Longitudinal connecting member with sleeved tensioned cords

Abstract

A dynamic fixation medical implant having at least two bone anchors includes a longitudinal connecting member assembly having rigid 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 flexible cord is initially slidingly received within the rigid sleeves, the spacer and the bumper. The spacer may include an optional inelastic inner liner, with at least one of the sleeves having an extension slidingly receivable within the liner. Some sleeves include apertures 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.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS[0001]This application claims the benefit of the following U.S. Provisional Patent Application Ser. Nos. 61 / 268,708, filed Jun. 15, 2009; 61 / 270,754, filed Jul. 13, 2009; 61 / 336,911 filed Jan. 28, 2010; 61 / 395,564 filed May 14, 2010; 61 / 395,752 filed May 17, 2010; and 61 / 396,390 filed May 26, 2010 (docket no. 11,183); all of which are incorporated by reference herein. This application is also a continuation-in-part of U.S. patent application Ser. No. 12 / 221,442 filed Aug. 1, 2008 that is a continuation-in-part of U.S. patent application Ser. No. 11 / 328,481 filed Jan. 9, 2006, both of which are also incorporated by reference herein. This application is also a continuation-in-part of U.S. patent application Ser. No. 12 / 148,465 filed Apr. 18, 2008 that claims the benefit of U.S. Provisional Patent Application Ser. No. 60 / 927,111 filed May 1, 2007, both of which are incorporated by reference herein. This application is also a continuation-in-part o...

AI Technical Summary

Benefits of technology

[0006]Longitudinal connecting member assemblies according to the invention for use between at least two bone anchors provide dynamic, protected motion of the spine and may be extended to provide additional dynamic sections or more rigid support along an adjacent length of the spine, with fusion, if desired. A dynamic longitudinal connecting member assembly according to the invention has an inner segment or core made from a cord in the disclosed embodiment, the core being tensioned and fixed at either end of the assembly. The core is received by at least one hard, inelastic segment or sleeve, the sleeve attachable to at least one bone anchor. In some embodiments, the core is received by at least a pair of such sleeves, each sleeve attachable to a bone anchor. In some embodiments, the sleeve or sleeves slidingly receive the core. In other embodiments, the sleeve or sleeves are either fixed or left unfixed to the core by the surgeon, resulting in a connecting member having variable segmental stiffness along a length thereof. A variety of embodiments according to the invention are possible. Additional sleeves may be attached to additional bone anchors and cooperate with additional cut-to-length spacers with or without cooperating liners to create longer assemblies. Sleeves may also be extended to provide inelastic rod, bar or tube extensions, especially on one end. Spacers and optional cooperating liners with different measures of rigidity may be connected according to embodiments of the invention. Either rigid lengths or cords may be of greater or lesser lengths for attaching to one or a plurality of bone anchors. In some embodiments, longitudinal connecting member assemblies may be dynamically loaded before insertion, or after being operatively attached to at least the pair of bone anchors along a patient's spine by tensioning the inner core and at least partially compressing an end bumper and / or at least one spacer located between the bone anchors. Typically, the at least one spacer with or without an inner liner has some flexibility in bending, with the spacer / liner combination protecting and limiting flexing movement of the inner core and providing shear resistance.

Problems solved by technology

Shear forces are not well resisted by the typical cord and spacer stabilization systems.

Such tensioned cord and spacer systems may also cause facet joint compression during spinal movement, especially flexion.

The complex dynamic conditions associated with spinal movement create challenges for the design of elongate elastic longitudinal connecting members that exhibit an adequate fatigue strength to provide stabilization and protected motion of the spine, without fusion, and that allow for some natural movement of the portion of the spine being reinforced and supported by the elongate elastic or flexible connecting member.

A further challenge are situations in which a portion or length of the spine requires a more rigid stabilization, possibly including fusion, while another portion or length may be better supported by a more dynamic system that allows for protective movement.

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