1. Field of the Invention
The present invention relates generally relates to a bone fixation systems. In particular, the present invention relates to a plate for a spinal fixation system for attaching various objects, such as prostheses or implants to bones, including for anchoring spinal instrumentations to vertebrae of the human rachis and may be used in conjunction with a drilling and aiming guide.
2. Description of the Related Art
U.S. Pat. No. 5,366,455 issued to Dove et al. on Nov. 22, 1994, U.S. Pat. No. 5,672,175 issued to Martin on Sep. 30, 1997, U.S. Pat. No. 5,733,284 issued to Martin on Mar. 31, 1998 and U.S. Pat. No. 5,437,672 issued to Alleyne on Aug. 1, 1995 disclose devices for anchoring various supports, e.g. spinal orthoses, to the rachis, these devices being adapted to obviously extend outwardly of I the spinous process or canal and thus of the spinal cord.
U.S. Pat. No. 5,800,433 issued to Benzel et al. on Sep. 1, 1998 and U.S. Pat. No. 5,954,722 issued to Bono on Sep. 21, 1999 teach anchoring systems having screws which are angled such as to converge towards each other.
U.S. Pat. No. 5,904,683 issued to Pohndorf et al., on May 18, 1999 and U.S. Pat. No. 5,980,523 issued to Jackson on Nov. 9, 1999 disclose anterior cervical vertebrae stabilizing devices held in place by various types of screws.
To try prevnting the screws from loosening, various systems have been used, such as directing the screws along different orientations (e.g. diverging or converging); providing a locking mechanism on the screw (e.g. counter-nut); modifying the screw's thread (height and depth); engaging each screw to two tissues having different densities; etc.
A vertebra disc may be subject to degeneration caused by trauma, disease, and/or aging. The degenerated vertebrae disk may have to be partially or fully removed from a spinal column. Partial or full removal of a vertebrae disk may destabilize the spinal column and may alter the natural separation between adjacent vertebrae. Individual nervew eminate at the brain and pass down the nmerve sheath located poseterior to the spine. These individual nervew eventually pass through thte intervertebral space to various body member, i.e., hands, feet, etc. Maintaining a natural separation between vertebrae is essential in order to prevent pressure from being applied to nerves that pass between the adjacent vertebrae. Excessive pressure applied to the nerves may cause pain and/or nerve damage. During a spinal fixation procedure, a spinal implant may be inserted in order to restore space created by the removal or partial collapse of a vertebral disk. A spinal implant may maintain the height of the spine, restore stability to the spine, and prevent nerve damage. Bone growth may fuse the implant to adjacent vertebrae thereby facilitating long term pain relief.
A spinal implant may be inserted during a spinal fixation procedure using an anterior, lateral, or posterior spinal approach. In some situations especially in the anterior cervical approach may result in less difficult surgery resulting in less muscle damage, less tissue damage, and/or less bone removal than other approaches.
A discectomy is a neurosurgical procedure to remove, or partially remove, a defective and/or damaged vertebrae disk. A discectomy creates a disk space so that a spinal implant may be inserted into the disk space created between one or more pair of vertebrae.
One or more spinal plates may be coupled to vertebrae after insertion of one or more spinal implants. A spinal plate may help stabilize the vertebrae and inhibit back out of the spinal implant from between the adjacent vertebrae. The spinal plate may share the compressive load applied to one or more spinal implants inserted between the vertebrae. Fasteners, e.g., bone screws may be used to couple the spinal plate to the vertebrae itself Spinal plates may be used to stabilize sections of cervical spine and/or sections of lumbar spine.
The current art for fastening plates to spinal vertebrae has at least one major problem: loosening of the fasteners. Loosening of the fasteners that may lead to compression and/or perforation of adjacent tissue. This loosening may be caused by resultant biomechanical forces, micro motions of the plate system and fasteners, or the poor quality of osteoporotic bone. The inability for a bone screw to properly purchase into the osteoporotic bone is a major problem for older patients, leading to loosening of the spinal plates and increasing the possibility of having the older patient undergo a second operation to reposition or otherwise retighten the spinal plates.
Therefore what is needed is a spinal plate that is securely affixed to the bone regardless of the quality of the bone, prevents the back out of the fasteners and/or the loss of purchase of a fastener due to the poor quality of the bone itself.
A spinal plate system that allows for increased spinal stability is provided. In an embodiment, a spinal plate system is provided that includes first and second slidable plates coupled together. Each of the first and second slidable plates includes first and second fasteners that are obliquely oriented relative to the corresponding slidable plate. The first and second fasteners are fixed to each other at their distal ends thereby forming a triangular frame consisting of the corresponding slidable plate and the first and second fasteners. In addition, a fastener guide is provided that facilitates the accurate placement of the first and second fasteners for each of the first and second slidable plates.
Aspects of the present invention are pointed out with particularity in the appended claims. The present invention is illustrated by way of example in the following drawings in which like references indicate similar elements. The following drawings disclose various embodiments of the present invention for purposes of illustration only and are not intended to limit the scope of the invention. For purposes of clarity, not every component may be labeled in every figure. In the figures:
The following detailed description sets forth numerous specific details to provide a thorough understanding of the invention. However, those skilled in the art will appreciate that the invention may be practiced without these specific details. In other instances, well-known methods, procedures, components, protocols, processes, and circuits have not been describe in detail so as not to obscure the invention.
A spinal plate system that may be used to stabilize a portion of a spinal column and a method of use are described in more detail below. The spinal plate system includes first and second plates that are slidably coupled to one another and allow for motion of each of the plates relative to the other. Each of the first and second plates is secured to the bone by an obliquely oriented post and screw system wherein the post and screw are oriented so as to converge to one another. The post includes an oblique threaded hole that receives the distal portion of the screw. In this manner, the post and screw interlock with one another such that the plate, the screw and the post form a structurally stable triangular frame. This triangular frame is inherently structurally stable and strong and therefore does not rely on the bone quality for its inherent stability or strength. Advantageously, this triangular frame structure prevents screw loosening and back out, increases the pullout strength of the plate, allows for removal of the plate due to the threaded connections, and shortens patient immobilization since the strength of fixation is now independent of bone quality.
In other cases however (posterior approach), the screws are longer and are generally directed on each side of the spinous canal in order to obviously prevent damage to the spinal cord.
Therefore, the present anchoring system S (for each of
The second screw 20 has a threaded stem of which at least a distal section is smaller the first screw 10 as the second screw 20 is adapted to extend through the opening 12 of the first screw 10 such as to threadably engage the same. Indeed the male threads of the second screw 20 are designed female threads of the opening 12 of the first screw 10 thereby securing together the distal ends of the two screws 10 and 20. With these distal ends so engaged and with the screws 10 and 20 extending in a convergent attitude, there is resistance, where the two screws 10 and 20 are engaged together, to the forces which tend to cause the screws to gradually loosen, whereby it is impossible for the screws 10 and 209 to loosen (unless the vertebra V itself is destructed where it is engaged by the screws 10 and 20, or unless one of the screws 10 and 20 breaks).
In fact, the first screw 10 acts as a nut for the second screw 20, and this within the vertebra V itself in
The first screw 10 is preferably provided at its head 14 with indicia (color, index, etc.) to indicate the position of its distal end so that the position or orientation of its threaded opening 12 can be more easily determined thereby facilitating the introduction of the second screw 20 therethrough. An aiming system maybe used as a guide during the screwing process. For instance, to ensure an accurate aiming of the two screws 10 and 20 and their relative engagement, a template may be used to guide both screws from an initial predetermined spacing, along a given plane and along predetermined angles. Alternatively, a neuro-navigation apparatus can also be used, that is a computer software capable of transposing digitized data taken from a pre-surgery medical imagery of, the stereotactic space in which the surgeon will operate.
The obliqueness of the threaded opening 12 through the first screw 10 depends on the angle, that is on the spacing on the plate P/P′ between the two screws 10 and 20 (i.e. generally the spacing between their heads 14 and 24) in a horizontal plane, as well as the directions of the screws 10 and 20 in the sagittal plane.
The two screws 10 and 20 extend in holes defined in the plate P/P′, and would normally have their heads 14 and 24 in abutment with the proximal surface of the plate P/P′ (as in
The two screws 10 and 20 and the plate P/P define a triangular frame (which is well shown in
In the case of the use of the anchoring system S to install the plate P′ onto the adjacent vertebrae VI and V2 of the cervical rachis (
In the case of the plate P of
In order to facilitate the engagement of the second screw 20 into the first screw 10, the opening 12 in the first screw 10 may instead of being threaded, have the form of a spherical socket that rotatably accommodates a ball. A hole extends, typically diametrically, through this ball and defines an interior thread, that is a female thread that can be screwably engaged by the male thread of the second screw 20. Therefore, the ball could rotate within the socket to allow for a correction in the direction of the second screw 20 relative to the first screw 10; in other words, if the second screw 20 is slightly off target in its orientation with respect to the hole defined in the ball of the first screw 10, the ball may be slightly rotated to align the longitudinal axis of its hole with the axis of the second screw 20.
It is also contemplated to provide a threadless opening in the first screw 10 instead of the threaded opening 12; in such a case, the opening would be self-tapping in that the male threads of the second screw 20 would tap a thread in the opening of the first screw 10 upon rotary engagement therein. Similarly, the above-mentioned ball could also be threadless and self-tapping. Furthermore, the first screw 10 could be replaced by a threadless pin or nail that would be translationally insertable in the bone and that would define an opening (threaded or self-tapping) at its distal end for receiving the second screw 20.
It is further contemplated to use elongated anchoring members other than the above-described and herein illustrated screws 10 and 20, as well as other means of securing the distal ends of such anchoring members together. For instance, the screws 10 and 20 could be replaced by threadless pins or nails that would be translationally inserted in the bone. In such a case, the distal end of a first one of the anchoring members could define an opening, such as an elongated slot, through which the distal end (which would, for instance, be flat) of a second one of anchoring members could be inserted. A locking mechanism between the two distal ends could take the form of a lateral pin extending from the distal end of the second anchoring member which, after having been passed beyond the elongated slot in the first anchoring member, would be rotated ¾ turn such as to extend behind the body of the first anchoring member thereby locking the distal ends together. Such a pin could be embodied in the distal end of the second anchoring member being L-shaped or T-shaped or defining a barb-shaped extension.
The common feature is two elongated members insertable in the bone and having distal ends capable of being interlocked for preventing unwanted withdrawal of any of the two elongated members from the bone.
Although the present anchoring system S has been shown herein in use to secure a plate P/P′ to one or more lumbar (
Every component of the anchoring system S is made of biocompatible material or of a material capable of being so coated.
According to another embodiment of the present invention depicted in
Plate 102 b includes a pair of holes 107 and 109 that are configured to receive a post 108 and a screw 110, respectively. In one embodiment, the hole 107 includes a key feature, such as a flat side forming a D shaped opening as depicted in
In general, the holes 103, 105 are oriented at an oblique angle and in general are converging toward one another. In particular, the holes are oriented such that the center line extending from hole 103 will intersect the center line from opening 105. Similarly, plate 102b includes holes 107 and 109 are oriented in a similar fashion such that center line extending from hole 107 will intersect with the center line from hole 109. In this way, the post 104 and screw 106 will intersect with one another as will post 108 and screw 110.
As depicted in
As discussed above, the plates 102a and 102b are able to slide relative to one another along the x-axis depicted in
In general, the sliding plates 102a-b, the posts 104 and 108, and screws 106 and 110 are constructed from 6AL4V Titanium ELI grade 5 titanium per ASTM-F-136-92. The sliding plates 102a-b may also have an curved shape conforming to the vertebrae shape both in the longitudinal axis (i.e., lordotic curvature) and the transverse axis. The curvature of the curve shape may be such that the sliding plates 102a-b are able to be securely fastened to vertebrae having both a radial curvature as well as a lordotic curvature.
As discussed above, both the holes 103 and 107 and the posts 104 and 108 include a key structure such as a flat portion forming a “D” shaped opening. This allows for a particular orientation of the post to be achieved in a consistent manner. Because it is important that the oblique opening 204 be oriented to receive the threaded portion 206 of the corresponding screw a consistent method of achieving the proper orientation is necessary. By forming the post with the appropriate key structure, the proper consistent orientation may be achieved. Any key structure may be used, and the “D” shaped hole used herein is but one example. Without limitation, any suitable key structure known in the art may be used.
The fastener guide 600 also includes first and second guide arms 612 and 614, respectively. The first and second guide arms 612 and 614 extend outward from the top surface 609 at an oblique angle, which is equal to the angle at which the post and screw are to be inserted into the bone. First and second guide arms each include a shaft 612a and 614a, respectively, that extends from the top surface 616 and 618 respectively, through the bottom surface 610. One shaft is provided with the key structure described above and in this embodiment, the attachment element 606 and the attachment opening 112 are configured and arranged such that the guide arm having the key structure will always be oriented over the opening 103 or 107 where the post will be disposed within that hole. In one embodiment, the shaft 612a and 614a will be accurate enough to allow an instrument to be inserted into the shaft and pass through the various openings in the spinal plate system described above. The instrument may be a drill, a fastener placement instrument, or a fastener tightener.
In another embodiment, the accuracy of shaft 612a and 614a is not sufficient and an additional insert is needed. In particular, guide insert 620 and 622 are used to provide the necessary increase in accuracy. Guide insert 620 is sized and dimensioned to fit securely within shaft 612 and has a shaft 620a that extends the length of the guide insert and communicates with the shaft opening 612c at the bottom surface 610. The shaft 620a is a highly accurately machined opening with high tolerances for the inner diameter. In general, shaft 620a is coaxially disposed within shaft 612a. Similarly, guide insert 622 is sized and dimensioned to fit securely within shaft 614 and has a shaft 622a that extends the length of the guide insert and communicates with the shaft opening 614c at the bottom surface 610. The shaft 622a is a highly accurately machined opening with high tolerances for the inner diameter and also includes any key structure present in the shaft 612a as discussed above. In general, shaft 622a is coaxially disposed within shaft 614a to allow an instrument to be inserted into the shaft and pass through the various openings in the spinal plate system described above. An instrument may be inserted into shaft 620a and 622a and may be a drill, a fastener placement instrument, or a fastener tightener as required. In another embodiment, the guide inserts 620 and 622 are used only for the drilling of the holes in the bone and the placement and tightening of the fasteners is performed using the shafts 612a and 614a.
It should be appreciated that other variations to and modifications of the above-described method and system for transferring and compressing medical image data may be made without departing from the inventive concepts described herein. Accordingly, the invention should not be viewed as limited except by the scope and spirit of the appended claims.
This application is a continuation-in-part of US Non-Provisional Patent application, Ser. No. 10/275,710 filed May 25, 2001, which is incorporated herein by reference, that was the US National Phase of international application PCT/CA01/00751 filed May 25, 2001 which designated the US and which claims priority to Provisional Application, Ser. No. 60/206,811 filed on May 25, 2000. and is also continuation-in-part of US Non-Provisional Patent application, Ser. No. 10/358,398, which is incorporated herein by reference, filed Feb. 5, 2003 that is a continuation in part of U.S. Ser. No. 10/296,392 filed Nov. 25, 2002 which is a National Entry of PCT/CA01/00739 filed on May 25, 2001 and claiming priority to US Provisional Applications Ser. No. 60/206,810 filed on May 25, 2000 and Ser. No. 60/264,309 filed Jan. 29. 2001
Number | Date | Country | |
---|---|---|---|
Parent | 10275710 | Nov 2002 | US |
Child | 11837937 | US | |
Parent | 10358398 | Feb 2003 | US |
Child | 10275710 | US | |
Parent | 10296392 | Sep 2003 | US |
Child | 10358398 | US |