This invention relates to a connection between a spinal rod and a vertebral anchor with a tapered locking surface that traps the vertebral anchor in the connection fitting.
Spinal implant systems provide a rod for supporting the spine and for properly positioning components of the spine and for various treatment purposes. Bolts, screws, and hooks are typically secured to the vertebrae for connection to the supporting rod. These vertebral anchors must frequently be positioned at various angles due the anatomical structure of the patient, the physiological problem being treated, and the preference of the physician. It is difficult to provide secure connections between the spinal support rod and these vertebral anchors at all the various angles and elevations that are required, especially where there are different distances between the rod and bolts and where these components are located at different heights on the patient.
What is needed is a connection assembly between a spinal rod and a vertebral anchor that allows the surgeon to fix the desired elevation between a rod and the bone anchor as well as fix the desired angle between the anchor and rod. The following invention is one solution to that need.
In one aspect, this invention is a connection assembly between a spinal implant rod and a vertebral anchor. The connection assembly includes a longitudinal member with a friction shoe at one end and an aperture at the other. The connection assembly also includes a housing. The housing has a passageway to receive a portion of the vertebral anchor and a bore to receive at least a portion of the shoe of the longitudinal member. The housing also includes a rod interface washer. The washer is positioned over the longitudinal member between the aperture of the longitudinal member and the face of the housing. The connection assembly further includes a compression member. The compression member is forceably, for example threadably, engageable into the aperture of the longitudinal member to urge the rod toward the vertebral anchor, whereby the shoe will be moved in the bore to urge the vertebral anchor toward the internal wall of the passageway in the housing, further pressing the housing and said rod interface washer together.
As used in this specification the term “shoe” means a structure that retards, stops, or controls the motion of another structure. WEBSTER'S NINTH NEW COLLEGIATE DICTIONARY 1088 (1990).
Specific language is used in the following description to publicly disclose the invention and to convey its principles to others. No limits on the breadth of the patent rights based simply on using specific language are intended. Also included are any alterations and modifications to the description that should normally occur to one of average skill in this technology.
A connection assembly 1 according to one embodiment of the invention is shown in
Additional details of longitudinal member 2 are shown in
Additional details of housing 3 are shown in
Details of rod interface washer 4 are shown in
The rod interface washer 4 has a housing connection surface 29 opposite the engagement surface 27. The housing connection surface 29 preferably includes structure for facilitating the engagement of the washer against rotational movement relative to the housing 3 against which it is pressed. This engagement structure is preferably a plurality of variable angle ridges 30, which radiate from the rotational center of the rod interface washer 4.
The rotable connection assembly and its manner of assembly are shown in cross-section in
Housing 3 and rod interface washer 4 are positioned on longitudinal member 2. Rod interface washer 4 rides over washer seat portion 14 of longitudinal member 2 (
Longitudinal member 2 is generally held in housing 2 by the insertion of the shank of a vertebral anchor “B” into passageway 8. When the shank is inserted into passageway 8, the frictional shoe 9 can no longer be removed from bore 17. A portion of the shank extends into bore 17 between end 10 and aperture 6, and pulling longitudinal member out of bore 17 places inwardly tapered seat surface 11 in contact with the shank of vertebral anchor “B”, preventing longitudinal member 2 from being further removed.
As a result of this arrangement, connection assembly 1 may be tightened to rod “A” and vertebral anchor “B” by threading compression member 5 into threaded opening 7. Threading compression member 5 into opening 7 clamps rod “A” between rod interface washer 4 and compression member 5. This action, in turn, interlocks connection surfaces 19 and 29 and pulls frictional shoe 9 from bore 17. Pulling frictional shoe 9 from bore 17 clamps the shank of vertebral anchor “B” between the sidewall of passageway 8 and the inwardly tapered seat surface 11 of shoe 9, locking the entire connection assembly against movement. Adjustments are then made loosening set screw 5 and then retightening the set screw when the preferred position has been located.
Several details should now be noted. First, the width of housing 3 and rod interface washer 4 is such that when connection assembly 1 is loaded, but not tightened, onto a rod and vertebral anchor, there is some freedom of movement of housing 3 and washer 4 over longitudinal member 2. And preferably, this freedom of movement is sufficient to allow washer connection surface 19 and housing connection surface 29 to slide past each other. Second, the aperture 6 of longitudinal member 2 and passageway 8 of housing 3 are larger in dimension than the cross-section of the rod “A” or vertebral anchor “B”, such that movement of each within their respective openings is possible. And third, it is generally preferable that washer seat portion 14 be of sufficient length and width to ride on bore 17 when connection assembly has not yet been tightened to a rod and vertebral anchor. In some applications, this may increase the ease with which connection assembly 1 can be tightened.
So being, the connection assembly 1 can be readily located most anywhere on a spinal rod, can be readily located most anywhere over the shank of a vertebral anchor, and connection assembly 1 can accommodate most any angle between the rod and the vertebral anchor. Additional details of the installation of such vertebral anchors and advantages of such multiple adjustments in the X, Y, and Z planes can be found in U.S. Pat. Nos. 5,643,263 and 5,885,285 to Simonson, the disclosures of which being specifically incorporated into this specification by reference.
Yet another alternative embodiment of connection assembly 1 is shown in
Additional details of longitudinal member 2 of this embodiment are shown in
Additional details of housing 3 of this embodiment are shown in
In contrast to the previous embodiments of this invention and referring back to
Yet another alternative embodiment of this invention is shown in
Instead of attaching connection assembly 1 directly to spinal implant rod “A”, spindle 35 is attached to rod “A” and secured by compression member 36. Connection assembly 1 is then secured to the offset connector by inserting projection portion 37 into aperture 6 and tightening connector assembly 1 as previously described.
While the invention has been illustrated and described in detail, this is to be considered illustrative and not restrictive of the patent rights. The reader should understand that only the preferred embodiments have been presented and all changes and modifications that come within the spirit of the invention are included if the following claims or the legal equivalent of these claims describes them.
This application is a continuation of and claims priority to U.S. patent application Ser. No. 09/694,702, filed Oct. 23, 2000, now issued as U.S. Pat. No. 6,520,962. This document is incorporated herein by reference.
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Number | Date | Country | |
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Parent | 09694702 | Oct 2000 | US |
Child | 10369090 | US |