Spinal connecting members with radiused rigid sleeves and tensioned cords
A spinal implant having at least two bone anchors includes a longitudinal connecting member assembly having hard, non-elastic sleeves for attachment to the bone anchors, at least one spacer engaging the bone anchors and the sleeves, and in some embodiments, an end elastic bumper. A cord is initially slidingly received within the rigid sleeves, the spacer and the bumper. The sleeves include a lower radiused surface for direct engagement with a radiused surface of a shank of the cooperating bone anchor. The sleeves include an aperture for receiving a closure top portion for locking the cord against the sleeve, or alternatively receiving a closure top that does not extend into the aperture, the slip or grip option provided by the aperture in each sleeve resulting in an overall connector with variable segmental stiffness.
1 . In a medical implant assembly having at least a pair of bone anchors cooperating with a longitudinal connecting member having a tensioned cord and a spacer located between the first and second bone anchors, the cord extending through the spacer, the bone anchors having opposed upstanding arms,
the improvement wherein at least one of the bone anchors is a polyaxial bone anchor having a shank pivotable with respect to a receiver, the shank having a first radiused surface, and further comprising:
at least one inelastic sleeve for attachment to the polyaxial bone anchor, the sleeve having a first through bore sized and shaped for slidably receiving the tensioned cord, a first aperture formed in the sleeve substantially transverse to the first through bore, the first aperture sized and shaped for receiving a portion of an optional cord gripping closure top and a first body portion sized and shaped for being closely received between the bone anchor arms, the sleeve having a second surface sized and shaped for directly engaging the shank first radiused surface at a variety of angular orientations of the shank with respect to the sleeve.
2 . The improvement of claim 1 wherein the sleeve is a first sleeve and the polyaxial bone anchor is a first polyaxial bone anchor and further comprising:
a) a second polyaxial bone anchor having a third radiused surface; and
b) a second inelastic sleeve for attachment to the second bone anchor, the second sleeve having a second through bore sized and shaped for slidably receiving the tensioned cord, a second aperture formed in the sleeve substantially transverse to the second through bore, the second aperture sized and shaped for receiving a portion of a second optional cord gripping closure top and a second body portion sized and shaped for being closely received between the second bone anchor arms, the second sleeve having a fourth surface sized and shaped for directly engaging the third radiused surface at a variety of angular orientations of the second shank with respect to the second sleeve.
3 . The improvement of claim 2 comprising at least a first closure top having an extended portion in gripping contact with the cord and fixed to one of the first and second sleeves.
4 . The improvement of claim 2 comprising at least a second closure top having a surface in gripping contact with one of the first and second sleeves, the closure top being spaced from the cord.
5 . The improvement of claim 1 wherein the sleeve includes an extension structure slidingly received over the cord and within the spacer.
6 . The improvement of claim 1 wherein the shank first surface is a convex top surface of the shank and the sleeve second surface is concave, the first and second surfaces having substantially the same radius.
7 . The improvement of claim 6 wherein the top surface is located on a drive feature of the shank.
8 . The improvement of claim 1 wherein the shank has an upper portion with a partially spherical surface, the spherical surface is the first radiused surface and the sleeve second surface is concave, the first and second surfaces having substantially the same radius.
9 . The improvement of claim 8 wherein the partially spherical surface is spaced from a drive feature of the shank.
10 . The improvement of claim 2 wherein at least one of the first and second sleeves includes an outer flange abutting against an outer surface of the spacer.
11 . The improvement of claim 10 wherein the outer flange is a first outer flange and further comprising a second outer flange substantially parallel to the first outer flange, each flange being disposed outside of the cooperating bone anchor.
12 . The improvement of claim 10 further comprising at least one tubular structure extending outwardly from the flange.
13 . The improvement of claim 10 wherein the outer flange is a first outer flange and further comprising a second outer flange disposed at an obtuse angle with respect to the first outer flange, each flange being disposed outside of the cooperating bone anchor.
14 . The improvement of claim 13 further comprising a first tubular structure having a first central axis extending outwardly from the first flange and a second tubular structure having a second central axis extending from the second flange, the first and second axes forming an obtuse angle.
15 . The improvement of claim 1 wherein the sleeve has an outer surface substantially flush with an outer surface of the bone anchor.
16 . In a medical implant assembly having at least first and second polyaxial bone anchors cooperating with a longitudinal connecting member, the improvement wherein the connecting member comprises:
a) a first hard, non-elastic sleeve for attachment to the first bone anchor, the first sleeve having a first radiused surface sized and shaped for frictional mating with the first polyaxial bone anchor shank, the shank having a mating surface with a second radius substantially similar to the first radiused surface;
b) a second non-elastic sleeve for attachment to the second bone anchor;
c) a spacer located between the first and second bone anchors, the spacer engaging the first and second sleeves; and
d) a tensioned cord slidingly received within the first and second sleeves and the spacer, the cord being in one of a fixed and slidable relation with respect to the first and second sleeves.
17 . The improvement of claim 16 wherein at least one of the first and second sleeves includes an extension structure slidingly received over the cord and slidingly received within the spacer.
18 . The improvement of claim 16 wherein the shank mating surface is at least one of a top surface of the shank located on a drive feature and a partially spherical surface spaced from the drive feature.
19 . The improvement of claim 16 wherein at least one of the sleeves has an aperture formed therein sized and shaped to receive a portion of a closure top, the closure top portion being fixed against the cord.
20 . In a medical implant assembly having at least first and second bone anchors cooperating with a longitudinal connecting member having a tensioned cord, the improvement comprising:
a) at least one non-elastic sleeve for attachment to the first bone anchor, the sleeve having a body portion for slidingly receiving the cord therethrough, the body portion sized and shaped for being closely received between opposed arms of the first bone anchor, the body portion having a concave surface sized and shaped for direct contact and frictional mating with a convex surface of a shank of at least one of the bone anchors;
b) a spacer located between the first and second bone anchors, the cord extending through the spacer and held in tension at least first and second ends of the connecting member; and
c) at least one blocker, the first bone anchor being located between the blocker and the spacer, the blocker located near the sleeve, the blocker being fixed to the tensioned cord.
21 . The improvement of claim 20 wherein the concave surface and the convex surface have substantially the same radius.
22 . The improvement of claim 20 wherein the blocker is adjacent the first bone anchor.
23 . The improvement of claim 20 wherein the blocker engages the sleeve.
24 . The improvement of claim 20 further comprising a bumper located between the blocker and the first bone anchor.
25 . The improvement of claim 20 wherein the at least one sleeve is a first sleeve and further comprising a second sleeve, the second sleeve being integral with a hard rod.
26 . The improvement of claim 25 wherein the second sleeve is fixed to the cord.
27 . The improvement of claim 26 wherein the second sleeve has a bore and cooperating pin, the pin extending through the bore and fixing the cord to the second sleeve.
28 . The improvement of claim 20 wherein the body portion has an aperture located adjacent the concave surface, the aperture sized for receiving a bone screw shank driving tool through the body portion and into a drive feature of at least one of the first and second bone anchors.