Spinal Stabilization Device
A flexible connection unit for use in a spinal fixation device, including: a longitudinal member having first end portion, a second end portion and a flexible member interposed between the first end portion and the second end portion, at least one of the first end portion and the second end portion configured to be coupled to a first bone securing member; and a spacer located between the first and second end portions, wherein at least a portion of the flexible member passes through an axial channel of the spacer and wherein the spacer comprises a resilient element configured to be coupled to a second bone securing member.
1 . A connection unit for use in a spinal stabilization device, the connection unit comprising:
a longitudinal member having a hollow interior cavity and a longitudinal axis, the longitudinal member configured to be secured to a first vertebra and a second vertebra by a first securing member and a second securing member, the longitudinal member including:
a first ungrooved section configured to be coupled to the first securing member, the first ungrooved section defining a first outer dimension;
a second ungrooved section configured to be coupled to the second securing member; and
a middle section coupled to the first ungrooved section and the second ungrooved section, the middle section including an outer surface and an opposed inner surface, the inner surface facing the hollow interior cavity, the outer surface defining a second outer dimension that is greater than the first outer dimension, the middle section further including a grooved section having at least one groove formed therein, the groove having:
(1) a groove length such that the groove extends along the outer surface from a first end to a second end; and
(2) a groove depth such that the groove extends through the middle section from the outer surface to the inner surface.
2 . The connection unit of claim 1 , wherein the at least one groove further defines a groove width measured along the longitudinal axis, a groove shape, and a groove to groove spacing measured along the longitudinal axis.
3 . The connection unit of claim 2 , wherein at least one of the groove depth, the groove width, the groove shape, or the groove to groove spacing of the at least one groove in the grooved section varies along at least a portion the grooved section along the longitudinal axis.
4 . The connection unit of claim 3 , wherein the groove depth tapers from a maximum near a center of the grooved section to a minimum near the boundary of the grooved section and one of the first and second ungrooved sections.
5 . The connection unit of claim 3 , wherein the groove width tapers from a maximum near a center of the grooved section to a minimum near the boundary of the grooved section and one of the first and second ungrooved sections.
6 . The connection unit of claim 3 , wherein the groove shape transitions from one enabling maximum flexure near a center of the grooved section to a shape enabling reduced flexure near the boundary of the grooved section and one of the first and second ungrooved sections.
7 . The connection unit of claim 3 , wherein the groove to groove spacing expands from a minimum near a center of the grooved section to a maximum near the boundary of the grooved section and one of the first and second ungrooved sections.
8 . The connection unit of claim 1 , wherein the longitudinal member comprises a material selected from a group of bio-compatible materials consisting of metals, metal alloys, organic polymers, naturally occurring resins, thermoplastics, elastomers and composite materials.
9 . The connection unit of claim 1 , wherein the second ungrooved section defines a third outer dimension and the second outer dimension is greater than the third outer dimension.
10 . The connection unit of claim 1 , wherein the longitudinal member defines a length that is measured from the first ungrooved section to the second ungrooved section along the longitudinal axis, and the grooved section is expandable and compressible such that the length can be increased and decreased respectively.
11 . The connection unit of claim 1 , wherein the grooved section comprises a spiral groove.
12 . The connection unit of claim 11 , wherein the spiral groove includes at least one hole.
13 . The connection unit of claim 12 , wherein the grooved section includes only a single spiral groove.
14 . The connection unit of claim 13 , wherein one of the at least one holes is positioned at an end of the single spiral groove.
15 . The connection unit of claim 14 , wherein one of the at least one holes is positioned at a middle portion of the single spiral groove.
16 . The connection unit of claim 1 , wherein the second outer dimension is a diameter.
17 . The connection unit of claim 16 , wherein the diameter is constant throughout the grooved section along the longitudinal axis.
18 . The connection unit of claim 16 , wherein the diameter is varied throughout the grooved section along the longitudinal axis.
19 . The connection unit of claim 18 , wherein the diameter is smallest near a central portion of the grooved section and gradually expands toward the ungrooved sections.