Surgery – Instruments – Internal pressure applicator
Reexamination Certificate
1999-09-30
2002-08-20
Milano, Michael J. (Department: 3731)
Surgery
Instruments
Internal pressure applicator
C606S064000, C606S185000
Reexamination Certificate
active
06436119
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a surgical device for dilating an opening formed in a bodily tissue structure. More particularly, it relates to a hand-held instrument configured to provide controlled dilation of an opening in a bodily tissue structure, such as an anulus of a spinal disc.
The vertebral spine is the axis of the skeleton upon which all of the body parts “hang”. In humans, the normal spine has seven cervical, twelve thoracic and five lumbar segments. The lumbar segments sit upon a sacrum, which then attaches to a pelvis, in turn supported by hip and leg bones. The bony vertebral bodies of the spine are separated by intervertebral discs, which act as joints, but allow known degrees of flexion, extension, lateral bending and axial rotation.
The typical vertebra has a thick interior bone mass called the vertebral body, and a neural (vertebral) arch that arises from a posterior surface of the vertebral body. Each narrow arch combines with the posterior surface of the vertebral body and encloses a vertebral foramen. The vertebral foramina of adjacent vertebrae are aligned to form a vertebral canal, through which the spinal sac, cord and nerve rootlets pass. The portion of the neural arch that extends posteriorly and acts to protect a posterior side of the spinal cord is known as the lamina. Projecting from the posterior region of the neural arch is a spinous process. The central portions of adjacent vertebrae are separated and supported by an intervertebral disc.
The intervertebral disc primarily serves as a mechanical cushion between the vertebral bones, permitting controlled motions within vertebral segments of the axial skeleton. The normal disc is a unique, mixed structure, comprised of three component tissues: The nucleus pulposus (“nucleus”), the anulus fibrosus (“anulus”), and two opposing vertebral end plates. The two vertebral end plates are each composed of thin cartilage overlying a thin layer of hard, cortical bone which attaches to the spongy, richly vascular, cancellous bone of the vertebral body. The end plates thus serve to attach adjacent vertebrae to the disc. In other words, a transitional zone is created by the end plates between the malleable disc and the bony vertebrae.
The anulus of the disc is a tough, outer fibrous ring that binds together adjacent vertebrae. This fibrous portion, which is much like a laminated automobile tire, is generally about 10 to 15 millimeters in height and about 15 to 20 millimeters in thickness. The fibers of the anulus consist of 15 to 20 overlapping multiple plies, and are inserted into the superior and inferior vertebral bodies at roughly a 30 degree angle in both directions. This configuration particularly resists torsion, as about half of the angulated fibers will tighten when the vertebrae rotate in either direction, relative to each other. The laminated plies are less firmly attached to each other.
Immersed within the anulus, positioned much like the liquid core of a golf ball, is the nucleus. The anulus and opposing end plates maintain a relative position of the nucleus in what can be defined as a nucleus cavity. The healthy nucleus is largely a gel-like substance having a high water content, and similar to air in a tire, serves to keep the anulus tight yet flexible. The nucleus-gel moves slightly within the anulus when force is exerted on the adjacent vertebrae with bending, lifting, etc.
The spinal disc may be displaced or damaged due to trauma or a disease process. A disc herniation occurs when the anulus fibers are weakened or torn and the inner tissue of the nucleus becomes permanently bulged, distended, or extruded out of its normal, internal anular confines. The mass of a herniated or “slipped” nucleus can compress a spinal nerve, resulting in leg pain, loss of muscle control, or even paralysis. Alternatively, with discal degeneration, the nucleus loses its water binding ability and deflates, as though the air had been let out of a tire. Subsequently, the height of the nucleus decreases, causing the anulus to buckle in areas where the laminated plies are loosely bonded. As these overlapping laminated plies of the anulus begin to buckle and separate, either circumferential or radial anular tears may occur, which may contribute to persistent and disabling back pain. Adjacent, ancillary spinal facet joints will also be forced into an overriding position, which may create additional back pain.
Whenever the nucleus tissue is herniated or removed by surgery, the disc space will narrow and may lose much of its normal stability. In many cases, to alleviate pain from degenerated or herniated discs, the nucleus is removed and the two adjacent vertebrae surgically fused together. While this treatment alleviates the pain, all discal motion is lost in the fused segment. Ultimately, this procedure places greater stress on the discs adjacent the fused segment as they compensate for the lack of motion, perhaps leading to premature degeneration of those adjacent discs. A more desirable solution entails replacing in part or as a whole the damaged nucleus with a suitable prosthesis having the ability to complement the normal height and motion of the disc while stimulating the natural disc physiology.
The first prostheses embodied a wide variety of ideas, such as ball bearings, springs, metal spikes and other perceived aids. These prosthetic discs were designed to replace the entire intervertebral disc space and were large and rigid. Beyond the questionable efficacy of these devices is the inherent difficulties encountered during implantation. Due to their size and inflexibility, these first generation devices require an anterior implantation approach as the barriers presented by the lamina and, more importantly, the spinal cord and nerve rootlets during posterior implantation, could not be avoided. Recently, smaller and more flexible prosthetic nucleus devices have been developed. With the reduction in prosthesis size, the ability to work around the spinal cord and nerve rootlets during posterior implantation has become possible.
Generally speaking, these reduced size prostheses are intended to serve as a replacement for the natural nucleus. In other words, the anulus and end plates remain intact, and the prosthesis is implanted within the nucleus cavity. Assuming that anulus integrity has not been overly compromised and that internal, lateral forces are minimized, the anulus will subsequently heal, resulting in a near-normal disc function. To this end, a number of different prosthetic nucleus designs have been developed. A common concern associated with these designs is minimizing stress placed on the anulus during implantation. In order to implant a prosthesis within the nucleus cavity, an appropriately sized passageway must be provided through the anulus. Obviously, reducing the overall size of the passageway minimizes resulting anulus trauma. With this in mind, two general design techniques have been identified for reducing the requisite anulus opening size. First, the prosthesis may be configured to increase from a relatively small size prior to implant, to a larger size following implant. With this approach, the reduced, pre-implant size of the prosthesis minimizes the requisite passageway size. Alternatively, the prosthesis may include several independent, relatively small portions, each of which are implanted through a correspondingly small passageway in the anulus. It should be understood that so long as it is minimized, “trauma” resulting from formation of the passageway is in no way permanent. Instead, the anulus tissue will regenerate, repairing the passageway.
While the particular prosthetic nucleus design selected has a distinct affect on resulting anulus damage, an equally important constraint is actual formation of the opening or passageway through the anulus. One technique entails complete removal of a plug of tissue from the anulus via an incision created by a scalpel, punch or similar tool. Entire removal of an anulus segment is highly traumatic, and limits the ability of th
Erb Steven J.
Norton Britt
Dicke, Billig & Czaja P.A.
Milano Michael J.
Raymedica, Inc.
Woo Julian W.
LandOfFree
Adjustable surgical dilator does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Adjustable surgical dilator, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Adjustable surgical dilator will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2949328