Patent Application
20060282020
The invention relates to intervertebral implants, and an particular it relates to a customized intervertebral implant and a method of providing same.
Patients with a broken vertebra and/or degenerative disc disease often have a deformed spine caused by trauma or the like due to a collapsed vertebra. The deformed spine results in a scoliotic or kyphotic spine. The usual treatment for such a condition where the adjacent vertebrae are collapsed is a fusion of the vertebrae concerned. With fusion, after accompanying repositioning of the spine during surgery, the deformed spine is returned to its desired anatomical shape. However, after fusion the adjacent levels of the spine experience increased movement as the adjacent levels must compensate for the immobility of the fused vertebrae. This results in higher strains for the adjacent levels and discs, leading to more disc disease problems and back pain.
While various artificial vertebrae have been proposed in the prior art to serve as a replacement for a damaged vertebra, and thus to help avoid the problems associated with fusion, this requires removal of the damaged vertebra. An example of such a replacement vertebra is shown in US Published Application 2005/0060034 to Berry et al.
Another major improvement in the treatment of the spine are intervertebral implants of the type which provide articulation such as universal movement between upper and lower endplates thereof, and hence between adjacent vertebrae. Examples of such intervertebral implants are those disclosed in US Published Applications 2005/0085917 (Marnay et al.) and 2004/0117022 (Marnay et al.); and examples of exemplary tools and methods for insertion of such intervertebral implants are those disclosed in International Published Application No. WO01/19295 (Beyersdorf et al.) and in US Published Applications 2004/0215198 (Marnay et al.), 2005/0021042 (Marnay et al), and 2004/0117022 (Marnay et al.). The disclosures of these published applications are hereby incorporated by reference. However, such intervertebral implants are not currently adaptable for use with broken or damaged vertebrae.
Besides trauma or the like which results in a deformity, natural miss-shaping of vertebrae may also result in a deformity or undesired curvature of the spine. Typical of such conditions are scoliosis or kyphosis.
In accordance with the present invention, a method for customizing an intervertebral implant is provided, wherein the intervertebral implant is implanted in an intervertebral space within a series of vertebrae because the series of vertebrae have a deformity. The deformity may result from trauma which results in a resultant damaged vertebra, or by malformation during growth. For convenience, hereafter such a damaged or malformed vertebra will be referred to as “abnormal”.
Also for convenience, the series of vertebra is considered to include an abnormal vertebra which is the cause of the deformity, a vertebra superior to the abnormal vertebra, and a vertebra inferior to the abnormal vertebrae. The customized intervertebral implant then replaces the disc between the abnormal surface of the abnormal vertebra and the surface adjacent to the abnormal surface of the adjacent vertebra, so that the abnormal vertebra is retained (not removed).
A particular advantage of the present invention is to provide a customized intervertebral implant wherein the implant is of the type described above having opposed endplates which are articulated so as to provide movement such as universal movement therebetween and hence between the adjacent vertebrae.
The method comprises the initial step of obtaining a 3D anatomy of the series of vertebrae in a computer. Next, a repositioning of the 3D anatomy of each vertebra of the series is made in the computer to eliminate as far as possible the deformity of the series. It is then determined whether a superior or inferior surface of the abnormal vertebra is an abnormal surface which causes the deformity of the series. In addition, an approximate gap between the abnormal surface of the abnormal vertebra and a desired normal or desired surface of the abnormal vertebra is also determined. Using that determination of the gap, a custom implant is constructed which will engage the abnormal surface and fill the determined gap. In this manner, when the implant is implanted between the abnormal surface of the abnormal vertebrae and an adjacent surface of an adjacent vertebrae of the series, the deformity is substantially or desirably compensated for.
In a preferred embodiment of the present invention, the constructing step includes constructing an adjacent surface of the implant with a height which will engage the abnormal surface and fill the determined gap. When the surface of the implant is so customized, preferably the abnormal surface is smoothed in the computer so that the custom surface of the implant is matched to the smoothed surface. Conveniently, the constructing step further includes the step of transferring data from the computer to a CAD/CAM milling machine which makes the custom surface.
In a preferred arrangement, wherein the implant is of the type having opposed endplates with articulation for relative movement therebetween and an inlay received in one of the endplates, the constructing step includes the constructing of the inlay with a varying height which will cause a surface of the endplate adjacent the abnormal surface to fill the determined gap. In this embodiment, the constructing step includes the step of smoothing of the abnormal surface in the computer so that the varied height of the inlay is matched to the gap of the smoothed surface. Further, the constructing step includes the step of transferring data from the computer to a CAD/CAM milling machine which makes the varying height inlay.
The present invention also includes a method for providing a custom designed intervertebral implant for insertion into an irregularly shaped intervertebral space, where the space is bounded on one side by an abnormal vertebra. This method comprises the steps of determining a shape of the irregular intervertebral space, custom designing an implant to match opposing vertebral surfaces of the intervertebral space, and then inserting the custom designed implant into the intervertebral space such that the custom designed implant essentially fills the intervertebral space.
Preferably, the custom designed implant is of the type wherein the endplates have articulation for relative movement therebetween. In addition, where the custom designed implant has keels, the invention further includes the step of forming a trial implant to assist in forming grooves for the keels in the adjacent vertebra.
The present invention further includes a method of providing a customized implant of the type having opposed endplates with articulation for relative movement therebetween. This method comprises the steps of determining the shape of an intervertebral space between adjacent vertebrae, shaping at least one component of the implant to fit the space shape, and inserting the custom designed implant into the space.
Also in accordance with the present invention, an intervertebral implant of the type having opposed endplates adapted to engage adjacent vertebral surfaces is provided. The implant has at least one component which is custom made to have a shape such that the implant matches a specific intervertebral space into which the implant is to be inserted.
In one embodiment, the component which is custom made is an exterior surface of one of the endplates, so that this surface is customized to fit an irregular shaped intervertebral space. In another embodiment, the component which is custom made is an inlay which is attached to an interior surface of one of the endplates, so that the inlay is customized to fit the implant into an irregular shaped intervertebral space.
It will be appreciated that the method for customizing an intervertebral implant is capable of compensating for the deformity in more than one plane.
It is an object of the present invention to treat an abnormal vertebra having a deformity without requiring removal of the abnormal but otherwise usable vertebra and without resorting to fusion of the abnormal vertebra. Instead, an intervertebral implant is customized to fit against the abnormal surface of the abnormal vertebra in a manner which compensates for the deformity caused by the abnormal vertebra.
It is also an object of the present invention to provide a custom designed universal implant for treatment of an abnormal vertebra.
It is also an object of the present invention to retain relatively full spinal mobility despite the damage or malformation of a vertebra.
Other features and objects of the present invention are stated in or apparent from detailed descriptions of presently preferred embodiments of the invention found hereinbelow.
a, 1b and 1c are, respectively, a left side, a front, and a front, top and left side perspective view of a series of vertebrae including a middle abnormal vertebra which results in a deformity of the series.
a, 2b and 2c are, respectively, a left side, a front, and a front, top and left side perspective view of the series of vertebrae including a abnormal vertebra of
a, 3b, and 3c are, respectively, a right side, a front, and a left side view of the series of vertebrae including the abnormal vertebra of
a and 4b are, respectively, a front, top and left side and a front, top and right side perspective view of the customized implant depicted in
a-d depict a trial implant in a) a front, top and left side perspective view, b) a front view, c) a left side view and d) a front, top and left side perspective view and with a vertebra surface cutting tool therein.
As noted above, the present invention is useful with either a damaged vertebra or, where appropriate or where a disc replacement is otherwise being made, with malformed vertebra. Where the present invention is used with malformed vertebrae, it will be appreciated that there will be a targeted vertebra whose abnormality is being compensated for or two adjacent targeted vertebra whose common disc is being replaced. While the targeted vertebra (or adjacent vertebrae) may contribute only to a part of the overall deformed curvature as in scoliosis, correction of that vertebra (or vertebrae) may be desired to reduce the overall curvature and achieve a meaningful improvement in the undesired curvature. In such a case, the targeted vertebra or both targeted vertebrae on either side of the disc being replaced may be overcompensated for in order to help correct the undesired curvature of the adjacent vertebra. For convenience, this overcompensation will still be referred to as “natural” even though it is beyond what would be the compensation to the “natural” surface location of a damaged vertebra which would not have adjacent vertebrae contributing to the curvature.
With reference now to the drawings in which like numerals represent like elements throughout the views, there is depicted in
In accordance with the present invention, in order to compensate for the curvature of series 10, a 3D anatomy of series 10 is obtained. This is simply and conveniently done with a CT scanning device 60 or the like (see
With the 3D anatomy of series 10 obtained and loaded into a computer 62, the 3D anatomy are depicted in a suitable screen 64 or the like as by the appearances of
Again using standard software typical in the art, the user is then able to determine where a desired surface 20′ of abnormal vertebra 14 would be if vertebra 14 were not damaged. The software then also determines an approximate gap between abnormal surface 20 and a desired surface 20′. With this gap determined, an intervertebral implant 30 is constructed. The construction advantageously takes places by downloading or transferring of data from computer 62 with suitable software to a CAD/CAM milling machine 66 or the like. It will be appreciated that the abnormal surface 20 is preferably smoothed somewhat in the computer before the gap is determined. This smoothing is performed because an exact match of abnormal surface with every (small) peak and valley of the abnormal is not needed; and to some extent, the smoothing will be dependent on the milling machine which is used and the degree of matching attainable with the milling process.
Implant 30 is shown in position in series 10 in
Prior to insertion of the implant 30, it is necessary to utilize a trial implant 70 to guarantee creation of keel grooves in the two vertebrae adjacent implant 30. Trial implants suitable for this purpose are shown in the above identified published application No. 2004/0215198.
In this embodiment of the present invention, implant 30, which is of the type which allows relative universal movement between the endplates, is customized as shown in
If there were no deformity resulting from vertebra 14, so that only the disc between vertebra 14 and 16 were being replaced with implant 30, superior endplate 32 would have a constant thickness or height like that of inferior endplate 34. However, as there has been damage to vertebra 14 so that there is a gap between the location of abnormal surface 20 of vertebra 14 and the desired surface 20′ of vertebra 14, it will be seen in
It will be appreciated that the build up of upper surface 36 has occurred over most of upper surface 36 thereof, starting from the right (as viewed) and building up to the left as well as back to front. Thus, built up upper surface 36 is not necessarily planar, or even angled in any one plane; rather it may be undulating, or as shown in
Depicted in
As inlay 46′ is the element which provides the compensation, implant 30′ is usable primarily where the abnormal surface of the vertebra is relatively planar. However, where appropriate, the use of a customized inlay may afford some advantages, such as easier and quicker fabrication since inlay 46′ is formed of polyethylene.
It will also be appreciated that where a disc between two vertebrae which are malformed as by scoliosis is to be replaced, the adjacent vertebral surfaces will be undamaged and thus implant 30 or 30′ is usable. As noted above, implant 30′ can be designed to overcompensate for the curvature so that the remaining malformed vertebra are advantageously oriented relative to the implant. In such a case, both endplates of implant 30 could have customized (built up) surfaces, or both the inlay of implant 30′ and the other endplate surface 36′ could be customized (built up). It will further be appreciated that besides building up inlay 46, or in addition thereto, the opposite facing surface of endplate 32 could be built up in the same manner as inlay 46.
It is anticipated that the methods described above can be accomplished relatively quickly and easily. Thus, such a method could even be performed while surgery is underway to repair a trauma. Once the 3D anatomy scan is made, the CAD/CAM machine would be immediately directed to make the needed customized implant part from a stock of parts ready to be milled.
While the present invention has been described with respect to exemplary embodiments thereof, it will be understood by those of ordinary skill in the art that variations and modifications can be effected within the scope and spirit of the invention.
