Patent Application
20080249569
The present invention relates generally to the field of replacing portions of the human structural anatomy with medical implants.
Spinal discs between the endplates of adjacent vertebrae in a spinal column of the human body provide critical support. However, due to injury, degradation, disease or the like, these discs can rupture, degenerate and/or protrude to such a degree that the intervertebral space between adjacent vertebrae collapses as the disc loses at least a part of its support function. This can cause impingement of the nerve roots and severe pain. In some cases, surgical correction may be required.
Some surgical corrections include the removal of the natural spinal disc from between the adjacent vertebrae. In order to preserve the intervertebral disc space for proper spinal-column function, an implant member can be inserted between the adjacent vertebrae.
Some implant members employ anchor members that fix the implant member in place between the adjacent vertebrae. Over time, due to micro motion of the vertebrae relative to the implant member, the anchor members may loosen and start to back out of vertebrae.
What is needed is an implant that reduces or eliminates anchor member back-out. The implants disclosed herein address one or more deficiencies in the art.
In one exemplary aspect, the present disclosure is directed to an implantable medical device attachable to bone structure using an anchor member. The device may include an implant member including an anchor member aperture sized to receive the anchor member, and also may include a faceplate sized to overlap at least a portion of the anchor member aperture and inhibit back-out of the anchor member from the anchor member aperture. The faceplate may be configured to snap onto the implantable member.
In another exemplary aspect, the present disclosure is directed to a faceplate for at least partially covering a plurality of anchor member apertures in an implantable member. The faceplate may include a main body sized to at least partially overlap the plurality of anchor member apertures of the implantable member and configured to inhibit anchor member back-out from the plurality of anchor member apertures. A locking tab may be associated with the main body, the locking tab being formed to at least partially elastically deform to engage the implantable member and secure the main body in place.
In yet another exemplary aspect, the present disclosure is directed to a method including introducing an implant member to a vertebral segment comprising an upper and a lower vertebra. Anchor members may be inserted through anchor member apertures in the implant member, the anchor members penetrating the upper and the lower vertebrae. The faceplate may be oriented to at least partially overlap the anchor member apertures, and the faceplate may be advanced until it snaps onto the implant member to inhibit anchor member back-out.
Further aspects, forms, embodiments, objects, features, benefits, and advantages of the present invention shall become apparent from the detailed drawings and descriptions provided herein.
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.
For the sake of further example, two of the vertebrae will be discussed with reference to a spinal segment 12 shown in
Some types of disc arthroplasty require that some or the entire natural disc that would have been positioned between the two vertebrae 14, 16 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 14, 16. Once the diseased or degenerated disc is removed, an implantable prosthetic device may be used to maintain the vertebral spacing and provide vertebral support. As shown in
In the embodiment shown, the upper and lower surfaces 108, 110 include bone engaging features 120 configured to reduce slipping or movement of the implant member 102 relative to the vertebrae 14, 16. In the exemplary embodiment shown, the bone engaging features 120 are angled teeth that permit introduction into the disc space, but also restrict removal. These may be any other known bone engaging features, including protrusions and keels, among others. Alternatively, the upper and lower surfaces 108, 110 may be relatively smooth. The side surfaces 112a-b each include a recessed slot 122 (best seen in
The front surface 116 and/or the upper and lower surfaces 108, 110 include anchor member apertures 126 that receive the anchor members 106 for attachment of the implant member 102 to the vertebral bodies 14, 16. In this exemplary embodiment, the anchor members 106 are bone anchor members. However, other anchor members are contemplated. The anchor members 106 extend through the anchor member apertures 126 in the front surface 116 and upper and lower surfaces 108, 110 and out the hollow center 118 and into the bearing endplates of the vertebrae 14, 16, thereby securely locating the implant member 102 entirely within the disc space. In this exemplary embodiment, the implant member 102 includes three apertures 126—two angled to allow anchor members 106 to attach to an upper vertebral endplate and one angled to allow an anchor member 106 to attach to a lower vertebral endplate. However, in other embodiments, other numbers and configurations of anchor members 106 may be used.
To reduce the chance of the anchor members 106 backing out of the vertebral bodies over time and causing the implant member 102 to become loose, the face plate 104 is configured to extend across at least a portion of the anchor member apertures 126 and physically block anchor member back-out.
The main body 128 includes a front surface 132, an interfacing surface 134, respective top and bottom surfaces 136, 138, and first and second ends 140, 142. The interfacing surface 134 lies against the front surface 116 of the implant member 102 and inhibits the anchor members 106 from backing out by being physically located within the back-out path. In this exemplary embodiment, the main body 128 extends substantially the entire length of the front surface 116 in an arcing shape, from one side surface 112a to the other side surface 112b. Its height is less than the height of the front surface 116, and it overlaps only a portion of each of the anchor member apertures 126, as shown in
The locking tabs 130, in this exemplary embodiment, extend as cantilevers from the first and second ends 140, 142 of the main body 128, generally in the same direction forming a U-shape. In other embodiments, the locking tabs 130 extend from the top and bottom surfaces 136, 138 of the face plate 104. Each locking tab 130 includes a body portion 144 and a locking protrusion 146 extending from the body portion 144. The body portion 144 of each locking tab 130 is configured to fit within the corresponding recessed slots 122 formed in the side surfaces 112a-b of the implant member 102, and the locking protrusions 146 are sized and configured to interface with the corresponding connecting impressions 124 in the recessed slots 122. In the embodiment shown, the locking protrusions 146 are angled protrusions having a leading tapered surface 148 and a trailing locking surface 150.
In the embodiment shown, the faceplate 104 is configured to attach to the exterior sides 112a-b of the implant member 102. Thus, the faceplate 104 may be sized to span the width of the implant member 102, and may have an outer width Wt. In other embodiments, the faceplate may be configured to attach to locations on the implant member 102 other than the exterior surfaces.
The faceplate 104 may be configured to snap onto the implant member 102, allowing simple installation once the anchor members 106 are placed during a surgical procedure. As used herein, the terms “snap onto,” and “snaps onto” are intended to mean attachment using features of the different components without the use of separate fasteners, such as screws or staples. To do this, in the embodiment shown, the locking tabs 130 may be configured to elastically deform when placing the faceplate 104 on the implant member 102, and then snap into place, thereby securing the faceplate 104 onto the implant member 102 and physically limiting back-out of the anchor members 106 from the implant member 102. An example of this is provided further below.
When the implantable device 100 is a spacer as shown in
In the embodiment shown, the face plate 104 may be constructed in whole or in part of biocompatible materials of various types. Examples of face plate materials include, but are not limited to, non-reinforced polymers, carbon-reinforced polymer composites, PEEK and PEEK composites, shape-memory alloys, titanium, titanium alloys, cobalt chrome alloys, stainless steel, ceramics and combinations thereof. If the face plate 104 is made from radiolucent material, radiographic markers can be located on the face plate 104 to provide the ability to monitor and determine radiographically or fluoroscopically the location of the face plate in the spinal disc space. Resorbable materials also may be used. Examples of resorbable materials that may be used include, but are not limited to, polylactide, polyglycolide, tyrosine-derived polycarbonate, polyanhydride, polyorthoester, polyphosphazene, calcium phosphate, hydroxyapatite, bioactive glass, and combinations thereof.
In alternative embodiments, instead of the locking protrusions 146, 158 being formed on the insertion tool 152 and/or on the faceplate 104, the locking protrusions are formed on the implant member 102 and the insertion tool 152 and/or faceplate 104 has connecting features, such as connecting impressions. Additionally, in some exemplary embodiments, the connecting impressions 124 are apertures, hooks or other protruding or recessed features. Further, in some exemplary embodiments, the insertion tool 152 and/or faceplate 104 connects to locations on the implant member 102 other than at the side surfaces 112a-b. For example, in some exemplary embodiments, the locking tabs 130 extend into bores formed in the surface of the implant member 102 adjacent the anchor member apertures 126. Other types and locations of attachments are contemplated.
In addition, although disclosed as being on the front surface 116 where the front surface is an anterior surface, it should be understood that the faceplate 104 may be disposed to cover any surface having an anchor member aperture 126 in the implantable device 102 to inhibit anchor member back-out. For example, some implant members 102 may be implanted posteriorly and may include anchor member apertures 126 on the rear side 114 or alternatively, on the lateral sides 112a-b. In these embodiments the face plate 104 may be disposed to cooperate with the apertures on those sides and inhibit anchor member back-out from those apertures.
Like the implantable member 102, the implantable member 202 includes side surfaces 208a-b, a rear surface 210, and a front surface 212. Anchor member apertures 214 are shown formed in the front surface 212 and allow attachment to the bearing endplates of the vertebrae 14, 16 in
One exemplary embodiment of the faceplate 204 is shown in
As can be seen in
The face plate 304 is shown in
The securing tabs 324, in this exemplary embodiment, extend from sides 336 of the main body 320 and are configured to interface with and extend into the recessed slots 314 on the implant member 302. These securing tabs 324 act as guides to help orient and place the face plate 304 during assembly.
The locking tabs 322, in this exemplary embodiment, extend from the top and bottom surfaces 330, 332 of the main body 320 and are formed off-centerline, as best seen in
Yet another exemplary embodiment of an implantable device is shown in
As can be seen in
The face plate 404 includes a main body 422 locking tabs 424. The main body 422 includes an interfacing surface 426 and respective top and bottom surfaces 428, 430. In the exemplary embodiment shown in
Referring now to
For ease of explanation, the faceplate 404 is shown with only a single projecting protuberance 432. However, in other embodiments, the main body 422 includes a projecting protuberance 432 that corresponds with each anchor member aperture 420 in the implant member 402. Accordingly, the main body 422 with the projecting protuberances 432 deters the anchor members from backing out by physically blocking them. As in other embodiments shown herein, the face plate 404 connects to the implant member 402 using, in this exemplary embodiment, the locking tabs 424.
The locking tabs 424, like those described with respect to other embodiments herein, may be configured to elastically deform when placing the face plate 404 on the implant member 402, and then snap into place, thereby securing the face plate 404 onto the implant member 402 and physically limiting back-out of the anchor members from the implant member 402.
A method of implantation is described below with reference to the first embodiment of the implantable device 100 disclosed herein. However, the method of implantation is intended to be equally applicable to all the disclosed embodiments.
The spacers may be implanted between the vertebrae 14, 16 using any common approach, including an anterior approach, a posterior approach, a posterior transforaminal approach, a far lateral approach, a direct lateral approach, among others. According to at least one of these approaches, an incision, such as a midline incision, may be made in the patient's back and some or all of the affected disc and surrounding tissue may be removed via the foramina. The endplate surface of the vertebra 14 may be milled, rasped, or otherwise resected to match the profile of the upper surface 108 of the implant member 102, to normalize stress distributions on the endplate surface of the vertebra 14, and/or to provide initial fixation prior to bone ingrowth. The preparation of the endplate of vertebra 14 may result in a flattened surface or in surface contours such as pockets, grooves, or other contours that may match the bone engaging features 120 on the upper surface 108. The endplate of the vertebra 16 may be similarly prepared to engage the lower surface 110 of the implant member 102 to the extent allowed by the exiting nerve root and the dorsal root ganglia. In some procedures, the natural facet joints of vertebrae 14, 16 may be trimmed or removed to provide access to the disc space.
The implant member 102 then may be attached to the insertion tool 152 and introduced into the intervertebral disc space between the upper and lower vertebrae 14, 16. Once properly positioned, the insertion tool 152 may be removed from the implant member 102 and anchor members 106 may be driven through the anchor member apertures 126 into the vertebral endplates. Alternatively, the anchor members 106 may be driven into the anchor member apertures 126 before the insertion tool 152 is removed. Once the anchor members 106 are driven into the bone, the anchor member apertures 126 may be covered with the faceplate 104 to prevent anchor member back-out.
The faceplate 104 may be introduced to the implant member 102 so that the locking tabs 130 align with the recessed slots 122. While advancing the faceplate 104, the tapered surfaces 148 of the locking protrusions 146 contact the implant member 102 and are elastically forced apart. Further advancement slides the locking protrusions 146 along the recessed slot 122 until the locking protrusions 146 reach the connecting impressions 124. Once there, the faceplate 104 snaps onto the implant member 102 because the locking tabs 130 deform toward their original positions as the locking protrusions 146 at least partially snap into the connecting impressions 124. The locking surface 150 on the locking protrusion 146 engages against the connecting impressions 124 and resists detaching the faceplate 104 from the implant member 102. The main body 128 of the faceplate 102 is now oriented to overlap at least a part of the anchor member apertures 126, and the surgical process may be completed in a manner known in the art.
Over time, due to micromotion of the vertebrae and the implant member 102, the anchor members 106 may loosen slightly. However, the anchor members 106 may be unable to back-out because they come into contact with the main body 128 of the faceplate 104. Thus, anchor member back-out is inhibited by the faceplate 104.
In some embodiments, after the faceplate 104 snaps onto the implant member 102, additional locking features, such as a screw fastener, may be used to further attach the faceplate 104 to the implant member 102.
In some embodiments, the implant member or individual components of the implantable member are constructed of solid sections of bone, other tissues, or resorbable materials. Tissue materials include, but are not limited to, synthetic or natural autograft, allograft or xenograft, and may be resorbable or non-resorbable in nature. Examples of other tissue materials include, but are not limited to, hard tissues, connective tissues, demineralized bone matrix and combinations thereof. Examples of resorbable materials that may be used include, but are not limited to, polylactide, polyglycolide, tyrosine-derived polycarbonate, polyanhydride, polyorthoester, polyphosphazene, calcium phosphate, hydroxyapatite, bioactive glass, and combinations thereof. The implantable device may be solid, porous, spongy, perforated, drilled, and/or open.
In some circumstances, it is advantageous to pack all or a portion of the hollow center of the implant member with a suitable osteogenetic material or therapeutic composition. Osteogenic materials include, without limitation, autograft, allograft, xenograft, demineralized bone, synthetic and natural bone graft substitutes, such as bioceramics and polymers, and osteoinductive factors. A separate carrier to hold materials within the device can also be used. These carriers can include collagen-based carriers, bioceramic materials, such as BIOGLASS®, hydroxyapatite and calcium phosphate compositions. The carrier material may be provided in the form of a sponge, a block, folded sheet, putty, paste, graft material or other suitable form. The osteogenetic compositions may include an effective amount of a bone morphogenetic protein, transforming growth factor β1, insulin-like growth factor 1, platelet-derived growth factor, fibroblast growth factor, LIM mineralization protein (LMP), and combinations thereof or other therapeutic or infection resistant agents, separately or held within a suitable carrier material.
It is understood that all spatial references, such as “top,” “inner,” “outer,” “bottom,” “left,” “right,” “anterior,” “posterior,” “superior,” “inferior,” “medial,” “lateral,” “upper,” “lower,” “front,” and “rear” are for illustrative purposes only and can be varied within the scope of the disclosure.
While embodiments of the invention have been illustrated and described in detail in the disclosure, the disclosure is to be considered as illustrative and not restrictive in character. All changes and modifications that come within the spirit of the invention are to be considered within the scope of the disclosure.
