Prosthesis (i.e. – artificial body members) – parts thereof – or ai – Implantable prosthesis – Bone
Reexamination Certificate
1999-05-26
2001-09-18
Smith, Jeffrey A. (Department: 3732)
Prosthesis (i.e., artificial body members), parts thereof, or ai
Implantable prosthesis
Bone
Reexamination Certificate
active
06290724
ABSTRACT:
TECHNICAL FIELD
The present invention relates to systems for separating and stabilizing adjacent vertebrae.
BACKGROUND OF THE INVENTION
Intervertebral spinal inserts are used to provide support and maintain normal distance between adjacent vertebrae in cases where a patient's vertebral discs have degenerated. Such degeneration can occur as a result of aging or trauma and typically results in pinched or damaged nerves between or proximal to the adjacent vertebrae. Moreover, such discal degeneration causes shifting of the loading along the patient's spinal column, which in turn further accelerates the vertebral degeneration.
Intervertebral inserts are typically used to reestablish normal intervertebral spacing, stabilize and reduce bone motion and, in conjunction with graft matter, to cause fusion between adjacent vertebral bodies.
A common problem with existing intervertebral inserts is that their insertion into the patient's spine is usually accomplished by invasive open surgical procedures. Such invasive surgery can be performed by entering either through the patient's back or through the abdomen. A major disadvantage of such invasive surgery is that it requires a considerable post-operative recovery time for the patient.
Another disadvantage is that, during such major surgery, the actual insertion of the intervertebral insert requires distraction of the adjacent vertebrae to first open a sufficiently large passage for the insertion of the insert therebetween. Such distraction is typically performed by dedicated instrumentation and invasive tools which must first enter the intervertebral space and then grip and hold apart the adjacent vertebrae.
A related disadvantage of current surgical methods of inserting intervertebral inserts is that they require cutting through, scarring and damaging either the posterior longitudinal ligament or the anterior longitudinal ligament, the facet joint capsules, interspinous ligaments and other paraspinal tissues. This reduces the amount of natural tension between the relevant vertebrae which reduces spinal column stability and may allow the inserts to move from their desired location.
An additional problem with the insertion of current intervertebral inserts is the requirement that portions of the adjacent vertebrae have to be drilled, chiseled away or otherwise removed to accommodate the particular geometric shape and orientation of the insert. Accordingly, in addition to the requirement of distracting the adjacent vertebrae, current systems typically also require drilling or chiseling away of the hard exterior surface of the vertebral endplates so that the insert can be received therein. This removal of the hard exterior endplate surface exposes the softer cancellous bone which is not sufficiently strong to bear the required load. Accordingly, the subsequent insertion of a typical metal cage-type insert into this softer cancellous portion of the vertebral bone requires the spinal load to be directed against a weaker supporting surface. A danger exists that such inserts may fail in their purpose of maintaining intervertebral spacing because they sink into softer bone.
Moreover, the shape of current inserts does not take advantage of the natural contoured shape of the adjacent vertebral surfaces such that an intervertebral insert can be provided which supports itself flush against the contour of the vertebral surfaces with the vertebrae being supported at a proper lordotic angle.
An additional problem with many current insert designs is that they often do not adequately promote or provide an opportunity for bone growth therethrough so as to firmly embed the insert within the spine over time.
SUMMARY OF THE INVENTION
The present invention provides methods for separating and stabilizing adjacent vertebrae as well as providing intervertebral inserts, systems and kits for use in performing these methods.
A method for separating and stabilizing adjacent vertebrae comprises introducing an insert between the vertebrae and rotating the insert to engage outwardly facing convexly curved camming surfaces thereon against the vertebrae thereby moving the vertebrae apart. As will be explained, an advantage of camming the vertebrae apart with such outwardly facing convexly curved camming surfaces is that side-to-side vertebral motion is minimized such that the adjacent vertebrae do not tend to move horizontally with respect to one another as they are cammed apart in a vertical direction.
In various preferred aspects of the invention, the insert can either be inserted temporarily (such as during a surgical procedure) or permanently (so as to provide long term intervertebral stabilization). In those aspects where the insert is to remain in position permanently, methods for anchoring the insert firmly between the adjacent vertebrae are provided. When the insert is rotated into position, it then supports the spinal load, and distracts the adjacent vertebrae. This tensions the intervertebral ligaments and can decompress neurological elements. Using the present methods, prior distraction of the adjacent vertebrae with dedicated instrumentation is either not required, or is substantially minimized.
In a preferred aspect, the insert is inserted into the patient's intervertebral space in a percutaneous, posterolateral fluoroscopically guided approach. Preferably, the posterolateral approach is made at an angle in the range of 35 to 90 degrees, and most preferably 45°, from the sagittal plane of the patient. Such an approach avoids and thus helps preserve the ligamentous structures which holds the vertebrae together, in particular, the anterior and posterior longitudinal ligaments, thereby providing additional stability to the spinal column during healing or fusion.
In further preferred aspects of the method, the insert is positioned through a percutaneous cannula having an oval, racetrack, or other non-symmetric cross-section. By aligning a major axis of the cross-section of the cannula in an orientation parallel to the intervertebral space between the adjacent vertebrae, the insert may be introduced in the desired orientation with the minor axis of the cross-section of the cannula spanning between the two adjacent vertebrae. Accordingly, in preferred aspects of the invention, the cannula is generally oval or racetrack-shaped in cross-section such that its cross-sectional area is substantially reduced from that of a generally circular cross-sectional cannula, reducing patient trauma and facilitating accurate placement of the insert into the patient's intervertebral space when the cannula is initially received into the patient.
Conveniently, the insert may be manipulated by an insertion tool which is removably attached to the posterior end of the insert. A torque wrench can be used in conjunction with the insertion tool to measure the amount of torque necessary to secure the insert into position. In addition, prior to introduction of the insert, an oval or racetrack shaped coring device can be used to cut a hole in the annulus of the disk as well as to remove osteophytes.
In one preferred aspect, the present insert is removable and is inserted only temporarily such that an increased intervertebral space can be provided allowing temporary increased surgical access therein, such as when performing a discectomy. In an alternative aspect, the insert is designed to be implanted permanently. In both aspects of the invention, the insert is introduced between adjacent vertebrae, preferably with minimal or no prior mechanical distraction, and rotated by about 90 degrees to establish increased intervertebral spacing by camming apart the adjacent vertebrae. If temporary, the insert has smooth flattened vertebral support surfaces so that it may be easily removed. If permanent, the insert has penetrating elements extending from flattened vertebral support surfaces, and the insert is firmly anchored into position by being rotated into position such that the penetrating elements extending therefrom are firmly embedded into the surfaces of the adjacen
NuVasive, Inc.
Smith Jeffrey A.
Townsend and Townsend / and Crew LLP
LandOfFree
Methods for separating and stabilizing adjacent vertebrae does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Methods for separating and stabilizing adjacent vertebrae, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Methods for separating and stabilizing adjacent vertebrae will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2485938