Surgery – Instruments – Electrode guide means
Reexamination Certificate
1999-04-29
2001-04-03
Jastrzab, Jeffrey R. (Department: 3762)
Surgery
Instruments
Electrode guide means
C604S175000, C607S116000
Reexamination Certificate
active
06210417
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an apparatus for securing implanted medical devices and more particularly to an apparatus for securing implanted medical devices such as electrical stimulation leads or catheters, or a combination thereof, within a cranial burr hole and for varying the functional location of the leads or catheters within the burr hole.
2. Description of the Related Art
Medical procedures involving access to the brain through a burr hole in the skull are under increasing use. Two such procedures are electrical stimulation of the brain for such purposes as relief of chronic pain and treatment of movement disorders, and the use of parenchymal catheters for infusing pharmaceutical agents. A typical electrical brain stimulation system comprises generally a pulse generator operatively connected to the brain by a lead having at its distal end at least one electrode designed to be implanted within the brain, and having at its proximal end a connector assembly designed to connect to the pulse generator. Use of a parenchymal catheter generally involves the insertion of a catheter within the brain to dispense pharmaceutical agents at a specific targeted location.
An important aspect of these procedures, and of any other such procedures that involve instrument access to the brain through a burr hole, is the precision with which any such inserted stimulation devices are placed. As can be appreciated, the functional location of the inserted stimulation device is of critical importance and once an inserted device is properly positioned, it is equally important that the device not be moved. Even one millimeter of travel of a properly positioned stimulation device may cause unsatisfactory results or, in some cases, severe injury to the brain. Accordingly, reliable methods and apparatus for locating and fixing the positioned stimulation device in the cranium burr hole are necessary.
Previous designs of systems for securing a positioned device within a burr hole have a number of drawbacks. U.S. Pat. No. 4,328,813 issued to Ray, incorporated herein by reference, discloses a burr hole ring and cap arrangement in which the cap is positioned so as to trap a positioned electrical stimulation lead between the ring and cap by friction. That arrangement involves securing the lead off center from the burr hole in a manner such that during installation of the anchoring cap the lead is secured in place. The lead, however, often needs to be manually supported in place while the anchoring cap is being installed. The lead is thus susceptible to inadvertent movement by the physician during the cap installation period. Further, during the interaction of the cap and ring, the lip of the cap tends to pull on the lead dislodging the lead from the targeted stimulation area.
Other current burr hole rings and caps force the lead body to the center of the burr hole ring and, due to the design, to the center of the burr hole itself. Problems occur if the burr hole is not centered on the desired projection path of the lead. The burr hole ring will force the lead body to the center of the burr hole ring, which is offset from the desired lead projection path, thereby placing a load on the lead body tip, which is implanted at the targeted stimulation area in the brain. The load on the lead body tip may force the electrodes away from the targeted stimulation area or it may place an undesirable amount of pressure on the brain. The present invention is directed to overcoming the disadvantages of the foregoing systems.
SUMMARY OF THE INVENTION
As explained in more detail below, the present invention overcomes the above-noted and other shortcomings of prior burr hole anchoring devices.
The present invention preferably comprises an apparatus fixing a lead at a cranial burr hole. One significant feature of the invention anchors the lead before the placement of a cap over the burr hole, thereby reducing the possibility of lead movement. This feature can be implanted directly into a cranium burr hole or it can be installed into a standard burr hole ring which is then implanted into the burr hole. A second significant feature of the present invention functionally locates the lead within a standard burr hole ring, thereby improving the location of the lead at the targeted stimulation area and reducing the possibility of injury to the brain.
Briefly, the present invention comprises several embodiments, more fully discussed below. One embodiment generally incorporates a cylindrical sleeve and a plurality of springs mounted within the cylindrical sleeve. The lead is inserted through the cylindrical sleeve between the plurality of springs which retain the lead in a substantially fixed position relative to the cylindrical sleeve. If a burr hole ring is used and mounted in the cranium burr hole, the cylindrical sleeve and accompanying springs are inserted in the burr hole ring. The lead may then be inserted into the sleeve between the springs. The invention accepts the lead and fixes the lead in the desired position before the burr ring cap is placed over the burr hole ring. If a smaller diameter burr hole is desired, for example, 3 or 4 millimeters, the present invention may be used as a stand-alone anchoring device without a burr hole ring, which typically cannot accommodate the smaller size burr holes. With this embodiment, the cylindrical sleeve may have a threaded, serrated, or knurled outer wall which allows the sleeve to be retained in the burr hole. The lead may then be inserted into the sleeve between the springs.
Another embodiment of the present invention comprises generally a rotatable disk having a slot. Received within the rotatable disk is a sleeve defining a second slot for capturing and fixing the lead relative to the rotatable disk. The previously identified sleeve and spring assembly may also be mounted in the rotatable disk. Significantly, the rotatable disk permits the implanted lead to be positioned at any location within the burr hole ring and thus anywhere within the burr hole. This functional positioning of the lead within the burr hole compensates for any offset between the burr hole and the desired projection path of the lead. Consequently, with these preferred embodiments, the lead may be located and maintained in a fixed position relative to the brain to allow electrical stimulation and/or drug infusion to the targeted area with improved precision and accuracy.
Examples of the more important features of this invention have been broadly outlined above in order that the detailed description that follows may be better understood and so that contributions which this invention provides to the art may be better appreciated. There are, of course, additional features of the invention which will be described herein and which will be included within the subject matter of the claims appended hereto.
REFERENCES:
patent: 4328813 (1982-05-01), Ray
patent: 4350159 (1982-09-01), Gouda
patent: 4805634 (1989-02-01), Ulrich et al.
patent: 5464446 (1995-11-01), Dreessen et al.
patent: 5662600 (1997-09-01), Watson et al.
patent: 5865842 (1999-02-01), Knuth et al.
patent: 5927277 (1999-07-01), Baudino et al.
patent: 6044304 (2000-03-01), Baudino
Baudino Michael D.
Cross, Jr. Thomas E.
Banner & Witcoff , Ltd.
Jastrzab Jeffrey R.
Medtronic Inc.
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