Surgery – Instruments – Orthopedic instrumentation
Reexamination Certificate
1999-10-19
2001-04-17
Mancene, Gene (Department: 3732)
Surgery
Instruments
Orthopedic instrumentation
C606S060000
Reexamination Certificate
active
06217578
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a vertebral osteosynthesis device that can be used to brace a spine, for example, following accidental fracture, or to strengthen or brace a deviated spine, as in the case scoliosis or kyphosis. More particularly, this invention is related to a novel cross connector which fixes the location and enhances the rigidity of longitudinally extending rods anchored to the spine.
2. Discussion of the Prior Art
As is known, from, for example, U.S. Pat. No. 5,055,562 to Cotrel, a pair of posterior rods may be coupled to the back of a spinal column by hooks held by screws supported by the pedicles of the vertebra. Generally, there are two rigid and substantially parallel support rods disposed one on each side of the spine supported by pedicle screws or hooks. These vertically aligned rods stabilize both short and long segments of the spine. Implantation of such a device requires the rods to be shaped to adapt to the curve in one or two planes of the spine, whether these are nature curves or curves resulting from scoliosis or kyphosis.
In order to provide enhanced rigidity, especially torsional rigidity, the pair of rods usually includes cross connecting devices which couple the rods together transverse to their longitudinal axis, i.e. transverse to an axis extending in the vertical direction when an individual is standing.
As can be seen from U.S. Pat. No. 5,005,562 these cross connector devices include a plurality hook shaped gripping elements which receive the rod. These elements are fixed to the rods by set screws which extend through a wall of the hook. Since the rods may be curved in the medial-lateral direction and the distance between the pair of rods may vary consequently, a method for varying the horizontal distance between the hooks is required. As can be seen in U.S. Pat. No. 5,002,562, one solution is to provide a threaded transverse rod on which the hooks may be threaded for movement therealong. Of course, this limits the adjustibility of the hooks, depending on the fineness of the thread and the required angular orientation necessary to engage the vertical rods.
Consequently, Cotrel, in his later U.S. Pat. Nos. 5,601,552 and 5,651,789 uses a transverse bar of polygonal shape which allows the hooks to slide and be fixed in any relative horizontal position along the bar. However, such a system exhibits only one degree of freedom since the hook surfaces always move in the same plane.
In U.S. Pat. No. 5,667,507 to Corin, et al., a cross locking member is provided, which includes an additional degree of freedom, allowing rotation in the vertical plane as well as length adjustment in the horizontal direction. Thus, two degrees of freedom are provided. Similarly, U.S. Pat. No. 5,752,955 provides two degrees of freedom by allowing rotation around a horizontally extending axis as well as allowing equalized extension via a telescoping connection between the hook bodies.
U.S. Pat. No. 5,443,465 to Pennig discloses a fracture fixation device having multiple degrees of freedom. However, this device requires several joints which have to be independently locked to fix the device in a given position.
U.S. Pat. No. 5,716,355 to Jackson, et al. relates to a pair of connectors slideable along each to two parallel spinal rods and having swivel connections to fix the final orientation of a transverse rod relative to the spinal rod. This design requires both connectors to be independently adjusted and locked to fix the transverse rod in its final position.
U.S. Pat. No. 5,261,907 to Vignaud, et al. relates to a cross connecting device having a pair of rods and a pair of clamps which can be fixed in place, utilizing a screw arrangements. This device is difficult to assemble because it includes two clamps, each receiving its own extension arm which arms are independently adjustable within the clamps.
None of the prior art discloses transverse cross connector having multiple degrees of freedom which cross connector can be locked in a desired position by a single locking mechanism.
SUMMARY OF THE INVENTION
It is therefore an object of the present invention to provide a cross connector device having a low profile but allowing for a substantial degree of freedom between the hooks at either end of the device.
It is also an object of the present invention to provide a cross connector device which, while providing multiple degrees of freedom, provides a surgeon with the ability to lock the device on a spinal rod with a set screw in a given orientation with a single locking mechanism, using only two tools, one for the locking mechanism and one for the set screw.
These and other objects of the invention are achieved by the present invention, which is a locking variable cross connector device which may be affixed to the rods of a dual rod spinal implant apparatus. This cross connector device includes a pair of rod engaging elements in the form of hooks.
The cross connector or link for connecting spinal rods of the present invention includes a first rod gripping element which, in the preferred embodiment, is in the form of a hook formed on a first end of the rod gripping element and including an arm or rod extending from a second end thereof along a first axis. A second rod gripping element is provided which also includes hook formed on a first end thereof and a bearing portion with a bearing surface surrounding a bore or hole integrally formed on a second end thereof. A pivot element is slidably and rotatably coupled to the arm on the first rod gripping element, via a bore in the pivot element for movement therealong and for rotation about the first axis. The pivot element includes a bearing surface engageable with the bearing surface formed on the second element. These bearing surfaces allow relative rotation between the pivot element and the second rod gripping element about a second axis which is not parallel to the first axis.
In the preferred embodiment, the second axis is perpendicular to the first axis to allow relative angular adjustment between the two hook portions in the vertical plane of the spine. As used herein, the vertical plane refers to the plane through the spine in the medial lateral direction which is parallel to the front or coronal plane.
The pivot element has a first clamping portion associated with the bore therein which engages the arm and a second clamping portion in the form of a lock nut which engages the bearing member on the second rod gripping element. The clamping portions of the pivot element are designed to clamp the arm and a bearing surface on the second rod gripping element to prevent all rotation about the first and second axis and all movement along the arm. This may be accomplished by the frictional engagement between a bearing surface on the second element while clamped between the lock nut, and the surface of the arm and the engagement of the first clamping portion in the bore of the pivot element contacting the opposite side of the arm.
In the preferred embodiment, the arm on the first bearing element may be in the form of a longitudinally extending rod or shaft having a circular cross section and the pivot element may include a head portion having the first clamping portion in the form of a part circular bore therethrough for receiving the arm. In the preferred embodiment, the cross section of the bore includes a first circular part having a diameter larger than the diameter of the arm and a second circular part having a diameter closely matching the diameter of the circular rod or arm. The centers of the two circular bore parts may be offset from one another, thus forming a pair of concentric circular areas. At the end of the pivot element opposite the head, the pivot element may be in the form of a threaded rod or screw shank which extends from the head portion along an axis which, upon assembly of the first and second rod gripping elements and the pivot element, is coaxial with the second axis.
In the preferred embodiment, the bore in the head of the pivot element extends al
Crozet Yves
Masson Martin
Lerner David Littenberg Krumholz & Mentlik LLP
Mancene Gene
Priddy Michael B.
Stryker Spine S.A.
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