Surgery – Instruments – Orthopedic instrumentation
Reexamination Certificate
2001-04-19
2003-01-07
Robert, Eduardo C. (Department: 3732)
Surgery
Instruments
Orthopedic instrumentation
Reexamination Certificate
active
06503250
ABSTRACT:
BACKGROUND
The present invention relates to devices for the fixation and/or support of bones. In particular, the present invention relates to a plate for the fixation and/or support of bones of the spinal column. The plate of the present invention has particular application in situations where compressional or “settling” forces, as well as torsional and flexing forces, of “fixed” vertebrae on a spinal plate cause significant stressing and potential failure of the spinal plate and/or plate components.
Vertebral fixation has become a common approach to treating spinal disorders, fractures, and for fusion of vertebrae at the time such fixation is instituted. Namely, one or more vertebrae are fixed in position relative to one or more other vertebrae above and/or below the vertebrae to be fixed. Generally, a spinal plate is the device of choice used for mechanically supporting such vertebral fixation. A typical spinal plate includes a plate having a plurality of apertures therethrough. A corresponding plurality of fasteners, i.e., bone screws, are generally positioned into and through respective apertures of the plate to secure the spinal plate to a bone, such as two respective upper and lower supporting adjacent spinal vertebrae. The screws are fastened to the respective support vertebrae to secure the spinal plate to the respective vertebrae. In general, such plate and screw assemblies can be utilized, generally, for anterior fixation of the spine for cervical, lumbar, and/or thoracic fixation.
The basis of anterior fixation or plating is to approach the spine from an anterior or anterio-lateral approach, and use the screws to solidly mount the spinal plate to the affected vertebrae. Often, in addition to the application of a spinal plate, graft material may be combined in attempt to permanently fuse together adjacent vertebrae. The graft material can consist of bone grafts obtained from bones of the recipient or another individual.
A common problem associated with the use of such spinal plates is the tendency of the bone screws to “back out” or pull away from the bone into which they are fixed. This problem occurs, primarily, due to the normal torsional and bending motions of the body and spine. This is a particularly important problem because as the screws become loose and pull away from the bone, the heads of the screws can rise above the surface of the spinal plate and, possibly, even work their way completely out of the bone. While this condition can cause extreme discomfort for the recipient, this condition can also create a number of potentially serious physiological problems given the significant amount of nervous and vascular structures associated at or near the potential locations of anterior spinal plate fixations.
A number of designs have been proposed in attempts to prevent screws from pulling away from the bone and/or to prevent the screws from backing out or pulling away from the surface of the spinal plate. Such mechanisms used to prevent bone screws from pulling out of bones include cams which engage and lock the screws, and the use of expanding head screws which expand outwardly when adequate force is applied thereto to engage the holes in the spinal plate. All of these designs have detriments including potential for breakage or requiring particular precision and alignment in their application in order to work correctly. Additionally, loose components and accessories of spinal plates which address the “backing-out” problem can get dropped and/or misplaced while the vertebral fixation surgical procedure is taking place, prolonging and complicating the procedure as well as creating substantial risk of harm to the recipient.
Yet another common problem associated with the use of such spinal plates is the tendency of the vertebrae being “fixed” to settle after spinal plate insertion adding compression forces to the above-listed forces which cause the bone screws to “back out” or pull away from the bone into which they were fixed. Zdeblick et al. (U.S. Pat. No. 5,324,290) attempted to address the problem of compression forces in the context of treating vertebral burst fractures, but fails to provide any functional means to prevent the screws pulling away as a result of torsional and flexing forces.
Therefore, it is an object of the invention to provide bone fixation apparatus which provides rigid bone-to-bone fixation and/or support, such as e.g. adjacent or second adjacent vertebrae, while allowing post-procedural compression between the respective bones.
It is another object of the invention to provide bone fixation apparatus which affords substantial protection against pulling away of affixing components which may result from torsional movement, flexing movement, or stress and/or dynamic load sharing of the vertebrae, thereby enhancing the bone rebuilding process.
It is yet another object of the invention to provide bone fixation apparatus which attenuates application of stress on the apparatus and affixing components. It is a further object of the invention to provide bone fixation apparatus comprising a support plate and fixation components, and fixation component support which reinforces the fixation components thus to prevent the fixation components from backing out of the support plate.
It is yet a further object of the invention to provide bone fixation apparatus which can be pre-assembled as a loose assembly such that no loose assembly parts or inter-procedural apparatus need be assembled to the assembly during installation of such bone fixation apparatus in a recipient.
SUMMARY
In a first family of embodiments, the invention comprehends a bone support plate for use in a bone support assembly. The bone support plate comprises a top surface, a bottom surface opposite the top surface and adapted to engage bone structure of a user; a fixed base portion, having first and second apertures extending therethrough, from the top surface to the bottom surface, for receiving bone fasteners therethrough, and a slot portion, having at least third and fourth apertures extending therethrough, from the top surface to the bottom surface, for receiving bone fasteners therethrough. A first base cover plate recess is disposed in the top surface at the fixed base portion for receiving a base cover plate thereonto and accommodating sliding movement of such base cover plate to impose and withdraw at least partial obstruction of the first and second apertures. Similarly, a second settle cover plate recess is disposed in the top surface at the slot portion for receiving a settle cover plate thereonto and accommodating sliding movement of such settle cover plate to impose and withdraw at least partial obstruction of the third and fourth apertures.
In preferred embodiments, the bone support plate is designed and configured to enable bidirectional sliding movement of a base cover plate connected thereto, wherein the bidirectional sliding movement is in substantial alignment with the top surface of the bone support plate.
Preferably, the bone support plate is designed and configured to enable bidirectional sliding movement of a settle cover plate connected thereto, wherein the bidirectional sliding movement is in substantial alignment with the top surface of the bone support plate.
In some embodiments, the bone support plate comprises a base cover plate fastener aperture extending therethrough, from the first base cover plate recess to the bottom surface of the bone support plate, for receiving a base cover plate fastener therethrough.
In some embodiments, the bone support plate comprises a settle cover plate fastener aperture extending therethrough, from the second settle cover plate recess to the bottom surface of the bone support plate, for receiving a settle cover plate fastener therethrough.
In some embodiments, at least a portion of the bottom surface of the support plate comprises a texturized surface, the texturized surface enhancing engagement of the support plate to the bone structure.
The apertures of the slot portion are preferably longitudinally slot-shaped, with respect t
Robert Eduardo C.
Wilhelm Thomas D.
Wilhelm Law Service
LandOfFree
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