Patent Application
20080228276
This disclosure is directed toward generally to a prosthesis, instruments, and methods of implanting the prosthesis, and more particularly, to an intervertebral disc, instruments and methods of implanting the intervertebral disc in an intervertebral space.
Disc arthroplasty is one way of treating injured, degraded, or diseased spinal joints. Some disc arthroplasty treatments include replacing injured discs of the joint with a motion-preserving spinal disc that allows some articulation or movement of the spinal joint. While the inserted disc may provide joint articulation to a patient, inserting the spinal disc can be an invasive and intensive procedure. For example, conventional spinal discs are installed anteriorly. Because anterior procedures often require displacement of organs, such as the aorta and vena cava, they must be performed with great care. Further, because scar tissue may grow about the surgical site, any required second treatment can be more difficult, and may introduce additional distress to the patient.
What is needed is an intervertebral prosthesis, instruments, and a surgical method for inserting the intervertebral prosthesis into an intervertebral space using a generally posterior transforaminal approach, a lateral approach, and/or a posterior lateral approach. The method of implanting an artificial disc disclosed herein overcomes one or more problems in the prior art.
In one exemplary aspect, the present disclosure is directed toward a method of implanting an intervertebral prosthesis in an intervertebral space between a first and a second vertebra of a patient's spinal column. The method may include making a first aperture at a first location to permit access to the intervertebral disc space. The first aperture may be sized to allow passage of at least a portion of the intervertebral prosthesis. A second aperture may be made at a second location to permit access to the intervertebral disc space. The second aperture may be sized to allow passage of a surgical instrument.
In one aspect, the second aperture is smaller than the first aperture.
In another aspect, the intervertebral prosthesis may be introduced into the intervertebral space through the first aperture.
In yet another aspect, the intervertebral space may be accessed with the surgical instrument through the second aperture.
In another aspect, the surgical instrument may connect to the intervertebral prosthesis through the second aperture.
In another aspect, the present disclosure is directed toward a method of implanting an intervertebral prosthesis in an intervertebral space between a first and a second vertebra of a patient's spinal column by making a first aperture at a first location laterally offset on a first side of a midline of the patient's spinal column. The first aperture may be configured to permit access to the intervertebral disc space and may be sized to allow passage of at least a portion of the intervertebral prosthesis. A second aperture may be made at a second location laterally offset on a second side of the midline of the patient's spinal column. The second side may be opposite the first side. The second aperture may be configured to permit access to the intervertebral disc space and may be sized to allow passage of an instrument. In addition, the second aperture may be smaller than the first aperture. A surgical instrument may be connected to the intervertebral prosthesis through the second aperture, and the intervertebral prosthesis may be inserted into the intervertebral space through the first aperture.
In yet another aspect, the present disclosure is directed to an intervertebral prosthesis for implantation into an intervertebral space between a first and a second vertebra of a patient's spinal column. The prosthesis may include a first end and a second end. A first bearing surface may extend between the first and second ends and may be configured to bear weight transferred from the first vertebra of the spinal column. A second bearing surface may be disposed opposite the first bearing surface and may be configured to transfer weight to the second vertebra of the spinal column. A first connecting element may be configured to cooperate with a surgical instrument operable from the first end of the intervertebral prosthesis. A second connecting element may be configured to cooperate with a surgical instrument operable from the second end of the intervertebral prosthesis.
In yet another aspect, a surgical instrument for implanting an intervertebral prosthesis in an intervertebral space between a first and a second vertebra of a patient's spinal column may be disclosed. The surgical instrument may include a distal end having a connector configured to engage the intervertebral prosthesis and pull the intervertebral prosthesis at least partially within the intervertebral disc space. A proximal end may be configured to be manipulated by a physician. The distal end may be responsive to the manipulation to pull the intervertebral prosthesis. A body may extend between the distal and proximal ends.
The present invention relates generally to a method and system of vertebral reconstruction, and more particularly, to a method and system for inserting an artificial intervertebral disc or prosthesis in an intervertebral space. For the purposes of promoting an understanding of the principles of the invention, reference will now be made to the embodiments, or examples, illustrated in the drawings and specific language will be used to describe the same. It will nevertheless be understood that no limitation of the scope of the invention is thereby intended. Any alterations and further modifications in the described embodiments, and any further applications of the principles of the invention as described herein are contemplated as would normally occur to one skilled in the art to which the invention relates.
Conventional spinal prosthetic devices are implanted using an anterior procedure, requiring a physician to access the spinal column using distressing and sometimes traumatic procedures. Once accessed, some types of disc arthroplasty require that some or all of the natural disc that would have been positioned between the two vertebrae 16, 18 be removed via a discectomy or a similar surgical procedure. Removal of the diseased or degenerated disc results in the formation of an intervertebral space between the upper and lower vertebrae 16, 18. A prosthetic vertebral disc may be installed in the intervertebral space, replacing the natural disc. Once a prosthetic vertebral disc is installed using an anterior procedure, scar tissue may quickly build on sensitive and important organs. If a second procedure is required, a physician is required to remove the scar tissue to access the previously placed prosthetic. This procedure can be sensitive and can cause distress to the patient. The methods and devices for implanting an artificial intervertebral disc disclosed herein may be advantageous over prior methods and devices because it may be installed using a posterior transforaminal approach, a lateral approach, or a posterior lateral approach, rather than an anterior one. Accordingly, a physician need not access and disturb the critical organs that reside anteriorly of the spinal column. Further, if a second procedure becomes necessary, the physician has easy access to the previously placed prosthesis without removing scar tissue off of sensitive organs. Accordingly, the procedure may be simplified and may cause less distress to the patient.
The artificial intervertebral disc 100 may provide relative pivotal and rotational movement between the adjacent vertebrae 16, 18 to maintain or restore relative motion. Preferably, the maintained or restored motion is substantially similar to the normal bio-mechanical motion provided by the natural intervertebral disc 14 of
The articular components 102, 104 of artificial intervertebral disc 100 may be formed of any suitable biocompatible material including, for example, metals such as cobalt-chromium alloys, titanium alloys, nickel titanium alloys, and/or stainless steel alloys. In one embodiment, the articular components 102, 104 are formed of a cobalt-chrome-molybdenum metallic alloy (ASTM F-799 or F-75). Ceramic materials such as aluminum oxide or alumina, zirconium oxide or zirconium, compact of particulate diamond, and/or pyrolytic carbon may also be suitable. Polymer materials may also be used, including any member of the polyaryletherketone (PAEK) family such as polyetheretherketone (PEEK), carbon-reinforced PEEK, or polyetherketoneketone (PEKK); polysulfone; polyetherimide; polyimide; ultra-high molecular weight polyethylene (UHMWPE); and/or cross-linked UHMWPE, among others. The various components comprising the arthroplasty halves 102, 104 may be formed of different materials thus permitting metal on metal, metal on ceramic, metal on polymer, ceramic on ceramic, ceramic on polymer, or polymer on polymer constructions.
The surfaces of the articular components 102, 104 that are positioned in direct contact with vertebral bone may include features or coatings which enhance the fixation of the implanted prosthesis. In one example, the surfaces of the articular components 102, 104 may be coated with a bone-growth promoting substance, such as, for example, a hydroxyapatite coating formed of calcium phosphate, tricalcium phosphate (TCP), and/or calcium carbonate. Alternatively, osteoinductive coatings, such as proteins from transforming growth factor (TGF) beta superfamily, or bone-morphogenic proteins, such as BMP2 or BMP7, may be used. In some embodiments, the surfaces of the articular components 102, 104 that are positioned in direct contact with vertebral bone are roughened prior to being coated with the bone-growth promoting substance to further enhance bone growth. Such surface roughening may be accomplished by way of, for example, acid etching, knurling, application of a bead coating, chemical etching, bead-blasting, sanding, grinding, serrating, and/or diamond-cutting or other methods of roughening that would occur to one of ordinary skill in the art. Other suitable features may include spikes, ridges, and/or other surface textures.
The articular component 102 includes a support plate 106 having an inner surface 108 and an opposite bearing surface 110. The support plate 106 may be sized and shaped to substantially correspond to the size and shape of the vertebral endplate of an adjacent vertebra. In one embodiment, the support plate 106 is shaped to facilitate a posterior transforaminal approach, a lateral approach, or a posterior lateral approach. As such, the support plate 106 includes curved side portions 112a, 112b, which are defined as the generally elongated portions of the support plate 106 extending between the inner surface 108 and the bearing surface 110. Although not shown, the support plate 106 can include one or more notches or other types of indicia for receiving and engaging with a corresponding portion of a surgical instrument (also not shown) to aid in the manipulation and insertion of the artificial intervertebral disc 100 within an intervertebral space between adjacent vertebrae. The surgical instrument (not shown) is preferably configured to hold the articular components 102, 104 at a predetermined orientation and spatial relationship relative to one another during manipulation and insertion of the artificial intervertebral disc 100, and to release the articular components 102, 104 once properly positioned between the adjacent vertebrae.
In one embodiment, the inner surface 108 includes a projection 114 having a convex shape, which may be configured as a spherical-shaped ball (half of which is shown). It should be understood that other configurations of the projection 114 are also contemplated, such as, for example, cylindrical, elliptical or other arcuate configurations or possibly non-arcuate configurations. It should also be understood that the remaining portion of inner surface 108 may take on planar or non-planar configurations, such as, for example, an angular or conical configuration extending about the projection 114.
The articular component 104 shown in
In one embodiment, the inner surface 122 includes a recess (not shown) having a profile that matches the profile of the projection 114. The recess may be configured to receive the projection 114, and form a ball and socket joint. It should be understood that the joint may be formed of other configurations, such as, for example, cylindrical, elliptical or other arcuate configurations or possibly non-arcuate configurations.
In the embodiment shown in
At the same time, the second connecting element 141 may be configured to connect to a surgical instrument configured to operate from the first end 101, or a trailing end, of the disc to push or manipulate the disc 100 into the intervertebral disc space. Such tools that aid in implantation by pushing from a trailing end are known in the art, and therefore, are not explained or shown in detail.
Flange members or keels 116, 130 extend from the respective bearing surfaces 110, 124 and may be configured for disposition within preformed openings in the respective adjacent vertebral endplates. In one embodiment, the keels 116, 130 extend perpendicularly from the bearing surface 110, 124 and are approximately centrally located along the bearing surface 110, 124. In some embodiments however, the position of the keels 116, 130 may be offset to help circumvent veins, arteries, bony portions, or other obstacles that may be in place during the insertion of the intervertebral disc 100.
In one embodiment, the keels 116, 130 transversely extend along a substantial portion of the support plate 106, 120. The keels 116, 130 may have a curved profile that in some examples is substantially similar to and congruous with the degree of curvature of the side portions 112a, 112b, 126a, 126b. Such an embodiment would accommodate insertion of the artificial intervertebral disc 100 using a posterior transforaminal approach, a lateral approach, or a posterior lateral approach, as opposed to the anterior approach discussed above. In a further embodiment, the keels 116, 130 may be angled, tapered, or configured in some other shape to facilitate the functional demands of the keel. In still another embodiment, the keels 116, 130 may be configured as a winged keel, including a transverse portion (not shown) extending across the main body portion of the keels.
In the embodiment shown in
In some embodiments, one or both of the keels 116, 130 may include a sharp forward edge, illustrated by edge 134 on the keel 130. By having such an edge, insertion of the keel into the associated vertebral body is facilitated. Also, the edges 134 can be of sufficient sharpness that the vertebral bodies do not require a slot for receiving the keels 116, 130, discussed in greater detail below. In some examples, the artificial intervertebral disc 100 includes only one of the keels 116, 130. Accordingly, the bearing surface 110, 124 not including a keel may be smooth or flat, or may include other features. In other embodiments, the artificial intervertebral disc 100 does not include any keels. When included, the keels 116, 130 need not have similar features, but may differ in relative location and structure, as would be apparent to one skilled in the art.
Referring to
An exemplary procedure for implanting the artificial intervertebral disc 100 between the vertebrae 16, 18 will now be described below with reference to
According to one example of the implantation procedure, a first incision or aperture may be made in the patient's back to provide access to the relevant vertebrae and spinal disc. The procedure will be described as though the first surgical aperture is made at the right side of a patient's midline, which may be defined by the patient's vertebral column. The first incision or approach could be part of an open procedure or a part of a procedure using a tube or retractor based technique. While the tube could be any suitable size, one exemplary tube is sized to have a diameter within the range of about 22-25 mm. The first incision, whether incorporating a tube or not, should be large enough to enable passage of the artificial intervertebral disc 100 into a space between the vertebrae. From the first incision, a physician may have a line-of-sight view as shown in
In order to provide orientation and aid during subsequent steps of the procedure, a second incision or aperture, relatively small when compared to the first incision, may be made on the side of the midline opposite the first incision, or in this case, on the left side of the patient's midline. The second incision may be only a small diameter stab wound. In one example, the second incision has a diameter of about 7 mm. Through the second incision, a small tube may be inserted to prop open the space. Alternatively, an endoscope may be placed directly in the absence of a tube. When a tube is placed, the endoscope may be inserted through the tube. The second incision, therefore, provides access to the area of the blind zone, as shown in
The present procedure differs from traditional transforaminal approaches because traditional transforaminal approaches have been purely unilateral approaches. When a traditional transforaminal approach is used, the incision is often larger than would occur using the present methods. Further, the present procedure differs from the traditional posterior approach because traditional posterior approaches have been either open or bilateral approaches with relatively equal sized incisions on each side. In contrast to the traditional transforaminal and posterior approaches, the present procedure opens one side of the spine a sufficient amount to provide traditional access, but opens the second side only in a micro-invasive manner. In some examples, the second incision is a stab wound, rather than a sized incision. Accordingly, the procedure is less invasive than prior procedures, reducing trauma to the patient and potentially less distressful to the spinal segment. Further, the present procedure provides better access to the intra-discal tissue than the purely unilateral approach of the traditional transforaminal procedure. In addition, the present procedure provides a much smaller surgical access port on one side than the traditional posterior procedure.
Once the incisions are made, and the muscle and ligaments are moved aside, some or all of the affected natural disc and surrounding tissue may be removed via the first incision. This may done using methods known in the art, using conventional tools sized to fit through the first incision.
In a traditional transforaminal approach, the left posterior corner of the intra-discal space is difficult to reliably reach, as it is within the blind zone 150 of
Because of the difficulty in viewing the blind zone when performing procedures using traditional transforaminal approaches, sometimes the vertebral space is not sufficiently cleared of discal tissue. Because of this, when the artificial intervertebral disc is placed, it may not seat as well as it otherwise would. The present approach, where the progress of the discal tissue removal process may be viewed and monitored, provides a better cleaning and prepping of the vertebrae, resulting in a better seat of the artificial intervertebral disc 100.
Once the discal tissue is removed, or alternatively, while removing the discal tissue, the superior endplate surface of the vertebra 18 may be milled, rasped, or otherwise resected to match the profile of the bearing surface 110 of the artificial intervertebral disc 100. A good match may normalize stress distributions on the endplate surface of the vertebra 18, and/or provide initial fixation prior to bone ingrowth. The preparation of the endplate of vertebra 18 may result in a flattened surface or in surface contours such as pockets, grooves, or other contours that may match corresponding features on the disc 100. The endplate of the vertebra 16 may be similarly prepared to fit the bearing surface 124. The natural facet joints of vertebrae 16, 18 may be trimmed if necessary to provide an access path for the intervertebral disc 100.
If the disc includes keels, as does the artificial intervertebral disc of
Once the vertebrae 16, 18 are prepared, the artificial intervertebral disc 100 may be inserted through the first incision into the intervertebral space, as shown in
During insertion, it is possible for the artificial disc to become stuck part way into the intervertebral space, particularly in the examples where keels are employed. If this occurs, and as shown in
The surgical tool 156 may include a distal end 158 and a proximal end 160. The distal end 156 may be configured with a connector 162 configured to cooperate with the first connecting element 140 on the intervertebral disc 100. The connector 162 may be configured to engage the intervertebral disc 100 in a manner to allow the disc to be pulled by the surgical tool 156 and may be, for example, a hook or finger. The proximal end 160 of the surgical tool 156 may include a handle 164 that may be held and/or manipulated by a physician performing the disc replacement procedure. As shown in
The surgical tool 156 may be a strong cable, thread, or similar leader that is configured to pass through the tube 154, into the intervertebral space, and removably connect with the first connecting element 140. The surgical tool 156 may be any component configured to attach to and pull an intervertebral disc from one side of an intervertebral disc space toward another and, in some examples, includes a hook, pincers, a bend or other configuration capable of operating to attach to the connecting element 140. In some examples, the surgical tool 156 is a rigid, curved cable, while in other examples, the tool is semi-rigid. In others, the surgical tool is flexible.
Once the surgical tool 156 is connected to the intervertebral disc 100, the tool may used to pull the disc into place. In some examples, the surgical tool 156 is used to pull the disc through the second incision at the same time that the disc is being pushed into the intervertebral space through the first incision by the connecting element 141. Pulling and pushing on the intervertebral disc 100 may greatly simplify the insertion process. Further, it may simplify moving and positioning the artificial intervertebral disc 100 after it is fully within the intervertebral space. Once the artificial intervertebral disc 100 is properly positioned in the intervertebral space, any bone fixation elements, such as screws, may be introduced, and the surgical tool 156 may be removed and the tube withdrawn, as shown in
The procedure disclosed herein allows for a better fit than traditional transforaminal procedures by providing access to the blind region, previously unmonitored during traditional transforaminal procedures. This enables the vertebral space to be better prepared to receive the intervertebral disc 100, making a better fit, and potentially reducing subsequent pain and trauma. Furthermore, it enables the disc to be guided into place from a leading edge, rather than just from the rear, as in traditional approaches. Accordingly, the disc may be implanted with less force and with less difficulty than when using traditional transforaminal approaches.
In addition, the procedure disclosed herein is less invasive than traditional posterior procedures because the second incision for the tube is relatively smaller than the first incision for the disc. Accordingly, the procedure may reduce the amount of trauma and distress occurring with traditional posterior procedures.
Because of its convenient nature, suppliers of the intervertebral disc 100 may sell the device in a kit. A kit may include, for example, the intervertebral disc 100 with the surgical tool 156 that is engagable with the first connection element 140 to pull the disc during implantation. The first connection 140 may be located on the leading end. In addition, the kit may include a second surgical tool engagable with the second connection element 141 to push the intervertebral prosthesis in a manner known in the art. Other combinations could also be used.
Although the illustration of
Although only a few exemplary embodiments have been described in detail above, those skilled in the art will readily appreciate that many modifications are possible in the exemplary embodiments without materially departing from the novel teachings and advantages of this disclosure. Accordingly, all such modifications and alternative are intended to be included within the scope of the invention as defined in the following claims. Those skilled in the art should also realize that such modifications and equivalent constructions or methods do not depart from the spirit and scope of the present disclosure, and that they may make various changes, substitutions, and alterations herein without departing from the spirit and scope of the present disclosure. It is understood that all spatial references, such as “horizontal,” “vertical,” “top,” “upper,” “lower,” “bottom,” “left,” “right,” “cephalad,” “caudal,” “upper,” and “lower,” are for illustrative purposes only and can be varied within the scope of the disclosure. In the claims, means-plus-function clauses are intended to cover the elements described herein as performing the recited function and not only structural equivalents, but also equivalent elements.
