Bi-directional motion spinal implant
A spinal implant includes first and second pedicle screws, each of which comprises a threaded shank coupled to a head. First and second cantilevered arms are coupled to the first and second pedicle screws, respectively. The first cantilevered arm includes a contact member arranged to contact and move over a contact portion of the second cantilevered arm.
1. A spinal implant comprising:
first and second pedicle screws, each of which comprises a threaded shank coupled to a head; and
first and second cantilevered arms coupled to said first and second pedicle screws, respectively, wherein said first cantilevered arm comprises a rollable contact member arranged to contact and move over a contact portion of said second cantilevered arm, said rollable contact member being movable in rotation and translation.
2. The spinal implant according to claim 1 , wherein an outer contour of said head is convex, and each of said first and second cantilevered arms comprises a concave inner portion, and said first and second cantilevered arms are secured to said first and second pedicle screws, respectively, with a fastener that presses said concave inner portion against said outer contour of said head.
3. The spinal implant according to claim 2 , wherein a fastener-interface portion of each of said first and second cantilevered arms is convex, and said fastener comprises a concave inner portion configured to press against said fastener-interface portion.
4. The spinal implant according to claim 1 , wherein said first and second cantilevered arms are parallel to each other.
5. The spinal implant according to claim 1 , wherein said contact member is convex and said contact portion is concave.
6. The spinal implant according to claim 1 , wherein said contact member comprises a round roller element, which is cylindrical or spherical.
7. The spinal implant according to claim 1 , wherein said second cantilevered arm comprises at least one side wall that straddles said contact member.
8. The spinal implant according to claim 1 , wherein said contact member is pivotally coupled to said first cantilevered arm.
9. The spinal implant according to claim 1 , wherein said contact member is fixedly coupled to said first cantilevered arm.
10. The spinal implant according to claim 1 , wherein said contact member is movable independently of both said first and second cantilevered arms.
11. The spinal implant according to claim 1 , wherein said first and second cantilevered arms are each pivoted about a pivot with respect to a base member that fits over said head.
12. The spinal implant according to claim 1 , wherein said contact member has a different hardness than said contact portion.
13. The spinal implant according to claim 1 , wherein said contact member is movable 360° in rotation without hindrance.