Spinal device locking mechanism

FIELD OF THE INVENTION

0001The present invention relates generally to spinal systems, and more particularly, to a spinal or other orthopedic device with a screw locking mechanism that prevents screws from pulling out of the device.

BACKGROUND

0002The treatment of injuries to the spine has advanced significantly, including treatment for many forms of spinal injuries and deformities that can occur due to disease, congenital effects, the effects of tumors, and, of course, fractures and dislocations attributable to physical trauma. For many years, the use of plates secured to the spine by screws has been helpful in the stabilization and fixation of the spine. Such plate and screw systems have not been limited to treating spinal injuries, but have also been used in the treatment of other bone injuries.

0003An important recognized requirement for a plating system is that the screws used to connect the plate or other device to the vertebrae or other bone mass must not loosen or back out from the plate over time.

0004US-A-6 139 550 and US-B1-6 540 785 disclose plating systems build according to the preambles of claims 1 and 15 of the present patent.

0005What is needed is a locking mechanism that is simple to fabricate, does not have a threaded surface and can be used with many different materials.

SUMMARY

0006The present invention provides a new and improved locking mechanism and spinal orthopedic device. In one embodiment, an improved spinal orthopedic device includes a key and a plate. The key includes a cover, a post and a heel, the post having a first end connected to the cover and a second end connected to the heel. The plate includes a heel receiving hole and a mechanical construct for engaging with an attachment mechanism, such as a bone screw hole for engaging with a bone screw. The key and plate are configured so that the heel is insertable through the heel receiving hole and is rotatable when inserted in the heel receiving hole. In addition, the cover is shaped so that when rotated, the cover overlaps at least a portion of the mechanical construct to thereby prevent disengagement of the attachment mechanism.

0007In another embodiment, an improved spinal device includes a plate including a heel receiving hole and a plurality of screw holes for engaging with a plurality of screws, and a locking mechanism connected to the plate. The plurality of screw holes are configured so that the plurality of screws may be inserted there through and may be further connected to a vertebrae of the spine, thereby securing the plate to the vertebrae. The locking mechanism includes a key having a cover connected to a post, further connected to a heel. The heel is shaped so that it is insertable through the heel receiving hole in one configuration, is rotatable when inserted, and is secured to the plate after being rotated. The cover is configurable so that when the heel is secured to the plate, the cover engages, at least in part, with the plurality of screws when the plate is secured to the vertebrae via the plurality of screws.

0008In another embodiment, an improved intervertebral joint prosthesis includes a ball component for engagement with a first vertebra, a trough component for engagement with a second vertebra, and first and second locking mechanisms. The ball component includes a generally convex surface, and a first flange plate at one end of said ball component for engaging the first vertebra. The first flange plate includes a first locking mechanism opening for engaging with the first locking mechanism and a first bone attachment opening for engaging with a first bone attachment mechanism. The trough component includes a generally concave surface, and a second flange plate at one end of said trough component for engaging the second vertebra. The second flange plate includes a second locking mechanism opening for engaging with the second locking mechanism and a second bone attachment opening for engaging with a second bone attachment mechanism. Each of the first and second locking mechanisms includes a cover connected to post further connected to a heel. The heel is configured so as to be insertable into and through the corresponding heel plate opening. The post being is configured so as to be rotatable within the heel plate opening after the heel is inserted there through. The cover is configured to secure an engaged bone attachment mechanism when the post is rotated within the heel plate.

0009Many objects and benefits of the invention will become apparent upon consideration of the following written description of the invention, together with the accompanying Figures.

BRIEF DESCRIPTION OF THE DRAWINGS

0010Figs. 1a-1c are front and cross-sectional views of an anterior cervical plate system implementing features according to one embodiment of the present invention.

0011Figs. 2a-2d are perspective and cross-sectional views of an intervertebral joint prosthesis implementing features according to another embodiment of the present invention.

0012Figs 3a-3c are side, bottom, and cross-sectional views-of the key portion of the screw locking mechanism according to one embodiment of the present invention.

0013Fig. 4 is a top perspective view of the plate portion of the screw locking mechanism according to one embodiment of the present invention.

0014Fig. 5 is a side cross-sectional view of the plate shown in Fig. 4.

0015Fig. 6 is a top perspective view of the plate shown in Fig. 4 with the key shown in Fig. 1 engaged.

0016Fig. 7 is a cross-sectional view of the plate with engaged key as shown in Fig. 6.

0017Fig. 8 is a side elevational view of the key portion of the screw locking mechanism according to another embodiment of the present invention.

0018Fig. 9 is a bottom perspective view of the key shown in Fig. 8.

DETAILED DESCRIPTION

0019For 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.

0020Referring to Figs. 1a, 1b, and 1c, an anterior cervical plate system 10 is an example of an orthopedic implant that can benefit from different embodiments of the present invention. In accordance with the present example, the plating system 10 includes an elongated plate 11 and one or more bone attachment mechanisms 12, such as bone screws, attached to adjacent vertebrae V1, V2. Other bone attachment mechanisms include bolts, staples, and protrusions that can help to secure the plate in a desired position, and are hereinafter generically referred to as bone screws. The bone screws 12 are held or retained to the plate 11 by way of one or more locking mechanisms 13, discussed in greater detail below. The elongated plate 11 is provided with a plurality of openings or holes 14 in a variety of arrangements. Further, the plate 11 includes recesses 15 between two or more of the holes 14.

0021The plate 11 and/or locking mechanisms 13 can be constructed of many different materials, including metal materials such as titanium or radiolucent material, such as a polymer based resin. An example of a plate 11 constructed substantially from a polyether ether ketone (PEEK) high temperature thermoplastic is discussed in greater detail in U.S. A-2004/0215195.

0022The plate 11 can further include one or more bone growth or fusion-promoting elements, such as bone, bone morphogenetic protein (BMP), demineralized bone matrix (DBM), LIM mineralization proteins (LMP), osteogenic pastes, and so forth. It is understood that such fusion-promoting elements are well known by those of ordinary skill in the art.

0023Referring to Figs. 2a-2d, an intervertebral joint prosthesis system 20 is another example of an orthopedic implant that can benefit from different embodiments of the present invention. In accordance with the present example, the prosthesis 20 includes a ball component 22 and a trough component 24 that are inter-engageable to form the prosthesis. In an intervertebral disc space D between two adjacent vertebrae V1, V2, ball component 22 is fixed to one of the adjacent vertebrae (e.g. vertebra V1), and trough component 24 is fixed to the other adjacent vertebra (e.g. vertebra V2) so that the components are inter-engaged within at least a portion of intervertebral space D.

0024Ball component 22 includes a generally convex surface 25. In a particular embodiment, generally convex surface 25 is substantially hemispherical in shape. A flange plate 26 is provided at one end of the ball component 22 for attaching the ball component to a vertebra, and is preferably formed to have a low profile. Trough component 24 includes a generally concave surface 27. A flange plate 28 is provided at one end of the trough component 24 for attaching the trough component to a vertebra, and is preferably formed to have a low profile. The ball and trough components 22, 24 are discussed in greater detail in U.S. Patent No. 6,540,785.

0025In a particular embodiment, flange plates 26 and/or 28 include one or more bone screw apertures 29, and in a specific embodiment, two bone screw apertures are provided in a symmetric relationship through each flange plate. In that specific embodiment, one or more bone screws 12 are threaded into the vertebra through the apertures 29 to fix the components 22, 24 to the vertebra. After the components 22, 24 are attached to the vertebrae using bone screw(s) 12, a locking mechanism 13 is used to secure the screws 12 in place. The locking mechanism 13 includes a locking key 30, both of which are discussed in greater detail, below.

0026The components 22, 24 and/or locking mechanisms 13 can be constructed of many different materials, including metal materials such as titanium or radiolucent material as discussed above with respect to Figs. 1a-1c. Also, the components 22, 24 can further include one or more bone growth or fusion-promoting elements, such as bone, BMP, DBM, LMP, osteogenic pastes, and so forth.

0027Referring to Figs. 3a-3c, in one embodiment, the locking mechanism(s) 13 used in the systems 10, 20 discussed above include a locking key 30. In accordance with the present embodiment, the key 30 includes a cover 31, a post 32 and a heal 33. The cover 31 has a top surface 34, a bottom surface 35 and a shoulder 36. The post 32 includes a first end 37, that is secured to the bottom surface 33 of the cover 31, and a second end 38. The heel 33 has a top surface 39, that is secured to the second end 38 of the post 32, and a bottom surface 40. The key 30 can be made from a combination of materials. For example, the heel 33 or the cover 31 may be made of a more deformable material or design, while the post 32 is made of a more rigid material.

0028Referring to Figs. 4-7, a plate 50 is representative of the plate 11 of Figs. 1a-1c or the flange plates 26 and/or 28 of Figs. 2a-2d. The plate 50 is designed to receive the heel 33 and post 32 of the key 30, includes one or more screw receiving holes 29, that each permit a screw, such as a spine or other bone screw, to pass through from the top side 53 through the bottom side 54. As shown in Fig. 7, when the key 30 is inserted in the plate 50, as is described below, the bottom surface 35 of the cover 31 covers a portion of the screw receiving holes 29 and engage the heads of screws inserted in the screw receiving holes 29 to prevent the screws from backing out of the plate 50.

0029The plate 50 also includes a heel receiving hole 55 that is shaped to permit the heel 33 of the key 30 to pass through such that the top surface 39 of the heel 33 extends beyond at least a portion of the bottom side 54 of the plate 50 adjacent to the heel receiving hole 55. A portion of the plate 50 surrounding the heel receiving hole 55 may be of a more deformable material than the remaining portions of the plate. The post 32 and heel receiving hole 55 are each shaped such that when the key 30 is fully inserted in the plate 50 and rotated, the post 32 is permitted to rotate within the heel receiving hole 55.

0030The heel 33 and heel receiving hole 55 are designed to permit the heel 33 to pass through the heel receiving hole 55, but once the key 30 is rotated, if one attempts to remove the key 30 from the plate 50, the top surface 39 of the heel 33 will engage the bottom side 54 of the plate 50 and prevent the key 30 from pulling out of the plate 50. It is appreciated that in order to provide for this relationship between the heel 33 and the heel receiving hole 55, the heel 33 must have a non-circular shape and at least a portion of the heel 33 must extend out from the diameter of the second end 38 of the post 32.

0031The bottom side 54 of the plate 50 is constructed with a lodgment 56 that is designed to receive and secure the heal 33, and thus the key 30, relative to the plate 50. In one embodiment, as shown in Figs. 2c, 3a, and 5a, the lodgment includes a corresponding bump and groove in the heal 33 and plate 50. The lodgment 56 engages when the key 30 is rotated within the heel receiving hole 55.

0032While the post 32 and the heel receiving hole 55 may be designed to allow the post 32 to rotate 360 degrees within the heel receiving hole 55, absent any other restriction created by the lodgment 56, they may also be designed such that the post 32 is only permitted to rotate sufficiently to enable the heal 33 top surface 39 to contact the plate 50 bottom side 54 when the key 30 is attempted to be removed from the plate 50. Additionally, in the present embodiment, the key 30 is only permitted to rotate relative to the plate 50 enough to secure the heel 33 with the lodgment 56.

0033It is understood that the lodgment need not be placed on the bottom side 54 of the plate 50, but could also be formed in the wall of the heel receiving hole 55 with the post 32 having a counterpart surface that can be secured in the lodgment. In other embodiments, the lodgment can be a wedge, a lip, or some other protrusion to help prevent the key 30 from rotating in the heel receiving hole 55. Further, the lodgment could be formed in the top side 53 of the plate 50 with the bottom surface 35 of the cover 31 having a counterpart surface to secure in the lodgment. In still other embodiments, the lodgment may be a roughened surface 40 of the heel 33 that engages with the corresponding vertebral body V1 or V2 (Figs. 1a, 2a, and 3a).

0034In order to rotate the key 30 inside the heel receiving hole 55, the cover 31 of the present embodiment is configured to allow for easy rotation. For example, in Figs. 8-9, a modification to the cover 31 is shown with two tool receiving holes 60 and 61 included in the top surface 34. These tool receiving holes 60 and 61 enable a tool to be inserted in the tool receiving holes 60 and 61 to assist with the rotation of the key 30. Similarly, the top surface 34 of the cover 31 could include a channel for receiving the end of a standard flat head screw driver to assist with the rotation of the key 30. Further, the cover 31 itself could be shaped in such a manner that a device could be placed around its circumference, such as a socket wrench, to assist with the rotation of the key 30. It should be appreciated that a number configurations of depressions in or structures affixed to the cover 31, or the shape of the cover 31 itself could be designed to cooperate with a tool, or to be more easily grasped by a hand, that would assist with the rotation of the key 30 to make it easier to rotate relative to the plate 50.

0035It is understood that while the cover 31 could at all times cover a portion of the screw receiving holes 29 when the key 30 is inserted in the heel receiving hole 55, it is only necessary for proper operation of the present invention that the cover 31 be positioned relative to the heel 33 such that when the heel 33 is secured in the lodgment 56, the cover 31 covers all or a portion of the heads of screws secured in the screw receiving holes 29, thus preventing them from backing out of the plate 50.

0036Additionally, it is understood that when the key 30 is secured relative to the plate 50, the bottom surface 35 of the cover 31 can smoothly engage the top side 53 of the plate 50, such that a smooth transition exists moving from the top side 53 of the plate 50 over the shoulder 35 to the top surface 34 of the cover.

0037The screw locking mechanism of the present invention includes many benefits. For example, the key and plate design does not require the use of a threaded surface. Further, the plate only requires a simple heel receiving hole with a non-complex lodgment. Finally, because of the use of deformation and lodgment, the screw locking mechanism of the current invention can be designed in an material that permits sufficient deformation to secure the key relative to the plate.

0038Although only a few exemplary embodiments of this invention 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 invention. Also, features illustrated and discussed above with respect to some embodiments can be combined with features illustrated and discussed above with respect to other embodiments. Accordingly, all such modifications are intended to be included within the scope of the invention as defined in the claims.