Systems and methods for posterior dynamic stabilization of the spine

Abstract

Devices, systems and methods for dynamically stabilizing the spine are provided. The devices include an expandable spacer having an undeployed configuration and a deployed configuration, wherein the spacer has axial and radial dimensions for positioning between the spinous processes of adjacent vertebrae. The systems include one or more spacers and a mechanical actuation means for delivering and deploying the spacer. The methods involve the implantation of one or more spacers within the interspinous space.

Description

FIELD OF THE INVENTION [0001] The present invention is directed towards the treatment of spinal disorders and pain. More particularly, the present invention is directed to systems and methods of treating the spine, which eliminate pain and enable spinal motion, which effectively mimics that of a normally functioning spine. BACKGROUND OF THE INVENTION [0002]FIG. 1 illustrates a portion of the human spine having a superior vertebra 2 and an inferior vertebra 4, with an intervertebral disc 6 located in between the two vertebral bodies. The superior vertebra 2 has superior facet joints 8a and 8b, inferior facet joints 13a and 13b, and spinous process 25. Pedicles 3a and 3b interconnect the respective superior facet joints 8a, 8b to the vertebral body 2. Extending laterally from superior facet joints 8a, 8b are transverse processes 7a and 7b, respectively. Extending between each inferior facet joints 13a and 13b and the spinous process 25 are laminal zones 5a and 5b, respectively. Simila...

AI Technical Summary

Benefits of technology

[0015] In certain embodiments, the expandable member is a helical body having a varying cross-section along its longitudinal axis, such that compression, squeezing, or other longitudinal translation of the helical body causes the helical body to expand in at least one direction. When placed between two spinous processes, the expansion allows support and stabilization of the processes relative to each other.

[0017] The stabilizing devices may be configured to stay stationary in the implant site on their own (or “float”) or may be further fixed or anchored to surrounding tissue, e.g., bone (e.g., spinous processes, vertebrae), muscle, ligaments or other soft tissue, to ensure against migration of the implant. In their final deployed state, the stabilizing devices may be flexible to allow some degree of extension of the spine or may otherwise be rigid so as prevent extension altogether. Optionally, the devices may include one or more markers on a surface of the expandable member to facilitate fluoroscopic imaging.

Problems solved by technology

Traumatic, inflammatory, metabolic, synovial, neoplastic and degenerative disorders of the spine can produce debilitating pain that can affect a spinal motion segment's ability to properly function.

Often, a disorder in one location or spinal component can lead to eventual deterioration or disorder, and ultimately, pain in the other.

While spine fusion generally helps to eliminate certain types of pain, it has been shown to decrease function by limiting the range of motion for patients in flexion, extension, rotation and lateral bending.

Furthermore, the fusion creates increased stresses on adjacent non-fused motion segments and accelerated degeneration of the motion segments.

Additionally, pseudarthrosis (resulting from an incomplete or ineffective fusion) may not provide the expected pain-relief for the patient.

Also, the device(s) used for fusion, whether artificial or biological, may migrate out of the fusion site creating significant new problems for the patient.

Unfortunately, the currently available artificial discs do not adequately address all of the mechanics of motion for the spinal column.

It has been found that the facet joints can also be a significant source of spinal disorders and debilitating pain.

Current interventions for the treatment of facet joint disorders have not been found to provide completely successful results.

Facetectomy (removal of the facet joints) may provide some pain relief; but as the facet joints help to support axial, torsional, and shear loads that act on the spinal column in addition to providing a sliding articulation and mechanism for load transmission, their removal inhibits natural spinal function.

Laminectomy (removal of the lamina, including the spinal arch and the spinous process) may also provide pain relief associated with facet joint disorders; however, the spine is made less stable and subject to hypermobility.

Problems with the facet joints can also complicate treatments associated with other portions of the spine.

In fact, contraindications for disc replacement include arthritic facet joints, absent facet joints, severe facet joint tropism, or otherwise deformed facet joints due to the inability of the artificial disc (when used with compromised or missing facet joints) to properly restore the natural biomechanics of the spinal motion segment.

While various attempts have been made at facet joint replacement, they have been inadequate.

This is due to the fact that prosthetic facet joints preserve existing bony structures and therefore do not address pathologies that affect facet joints themselves.

As the lamina is a very complex and highly variable anatomical structure, it is very difficult to design a prosthesis that provides reproducible positioning against the lamina to correctly locate the prosthetic facet joints.

In addition, when facet joint replacement involves complete removal and replacement of the natural facet joint, as disclosed in U.S. Pat. No. 6,579,319, the prosthesis is unlikely to endure the loads and cycling experienced by the vertebra.

Thus, the facet joint replacement may be subject to long-term displacement.

Furthermore, when facet joint disorders are accompanied by disease or trauma to other structures of a vertebra (such as the lamina, spinous process, and / or transverse processes) facet joint replacement is insufficient to treat the problem(s).

While this system is able to provide load sharing and restoration of disc height, because it is so rigid, it does not effective in preserving the natural motion of the spinal segment into which it is implanted.

Because these types of systems require the use of pedicle screws, implantation of the systems are often more invasive to implant than interspinous spacers.

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