Patent Application
20090112217
1. Field of the Invention
The present invention relates to implant insertion devices, such as for orthopaedic devices and more particularly to implant insertion devices for spinal implants.
2. Related Art
Devices for insertion of implants are known. U.S. Pat. No. 6,066,174 and U.S. Pat. No. 5,782,830 describe the use of a grabbing element which is integral to an insertion handle. A movable sleeve slides over the neck of the grabbing element. Through the use of interfering tapers, the grabbing element increases its grip on vertebral body spacer.
U.S. Pat. No. 6,159,215 describes the Acromed Keystone Inserter. This device also makes use of interfering tapers to generate a grip on a vertebral body spacer. In this case, the sleeve is held fixed to a front handle portion and the grabbing element is retracted using a rear handle portion. The rear handle is connected to the grabbing element so as to create a mechanical advantage in retracting it and consequently creating a grip on the implant.
U.S. Pat. No. 6,319,257B1 describes the use of a drive thread to create a mechanical advantage on the grabbing element. The grip is generated using interfering tapers.
a-d depict a preferred embodiment of this invention.
a-b depict an alternate and more general embodiment of this invention.
a-c depict interactive aspects of the housing with the grabber tips for a preferred embodiment of the invention.
One embodiment of this invention is directed toward a device for inserting an implant comprising:
Another embodiment of this invention is directed toward a sterile implant system contained in a sterile package comprising:
Yet another embodiment relates to a method for manufacture of a sterile implant system comprising:
Preferably, the inserter is made of a radiolucent material.
The present invention is a device for inserting a spinal implant. More specifically, this device is intended for use with artificial discs.
a-d show inserting device 1 grasping an implant 10. Device 1 comprises housing 30, shaft 20 comprising grasping tips 22 located at the distal end of shaft 20 and handle 24 located at the proximal end 24 as shown in
The inserting device can be packaged with the implant in the configuration shown in
In use, inserting device 1 and implant 10 are first removed from sterile packaging. Holding the handle 24, the implant 10 is inserted into the cleared space of implantation. To detach the grabbing tips from the implant, the handle 24 is moved toward grip 34. The intended technique for release of the disc is analogous to depressing the plunger on a syringe.
An alternate embodiment for the present invention is shown in
a-c show a preferred feature of the device of this invention. This feature is directed to a dual tapered housing at the housing's distal end and corresponding dual tapered grasping tips. This feature allows for large mechanical advantage without the need for large axial travel of the gripping tips with respect to the housing whereas the prior art makes use of a single taper.
Referring to
The different positions involved in securing an implant are described below, namely the interaction of the grasping tips 22 with the housing opening 32.
a shows the open position of the device wherein the housing shaft 20 is fully extended by the user (by urging the handle toward the grip) thereby permitting the grasping tips 22 to open. This position is used prior to grasping and releasing the implant.
b shows the gripping or grasping position of the device wherein the handle is partially released and compressed spring 40 causes the housing 32 to move toward the grasping tips 22. The end of the housing 32 encounters the first steep taper 22a on the neck of the grasping tips 22. The grasping tips 22 close quickly with little change in housing 32 position/travel. The steeper taper angle of 22a provides less mechanical advantage in terms of closing the grasping tips 22 but, during this phase, the grasping tips 22 are not in firm contact with the implant and therefore little closing force is required.
c shows the gripping or grasping phase, wherein the grasping tips 22 are in firm contact with the implant. The neck of the housing 32 encounters the shallow taper 22b on the grasping tips 22. This shallow taper 22b allows a relatively weak spring to be used in generating the necessary forces to securely hold the implant. A weak spring allows the surgeon to move the housing (with respect to the grasping tips) without the need for mechanical advantage. This may reduce the complexity of the device.
It should be noted that if a single shallow taper were used, the amount of handle/spring travel would be excessively large. Therefore, the initial steep taper 22a is used to bring the grabber tips in contact with the implant. The shallow taper 22b engages only when a high compressive force is required to secure the implant.
In yet another embodiment, the invention is directed toward an implant system comprising an implant and an implant inserter. The system preferably is sterile and packaged sterile.
While the inserter may be made of any material of sufficient strength and rigidity suitable for medical use, a preferred embodiment includes the advantage or convenience of having an implant provided with a radiolucent inserter. These advantages include the ability to more precisely insert an implant wherein the radiolucent nature of the inserter does not obscure placement during fluoroscopic imaging or radiographic imaging (i.e., no need to remove the inserter as with conventional metal inserters); less likely to result in damage to the implant as radiolucent materials are predominately plastic; lightweight as compared to conventional metal inserters; and can be made disposable due to the relatively lower cost of injection molded components.
The inserter components may be made by injection molding techniques known in the art. Thus each element of the inserter, e.g., in referring to
Thus in a preferred embodiment, all of the components of the inserter are desirably made of radiolucent materials which are materials well known in the art and have the characteristics of being relatively penetrable by x-rays and other forms of radiation. It should be understood, however, that there may be embodiments wherein the user will only require the part of the inserter that will find itself in a fluoroscopic or radiographic field to be in made of a radiolucent material. Radiolucent materials allow for fluoroscopic or radiographic viewing which facilitates the precise placement of the implant, relatively unobscured as compared with radiopaque materials such as metals. Examples of suitable radiolucent materials include plastics and plastic composites. These materials are generally easy to extrude, well suited for compression molding techniques, and easily used in injection molding techniques. The plastic composites may include a reinforcement material for structural strength or rigidity. Such reinforcement materials include carbon fiber, glass, or fiberglass. The plastics can be thermoset or thermoplastic in nature.
For instances where the inserter will be reused by the hospital, the radiolucent material is preferably one that can be subjected to standard hospital sterilization procedures without substantial degradation. Polymers, copolymers and composites may be used. A heat resistant thermoplastic such as RADEL® polyarylethersulfone (PAES) may be used since it is understood to be sterilizable in a steam autoclave. RADEL® PAES is understood to be available from Amoco Polymers, Inc. of Alpharetta, Ga., and from suppliers such as Piedmont Plastics, Inc. of Charlotte, N.C. It may be desirable to use a different material that is more radiolucent. At least some commercially available acetal copolymers can be used, such as DELRIN® material available from E.I. DuPont de Nemours and Co. of Wilmington, Del. and CELCON® polyoxymethylene available from Celanese Corporation through Ticona-US of Summit, N.J. Also useful are acrylonitrile-butadiene-styrene (ABS) copolymers. In addition, aluminum can be used for some of the radiolucent materials. In some instances, the radiolucent material may be made of anodized aluminum. When hollow parts such a housing 30 are used as they should be adequately radiolucent. It should be understood that the present invention is not limited to any particular radiolucent material or to any particular degree of radiolucency unless expressly called for in the claims. Generally, use of the term “radiolucent” is intended herein to include any material that will allow the surgeon to view anatomic landmarks either fluoroscopically or radiographically.
Preferred radiolucent materials include RADEL® polyarylethersulfones, Delrin® acetal copolymers, polycarbonates, nylon, and acrylonitrile-butadiene-styrene (ABS) copolymers.
Example of implants that can be used with the inserters of this invention include spinal implants and other orthopaedic implants. Example of suitable spinal implants include vertebral body spacers (fusion cages and bone grafts), vertebral body replacements, and artificial discs. Suitable orthopaedic implants include bone grafts and bioabsorbable implants comprising bone anchors and screws.
Another embodiment of this invention is directed toward a sterile implant system contained in a sterile package comprising:
Yet another embodiment relates to a method for manufacture of a sterile implant system comprising:
It should be understood that the foregoing disclosure and description of the present invention are illustrative and explanatory thereof and various changes in the size, shape and materials as well as in the description of the preferred embodiment may be made without departing from the spirit of the invention.
