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 is a continuation of U.S. patent application Ser. No. 12 / 802,849, filed Jun. 15, 2010. Application Ser. No. 12 / 802,849 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. This application is also a continuation-in-part of U.S. patent application Ser. No. 12 / 221,442 filed Aug. 1, 2008. All of which are incorporated by reference herein.BACKGROUND OF THE INVENTION[0002]The present invention is directed to dynamic fixation assemblies for use in bone surgery, particularly spinal surgery, and in particular to longitudinal connecting members and cooperating bone anchors or fasteners for such assemblies, the connecting members being attached to at least two bone anchors.[0003]Historically, it has been common ...

AI Technical Summary

Benefits of technology

[0007]An object of the invention is to provide a lightweight, reduced volume, low profile assemblies for use with at least two bone anchors. Furthermore, it is an object of the invention to provide apparatus and methods that are easy to use and especially adapted for the intended use thereof and wherein the apparatus are comparatively inexpensive to make and suitable for use.

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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