Anti-Rotation Fixation Element for Spinal Prostheses
Prostheses, systems, and methods are provided for replacement of natural facet joints between adjacent vertebrae with vertebral prostheses. A portion of the vertebral prosthesis includes anti-rotation and/or anti-pullout elements to prevent or reduce prosthesis fastener rotation or pull out as a result of torques applied to the prosthesis. Various tools and methods aid the process of surgically adding the vertebral prosthesis to a patient's vertebra.
This patent application is a continuation application claiming priority to U.S. patent application Ser. No. 10/831,657, filed on Apr. 22, 2004, the entire contents of which are incorporated by reference.
FIELD OF THE INVENTIONThis invention relates to prostheses, systems, and methods for treating various types of spinal pathologies, and in particular relates to attachment of prostheses to spinal vertebrae.
BACKGROUND OF THE INVENTIONThe human spinal column 10, as shown in
At the posterior end of each pedicle 16, the vertebral arch 18 flares out into broad plates of bone known as the laminae 20. The laminae 20 fuse with each other to form a spinous process 22. The spinous process 22 serves for muscle and ligamentous attachment. A smooth transition from the pedicles 16 to the laminae 20 is interrupted by the formation of a series of processes.
Two transverse processes 24 thrust out laterally on each side from the junction of the pedicle 16 with the lamina 20. The transverse processes 24 serve as levers for the attachment of muscles to the vertebrae 12. Four articular processes, two superior 26 and two inferior 28, also rise from the junctions of the pedicles 16 and the laminae 20. The superior articular processes 26 are sharp oval plates of bone rising upward on each side of the vertebrae, while the inferior processes 28 are oval plates of bone that jut downward on each side.
The superior and inferior articular processes 26 and 28 each have a natural bony structure known as a facet. The superior articular facet 30 faces upward, while the inferior articular facet 31 (see
The facet joint 32 is composed of a superior half and an inferior half. The superior half is formed by the vertebral level below the joint 32, and the inferior half is formed by the vertebral level above the joint 32. For example, in the L4-L5 facet joint, the superior half of the joint 32 is formed by bony structure on the L5 vertebra (i.e., a superior articular surface and supporting bone 26 on the L5 vertebra), and the inferior half of the joint 32 is formed by bony structure on the L4 vertebra (i.e., an inferior articular surface and supporting bone 28 on the L4 vertebra).
An intervertebral disc 34 between each adjacent vertebrae 12 permits gliding movement between the vertebrae 12. The structure and alignment of the vertebrae 12 thus permit a range of movement of the vertebrae 12 relative to each other.
Back pain, particularly in the “small of the back” or lumbosacral (L4-S1) region, is a common ailment. In many cases, the pain severely limits a person's functional ability and quality of life. Such pain can result from a variety of spinal pathologies.
Through disease or injury, the laminae, spinous process, articular processes, or facets of one or more vertebral bodies can become damaged, such that the vertebrae no longer articulate or properly align with each other. This can result in an undesired anatomy, loss of mobility, and pain or discomfort.
For example, the vertebral facet joints can be damaged by either traumatic injury or by various disease processes. These disease processes include osteoarthritis, ankylosing spondylolysis, and degenerative spondylolisthesis. The damage to the facet joints often results in pressure on nerves, also called “pinched” nerves, or nerve compression or impingement. The result is pain, misaligned anatomy, and a corresponding loss of mobility. Pressure on nerves can also occur without facet joint pathology, e.g., a herniated disc.
One type of conventional treatment of facet joint pathology is spinal stabilization, also known as intervertebral stabilization. Intervertebral stabilization prevents relative motion between the vertebrae. By preventing movement, pain can be reduced. Stabilization can be accomplished by various methods. One method of stabilization is spinal fusion. Another method of stabilization is fixation of any number of vertebrae to stabilize and prevent movement of the vertebrae.
Another type of conventional treatment is decompressive laminectomy. This procedure involves excision of the laminae to relieve compression of nerves.
These traditional treatments are subject to a variety of limitations and varying success rates. None of the described treatments, however, puts the spine in proper alignment or returns the spine to a desired anatomy or biomechanical functionality. In addition, stabilization techniques hold the vertebrae in a fixed position thereby limiting a person's mobility.
Prostheses, systems, and methods exist which can maintain more spinal biomechanical functionality than the above discussed methods and systems and overcome many of the problems and disadvantages associated with traditional treatments for spine pathologies. One example of such prosthesis is shown in
The spinal column permits the following types of movement: flexion, extension, lateral movement, circumduction and rotation. Each movement type represents relative movement between adjacent vertebra or groups of vertebrae. In addition, these relative movements may be simple movements of a single type but it is more likely that a single movement of the spine may result in several movement types or compound movement occurring contemporaneously. In the illustration of
The existence of enormous amounts of torque presents significant problems for permanent fixation of facet joint prostheses into vertebra. Over time, this torque can act to loosen conventional fixation elements, ruin the facet joint, and require more surgical intervention to restore the facet joint prostheses in the vertebra.
Thus, what is needed is a solution to the torque problem experienced by facet joints of artificial vertebral prostheses.
SUMMARY OF THE INVENTIONThe present invention provides prostheses, systems, and methods designed to replace natural facet joints and possibly part of the lamina at virtually all spinal levels including L1-L2, L2-L3, L3-L4, L4-L5, L5-S1, T11-T12, and T12-L1, using attachment mechanisms for securing the prostheses to the vertebrae. The prostheses, systems, and methods help establish a desired anatomy to a spine and return a desired range of mobility to an individual. The prostheses, systems, and methods also help lessen or alleviate spinal pain by relieving the source nerve compression or impingement.
For the sake of description herein, the prostheses that embody features of the invention are identified as either “cephalad” or “caudal” with relation to the portion of a given natural facet joint they replace. As previously described, a natural facet joint, such as facet joint 32 (
In one aspect, a vertebral prosthesis includes a first bearing element and a first fixation element coupled to the first bearing element. The first bearing element can be shaped to form a facet joint with a second bearing element. The first fixation element can be inserted into a hole in a vertebra.
The first fixation element can include an anti-rotation element. The anti-rotation element can be coupled to at least a portion of the vertebra. This portion of the vertebra can define the hole in the vertebra. The anti-rotation element can be adapted to resist a rotational force. With no resistance, the rotational force may cause rotation of the first fixation element within the hole in the vertebra.
In some embodiments, the hole in the vertebra may be just one hole. In other embodiments, there may be multiple holes in the vertebra. In the case of multiple holes in the vertebra, the first fixation element can be inserted into just one hole in the vertebra, or into multiple holes in the vertebra. Also in the case of multiple holes in the vertebra, the rotation force may cause rotation of the first fixation element within just one hole in the vertebra, or within multiple holes in the vertebra.
In various embodiments, the second bearing element with which the first bearing element forms a facet joint, can be part of a second prosthesis, or part of a natural vertebra. If the second bearing element is part of a second prosthesis, the second prosthesis can be one of the embodiments discussed herein, or another type of prosthesis.
The fixation element may be secured directly into the vertebral body, or can be attached and/or “fixed” using a supplemental fixation material such as bone cement, allograft tissue, autograft tissue, adhesives, osteo-conductive materials, osteo-inductive materials and/or bone scaffolding materials. In one embodiment, the first fixation element can be enhanced with a bony in-growth surface, such as surfaces created using sintering processes or chemical etching (Tecomet Corporation of Woburn, Mass.) which can help fix the fixation element within a vertebra. The bony in-growth surface can cover a portion or all of the first fixation element.
A width of the prosthesis may be constant, or vary. For example, a width of a proximal end of the first fixation element can exceed a width of a distal end of the first fixation element. A width of a proximal end of the anti-rotation element can exceed a width of a distal end of the anti-rotation element. In an alternate embodiment, a width of a distal end of the first fixation element can exceed a width of a proximal end of the first fixation element.
The anti-rotation element can be coupled to the vertebra by being directly connected to the vertebra. The anti-rotation element also can be coupled with at least cement to the vertebra.
In some embodiments, the anti-rotation element includes a wing. The wing can be positioned at a proximal of distal portion of the first fixation element. When the first fixation element is inserted into a first hole or holes in the vertebra, the wing can be inserted into a second hole of the vertebra.
In some embodiments, the anti-rotation element includes a blade. The blade can be positioned at a proximal or distal portion of the first fixation element. When the first fixation element is inserted into a first hole or holes in the vertebra, the blade can also be inserted into the first hole in the vertebra.
In some embodiments, the anti-rotation element includes a paddle. The paddles can be positioned at a distal or proximal portion of the first fixation element. The first fixation element can be straight, or include one or more bends. The anti-rotation element can include one or more grooves positioned distally and/or proximally from the paddle. The anti-rotation element can also include other features, such as one or more wings positioned proximally or distally from the paddle, and/or one or more blades positioned proximally or distally from the paddle.
In some embodiments, the anti-rotation element includes an intersection of three or more projections. The intersection can be positioned at a distal or proximal portion of the first fixation element.
In some embodiments, the anti-rotation element includes a helical projection. The anti-rotation element can include an intersection of two or more helical projections.
In some embodiments, the anti-rotation element includes a longitudinal depression. The longitudinal depression can have a longitudinally varying profile. The longitudinal depressions can be a helical longitudinal depression, a groove, or a flute. The longitudinal depression can help define a spline. The anti-rotation element may further include a perimeter (circumferential) depression. The perimeter depression can be a perimeter undercut.
In some embodiments, the anti-rotation element can include separated members. The first fixation element can include a longitudinal hole. A filling element can be inserted into the longitudinal hole and spread the separated members of the anti-rotation element. The separated members can be positioned at a distal portion of the first fixation element.
In various embodiments, the anti-rotation element can define a hole, into which the first fixation element is inserted. Alternatively, the first fixation element can define a hole into which the anti-rotation element is inserted. In various embodiments, the hole can be tapered (using, for example, a tapered broach) and/or the first fixation element can have a taper. The anti-rotation element can have a taper. The anti-rotation element can be coupled to the first fixation element by an interference fit. The anti-rotation element can include a bend, or be straight. The first fixation element can be straight, or include a bend.
In some embodiments, the anti-rotation element includes one or more proximal projections.
In another aspect, a vertebral prosthesis includes a first bearing element and a first fixation element. The first bearing element can be shaped to form a facet joint with a second bearing element. The first fixation element can be coupled to the first bearing element. The first fixation element can be inserted into a hole in the vertebra. The first fixation element can be shaped to resist a rotational force. With no resistance, the rotational force may cause rotation of the first fixation element within the hole in the vertebra.
In various embodiments, the second bearing element with which the first bearing element forms a facet joint, can be part of a second prosthesis, or part of a natural vertebra. If the second bearing element is part of a second prosthesis, the second prosthesis can be one of the embodiments discussed herein, or another type of prosthesis.
The first fixation element can be enhanced with a bony in-growth surface, which can help fix the fixation element within a vertebra. The bony in-growth surface can cover a portion or the entire first fixation element.
A width of the prosthesis may be constant, or vary. For example, a width of a proximal end of the first fixation element can exceed a width of a distal end of the first fixation element. A width of a proximal end of the anti-rotation element can exceed a width of a distal end of the anti-rotation element. In another embodiment, the width of a distal end of the anti-rotation element can exceed a width of a proximal end of the anti-rotation element.
The anti-rotation element can be coupled to the vertebra by being directly connected to the vertebra. The anti-rotation element also can be coupled with at least cement to the vertebra.
In some embodiments, the first fixation element can be shaped with a bend. The first fixation element can have a taper.
In another aspect, a vertebral prosthesis method includes coupling a first bearing element to a first fixation element, coupling an anti-rotation element to the first fixation element (as a feature of the component or as a separate component), and inserting the first fixation element into a hole in the vertebra. The first bearing element can be shaped to form a facet joint with a second bearing element. The anti-rotation element can be adapted to resist a rotational force. With no resistance, the rotational force may cause rotation of the first fixation element within the hole in the vertebra.
In another aspect, a vertebral prosthesis preparation method includes perforating a vertebra with at least a first hole, supporting a perforation guide with a guide support, guiding a perforation tool with the perforation guide, and perforating the vertebra with a second hole (or shaped cavity) aligned by the perforation guide. The first hole can be shaped to receive a prosthetic fixation element. The guide support can be positioned by a portion of the vertebra defining a hole. The second hole can be shaped to receive a first prosthetic anti-rotation element.
In some embodiments, the method can include the step of using the perforation tool while at least partly removing the guide support.
Various embodiments include the step of perforating the vertebra with a third hole aligned by the perforation guide. The third hole can be shaped to receive a second prosthetic anti-rotation element.
In some embodiments, the method can include the step of using the perforation tool while least partly removing the guide support.
The guide support can be inserted while perforating the vertebra with the first hole. The guide support can be inserted after perforating the vertebra with the first hole.
In yet another aspect, a vertebral prosthesis tool includes a guide support and a perforation guide.
The guide support can be stabilized by a first hole of the vertebra. The first hole can be shaped to receive a prosthetic fixation element of the vertebral prosthesis. The vertebral prosthesis can form a facet joint with a second vertebral prosthesis.
The perforation guide can be coupled to the guide support. The perforation guide can guide a perforation tool to perforate the vertebra with a second hole aligned by the perforation guide. The second hole can be shaped to receive a prosthetic anti-rotation element of the vertebral prosthesis.
Other features and advantages of the invention are set forth in the following description and drawings, as well as in the appended claims.
In some embodiments, a system for vertebral implantation comprises a first vertebral prosthesis comprising a first fixation element adapted to be inserted into a first hole formed in a vertebra, the first fixation element having a first longitudinal axis; a second vertebral prosthesis comprising a second fixation element adapted to be inserted into a second hole formed in the vertebra, the second fixation element having a second longitudinal axis; and a cross-bar connecting the first vertebral prosthesis and the second vertebral prosthesis; wherein the first vertebral prosthesis comprises an anti-rotational element extending along the first fixation element of the first vertebral prosthesis, wherein the anti-rotational element is configured to resist a rotational force that would cause rotation of the first fixation element in the first hole of the vertebra.
In other embodiments, a system for vertebral implantation comprises a first vertebral prosthesis comprising a first proximal shaft having a longitudinal axis and a first distal shaft having a longitudinal axis that differs from the longitudinal axis of the proximal shaft, wherein the first distal shaft is configured to be inserted into a first hole formed in a vertebra; a second vertebral prosthesis comprising a second proximal shaft and a second distal shaft, wherein the second distal shaft is configured to be inserted into a second hole formed in the vertebra; and a cross-bar connecting the first vertebral prosthesis and the second vertebral prosthesis; wherein the first vertebral prosthesis comprises one or more anti-rotational elements extending along the first distal shaft of the first vertebral prosthesis, wherein the one or more anti-rotational elements are configured to resist a rotational force that would cause rotation of the first distal shaft in the first hole of the vertebra.
In other embodiments, a system for vertebral implantation comprises a first vertebral prosthesis comprising a first proximal shaft having a longitudinal axis and a first distal shaft having a longitudinal axis that differs from the longitudinal axis of the proximal shaft, wherein the first proximal shaft transitions into the first distal shaft via a bend; a second vertebral prosthesis comprising a second proximal shaft and a second distal shaft, wherein the second proximal shaft transitions into the second distal shaft via a bend; and a cross-bar connecting the first vertebral prosthesis and the second vertebral prosthesis; wherein the first vertebral prosthesis comprises one or more anti-rotational elements extending along a length of the first vertebral prosthesis.
Although the disclosure presented herein provides details to enable those skilled in the art to practice various embodiments of the invention, the physical embodiments disclosed herein merely exemplify the invention, which may be embodied in other specific structure. Accordingly, while preferred embodiments of the invention are described below, details of the preferred embodiments may be altered without departing from the invention. All embodiments that fall within the meaning and scope of the appended claims, and equivalents thereto, are intended to be embraced by the claims.
Embodiments of the present invention may be used, with advantage, on a wide variety of prosthesis devices, particularly spinal prostheses. Some of these prostheses, systems, and methods are discussed in the following applications entitled: “Facet Arthroplasty Devices And Methods”, by Mark A. Reiley, Ser. No. 09/693,272, filed Oct. 20, 2000, now U.S. Pat. No. 6,610,091, issued Aug. 26, 2003; “Prostheses, Tools And Methods For Replacement Of Natural Facet Joints With Artificial Facet Joint”, by Lawrence Jones et al., Ser. No. 10/438,295, filed May 14, 2003; “Prostheses, Tools And Methods for Replacement Of Natural Facet Joints With Artificial Facet Joint”, by Lawrence Jones et al., Ser. No. 10/438,294, filed May 14, 2003; “Prostheses, Tools And Methods For Replacement Of Natural Facet Joints With Artificial Facet Joint”, by Lawrence Jones et al., Ser. No. 10/615,417, filed Jul. 8, 2003; “Prosthesis For the Replacement of a Posterior Element of a Vertebrae”, by T. Wade Fallin et al., U.S. Pat. No. 6,419,703; “Multiple Facet Joint Replacement”, by E. Marlowe Goble et al., U.S. Pat. No. 6,565,605; “Facet Joint Replacement”; by E. Marlowe Goble et al., U.S. Pat. No. 6,579,319; “Method and Apparatus for Spine Joint Replacement”; by E. Marlowe Goble et al., Ser. No. 10/090,293, filed Mar. 4, 2002; and “Polyaxial Adjustment Of Facet Joint Prostheses, by “Mark A. Reiley et al., Ser. No. 10/737,705, filed Dec. 15, 2003, all of which are hereby incorporated by reference for all purposes.
Alternative embodiments of the vertebral prosthesis portion 500 may have one blade, three blades, or more blades. Alternative embodiments can also employ a different amount of spacing other than 180 degrees between multiple blades for embodiments with multiple blades, and the spacing can be the same or different between the multiple blades. While the embodiment illustrated in
The vertebral prosthesis portion 600 has a distal end 601 and a proximal end 602. The proximal end 602 is configured to accept tooling and instruments to secure the vertebral prosthesis portion 600 into the vertebra and/or to provide an attachment point to another vertebral prosthesis component. A distal portion of a fixation element has a paddle 604 configured to act as an anti-rotation element to prevent the rotation of the vertebral prosthesis portion 600 once implanted into a vertebra. Alternative embodiments of the vertebral prosthesis portion 600 can have multiple paddles. Although the illustrated paddle 604 has a rounded profile, alternative embodiments may have different profiles including, for example, one or more corners. Although the illustrated paddle 604 is flat, alternative embodiments can have nonflat contours, with one or more concave and/or convex features.
The vertebral prosthesis portion 700 also illustrates an embodiment of a modular prosthesis fastener concept. For example, in some embodiments, the shaft 735 is detachably fastened to the attachment point 740. The shaft 735 has a length “1” between the attachment point 740 and the proximate end of the paddle 704. The shaft 735 is detachably coupled to the attachment point 740 to allow for shafts 735 of different lengths to be used with different configurations of the vertebral prosthesis portion 700 thereby providing a modular vertebral prosthesis. As such, in use, the shaft 735 may be detached from the attachment point 740 and replaced with a shaft 735 having a different length “1” as needed until the proper alignment of the vertebral prosthesis is achieved. Modular components can be attached to the prosthesis using one or more attachments methods well known in the art, including threaded screws, morse tapers, adhesives or set screws.
While the modular concept has been described with regard to the vertebral prosthesis 700, it is to be appreciated that other embodiments of the vertebral prosthesis portions described herein may have a portion or portions that are detachably coupled in furtherance of the modular vertebral prosthesis concept. For an alternative example, the shaft 735 may be of fixed length and permanently attached to the attachment point 740 while the detachable attachment point is positioned between the shaft 735 and the paddle 704 thereby allowing paddles 704 of different lengths to be used. In yet another alternative, both the shaft and the paddle may have detachable attachment points thereby allowing various shaft lengths and configurations and paddle lengths and configurations to be used in furtherance of the modular vertebral prosthesis concepts described herein. It is to be appreciated that the detachable attachment point may be positioned between any portion or portions of the embodiments of the vertebral prosthesis portions described herein and elsewhere in this patent application.
In an alternate embodiment, one or more sections of the vertebral prosthesis may be made of a deformable or shape-memory material (such as Nitinol or similar materials), which permits the physician to make adjustments to the prosthesis geometry to “form-fit” the implant to the patient's specific anatomy. In the case of Nitinol, the material can be heated or cooled away from the body temperature (depending upon the type of material and it's martensitic/austenitic properties), be deformed to a desired shaped, and then held in the deformed position and allowed to return to the body temperature, thereby “hardening” into the desired shape or form. Such an embodiment would facilitate a reduction in the number of sections or “modules” required for a modular prosthesis, as each module could assume a variety of desired positions.
While the angle of the illustrated bend 710 is acute, other embodiments of the vertebral prosthesis portion 700 can have bend 710 having a right angle or an obtuse angle. Alternative embodiments of the vertebral prosthesis portion 700 may include two, three, or more bends 710. In the illustrated embodiment, the paddle 704 has a flat surface 720 and a proximal end having a transition portion 730. The flat surface 720 is illustrated in the same plane in which the fixation element has the bend 710. In other embodiments, the paddle 704 has a flat surface 720 in another plane, and/or a nonflat contour, with one or more concave and/or convex features or have paddle shapes similar to the distal portions illustrated in
Embodiments of the vertebral prosthesis portion 800 may have paddle 804 embodiments similar to the paddle embodiments shown and described with regard to vertebral prosthesis portion 700 (see e.g.,
In addition to having paddle surfaces 820 of varying shape than earlier described paddle embodiments, embodiments of the paddle 804 also include compound or more than one anti-rotation elements. As discussed above, the paddle surfaces generally provide an anti-rotation or rotation-resistant component to the vertebral prosthesis. Additionally, embodiments of paddle 804 include other anti-rotational elements such as the enlarged distal tip 812 having grooves 815 and projections 819. The enlarged distal tip 812 may have one or more grooves 815 positioned distally from the paddle 804. In some embodiments, the grooves occur in the same plane as the plane of the paddle 804. In other embodiments, grooves can occur in multiple planes and/or planes that are different from the plane of the paddle 804. Similarly, the distal tip may have projections 819 in the same or different plane with the faces of paddle 804. While the illustrated projections 819 appear identical in shape and size and are arranged parallel to the axis of the proximal shaft 860, it is to be appreciated that the projections 819 may have different configurations. The projections 819 may not all be the same size or have the same overall shape, have an asymmetrical orientation relative to the paddle 804 or be positioned in a non-parallel arrangement with regard to the axis of the proximal shaft 860.
One notable difference between the prosthesis portions 900, 990 and the prosthesis portion 600 is the addition of the proximal anti-rotation sections 920, 922. The proximal anti-rotation sections 920, 922 include a shank having a diameter less than the shank 915 and a plurality (two in the illustrated embodiments) of ridges that act as proximal anti-rotation elements. Vertebral prosthesis portion 900 has a proximal anti-rotation portion 920 and ridges 925 having an overall height h1. Vertebral prosthesis portion 990 has a proximal anti-rotation portion 922 and ridges 927 having an overall height h2 These embodiments advantageously provide reduced shank sizes thereby allowing for increased cement mantle (if cement is desired), while still providing a mechanical “interlock” with the surrounding tissue that resists prosthesis rotation (In various embodiments, the ridges can desirably engage surrounding cortical bone at the pedicle entry point, which is often stronger than the cancellous bone contained within the vertebral body, although the ridges' engagement with either or both types of bone will serve to resist rotation to varying degrees). In a specific embodiment of the prosthesis portion 900 the height h1 is 8.25 mm and the proximal anti-rotation section diameter is 6.5 mm but still maintains a moment of inertia (Iy) equal to that of a 7 mm rod. In a specific embodiment if the prosthesis portion 990, the overall ridge height h2 is 8.75 mm and the proximal anti-rotation section diameter is 6.0 mm but the embodiment still maintains a moment of inertia (Iy) equal to that of a 7 mm rod.
It is to be appreciated that the vertebral prosthesis portions 900 and 990 may differ from the illustrated embodiments. For example, there may be one or more ridges present in the proximal anti-rotation sections (as opposed to the pair of ridges disclosed above). The additional ridges need not have uniform cross sections or be uniformly spaced about the perimeter of the proximal anti-rotation section. The paddle face 960 may have a different face such as convex, concave or other compound shape or combinations thereof.
Vertebral prosthesis portion 1150 illustrates and alternative embodiment of the helical ridge anti-rotation element (
In an alternative embodiment to the single ridge anti-rotation element (
It is to be appreciated that each of the longitudinal grooves or depressions 1350 has a longitudinally varying profile, narrowing as the groove extends proximally. In alternative embodiments, the longitudinally varying profile can widen or remain constant as the longitudinal depression or groove extends proximally (if desired, they can change in depth as they narrow in width). Although in the illustrated embodiment, all of the longitudinal depressions or grooves 1350 are identical, in other embodiments, the multiple longitudinal depressions can differ, for example by having different profiles, lengths, starting and/or ending points, etc. Alternative embodiments can have one longitudinal depression, two longitudinal depressions, three longitudinal depressions, five longitudinal depressions, or more longitudinal depressions. Alternative embodiments can also employ a different amount of spacing other than 90 degrees between multiple longitudinal depressions for embodiments with multiple longitudinal depressions, and the spacing can be the same or different between the longitudinal depressions.
The proximal grooved section 1330 has fewer grooves 1335 than previously described proximal grooved sections (e.g.
The distal shaft 1417 includes a plurality of longitudinal depressions 1423 extending from the distal end 1404 to a point beyond the tapered section 1430. The proximal end of the longitudinal depressions 1423 has a bulbed section 1460. The distal shaft 1417 also includes a reduced diameter section 1440. The reduced diameter section 1440, longitudinal grooves 1423 and bulbed section 1460 may be used to increase the surface area of the vertebral prosthesis portion 1440 that is, when implanted, within a vertebra of the spine. The increased surface area allows for more area to support the cement mantle for applications using cement or, bony ingrowth for applications using bone ingrowth. It is to be appreciated that the longitudinal grooves 1423 may also be varied as described elsewhere with regard to other grooves and, for example, as described with regard to
It is to be appreciated that each of the longitudinal depressions 1423 has a longitudinally varying profile, narrowing as the longitudinal depression extends proximally. In alternative embodiments, the longitudinally varying profile can widen or remain constant as the longitudinal depression extends proximally. Although in the illustrated embodiment all of the longitudinal depressions are identical, in other embodiments, the multiple longitudinal depressions can differ, for example by having different profiles, lengths, starting and/or ending points, etc. Alternative embodiments can have one longitudinal depression, two longitudinal depressions, four longitudinal depressions, five longitudinal depressions, or more longitudinal depressions.
In the illustrated embodiment, the grooves 1530, 1545 and 1560 are of similar size, shape and orientation. The grooves have a rounded cross section profile best seen in
In the illustrated embodiments, the distal portion of the vertebral prosthesis fixation element 1600 has four separable members 1625 separated by the longitudinal hole 1626. The longitudinal hole 1626 permits a filling member 1628 to be inserted from the proximal end of the vertebral prosthesis fixation element 1600, causing the separable members 1625 to spread apart into the deployed configuration (i.e., vertebral prosthesis fixation element 1610) with deployed spacing 1640 separating adjacent separable members 1625. The exterior surface of each separable member 1625 has a plurality of continuous ridges 1635. Continuous ridges are single ridges that extend along the surface of a separable member from one spacing 1640 to the next adjacent spacing 1640. It is to be appreciated that the ridges may be segmented ridges meaning more than one ridge between adjacent spacings 1640. The ridges 1635 in the illustrated embodiment are all continuous and the ridges 1635 on each separable member 1625 are similarly oriented relative to the separable members. It is to be appreciated that other ridge configurations are possible, such as for example, combinations of continuous and segmented ridges on a single separable member, as well as different ridge orientations on the same separable member or different ridge orientations on different separable members. In addition, alternative embodiments can have more or fewer ridges than the illustrated embodiment, or be at least partly smooth.
Additionally, other embodiments of the vertebral prosthesis fixation element 1600 can have two, three, five, or more separable members 1625. The filling member can be a smooth peg as shown, or alternatively a bar, a wire, or any other shape that, upon insertion into the longitudinal hole 1626, causes the separable members 1625 to move from a stowed configuration 1605 to a deployed configuration 1610.
In one embodiment, a vertebral prosthesis fixation element 1600 is used to secure a vertebral prosthesis implanted between two vertebrae to provide restoration of movement between the vertebrae. Features of the vertebral prosthesis fixation element 1600, such as the shape, size and orientation of the ridges 1635, advantageously secure the implanted vertebral prosthesis while providing anti-rotation capability for the torques generated within the implanted prosthesis and applied to the vertebral prosthesis fixation element 1600. In another embodiment, a vertebral prosthesis fixation element 1600 is used to secure at least a portion of a vertebral prosthesis connecting two adjoining vertebrae to restore movement between the adjoining vertebrae. In this embodiment, when the separable members are in a deployed configuration, at least a portion of the ridges on at least one separable member engages the surrounding vertebrae and counteracts the forces generated by relative motion between the adjoined vertebrae, and/or the forces generated between the vertebral prosthesis and the vertebrae attached to the vertebral prosthesis.
For purposes of illustration and explanation of the anti-rotation and/or anti-pullout advantages of embodiments of the present invention, vertebral prosthesis portions have been illustrated and described in axial shaft configurations (e.g.,
While preferred embodiments of the invention have been illustrated and described, it will be appreciated that various changes can be made therein without departing from the spirit and scope of the invention.
Claims
1. A system for vertebral implantation, comprising:
- a first vertebral prosthesis comprising a first fixation element adapted to be inserted into a first hole formed in a vertebra, the first fixation element having a first longitudinal axis;
- a second vertebral prosthesis comprising a second fixation element adapted to be inserted into a second hole formed in the vertebra, the second fixation element having a second longitudinal axis; and
- a cross-bar connecting the first vertebral prosthesis and the second vertebral prosthesis;
- wherein the first vertebral prosthesis comprises an anti-rotational element extending along the first fixation element of the first vertebral prosthesis, wherein the anti-rotational element is configured to resist a rotational force that would cause rotation of the first fixation element in the first hole of the vertebra.
2. The system of claim 1, wherein the first fixation element comprises a tapered section.
3. The system of claim 1, wherein the anti-rotational element comprises a longitudinal depression.
4. The system of claim 3, wherein the longitudinal depression is helical.
5. The system of claim 1, wherein the first vertebral prosthesis further comprises a bearing surface.
6. The system of claim 1, wherein the first vertebral prosthesis comprises a socket element for attachment to a vertebral prosthesis.
7. The system of claim 1, wherein the cross-bar is inserted into openings in the first vertebral prosthesis and the second vertebral prosthesis.
8. A system for vertebral implantation, comprising:
- a first vertebral prosthesis comprising a first proximal shaft having a longitudinal axis and a first distal shaft having a longitudinal axis that differs from the longitudinal axis of the proximal shaft, wherein the first distal shaft is configured to be inserted into a first hole formed in a vertebra;
- a second vertebral prosthesis comprising a second proximal shaft and a second distal shaft, wherein the second distal shaft is configured to be inserted into a second hole formed in the vertebra; and
- a cross-bar connecting the first vertebral prosthesis and the second vertebral prosthesis;
- wherein the first vertebral prosthesis comprises one or more anti-rotational elements extending along the first distal shaft of the first vertebral prosthesis, wherein the one or more anti-rotational elements are configured to resist a rotational force that would cause rotation of the first distal shaft in the first hole of the vertebra.
9. The system of claim 8, wherein the first distal shaft of the first vertebral prosthesis is tapered.
10. The system of claim 8, wherein the anti-rotational elements comprise longitudinal depressions.
11. The system of claim 10, wherein the longitudinal depressions are helical.
12. The system of claim 8, wherein the first proximal shaft has a different diameter from the first distal shaft of the first vertebral prosthesis.
13. The system of claim 8, wherein the first proximal shaft transitions into the first distal shaft via a bend.
14. The system of claim 8, wherein the proximal shaft includes a socket element.
15. A system for vertebral implantation, comprising:
- a first vertebral prosthesis comprising a first proximal shaft having a longitudinal axis and a first distal shaft having a longitudinal axis that differs from the longitudinal axis of the proximal shaft, wherein the first proximal shaft transitions into the first distal shaft via a bend;
- a second vertebral prosthesis comprising a second proximal shaft and a second distal shaft, wherein the second proximal shaft transitions into the second distal shaft via a bend; and
- a cross-bar connecting the first vertebral prosthesis and the second vertebral prosthesis;
- wherein the first vertebral prosthesis comprises one or more anti-rotational elements extending along a length of the first vertebral prosthesis.
16. The system of claim 15, wherein the anti-rotational elements comprises depressions.
17. The system of claim 15, wherein the first proximal shaft has a different diameter from the first distal shaft.
18. The system of claim 15, wherein the first distal shaft is tapered and configured to fit into a first hole of a first vertebra.
19. The system of claim 15, wherein the first proximal shaft comprises a socket element.
20. The system of claim 15, wherein the first proximal shaft comprises a bearing surface for slidably engaging a corresponding bearing surface of another prosthesis.
Type: Application
Filed: Mar 29, 2012
Publication Date: Nov 15, 2012
Inventors: Leonard J. Tokish, JR. (Issaquah, WA), Mark T. Charbonneau (Bellevue, WA), Mark A. Reiley (Piedmont, CA), Robert M. Scribner (Niwot, CO)
Application Number: 13/434,064
International Classification: A61B 17/70 (20060101);