Cervical spine rod fixation system

• US 5,653,708 A
• Filed: 09/09/1994
• Issued: 08/05/1997
• Est. Priority Date: 12/28/1992
• Status: Expired due to Term

• Current Assignee: Wenzel Spine, Inc.
• Original Assignee: Advanced Spine Fixation Systems, Inc. (Enovis Corp.)
• Inventors: Howland, Robert S.
• Primary Examiner(s): Tucker, Guy V.
• Application Number:
  US08/303,580
• Time in Patent Office: 1,061 Days
• Field of Search: 606/61, 606/57, 606/73, 606/105, 606/60, 606/53, 606/54, 606/59, 606/72
• US Class Current: 606/264
• CPC Class Codes: A61B 17/701 Longitudinal elements with a non-circular, e.g. rectangular, cross-section A61B17/7005, A61B17/7007 take precedence
• CPC Class Codes: A61B 17/7041 with single longitudinal rod offset laterally from single row of screws or hooks A61B17/7044 takes precedence
• CPC Class Codes: A61B 17/7049 Connectors, not bearing on the vertebrae, for linking longitudinal elements together A61B17/7055, A61B17/7053, A61B17/7019 take precedence
• CPC Class Codes: A61B 17/7055 connected to sacrum, pelvis or skull

Abstract

A cervical spine fixation system is described. The fixation system comprises a bone screw for implanting in the cervical vertebrae of the spine and for accommodating a clamping assembly. The clamping assembly comprises a rod receiving aperture which is angularly oriented a predetermined amount from perpendicular with respect to a longitudinal axis of the bone screw.

Claims

1. A cervical spine fixation system comprising:

a bone screw, having a longitudinal axis, for implanting in cervical vertebrae of the spine and for accommodating a clamping assembly;

a clamping assembly mounted on the bone screw, wherein the clamping assembly comprises;

an upper saddle comprising a rod receiving half-aperture angularly oriented at a predetermined fixed angle with respect to a plane perpendicular to the longitudinal axis of the bone screw to thereby maintain a rod received into the rod receiving aperture in generally parallel alignment with the plane of the spinal column wherein the predetermined fixed angle ranges from about 10°

to about 25°

;

a lower saddle comprising a rod receiving half-aperture angularly oriented a predetermined amount from a plane perpendicular with respect to the longitudinal axis of the bone screw which mates in parallel relation with the upper saddle to form a rod receiving aperture, the mating saddles further comprising an upper and lower surface on each of the upper and lower saddles, an aperture in the upper surface of the upper saddle, and a lock washer having a plurality of spaced tangs mounted on the upper surface of the upper saddle wherein one of the tangs of the lock washer is received in the aperture to secure the lock washer to the upper saddle; and

means for attaching the clamping assembly to the bone screw.

2. A cervical spine fixation system comprising:

a bone screw having a longitudinal axis, a first threaded end for implanting into a cervical spine vertebra, a second threaded end, and a flange oriented in a plane perpendicular to the longitudinal axis of the bone screw and between the first threaded end and the second threaded end of the bone screw;

a clamp assembly, having a generally flat bottom face mounted on the second threaded end of the bone screw and supported by the flange, comprising a rod receiving aperture, the rod receiving aperture being angularly oriented at a predetermined fixed angle with respect to the plane perpendicular to the longitudinal axis of the bone screw such that a rod is located in parallel relation to the rod receiving aperture and wherein the predetermined fixed angle ranges from about 10°

to about 25°

the clamp assembly further comprising an upper and a lower saddle each of which includes parallel side faces at either end of the rod-receiving half aperture wherein the axial dimension of a side face at one end of the rod-receiving half aperture is of a different axial dimension than the side face at the other end of the rod-receiving half aperture;

the rod, having a longitudinal axis, and received in the rod receiving aperture; and

means to secure the clamp assembly to the bone screw whereby the rod is securely fixed in the rod receiving aperture.

3. A cervical spine fixation system comprising:

a bone screw comprising;

a longitudinal axis;

a first threaded end for implantation into a cervical spine vertebra;

a clamp receiving section including a rotation preventing means;

a second threaded end spaced from the first threaded end; and

a flange between the threaded ends;

a clamp assembly, for mounting on the bone screw, comprising;

a lower saddle comprising;

an aperture for mounting the lower saddle on the second threaded end of the bone screw to abut the flange of the bone screw wherein the aperture has a longitudinal axis which is collinear with the longitudinal axis of the bone screw when mounted on the bone screw;

a clamp rotation prevention means in the aperture for cooperating with the rotation preventing means of the bone screw whereby the lower saddle is fixed against rotation with respect to the bone screw; and

a rod receiving half-aperture spaced laterally from the aperture and angularly oriented at a predetermined angle with respect to a plane perpendicular to the longitudinal axis of the aperture and wherein the predetermined angle ranges from about 10°

to about 25°

;

an upper saddle comprising;

an aperture, with a longitudinal axis for mounting the upper saddle on the second threaded end of the bone screw wherein the aperture in the upper saddle is alignable with the aperture of the lower saddle; and

rod receiving half-aperture spaced laterally from the aperture and angularly oriented at a predetermined angle with respect to a plane perpendicular to the longitudinal axis of the aperture such that the rod receiving half-aperture of the upper saddle is in parallel relation with the rod receiving half-aperture of the lower saddle when mounted on the bone screw; and

a rod receiving aperture, formed by the mating of the lower and upper saddles, wherein a rod received in the rod receiving aperture is in parallel relation to the rod receiving aperture and angularly oriented at the predetermined angle with respect to a plane perpendicular to the longitudinal axis of the bone screw; and

means to secure the mating saddles together and against the flange on the bone screw whereby the rod is securely fixed in the rod receiving aperture.

4. A cervical spine fixation system as recited in claim 3 wherein the system comprises a plurality of bone screws forming pairs adapted to be located on each side of the cervical spine.

5. A cervical spine fixation system as recited in claim 3 wherein the mating saddles further comprise a lock washer having a plurality of spaced tangs mounted on the upper surface of the upper saddle wherein one of the tangs of the lock washer is received in the aperture to secure the lock washer to the upper saddle.

6. A cervical spine fixation system as recited in claim 3 wherein the means to secure the mating saddles together and against the flange on the bone screw comprises a sleeve nut, wherein the sleeve nut is substantially recessed into the clamping assembly when the bone screw and clamps are assembled.

7. A cervical spine fixation system as recited in claim 3 wherein the system further comprises a spacer located over the first threaded end of the bone screw.

8. A cervical spine fixation system comprising:

a bone screw having a longitudinal axis, a first threaded end for implanting into a cervical spine vertebra, a second threaded end, and a flange oriented in a plane perpendicular to the longitudinal axis of the bone screw and between the first threaded end and the second threaded end of the bone screw;

a clamp assembly, having a generally flat bottom face mounted on the second threaded end of the bone screw and supported by the flange, comprising a rod receiving aperture, the rod receiving aperture being angularly oriented at a predetermined fixed angle with respect to the plane perpendicular to the longitudinal axis of the bone screw such that a rod is located in parallel relation to the rod receiving aperture and wherein the predetermined fixed angle ranges from about 10°

to about 25°

the clamp assembly further comprising an upper and lower saddle each of which includes an upper and lower surface, an aperture in the upper surface of the upper saddle, and a lock washer having a plurality of spaced tangs mounted on the upper surface of the upper saddle wherein one of the tangs of the lock washer is received on the aperture to secure the lock washer to the upper saddle;

the rod, having a longitudinal axis, and received in the rod receiving aperture; and

means to secure the clamp assembly to the bone screw whereby the rod is securely fixed in the rod receiving aperture.