The present invention relates generally to spinal implants and methods, and more particularly, to intervertebral prosthetic joint devices and methods for use in total or partial replacement of a natural intervertebral disc.
In the treatment of disease, injuries and malformations affecting spinal motion segments, and especially those affecting disc tissue, it has been known to remove some or all of a degenerated, ruptured or otherwise failing disc. In cases involving intervertebral disc tissue that has been removed, or is otherwise absent from a spinal motion segment, corrective measures are typically desirable.
In one approach, the two adjacent vertebrae are fused together using transplanted bone tissue, an artificial fusion component, or other compositions or devices. Spinal fusion procedures, however, have raised concerns in the medical community that the biomechanical rigidity of the intervertebral fusion may predispose neighboring spinal motion segments to rapid deterioration. Unlike a natural intervertebral disc, spinal fusion prevents the fused vertebrae from pivoting and rotating with respect to one another. Such lack of mobility tends to increase stress on adjacent spinal motion segments. Additionally, conditions may develop within adjacent spinal motion segments, including disc degeneration, disc herniation, instability, spinal stenosis, spondylosis and facet joint arthritis as a result of the spinal fusion. Consequently, many patients may require additional disc removal and/or another type of surgical procedure as a result of the spinal fusion. Alternatives to spinal fusion are therefore desirable.
Several different types of intervertebral disc arthroplasty devices have been proposed for preventing the collapse of the intervertebral space between adjacent vertebrae while maintaining a certain degree of stability and range of pivotal and rotational motion therebetween. Such devices typically include two or more articular elements that couple to respective upper and lower vertebrae. The articular elements are conventionally anchored to the upper and lower vertebrae by a number of methods, including the use of bone screws that pass through corresponding openings in each of the elements and thread into vertebral bone, and/or by the inclusion of spikes or teeth that penetrate the vertebral endplates to inhibit migration or expulsion of the device. The articular elements are typically configured to allow the elements, and correspondingly the adjacent vertebrae, to pivot and/or rotate relative to one another.
Existing intervertebral disc arthroplasty devices are relatively difficult to implant between adjacent vertebrae. To implant such devices, the adjacent vertebrae are spread apart a distance that is somewhat greater than the normal distance separating the vertebrae so that the device can be maneuvered between the vertebrae and the anchors can be engaged to the vertebral endplates. Such an operation presents a risk of injury to the vertebrae caused by misplacement and/or scratching of the vertebral endplates or other tissue by the anchors. The operation also presents a risk of injury resulting from over-distraction of the intervertebral space. Further, existing arthroplasty devices requiring the threading of bone screws into the adjacent vertebrae require precise placement and orientation of the bone screws to provide adequate anchoring and to avoid injury to adjacent tissue or vertebral structures.
Another disadvantage of existing arthroplasty devices is that they typically may not be manipulated in position after being inserted into the disc space. Most arthroplasty devices employ teeth, keels or spikes which prevent manipulation of the implant once positioned within the intervertebral space.
Thus, there remains a need in the art for improved intervertebral prosthetic disc devices and methods of use thereof. The devices and methods disclosed herein address these needs.
The shortcomings of the prior art are overcome and additional advantages are provided, in one aspect, through provision of an intervertebral prosthetic device which includes at least one staple comprising at least two prongs, including a first prong and a second prong, and at least one component configured to reside within an intervertebral space between a first vertebral body and a second vertebral body. The at least one component includes at least one vertebral bearing surface configured to engage at least one of the first vertebral body and the second vertebral body, and to facilitate repositioning of the at least one component within the intervertebral space prior to engageable coupling thereof to the at least one of the first vertebral body and the second vertebral body employing the at least one staple. In addition, the at least one component is configured to receive the first prong of the at least one staple. When the at least one component is disposed in the intervertebral space, the at least one staple couples the at least one vertebral bearing surface of the at least one component to the at least one first vertebral body and second vertebral body, with the first prong thereof being received by the at least one component and the second prong engaging the at least one first vertebral body and second vertebral body.
In another aspect, an intervertebral prosthetic device is provided which includes at least one staple with at least two prongs, including a first prong and a second prong, and an arthroplasty implant configured to reside within an intervertebral space between a first vertebral body and a second vertebral body. The at least one staple is formed of a shape memory material having a memorized state and a deformed state. The arthroplasty implant includes at least one vertebral support plate configured to engage at least one of the first vertebral body and the second vertebral body. The at least one vertebral support plate is further configured to receive the first prong of the at least one staple. When the arthroplasty implant is disposed in the intervertebral space, the at least one staple couples the at least one vertebral support plate of the arthroplasty implant to the at least one first vertebral body and second vertebral body when in the deformed state, and thereafter transitions to the memorized state resulting in compressive force being applied between the at least one vertebral support plate and the at least one first vertebral body and second vertebral body.
In a further aspect, a method of providing a prosthetic intervertebral disc replacement is disclosed. The method includes obtaining an intervertebral prosthetic device comprising at least one staple and an arthroplasty implant, the at least one staple including a first prong and a second prong, and being formed of a shape memory material having a memorized state and a deformed state, and the arthroplasty implant being configured to reside within an intervertebral space between a first vertebral body and a second vertebral body, the arthroplasty implant including at least one vertebral support plate configured for engaging at least one of the first vertebral body and the second vertebral body, and the at least one vertebral support plate being configured to receive the first prong of the at least one staple. The method further includes: preparing the intervertebral disc space to receive the intervertebral prosthetic device; positioning the arthroplasty implant within the intervertebral space; inserting the at least one staple in the deformed state into engageable contact with the at least one vertebral support plate and the at least one first vertebral body and second vertebral body; and allowing the at least one staple to at least partially return to the memorized state, thereby applying a compressive force between the at least one vertebral support plate and the at least one first vertebral body and second vertebral body.
Further, additional features and advantages are realized through the techniques of the present invention. Other embodiments and aspects of the invention are described in detail herein and are considered a part of the claimed invention.
The subject matter which is regarded as the invention is particularly pointed out and distinctly claimed in the claims at the conclusion of the specification. The foregoing and other objects, features, and advantages of the invention are apparent from the following detailed description taken in conjunction with the accompanying drawings in which:
Intervertebral prosthetic devices are disclosed which are configured for disposition within an intervertebral space between a first vertebral body and a second vertebral body. In one example, the intervertebral prosthetic device includes at least one staple comprising a first prong and a second prong, and at least one component configured to reside within the intervertebral space between the first vertebral body and the second vertebral body. The at least one component includes at least one vertebral bearing surface configured to engage at least one of the first vertebral body and the second vertebral body and to facilitate repositioning of the at least one component when positioned within the intervertebral space. Further, the at least one component is configured to receive the first prong of the at least one staple. When the at least one component is disposed in the intervertebral space, the at least one staple engagably couples the vertebral bearing surface of the at least one component to the at least one first vertebral body and second vertebral body, with the first prong thereof being received by the at least one component and the second prong engaging the at least one vertebral body and second vertebral body.
In various embodiments described herein, the at least one component is part of a spinal arthroplasty implant comprising a first vertebral support plate and a second vertebral support plate, each of which has at least one prong-receiving opening, hole, receptacle, etc. Further, the intervertebral prosthetic device includes two or more staples, with a first prong of each staple being configured to engage a respective prong-receiving opening in one of the vertebral support plates of the arthroplasty implant. Still more particularly, the two or more staples may be formed of a shape memory material, wherein the first and second prongs of each staple are substantially parallel in a deformed state and are angled toward one another when transformed towards a memorized state. Thus, the shape memory material staples are employed in the deformed state to engagably couple the arthroplasty implant to the first vertebral body and the second vertebral body, and then allowed to transform to their memorized state, thereby applying a compressive force between the vertebral support plate of the arthroplasty implant and the respective first vertebral body and second vertebral body.
The above-outlined aspects of the present invention, as well as further aspects thereof, are described in greater detail below with reference to
Each vertebral body 102, 104 comprises an outer cortical rim composed of cortical bone, with an inner cancellous bone disposed within the cortical rim. The cortical rim is often referred to as the apophyseal rim or apophyseal ring. Further, the cancellous bone is softer than the cortical bone of the cortical rim. It is well known in the art that the vertebrae that make up the vertebral column have slightly different appearances as they range from the cervical region to the lumbar region of the vertebral column. However, all of the vertebrae, except the first and second cervical vertebrae, have the same basic structures, e.g., the structures described above in conjunction with
If intervertebral disc 116 is diseased, degenerated, damaged, or otherwise in need of replacement, the disc can be at least partially removed and replaced with an intervertebral prosthetic disc such as illustrated in
The articulating joint provides relative pivotal and rotational movement between the adjacent vertebral bodies to maintain or restore motion substantially similar to the normal bio-mechanical motion provided by a natural intervertebral disc. Specifically, the articulating vertebral support plates 220, 240 are permitted to pivot relative to one another about a number of axes, including a lateral or side-to-side pivotal movement about a longitudinal axis, and an anterior-posterior pivotal movement about a transverse axis. Further, it should be understood that these articular components are permitted to pivot relative to one another about any axis that lies in a plane that intersects the longitudinal axis and the transverse axis. Additionally, the articular components are preferably permitted to rotate relative to one another about a rotational axis. Although the articulating joint is illustrated and described as providing a specific combination of articulating motion, it should be understood that other combinations of articulating movement are also possible and are contemplated as falling within the scope of the present invention. Further, it should be understood that other types of arthroplasty implants allowing articulating movement are also contemplated, including for example, single-component and three-component or more prosthetic discs.
Although the articulating vertebral support plates 220, 240 of the prosthetic joint may be formed from a wide variety of materials, including metal-containing materials, polymer materials, or composite materials that include metals, polymers, or combinations of metals and polymers, in one embodiment, the components are formed of a cobalt-chrome-molybdenum metallic alloy (ASTM F-999 or F-75). However, in alternative embodiments, the support plates may be formed of other materials, including ceramic material, other metallic material, such as titanium or stainless steel, polymeric material (such as polyurethane material, polyolefin material, polyether material, silicone material, or a combination thereof), or any other biocompatible material that would be apparent to one of ordinary skill in the art. Further, depending upon the implant configuration, nucleus 260 may comprise the same material as vertebral support plates 220, 240, or a different material. For example, nucleus 260 could be an implantable grade PEEK material. One example of a suitable medical grade material is marketed as PEEK® Optima available from Invibio, Inc., of Greenville, S.C., USA.
As shown in
Vertebral contact surfaces 222, 242 are designed to be in direct physical contact with the respective vertebral bodies and may be coated or textured to promote osteointegration. For example, a bone-growth promoting substance such as, for example, hydroxyapatite coating formed of calcium phosphate may be employed. Additionally, the vertebral contacting surfaces 222, 242, may be roughened prior to being coated with the bone-growth promoting substance to further enhance bone on-growth. Such surface roughening may be accomplished by way of, for example, acid etching, knurling, application of a bead coating (e.g., cobalt chrome beads), application of a roughening spray (e.g., titanium plasma spray (TPS)), laser blasting, or other methods of roughening that are known to one skilled in the art.
Also shown in
As shown in
Thus, in accordance with an aspect of the present invention, the intervertebral prosthetic device further includes at least one staple having at least two prongs, that is, a first prong and a second prong. Each staple may be manufactured from a conventional implant material, such as stainless steel or titanium, or in another embodiment, the staples may be manufactured of shape memory material or alloy, such as nickel titanium, to provide a compressive fixation which does not interfere with the implant's articulation surfaces. One example of a shape memory alloy is Nitinol sold by Memry Corporation of Melno Park, Calif. One embodiment of a shape memory staple, generally denoted 400, is illustrated in
Staple 400 is generally U-shaped with a crossbar 401 connecting prongs 402 and 403. In this embodiment, prong 202 has a pointed tip 204, while prong 203 has a pointed tip 205. Depending on the orientation of staple 400, pointed tips 204, 205 may facilitate insertion of the respective prong into the cortical rim of one of the vertebral bodies. It should be understood, however, that tips 404, 405 may have a variety of configurations. Staple 400, which is symmetrical about a center line 415, includes an inner surface 410 and an outer surface 420. In the illustrated embodiment, crossbar 401 includes notches 421 on outer surface 420 for facilitating final seating of the staple, for example, into bone. Notches 421 allow a surgeon to drive each prong independently as necessary. Although two prongs are shown, those skilled in the art will understand from the following description, that a staple with three, four or more prongs could alternately be employed. Various dimensions and tolerances for the staples to be employed in the intervertebral prosthetic device described herein will be apparent to a person of ordinary skill in the art. While various examples of staple configurations are described further below, certain general features are reviewed here.
As noted, the staples may be a shape memory material, for example, made of Nitinol, which is a biocompatible, shape memory metal alloy of titanium and nickel. Such staples are capable of being bent when cooled and transformed to their original shape when reheated. It is also possible to take advantage of the shape memory alloy's ability to transform from its austentic state to a stress-induced martensitic state. The metal changes shape with temperature or under the influence of stress because of crystalline phase changes. Thus, a staple made of a shape memory alloy can be inserted in two different ways as desired. In one embodiment, the shape memory alloy staple is cooled and then deformed while at a temperature less than the transformation temperature at which it is in the martensitic phase. The staple is then inserted in its deformed shape (shown in phantom in
The metal's properties at the higher temperature (austenite phase) are similar to those of titanium. The temperature at which the staples will undergo the shape transformation can be controlled by the manufacturing process and the selection of the appropriate alloy composition. Injury to the surrounding tissues should be negligible if the transformation temperature is near body temperature. There is no threat of thermal injury to the spinal cord or nerves, or adjacent vascular structures. Nitinol has a very low corrosion rate and has been used in a variety of medical implants (i.e., orthodontic appliances, stents). Implant studies in animals have shown minimal elevations of nickel in the tissues in contact with the metal, and the levels of titanium are comparable to the lowest levels found in tissues near titanium hip prostheses.
A method of fixing the intervertebral prosthetic device in an intervertebral space, in accordance with aspects of the present invention, is illustrated in the lateral views of
A number of general surgical instruments are used in the procedure, along with specific implants and instruments for affixing the staples between the implant and the vertebral bodies. The instruments used in this procedure may include one or more of: an implant inserter, a staple awl, a staple opener, a straight staple inserter, an angled staple inserter, a staple impactor, and a staple extractor.
To insert the staples, pilot holes may be made using the staple awl. The pilot holes are made anterior to the mid-body of the vertebrae. The staple awl is inserted part way and position is checked using, e.g., an x-ray or image intensifier. Prior to removal of the staple awl from the pilot holes, an electric cauterizer (Bovie) can be placed in contact with the endcap of the staple awl to minimize bleeding from the pilot holes. In one embodiment, two sets of pilot holes are made, one at each level to accommodate two staples per disc space. The two staples are then inserted, using for example, the straight staple inserter or the angled staple inserter, each with one prong thereof in one of the pilot holes previously made by the staple awl, and another prong in a respective prong-receiving opening 230, 250 formed in the vertebral support plates 220, 240 of the arthroplasty implant 200. The inserter may be tapped with a mallet to facilitate placement of the staple in the respective vertebral body. The staple is then released from the inserter and the instrument is removed. If further seating of the staple is required, the staple impactor may be used in conjunction with a mallet for final seating of a staple prong into either the bone, or the arthroplasty implant. The aforementioned steps are repeated for each staple.
As noted, in one embodiment, staple 400 is a shape memory alloy staple which has a deformed state when cooled, shown in phantom in
In
A similar disposition of prong-receiving openings is employed in both the first vertebral support plate 821 and second vertebral support plate 841 in the embodiment of
Advantageously, the intervertebral prosthetic device and method of disc replacement described above allow inter-operative flexion/extension radiography, or other simulation of the implant's range of motion in situ prior to final positioning of the device. The implant may be placed into the intervertebral space fully assembled and then repositioned within the space until the device is located within the anatomic center of rotation for the surrounding anatomy. Further, because the vertebral bearing surfaces of the implant are keel-less or anchor-less, the device could be employed with ceramic support plates. Once the device is in proper position, staples, such as shape memory staples, can be inserted into the blind openings in the vertebral support plates and into the adjacent vertebral bodies. Shape memory staples have the further advantage of providing a compressive force between the vertebral support plates of the implant and the vertebral endplates of the surrounding vertebrae.
Although preferred embodiments are depicted and described in detail herein, it will be apparent to those skilled in the relevant art that various modifications, additions, substitutions and the like can be made without departing from the spirit of the invention and these are therefore considered to be within the scope of the invention as defined in the following claims. For example, various components in the embodiments described herein are referred to as “superior” and “inferior” for illustrative purposes only, in that one or more of the features described as part of or attached to a respective half may be provided as part of or attached to the other half in addition to or in the alternative.
This application contains subject matter which is related to the subject matter of the following applications/patents, which are hereby incorporated herein by reference in their entirety: “Intervertebral Spinal Implant Devices and Methods of Use”, Heinz et al., U.S. Ser. No.: 11/343,954 filed Jan. 31, 2006; “Intervertebral Prosthetic Disc”, Heinz et al., U.S. Ser. No.: 11/343,935, filed Jan. 31, 2006; “Constrained Artificial Spinal Disc”, Marik et al., U.S. Ser. No.: 10/806,961, filed Mar. 23, 2004, and published on Sep. 29, 2005 as Patent Application Publication No. US 2005/0216086 A1; “Intervertebral Prosthetic Joint”, Eisermann et al., U.S. Ser. No.: 10/620,529, filed Jul. 16, 2003, and published on Apr. 15, 2004 as Patent Application Publication No. US 2004/0073312 A1; “Method for the Correction of Spinal Deformities Through Vertebral Body Tethering Without Fusion”, Ogilvie et al., U.S. Ser. No.: 09/905,018, filed Jul. 13, 2001, and published on Jan. 17, 2002 as Patent Application Publication No. US 2002/0007184 A1; “Shape Memory Alloy Staple”, Ogilvie et al., U.S. Pat. No. 6,773,437 B2, issued Aug. 10, 2004; “Intervertebral Prosthetic Joint”, Eisermann et al., U.S. Pat. No. 6,740,118 B2, issued May 25, 2004; “Method for the Correction of Spinal Deformities Through Vertebral Body Tethering Without Fusion”, Ogilvie et al., U.S. Pat. No. 6,616,669 B2, issued Sep. 9, 2003; and “Shape Memory Alloy Staple”, Ogilvie et al., U.S. Pat. No. 6,325,805 B1, issued Dec. 4, 2001.