Prosthesis (i.e. – artificial body members) – parts thereof – or ai – Implantable prosthesis – Bone
Reexamination Certificate
2000-12-11
2002-11-26
Isabella, David J. (Department: 3738)
Prosthesis (i.e., artificial body members), parts thereof, or ai
Implantable prosthesis
Bone
C128S898000, C606S064000
Reexamination Certificate
active
06485518
ABSTRACT:
TECHNICAL FIELD
The present invention relates to intervertebral support systems, and to systems for promoting intervertebral bone fusion.
BACKGROUND OF THE INVENTION
A variety of support assemblies currently exist which may be surgically implanted into a patient's intervertebral space so as to provide support between two (or more) adjacent vertebrae. Surgical implantation of such systems is typically used to provide support along the spinal column in cases where a portion of the patient's intervertebral anatomy has become diseased or destroyed. In addition, such support systems are also commonly used following a diskectomy, wherein the patient's intervertebral disk is surgically removed.
A drawback of these existing support systems is that they tend to be somewhat large and bulky, especially when these systems operate to provide support across a large portion of the patient's vertebral region. Being large and bulky, surgical implantation of these systems into a patient's vertebral region often creates a substantial amount of trauma to the patient.
Moreover, the installment of such large, bulky support systems into a patient's intervertebral space typically also requires a large amount of tissue to first be removed from the patient's intervertebral space so as to make way for the device.
Most commonly, existing support systems typically operate by inhibiting (normal) movement between the adjacent vertebrae, thereby holding these vertebrae at fixed positions relative to one another, with the mechanical body of the supporting structure providing the needed support along the patient's spinal column. Such supporting systems are typically made of stainless steel or titanium, and are designed to permanently remain within the patient's body.
SUMMARY OF THE INVENTION
The present invention provides a novel system of intervertebral support using a pair of bone allografts and a pair of facet screws.
An advantage of the present system is that, by inhibiting motion between two adjacent vertebrae, it facilitates natural bone fusion between these vertebrae. An advantage of the present invention's use of bone allografts (positioned between the vertebrae) is that these allografts will eventually be resorbed into the patient's body as bone growth between the immobilized vertebrae progresses. In contrast, existing mechanical (e.g.: metallic) intervertebral support structures simply remain as large permanent foreign structures within the patient's body. In preferred aspects, motion between the two adjacent vertebrae is specifically inhibited by the facet screws, as will be explained.
The present system advantageously provides intervertebral support at three locations in particular, with these three locations together forming a triangle. Specifically, each of the facet screws provides support at the facet joints (which are disposed at two symmetrically spaced apart locations at the posterior or rear of the vertebral column). The bone allografts are preferably positioned to provide support at an anterior (i.e. front), central location in the vertebral column. An advantage of the present three point (i.e.: triangular) support system is that support is provided in three perpendicular directions, (thereby providing support with respect to forward-backward bending, side-to-side bending and torsion of the spine). Furthermore, the present three point (i.e.: triangular) support system provides support at three separate locations which are spaced apart over a relatively large section of the patient's spinal column, providing enhanced stability. Specifically, the three sides of the present support triangle correspond to the locations of the two facet joints and the inter vertebral disc.
An important advantage of the present system is that it can be assembled in a minimally invasive percutaneous (preferably cannulated) surgical approach. In contrast, existing systems which provide support across a wide area of the patient's vertebrae typically comprise a single large integrated structure which substantially fills the patient's intervertebral space, and which is typically installed during a major invasive open surgical procedure. A further advantage of the present assembly is that since it comprises four separate components, (two bone allografts and two facet screws), these four components can be installed sequentially, with each of the components being installed through a cannula. In contrast, existing intervertebral support systems typically comprise a single large assembly which cannot be installed through a cannula.
In preferred aspects, the two bone allografts are positioned at an angle to one another. An advantage of having the bone allografts disposed angled to one another is that they provide support in perpendicular directions (i.e.: along two axes which are angled to one another). Specifically, in a preferred case using long, narrow shaped bone allografts, the bone allografts are preferably positioned with their long central longitudinal axes disposed at an angle to one another.
Since the present pair of bone allografts are positioned at an angle to one another, tall, narrow bone allografts can be used. Advantages of using a tall, narrow bone allograft include its fabrication requiring less bone material than would be used in conventionally manufactured allografts (which tend to be both flatter and wider, or large in diameter and length, e.g.: cylindrical). In addition, the present narrow bone allografts are more easily inserted into the patient through a (narrower) cannulated passageway.
In preferred aspects, two cannulae are used for positioning the pair of bone allografts, with the cannulae positioned at opposite posterolateral angles to one another. One cannula is used to position the first bone allograft and one cannula is used to position the second bone allograft. In this aspect, the angle between the bone allografts preferably corresponds to the angle between the cannulae. Accordingly, each of the bone allografts can be inserted directly into the patient's intervertebral space in a relatively straight path through the cannula(e) and into the patient's intervertebral space. As such, the present pair of bone allografts are easily positioned at a preferred angle to one another when initially deployed in a percutaneous posterolateral approach procedure. Moreover, in preferred aspects, the bone allografts can be inserted into the intervertebral space and then rotated by approximately 90° to achieve vertebral distraction, tensioning the annulus and opening the foramen, thereby decompressing the nerve root.
As stated above, in a preferred aspect of the present invention, both the bone allografts and the facet screws are positioned in the patient's spinal region through a posterolateral minimally invasive approach, which may optionally include a cannulated approach.
Prior to installing the present bone allografts and facet screws, a portion (or all) of the patient's intervertebral disk may be removed (i.e.: a “diskectomy” may be performed). Thereafter, the opposite vertebral endplates of the adjacent vertebrae may optionally be decorticated, which may produce a natural healing (bone fusion) response, if desired.
Thereafter, and in accordance with the present invention, the pair of bone allografts are positioned in the patient's intervertebral space. Preferably the bone allografts are inserted through posterolaterally introduced cannulae. In preferred aspects, two cannulae are used, with one positioning each bone allograft; however, the use of a single cannula to place the two bone allografts one after another (in opposite posterolateral approaches) is also contemplated. Additionally, the two bone allografts could be placed through one cannula positioned from only one posterolateral direction. Advantageously, each of the pair of bone allografts can be positioned (i.e.: inserted into the intervertebral space) through a separate cannula with the posterolateral angle at which the cannulae are disposed cor
Ahlgren Dan
Cornwall Bryan
Marino James F.
Wooley Troy
NuVasive
Spangler Jonathan
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