Prosthesis (i.e. – artificial body members) – parts thereof – or ai – Implantable prosthesis – Bone
Reexamination Certificate
1997-09-05
2001-06-19
Snow, Bruce (Department: 3738)
Prosthesis (i.e., artificial body members), parts thereof, or ai
Implantable prosthesis
Bone
C606S064000
Reexamination Certificate
active
06248131
ABSTRACT:
TECHNICAL FIELD
The present invention relates to methods, apparatuses, materials and systems for the repair of movable and mixed articulating joints in the body.
BACKGROUND OF THE INVENTION
The joints of the body can be classified as between those that provide immovable articulations (synarthroidal), mixed articulations (amphiarthroidal), and movable articulations (diarthroidal). The ability of amphiarthroidal and diarthroidal joints to provide effective and pain-free articulation, and/or to serve their weight-bearing function, is generally dependent on the presence of intact, healthy fibrocartilage within the joint.
In an amphiarthroidal joint such as the lumbar joint of the back, the vertebra are separated by an intervertebral disc formed of fibrocartilage. More particularly, the intervertebral disc is comprised of an outer annulus fibrosis formed of fibrocartilage. The annulus, in turn, surrounds and contains a more fluid material known as the nucleus pulposus. By virtue of its fluidity, the nucleus allows for both movement and weight-bearing energy transfer. In healthy, generally younger individuals, the annulus is intact and the nucleus pulposus remains quite fluid.
As people age, however, the annulus tends to thicken, desiccate, and become more rigid. The nucleus pulposus, in turn, becomes more viscous and less fluid and sometimes even dehydrates and contracts. The annulus also becomes susceptible to fracturing or fissuring. These fractures tend to occur all around the circumference of the annulus, and can extend from both the outside of the annulus inward, and from the interior outward. Occasionally, a fissure from the outside will meet a fissure from the inside and will result in a complete rent through the annulus fibrosis. In a situation like this, the nucleus pulposus may extrude out through the intervertebral disc. The extruded material, in turn, can impinge on the spinal cord or on the spinal nerve rootlets as they exit through the intervertebral foramen, resulting in the symptoms associated with the classic “ruptured disc”.
The current surgical approach to treating a degenerated intervertebral disc generally involves the process of microdiscectomy, in which the site is accessed and the protruded material is removed. This often produces significant relief, provided it is a fairly minor, or mild, localized disc protrusion. In such a procedure a small incision is made, through which the disc is visualized. The area of protruded material is removed, thus decompressing the nerve rootlet that has been impinged on by the extruded material.
In more severe situations, however, the annulus fibrosis becomes degenerated to the point where very little disc space remains, and much of the nucleus pulposus is either contracted or has been extruded. Regional osteophytes can also develop around these areas. The combination of the extruded material and the osteophytes, together with the narrowing of the intervertebral disc space produces a marked narrowing of the intervertebral foramen and impingement on the spinal nerve rootlet as it exits the canal. This is the classical situation that results in radicular pain with axial loading.
When this occurs it becomes necessary to reestablish the intervertebral space. The current approach to this more severe situation is a lumbar laminectomy (to decompress the nerve rootlet) with fusion of the disc space. The bony lamina is removed to decompress the intervertebral foramina and the bone graft is taken from the anterior iliac crest and attached from one vertebrae body to the next. The resulting fusion will maintain stability at that point and also help maintain the separation of the vertebrae.
Recent advances in this technology have been developed by such companies as Spine-Tech, Minneapolis, Minn., which involves the use of a titanium alloy cylinder. The cylinder is screwed into the intervertebral space to assure the stability of the spacing until a fully bony ankylosis can be obtained. The cylinders are packed with bone and are fenestrated so that the packed bone can grow out into the adjacent vertebrae and solidify the fusion. To date, however, clinical results on the long-term follow up of these patients are not available and the efficacy is still in doubt with many spine surgeons.
It would therefore be particularly useful to be able to repair such injuries in a manner that avoids invasive surgical procedures and the problems associated therewith.
SUMMARY OF THE INVENTION
The present invention provides a method and related materials and apparatus for using minimally invasive means to repair (e.g., reconstruct) tissue such as fibrocartilage, and particularly fibrocartilage associated with diarthroidal and amphiarthroidal joints. The method involves the use of minimally invasive means to access and prepare damaged or diseased fibrocartilage within the body, and to then deliver a curable biomaterial to the prepared site, and to cure the biomaterial in situ in order to repair the fibrocartilage. The cured biomaterial provides an optimal combination of such properties as deliverability and curability, as well as biocompatability, biostability, and such physical performance characteristics as strength, elasticity, and lubricity.
In one embodiment, the method comprises the steps of:
a) using minimally invasive means to remove damaged or diseased fibrocartilage from a diarthroidal or amphiarthroidal joint, and to create a mold capable of containing curable biomaterial in a desired position within the joint,
b) providing one or more curable biomaterials to the structure previously occupied by the removed fibrocartilage, and
c) curing the biomaterials in order to provide a replacement for the fibrocartilage.
The mold created within the joint is preferably of sufficient shape and dimensions to allow the resulting cured biomaterial to replace or mimic the structure and function of the removed fibrocartilage. The mold can be formed of synthetic and/or natural materials, including those that are provided exogenously and those provided by the remaining natural tissues. The mold can either be removed from the site, upon curing of the biomaterial, or is sufficiently biocompatible to allow it to remain in position.
The mold can take the form of either a positive and/or negative mold. For instance, the mold can take the form of an outer shell, capable of retaining biomaterial within its interior cavity. Optionally, the mold can also take any other suitable form, including to serve as an interior core (e.g., to create a doughnut shaped biomaterial), or as an anchor point for the stable attachment and localization of delivered biomaterial.
In a particularly preferred embodiment, the method is used to repair an amphiarthroidal joint such as an intervertebral disc and comprises the steps of:
a) using microsurgical techniques to perform a discectomy while preserving an outer annular shell,
b) providing one or more curable biomaterials to the interior of the annular shell, and
c) curing the biomaterials in order to provide a replacement disc.
In such a preferred embodiment, the distraction of the disc space is accomplished by means of a suitable distraction means, such as an inflatable, yet rigid, balloon or bladder. The balloon can be delivered in deflated form to the interior of the annulus and there inflated in order to distract the disc space and provide a region for the delivery of biomaterial. The balloon is preferably of sufficient strength and suitable dimensions to distract the space to a desired extent and for a period long enough for the biomaterial to be delivered and cured.
In other aspects, the invention provides biomaterials, including polymer systems, useful for performing such a method, as well as methods of preparing and using such biomaterials. In yet further aspects, the invention provides a diarthroidal or amphiarthroidal joint having interposed therein a biomaterial that has been cured in situ.
DETAILED DESCRIPTION
Applicants have discovered a means for producing spinal separation to achieve pain relief, which involves the step of interpos
Baker Matthew W.
Bourgeault Craig A.
Felt Jeffrey C.
Advanced Bio Surfaces, Inc.
Fredrikson & Byron , P.A.
Snow Bruce
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