well as the sidewalls.
The surfaces and walls of the prosthesis may define a geometric profile of the spinal prosthesis 110, where the geometric profile may include the particular dimensions of the surfaces involved, the angular orientation, and/or any curvature or arcuate orientation of a portion of the prosthesis. For example, the walls may define a particular curved or arcuate periphery, while the height of the walls may include a particular height desired for implantation.
In particular, the first and second walls 112, 114, respectively, may be contoured or define an arcuate shape in one or more directions or planes. For example, the first wall 112 may define convex curve extending in a direction along the width of the first wall between the sidewalls 116, 116′, as illustrated in
Moreover, the second wall 114 of the prosthesis may define a height smaller than a height defined by the first wall 112, such that the first and/or second surfaces of the prosthesis are angled in a nonparallel configuration with respect to each other. Moreover, the first and/or second surfaces may have an arcuate shape, such as a convex curve, for example, extending between the first and second walls. The arcuate or angular shape or orientation of the first and second surfaces may be apparent when viewed from a side along one or more bases of sequential teeth, if present (as shown in
The sidewalls 116, 116′ may also define an arcuate configuration as part of the geometric profile of the prosthesis 110. For example, as shown in
The arcuate contours and shapes of the prosthesis as described and shown herein provide an improved reduction in the likelihood of subsidence into the surrounding vertebrae upon implantation due to improve force transfer and cross-sectional support characteristics. These improved characteristics provided by the contoured shape and configuration of the prosthesis disclosed herein provides significant improvement over existing annular, rectangular, or other similarly shaped prostheses. These prior art devices often succumb to increased instances of subsidence within a spinal segment after implantation, thereby reducing the overall effectiveness of the device.
Now referring to
The one or more passages of the prosthesis may further be angled to provide for increased pull strength to securely anchor the prosthesis and to further resist movement of an inserted affixation element when implanted. For example, the first, second, and/or third passages may be oriented between the first and second surfaces of the prosthesis such that a longitudinal axis 136 extending through each of the respective passages is at an angle with the midline 124 of the prosthesis between approximately 35 degrees and approximately 45 degrees, as shown in
One or more openings (not shown) may also be provided on the spinal prosthesis 110 for coupling the prosthesis to a surgical tool to aid in the placement and manipulation of the prosthesis during a particular procedure. For example, the first wall 112 of the prosthesis may include a first and second opening into a cavity and/or depression into the body of the prosthesis, which may include threading or other coupling elements to improve the grip and engagement between a tool and the implant. In addition and/or alternatively, a positioning or gripping tool may engage or otherwise couple to the implant through the one or more passages that will ultimately receive an affixation element such as a pedicle screw or the like.
The first and second surfaces and/or a portion of the first and second walls of the prosthesis may include one or more surface portions 140 void of any teeth, where these surface portions 140 may further be depressed or below a point of one or more bases of the protruding teeth. The depressions may provide additional room for maneuverability during the insertion of the prosthesis where a distraction tool is situated about the surgical site. In a typical procedure, a spinal distraction tool is used to separate two intervertebral discs for the subsequent placement of a prosthesis. By providing a smooth and/or recessed portion on the prosthesis, the prosthesis may be maneuvered around a distraction tool already in place about the surgical site. As a result, the interference with the tool and surrounding tissue is minimized while the prosthesis 110 is maneuvered into a desired position. The smooth and/or recessed portions 140 of the prosthesis may be centered about the centerline 126 of the prosthesis, and may include dimensions adapted for receiving and/or being positionable about a spinal distraction tool.
In accordance with another aspect of the present invention, the spinal prostheses disclosed herein may be coupled with or otherwise paired to a tissue scaffold element to enhance, stimulate, or otherwise induce tissue growth to aid in the securement and incorporation of the prosthesis into the surrounding implantation site. Now referring to
The tissue scaffold element 142 may be sterilized, prepared, or otherwise processed to include any additional components or compounds prior to mating with or insertion into the prosthesis 110. In particular, the tissue scaffold may be freeze-dries or otherwise prepared to preserve the biological qualities of the scaffold element 142 prior to implantation. Subsequently, the scaffold element 142 may be milled, contoured, or otherwise shaped to fit within the aperture 122 of the prosthesis 110. Finally, the scaffold element 142 may be affixed to the prosthesis 110 by an adhesive, such as a methyl-methacrylate or the like, or through an interference fit with the aperture 122. The scaffold element 142 may conform to the contours and curvature of the aperture 122, and may further have inferior and superior surfaces that receded or are otherwise undersized compared to the height and depth of the first and second surfaces, respectively, of the prosthesis. Affixing the tissue scaffold to the prosthesis, with its optional allograft and bone morphogenetic protein compositions, may decrease complications associated with the exclusive use of allograft or autograft materials, and further eliminates the need to harvest autogenous bone during a particular operation or procedure.
It will be appreciated by persons skilled in the art that the present invention is not limited to what has been particularly shown and described herein above. In addition, unless mention was made above to the contrary, it should be noted that all of the accompanying drawings are not to scale. A variety of modifications and variations are possible in light of the above teachings without departing from the scope and spirit of the invention, which is limited only by the following claims.
This application is a continuation-in-part-of pending patent application Ser. No. 11/732,137, filed Apr. 02, 2007, entitled SPINAL IMPLANT SYSTEM, the entirety of which is incorporated herein by reference.
| Number | Date | Country | |
|---|---|---|---|
| Parent | 11732137 | Apr 2007 | US |
| Child | 12123506 | US |
