METHODS, TOOLS, AND KITS FOR SUBCUTANEOUSLY IMPLANTING ARTICLES
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates generally to medical devices and methods.
More particularly, the present invention relates to methods, tools, and kits for subcutaneously implanting articles, such as vascular access ports.
Access to a patient's vascular system can be established by a variety of temporary and permanently implanted devices. Most simply, temporary access can be provided by the direct percutaneous introduction of a needle through the patient's skin and into a blood vessel. While such a direct approach is relatively simple and suitable for applications, such as intravenous feeding, intravenous drug delivery, and other applications which continue over only a short time, they are not suitable for hemodialysis, peritoneal dialysis, hemofiltration, chemotherapy, drug delivery, and other extracorporeal procedures that must be repeated periodically, often for the lifetime of the patient.
For long-term vascular access suitable for hemodialysis, hemofiltration, and the like, the most common approach is to create a subcutaneous arteriovenous (A-N) fistula. The fistula is preferably created by anastomosing an artery, usually the radial artery, to a vein, usually the cephalic vein. The vein dilates and eventually arterializes, becoming suitable for repeated puncture using a needle for access. A-N fistulas may also be created using autologous or heterologous veins, by implanting synthetic blood vessels, typically PTFE tubes, and the like.
As an alternative to the use of an A-N fistula, a variety of implantable ports have been proposed over the years for use in hemodialysis, hemofiltration, drug delivery, and other treatments. Typically, the port includes a chamber having an access region, such as a septum or a valve aperture, and the port is attached to an implanted cannula which in turn is secured to a blood vessel. In the case of veins, the cannula is typically indwelling, and in the case of arteries, the cannula may be attached by conventional surgical technique. The present invention is particularly concerned with the manner of implanting such ports as well as other subcutaneously implantable devices. Prior to the present invention, ports were typically implanted by creating a large subcutaneous pocket into which the port was placed and usually connected to the vasculature by a cannula or other implanted conduit. As described in copending application no. 09/161,068, assigned to the assignee of the present application, and illustrated in Figs. 1A and IB herein, a port P may be implanted by creating a tissue pocket TP by making an incision in the skin S and forming the pocket laterally from the incision. Generally, it is desirable if not necessary to form the pocket by first creating a generally vertical incision and then extending the incision generally laterally so that the port may be placed in a pocket which is offset from the vertical incision. In this way, a needle or other access device which is percutaneously penetrated into the port will not pass through the vertical incision. The incision and laterally extending pocket were usually formed with a conventional surgical scalpel, and the surgeon would use her or his best judgment in determining the size of the pocket needed to accommodate a port P. While in some instances the surgeon would create an optimum size for the pocket, in many cases, the pocket initially created would either be too large or too small. If the pocket is too large, the patient might need additional suturing in order to close the pocket. Additionally, large tissue pockets increase the likelihood of hematoma and infection. If it is too small, the surgeon would have to take additional time to enlarge the pocket prior to implanting the port. While neither of these problems is of a great magnitude, they do make the procedure more difficult for the surgeon and expose the patient to a possibly lengthened procedure with additional (although minor) trauma and increased risk of infection.
For these reasons, it would be desirable to provide improved methods, tools, and kits for implanting subcutaneous devices, such as vascular access ports. In particular, it would be desirable to provide such methods, tools, and kits which reduce the time and skill required to form a subcutaneous tissue pocket for receiving the implantable device and/or which increase the accuracy of the size of the tissue pocket which is created. Preferably, the methods, tools, and kits will both reduce the time and increase the accuracy of tissue pocket creation. The tools should be of simple, low cost construction, and their use should be within the normal skills of a surgeon expected to perform the procedure. Preferably, the methods will comprise a minimum number of steps which, if performed according to a simple protocol, will, result in a tissue pocket having a size and depth which is both accurate and appropriate for the device to be implanted. At least some of these objectives will be met by the invention described hereinafter. 2. Description of the Background Art
Vascular access ports which can be implanted using the methods, tools, and kits of the present invention, are described in U.S. Patent Nos. 5,562,617; 5,713,859; 5,807,356; 6,042,569; and 6,007,516. Copending application no. 09/161,068, has been described above. The full disclosures of each of these patents and copending application are incorporated herein by reference.
SUMMARY OF THE INVENTION The present invention provides improved methods, tools, and kits for subcutaneously implanting articles in a patient. The invention is particularly suitable for creating a tissue pocket as part of a procedure for implanting a vascular access port, where the access port can be intended for anyone of a variety of purposes, such as hemodialysis, hemofiltration, hemodiafiltration, apheresis, peritoneal dialysis, chemotherapy, drug delivery, and the like. In addition, the present invention could be used for implanting a variety of other devices, such as cardiac pacemakers, implantable drug delivery pumps, and the like.
The present invention incorporates a unique dissection tool for forming a tissue pocket having dimensions which are chosen for the article to be implanted. The dissection tool will include a blade having a cutting edge with a geometry which corresponds to a geometry of the article. Usually, the cutting blade will be planar, and the cutting edge will have or define a line which corresponds to or matches a peripheral geometry or shape of the article to be implanted. By "corresponds to," it is meant that the shape of the line defined by the cutting edge may precisely match a peripheral geometry or shape of the article (usually a side of the article when viewed in a plan orientation). More usually, however, the geometry of the cutting edge will have the same shape but be slightly larger than the actual plan and dimensions of the article to be implanted.
In the exemplary embodiment, the article to be implanted is a vascular port having a circular base, and the cutting edge of the dissection tool blade is semicircular. In this way, as the blade is advanced through tissue, the cutting edge forms a pocket having a semicircular leading edge. Usually, the radius of the semicircular leading edge will be slightly larger than the radius of the base of the implanted article, allowing sufficient space for the article to be implanted without excess cutting of tissue.
Methods according to the present invention comprise providing a dissection tool including a blade with a cutting edge having a geometry corresponding to that of the article. The blade of the dissection tool is advanced through tissue to create a subcutaneous pocket having peripheral dimensions corresponding to the geometry of the blade. Usually, a generally vertical incision is first created through the skin to a desired depth and with a desired width corresponding to the width of the tissue pocket. The vertical incision may be made with the cutting tool but will more usually be made with a scalpel or other conventional surgical cutting instrument. Usually, it is desirable that the initial vertical incision will have a generally straight, horizontal distal edge to define the horizontal plane in which the tissue pocket is to be formed. Thus, use of a dissection tool having a non-linear cutting edge will usually not be preferred. Once the initial vertical incision has been created, the dissection tool is introduced vertically through the incision until the cutting edge of the blade reaches the desired depth of implantation. At that point, the blade is turned and the cutting edge advanced horizontally to create the pocket. Usually, the dissection tool will have a mark or other feature which indicates when the cutting edge has reached the desired depth. As the cutting edge is advanced horizontally, it will create a distal edge or wall of the tissue pocket having the desired shape which corresponds to the geometry of the article to be implanted.
While the use of the cutting tool having a semicircular cutting blade is useful for implanting circular articles, i.e., articles having at least one circular dimension such as a base dimension, the shape of the cutting edge may be varied to correspond to a variety of other regular and irregular shapes and geometries of other implantable articles. For example, the cutting edges may be polygonal, ovoid, zig-zag, serpentine, or have any other desired geometry.
Tools according to the present invention will be designed specifically for use in combination with a particular article to be implanted. Dissection tools will comprise a blade having a desired geometry, usually including a semicircular cutting edge. A handle will be attached to the blade on a side opposite to that of the cutting edge, and the plane of the blade will be at an angle relative to an axis of the handle in the range from 15° to 75°, usually from 30° to 60°, and preferably from 40° to 50°. In the preferred case of a semicircular cutting edge, the cutting edge will have a radius in the range from 1 cm to 6 cm, usually from 2 cm to 4 cm. The blade may further include other features, such as suture hole markers, radiopaque markers, depth gauge indicia, or the like. In other embodiments, the blade will incorporate a tab or other extension which defines the depth of insertion. The depth may be provided on a scale on the tab. Alternatively, the depth may be established by the point at which the handle is attached to the tab. The dissection tool may be formed from virtually any surgically acceptable material or materials. Usually, at least the cutting edge will be formed from the material that can be honed and remain sharp during use. Suitable materials include surgical stainless steel and a variety of hard plastics. Of course, different components of the tool may be formed from different materials which are permanently or removeably attached to each other. Depending on the particular materials, the tool can be sterilizable (reusable) or disposable. In some cases, it may be possible to form the blade or even the cutting edge of the blade from a disposable material, while the rest of the tool is sterilizable and reusable. Kits according to the present invention comprise an implantable article having a peripheral geometry, such as an implantable vascular port having a circular base. The kits further comprise a dissection tool having a blade with a geometry corresponding to the peripheral geometry of the article, e.g., a semicircular cutting edge corresponding to the circular geometry of the implantable vascular access port. The kits will still further include a container to hold the article and the dissection tool, typically a box, pouch, tube, tray, or other conventional medical device package. Conveniently, both the article to be implanted and the dissection tool will be maintained sterilely within the package. Usually, the kit will further comprise instructions for use setting forth any of the methods described above.
BRIEF DESCRIPTION OF THE DRAWINGS
Figs. 1 A and IB illustrate prior art techniques for implanting vascular access ports.
Fig. 2 illustrates a dissection tool constructed in accordance with the principles of the present invention. Fig. 3 illustrates an exemplary vascular access port which may be implanted using the methods, tools, and kits of the present invention.
Figs. 4A-4E illustrate use of the dissection tool of Fig. 2 for subcutaneously implanting the port of Fig. 3 in a patient.
Fig. 5 is a plan view showing the geometry of the tissue pocket and the implanted port resulting from the implantation protocol of Figs. 4A-4E.
Fig. 6 illustrates a kit constructed in accordance with the principles of the present invention. DESCRIPTION OF THE SPECIFIC EMBODIMENTS A dissection tool 10 constructed in accordance with the principles of the present invention is illustrated in Fig. 2. The dissection tool 10 comprises a cutting blade 12 attached to a handle 14, usually by an intermediate section or connecting tab 16. The blade 12 has a cutting edge 18 which forms the leading edge of the dissection tool 10. That is, the handle 14 is attached to the blade on a side opposite to that of the cutting edge so that forward advancement of the tool using the handle 14 causes the cutting edge 18 to dissect tissue. It will be appreciated that the geometry of the cutting edge will thus be imparted to the tissue as it is cut. For tool 10, the cutting edge 18 is semicircular and has a radius which corresponds to (is slightly larger than) the diameter of a circular article to be implanted, such as implantable port 30 discussed below. The blade 12 will be attached to the intermediate section 16 at an angle alpha (α), typically in the range from 40° to 50°. This angle facilitates turning of the blade from vertical to horizontal, as will be described in more detail later. Preferably, handle 14 is attached to the intermediate section 16 at an angle beta (β) in the range from 0° to 60°, usually from 10° to 45°. Preferably, the alpha (α) and beta (β) angles will be equal so that the handle is generally parallel to the plane of cutting blade 12. In this way, there is an offset d between the plane of the cutting blade 12 and the handle, usually in the range from 0 cm to 6 cm, preferably in the range from 1 cm to 3 cm. Such an offset also facilitates the ability to first vertically introduce the tool and thereafter turn the tool horizontally to create the desired tissue pocket, as described in more detail below.
Referring now to Fig. 3, a vascular access port 30 includes a circular base 32 having a plurality of suturing holes 34 therein. The vascular access port includes a needle access aperture 36 with a connector 38 for attaching to a cannula which may in turn may be attached to the patient's vasculature. The construction of such a vascular access port is described in detail in U.S. Patent No. 6,007,516, the full disclosure which has previously been incorporated herein by reference. While the tools and methods of the present invention are particularly suitable for implanting such vascular access ports, it will be appreciated that they are also useful for implanting a wide variety of other implantable articles, such as those mentioned above. Usually, the base of the implantable article 30 will have a radius of about 3 cm. In such a case, it is desirable that the cutting edge 18 of the dissection tool 10 have a radius of about 3 cm. Referring now to Figs. 4A-4E, implantation of the vascular access port 30 using the dissection tool 10 will be described. In Fig. 4A, a section of patient tissue comprising an overlying skin or cutaneous layer S and the underlying subcutaneous layer Q is illustrated. It is desired to implant the access port 30 in a target region TR. In an exemplary method according to the present invention, a vertical incision VI is first made first through the skin S and into the subcutaneous layer Q to the depth of the target region TR, as shown in Fig. 4B. Usually, the incision will be made with a scalpel or other conventional surgical tool. While it is preferred that the incision be generally vertical, the actual angle relative to the plane normal to the tissue surface can vary somewhat, typically being between 0° to ±45°, usually from 0° to ±20°. Thus, as used herein, the phrase "vertical incision" is meant to describe an incision which is generally vertical within the range of angles set forth above.
After the vertical incision VI has been formed, the blade 12 of tool 10 is inserted downward in a generally vertical direction through the incision until it reaches a desired depth. As noted above, the depth is optionally determined with reference to an indicia or other feature on the handle itself. Once at the desired depth, the blade is turned in a horizontal direction, as indicated by arrow 28 in Fig. 4C. The blade is then advanced to form a generally horizontal incision HI, as shown in broken line in Fig. 4C and in full line in Fig. 4D. The implantable port 30 may then be introduced into the horizontal incision which defines the tissue pocket, the port sutured in place, and the vertical incision VI sutured closed, as shown in Fig. 4E. Advancement of the semicircular cutting edge 18 creates a vertical incision having a semicircular edge 40, as shown in broken line in Fig. 5. The semicircular edge 40 corresponds to, but may be slightly larger than, the diameter of base 32 of the implantable port 30. In this way, it can be seen that the size and shape of the tissue pocket created by the horizontal incision HI has been optimized for the implanted article.
Referring now to Fig. 6, a dissection tool according to the present invention, such as tool 10, an article to be implanted, such as vascular access port 30, may be packaged together in a kit. Usually, the kit will include a conventional package 100 for receiving and containing both the dissection tool and article to be implanted, and the package may be in a form of a pouch, tray, box, tube, or the like. Usually, both the dissection tool and article to be implanted will be maintained sterilely within the package 100, and optionally instructions for use (IFU) may also be provided. The instructions for use may set forth any of the methods for implanting the article using the dissection tool 10, as described generally above. The instructions for use will usually be set forth on a separate printed sheet, but may also be incorporated in whole in part on the packaging itself.
While the above is a complete description of the preferred embodiments of the invention, various alternatives, modifications, and equivalents may be used. Therefore, the above description should not be taken as limiting the scope of the invention which is defined by the appended claims.