Compression-distraction spinal fixation system and kit
Compression-distraction spinal fixation systems, and methods of performing compression-distraction spinal fixation, are provided that include screw-rod constructs having a ratcheting mechanism. Bone screws of the screw-rod constructs can have a pawl that engages ratchet teeth on the rod of the screw-rod construct. The bone screw can be unidirectionally ratcheted along the length of the rod to apply compressive or distractive forces. Tools for manipulation of the screw-rod constructs are also provided, which tools include distal tips configured to engage the bone screws.
1. A compression-distraction spinal fixation system comprising:
a bone screw comprising a pawl; and
a toothed rod having a plurality of ratchet teeth,
wherein the pawl includes a blade portion arranged to engage the ratchet teeth on the toothed rod when the pawl is in a first position,
wherein the bone screw is releasably coupled to the toothed rod and selectively moveable in a movement direction having a movement axis along the toothed rod,
wherein the blade portion extends from the bone screw in a direction along the movement axis and engages the ratchet teeth of the toothed rod to allow unidirectional movement of the bone screw in the movement direction along the toothed rod, and
wherein the pawl is rotatable from the first position relative to the toothed rod to disengage the pawl from the ratchet teeth on the toothed rod,
wherein the pawl is rotatable approximately 180° from the first position to a second position, to engage the blade portion with the ratchet teeth on the toothed rod.
2. The compression-distraction spinal fixation system of claim 1 , wherein the pawl is rotatably connected to the bone screw.
3. The compression-distraction spinal fixation system of claim 2 , wherein the pawl is selectively rotatable about the bone screw between the first position and the second position.
4. The compression-distraction spinal fixation system of claim 1 , wherein the bone screw further comprises a set screw, and the pawl is rotatably coupled to the set screw.
5. The compression-distraction spinal fixation system of claim 4 , wherein the pawl is retained on the set screw by a retaining ring.
6. The compression-distraction spinal fixation system of claim 4 , wherein the blade portion extends substantially parallel to an axis of the set screw.
7. The compression-distraction spinal fixation system of claim 4 , wherein the blade portion extends away from the set screw at an angle.
8. The compression-distraction spinal fixation system of claim 4 , wherein the blade portion extends toward the set screw at an angle.
9. The compression-distraction spinal fixation system of claim 4 , wherein the pawl covers a top surface of a screw head of the bone screw.
10. The compression-distraction spinal fixation system of claim 9 , wherein an edge of the top surface of the screw head is chamfered and the pawl includes an angled surface configured to engage the chamfered edge.
11. The compression-distraction spinal fixation system of claim 10 , wherein the pawl includes a detent in the angled surface arranged to engage a non-threaded portion of the screw head to selectively prevent rotation of the pawl relative to the screw head.
12. The compression-distraction spinal fixation system of claim 10 , further comprising the blade portion extending from the angled surface of the pawl and configured to engage the ratchet teeth on the toothed rod.
13. The compression-distraction spinal fixation system of claim 1 , further comprising a second bone screw comprising a pawl, wherein the second bone screw is releasably coupled to and selectively moveable along the toothed rod, and wherein the pawl of the second bone screw engages the ratchet teeth of the toothed rod, whereby the first and second bone screws are selectively moveable toward or away from one another to alter a distance therebetween.
14. The compression-distraction spinal fixation system of claim 1 , wherein the blade portion that engages the ratchet teeth in the first position is the same blade portion that engages the ratchet teeth in the second position.
15. A spinal fixation kit, comprising:
a bone screw comprising a pawl;
a toothed rod having a plurality of ratchet teeth,
wherein the pawl includes a blade portion arranged to engage the ratchet teeth on the toothed rod,
wherein the bone screw is configured to be releasably coupled to and selectively moveable along a movement axis along the toothed rod,
wherein the blade portion extends from the bone screw in a direction along the movement axis and is configured to engage the ratchet teeth of the toothed rod to allow unidirectional movement of the bone screw in a first movement direction along the toothed rod,
wherein the pawl is rotatable approximately 180° relative to the toothed rod and configured to engage the ratchet teeth of the toothed rod to allow unidirectional movement of the bone screw in a second movement direction along the toothed rod; and
a compression tool including:
first and second handle portions pivotably coupled to one another about a common fulcrum; and
first and second extension portions connected, respectively, to the first and second handle portions and including distal tips configured to engage a portion of the bone screw to allow manual manipulation of the bone screw unidirectionally along a toothed rod of the spinal fixation system.
16. A spinal fixation kit, comprising:
a bone screw comprising a pawl;
a toothed rod having a plurality of ratchet teeth,
wherein the pawl includes a blade portion arranged to engage the ratchet teeth on the toothed rod,
wherein the bone screw is configured to be releasably coupled to and selectively moveable in a movement direction having a movement axis along the toothed rod,
wherein the blade portion extends from the bone screw in a direction along the movement axis and is configured to engage the ratchet teeth of the toothed rod to allow unidirectional movement of the bone screw along the toothed rod, and
wherein the pawl is rotatable approximately 180° relative to the toothed rod and configured to engage the ratchet teeth of the toothed rod to allow unidirectional movement of the bone screw in a second movement direction along the toothed rod; and
a distraction tool including:
first and second handle portions pivotably coupled to one another at a pivot point; and
first and second extension portions connected, respectively, to the first and second handle portions and including distal tips configured to engage a portion of the bone screw to allow manual manipulation of the bone screw unidirectionally along a toothed rod of the spinal fixation system.