Dynamic spinal stabilization system

Abstract

A dynamic stabilization system includes a stabilization element, such as a spinal rod, a plurality of bone anchors, such as bone bolts, and a like plurality of connectors for connecting the bolts to the spinal rod. At least some of the connectors include a flexible element between the bone anchor and the rod and an adjustment element for adjusting the flexibility of the flexible element, to thereby adjust the dynamic flexibility between the rod and the bone anchor. In one embodiment, the flexible element is a flexible bearing element of a rod end bearing.

Description

[0001] The present invention relates to spinal implant systems, and particularly to systems for stabilization of the spine. The invention provides a dynamic stabilization system that permits limited relative movement between the instrumented vertebrae and the stabilization system. [0002] In the past, the principal protocol for the treatment of the spine has been rigid fixation combined with fusion of the affected vertebral body or intervertebral disc. Arthrodesis, as this approach is known, has been achieved with a variety of rigid fixation elements, such as spinal rods or plates that are rigidly fixed to a vertebra using bone screws, bone bolts and spinal hooks. However, spinal fusion has been recognized to have limitations in the treatment of disc degeneration, especially in the earlier stages of the degeneration where it may be unnecessary to eliminate motion of the spinal motion segments. [0003] Clinical studies suggest that cells of the intervertebral disc respond favorably to ...

AI Technical Summary

Benefits of technology

[0009] The DSS System employs still another approach by including a spring element connected to pedicle screws. The spring element is contained within a polyurethane tube to prevent tissue ingrowth. Finally, some systems utilize a rigid member, such as a spinal plate, spanning between vertebrae. The flexible stabilization feature is incorporated into the interface between the pedicle screw and the rigid member, such as through a flexible washer or a spherical screw-plate interface.

[0012] In response to these limitations of the prior art, the present invention contemplates a dynamic stabilization system that relies upon flexible elements interposed between a bone anchor, such as a bone screw or spinal hook and a stabilization member, such as a rod or a plate. Furthermore, the present invention incorporates features that allow “fine tuning” of the dynamic flexibility of the total construct during the initial spinal instrumentation surgery, and even later during a revision procedure.

[0022] One benefit of the present invention is that it can be readily adapted to existing stabilization constructs and can be integrated with known constructs that are fixed or that permit limited micro-motion. Another benefit is that the invention provides the orthopaedic surgeon with a great deal of flexibility in the initial surgical procedure or in a subsequent revision procedure.

Problems solved by technology

However, spinal fusion has been recognized to have limitations in the treatment of disc degeneration, especially in the earlier stages of the degeneration where it may be unnecessary to eliminate motion of the spinal motion segments.

Consequently, many of these systems are susceptible to over-loading the disc annulus or are, by necessity, unduly restrictive with respect to motion of the spinal segment.

Moreover, these prior systems are not capable of altering the stiffness of a segment in various loading modes (e.g., flexion / extension, compression, lateral bending and axial rotation).

Furthermore, these early approaches to arthrodesis do not allow selection of where, or at which motion segment, dynamic movement is permitted.

Finally, no system exists that can readily convert to and from a soft stabilization to a more rigid or completely rigid system.

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