Adjustable medical lead fixation system

Abstract: There is disclosed an adjustable medical apparatus for anchoring a lead to a cranial burr hole. The apparatus comprises generally an anchoring plate 12 mounted to and over a cranial burr hole, an anchoring arm 14 pivotally mounted to the anchoring plate, and a resilient sleeve 16 mounted between the anchoring plate and the anchoring arm. The resilient sleeve defines an aperture 18 for receiving the lead. Once an implanted lead is inserted into the aperture in the resilient sleeve 16, the anchoring arm 14 is pivoted around the sleeve creating a clamping force on the resilient sleeve. The resilient sleeve in turn creates a clamping force on the lead body, thereby anchoring the lead relative to the anchoring apparatus and thus relative to the cranium. Significantly, the anchoring apparatus accommodates various sized lead bodies which are used within various sized burr holes.

Description: 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 to various sized cranial burr holes. Medical procedures involving access to the brain through a burr hole in the skull are under increasing use. One such procedure is electrical stimulation of the brain for such purposes as relief of chronic pain and treatment of movement disorders. 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. An important aspect of this procedure, 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. Accordingly, reliable methods and apparatus for stabilizing and fixing the positioned stimulation device in the cranial burr hole are necessary. Previous designs of systems for securing a positioned device within a burr hole have a number of drawbacks. U.S. Patent No. 4,328,813 issued to Ray, 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. The ring and cap arrangement in Ray, however, is limited by the size of the lead bodies which can be used within a single burr hole ring. Other known burr hole ring and cap assemblies have the same drawbacks. US 5,267,970 discloses a clamp or sleeve lock having a pair of sleeve holding members hinged together to open and close and to form a hollow cylindrical tube when in the closed position. US 5,026,352 discloses an adjustable flange for a trachestomy tube having two arms hingedly connected together. A single burr hole ring can only accommodate a limited size or range of sizes of the lead bodies. The present invention is directed to overcoming these disadvantages of the present burr hole ring and cap anchoring assemblies. As explained in more detail below, the present invention overcomes the above-noted and other shortcomings of prior burr hole anchoring devices by providing an adjustable medical apparatus for fixing a lead in a cranium burr hole comprising: an anchoring plate adapted to be mounted over the cranium burr hole, an inner sleeve mounted to the anchoring plate; and an anchoring arm having a pivot end pivotally mounted to the anchoring plate, and a free end opposite the pivot end, adapted to be fastened or fixed to the anchoring plate, thereby holding the inner sleeve in a clamped position. An important feature of the invention is that the disclosed anchoring apparatus may be used with various sized lead bodies which may be implanted in various sized burr holes. A second important aspect of the invention is that the disclosed device can be used with various sized burr holes. Thus, one anchoring device of the present invention will accommodate numerous lead bodies and burr holes of differing diameters. Briefly, the present invention generally comprises an anchoring plate, a pivotable anchoring arm, and a resilient inner sleeve. The resilient inner sleeve preferably defines a slit which extends along the longitudinal length of sleeve and an aperture for receiving various sized lead bodies. As assembled, the anchoring plate is fastened to the cranium. Pivotally attached to the anchoring plate is the anchoring arm. The anchoring plate and anchoring arm define an opening to receive the resilient inner sleeve. In use, a lead is inserted through the aperture of the resilient inner sleeve into the cranial burr hole. Once the lead is located along the proper track to the desired depth and location in the brain, the inner sleeve is positioned within the opening formed in the anchoring plate. The anchoring arm is then closed around the inner sleeve creating a uniform clamping force on the inner sleeve. The inner sleeve defining a longitudinal slit, in turn, permits the inner sleeve to close around the lead body, creating a uniform clamping force on the lead body, thereby anchoring the lead relative to the cranium. Significantly, the opening formed by the anchoring plate and arm, and the design of the inner sleeve, accommodate numerous lead bodies of varying diameters. Moreover, the present invention can be used with smaller leads in larger burr holes where the lead may be positioned off-center in the burr hole. Examples of the more important features of this invention have been broadly outlined above in order that the detailed description that follows (which is given by way of example only) 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. The preferred embodiments of the invention will be described in relation to the accompanying drawings. In the drawings, the following figures have the following general nature: Fig. 1 is a top plan view of an adjustable lead anchoring device according to the present invention. Fig. 2 is another top plan view of the invention of Fig. 1. Fig. 3 is a side view of the invention of Fig. 1. In the accompanying drawings, like reference numbers are used throughout the various figures for identical structures. Referring to Figs. 1-3, a preferred adjustable medical lead anchoring system is depicted. The preferred anchoring system 10 comprises generally an anchoring plate 12, an anchoring arm 14 and a resilient inner sleeve 16. The resilient inner sleeve defines an aperture 18 for receiving medical leads of varying diameters. As used herein, the term "lead" may refer to any elongate medical apparatus having an electrode providing electrical stimulation, or a parenchymal catheter for infusing pharmaceutical agents. The selection of one lead over another will depend on numerous factors such as the therapy being delivered. The selection of the burr hole size will depend on numerous factors including surgical preference. As most preferred, the aperture 18 accommodates lead bodies which fit within burr holes having varying diameters of up to 14 millimeters. The anchoring plate 12 is preferably a rigid flat plate anchored to the cranium through the use of mounting screws, not shown. As conventional, three mounting screws are used to stabilize and fix the plate 12 to the cranium. The anchoring plate 12 defines a plurality of mounting holes 22 for receiving the mounting screws. The plate 12 also defines a semi-circular opening 24 sized and shaped to receive the inner sleeve 16. That is, the opening 24 has a diameter slightly larger than the outer diameter of the sleeve 16 in its unsprung state. As depicted in plan view, the plate 12 has a preferably semi-circular shaped body with three anchoring legs 28 radially protruding outward from the semi-circular body. Located within each of the three anchoring legs are the mounting holes 22. As one can imagine, other similar means for anchoring the plate to the cranium may be used and are considered within the scope of the present invention. Pivotally mounted to the anchoring plate 12 is the anchoring arm 14. The anchoring arm 14 is pivotally mounted to the anchoring plate 12 by means of a pivot pin 30. The anchoring arm 14 is also a rigid flat plate. In plan view, the anchoring arm 14 is arcuate in shape and defines a mounting hole 22. The arcuate shaped anchoring arm forms a curve or radius 32 which is sized and shaped to match the contour of the inner sleeve 16. The anchoring plate and arm may be made of stainless steel, rigid plastic, or any other suitable rigid material. In use, once the inner sleeve 16 is positioned within the opening 24, the anchoring arm 14 is pivoted around the inner sleeve with the curve 32 contacting the inner sleeve 16. As the anchoring arm is further pivoted around the inner sleeve 16, the anchoring arm 14 and the anchoring plate 12 exert a clamping force on the exterior of the inner sleeve. As discussed in further detail below, the inner sleeve, which envelops the lead body, in turn, exerts a clamping force on the lead body, thereby stabilizing and fixing the lead relative to the anchoring plate and the cranium. Advantageously, prior to anchoring the plate 12 to the cranium, the lead may be positioned anywhere within the larger sized burr holes, to accommodate off-center lead tracks. The free end of the anchoring arm, opposite the pivot end, is then fixed or fastened to the anchoring plate, thereby holding the inner sleeve in the clamped position. The resilient inner sleeve 16 is positioned above the cranial burr hole and within the opening 24 of the anchoring plate 12. The inner sleeve further defines a cylindrical body having a slit 36 extending along the longitudinal length of the body. The slit 36 permits the radial expansion and contraction of the sleeve 16 to accommodate the various sized lead bodies. The cylindrical ends 38 of the sleeve 16 are angled to permit the sleeve to snap around the lead body. The inner sleeve 16 further defines the aperture 18 for receiving lead bodies of various diameters. As preferred, the sleeve 16 defines an unsprung outer diameter sized to fit within the opening 24. The inner sleeve may be made of rubber or other similar elastomeric material. As depicted in Fig. 3, the inner sleeve 16 may form around the top and bottom of the plate 12. That is, inner sleeve material may protrude radially outward on the bottom of the plate 12. This additional material, identified by item 17, serves as a seal to prevent leakage of cerebrospinal fluid (CSF). In addition, inner sleeve material may protrude radially outward on the top of the plate 12. This material, identified by item 19, forms a crown or radius to permit the lead to be bent over the plate 12. Radial grooves may be formed in this additional material to guide the lead in a radial direction away from the burr hole. Other shapes and designs of the inner sleeve which permit clamping around the lead body are contemplated . Once the lead is properly located and positioned within the cranial burr hole, the anchoring system 10 may be positioned around the lead anchoring the lead to the cranium. The method for anchoring the lead includes the following steps. First, the sleeve is pretooled or positioned within the opening 24 in the anchoring plate 12. Next, the anchoring system 10 is placed around the lead body, with the lead passing through the opening 24 in the sleeve, and lowered to the cranium. Then the anchoring arm 14 is pivoted around the sleeve closing the sleeve around the lead body. The anchoring device is then anchored, through the use of anchoring screws, to the cranium over the burr hole. Advantageously, the closure of the sleeve around the lead creates a clamping force on the lead body fixing the lead in the desired position.

Claims: An adjustable medical apparatus for fixing a lead in a cranium burr hole comprising: an anchoring plate (12) adapted to be mounted over the cranium burr hole, an inner sleeve (16) mounted to the anchoring plate; and an anchoring arm (14) having a pivot end pivotally mounted to the anchoring plate (12), and a free end opposite the pivot end, adapted to be fastened or fixed to the anchoring plate, thereby holding the inner sleeve in a clamped position. The adjustable medical apparatus of claim 1 wherein the anchoring plate (12) and anchoring arm (14) define an opening (24) for receiving the inner sleeve (16). The adjustable medical apparatus of claim 1 or 2 wherein the inner sleeve (16) is resilient. The adjustable medical apparatus of claim 1, 2 or 3 wherein the inner sleeve (16) defines an aperture (18) for receiving the lead. The adjustable medical apparatus of any preceding claim wherein the inner sleeve (16) defines a cylindrical body having a slit (36) extending along the longitudinal length of the cylindrical body. The adjustable medical apparatus of any preceding claim wherein the anchoring plate (12) defines a plurality of attachment holes (22) for mounting the anchoring plate to the cranium. The adjustable medical apparatus of claim 6 wherein the anchoring arm (14) further includes an attachment hole (22) that is adapted to align with one of the attachment holes (22) of the anchoring plate (12) when the anchoring arm (14) is moved relative to the anchoring plate (12) to a position clamping a lead. The adjustable medical apparatus of any preceding claim in which the inner sleeve (16) is formed around at least one of the top or bottom of the anchoring plate (12) to form a seal adapted to prevent leakage of cerebral spinal fluid. The adjustable medical apparatus of claim 8 in which the inner sleeve (16) is formed around the top and bottom of the anchoring plate (12) to form a seal adapted to prevent leakage of cerebral spinal fluid. A combination of a medical electrical lead with the adjustable medical apparatus of any of the preceding claims. An implantable medical device comprising the apparatus of any of claims 1 to 9.

Inventors: KNUTESON ERIC A, KNUTESON, ERIC A.
Applicants: MEDTRONIC INC, MEDTRONIC, INC.
Application year: 2000
Main classification: A61N1
IPC codes: A61N1, A61M25