Surgery – Means for introducing or removing material from body for... – Treating material introduced into or removed from body...
Reexamination Certificate
1999-03-31
2003-04-29
Casler, Brian L. (Department: 3763)
Surgery
Means for introducing or removing material from body for...
Treating material introduced into or removed from body...
C604S165030, C604S174000
Reexamination Certificate
active
06554802
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates generally to the techniques for devices for delivering medicaments to selected sites in tissue. Specifically, this invention relates to an apparatus for securingly positioning a drug or medication delivering catheter after the catheter is positioned in the brain, spinal epidural space, the intrathecal space or in a peripheral nerve application or in other tissue.
2. Description of the Related Art
Medication delivery to the brain, spinal cord, cerebrospinal fluid or other tissue throughout the body is useful in treating many maladies, diseases and illnesses. Through the use of an implantable pump and catheter, precise drug doses can be directly delivered to the area of interest to treat the malady, disease or illness or its symptoms.
Controlled placement of drug delivering catheters in the position of interest is highly desirable. This allows highly concentrated drugs or other medicaments to be delivered to a specific site where, because the drug or medicament is highly concentrated, the therapeutic effect will be maximnized. Further, because only a small amount of such highly concentrated drug or medicarnent is needed at the site to be therapeutically beneficial, side effects from receiving relatively large doses of the drug orally or intravenously are minimized.
In view of the desirability of placing the highly concentrated drug or medicament at a specific site, movement of the catheter from its desired position is highly problematic. This is a problem known as “dislodgment”. Dislodgment means that the distal tip of the catheter is moved enough from its desired position for the therapy to be affected. For some therapies, for example, intrathecal administration of drugs to the spinal cord, movement on the order of 0.5 inch or less may cause a noticeable decrease in therapy. For others, such as when a catheter is implanted in the intrathecal space of the spinal cord, the catheter must exit the intrathecal space to cause a change in therapy. This can be as much as 8 inches.
It is rare for the anchor to move relative to the tissue it is attached to. It is much more likely for the catheter to move relative to the anchor (slip through). Where the catheter is implanted in the spine, an anchor is typically placed outside the spine and is anchored to a ligament. In this case, it is not uncommon for the catheter to exit the spine and “bunch up” just distal to the anchor between the anchor and the entrance to the spine.
Dislodgment causes the highly concentrated drug or other medicament to not be delivered to the desired location. As a result, the desired therapeutic effect is not achieved. In addition, applying the highly concentrated drug or medicament to another site may produce undesired effects. Therefore, dislodgment is a condition to be avoided.
There are currently several ways physicians attempt to solve the problem of dislodgment. One way is to suture the catheter to tissue to “anchor” the catheter to the tissue. A problem with this approach is that often the suture cuts through or occludes the catheter thereby disabling the catheter. This prevents the desired drug or medicament from passing to the distal end of the catheter to be delivered to the target site. In addition, the drug or medicament then leaks out of the cut area where it may possible cause undesirable effects.
Another way to solve the dislodgment problem is to place an “anchor” around the catheter and then secure the anchor to tissue. In this way, the anchor prevents the catheter from moving relative to the anchor and the anchor itself is prevented from moving relative to tissue because the anchor is securely fastened to the tissue.
An example of such an anchor is shown in
FIGS. 1-4
labeled generally
2
. The anchor
2
has a tubular body
4
and a pair of opposed wings
6
. Body
4
has a central channel
8
. Central channel
8
is typically sized to be the same diameter as the outer diameter of a catheter
14
that is to be secured by the anchor
2
. Body
4
often has a longitudinal slit
10
that extends entirely through body
4
along the entire length of body
4
.
The wings
6
each have an eyelet
12
. In use, a catheter
14
is placed through slit
10
into channel
8
. Because of the tight tolerance in the diameter of central channel
8
and the outer diameter of catheter
14
, it is very difficult if not impossible to thread catheter
14
through channel
8
. Thereafter, anchor
2
is moved to the desired position. Wings
6
are pinched together toward slit
10
. A suture
16
is placed through eyelets
12
and tissue
18
to secure the catheter
14
in the anchor
2
and anchor
2
to tissue
18
(FIG.
4
).
A problem with this design for anchor
2
is that as wings
6
are brought together, the material of body
4
develops hoop stresses. Hoop stresses are the stresses that develop as a tightening force is applied to a hoop and the hoop resists being inwardly compressed. In this case, the hoop is the cross-section of the body
4
of the anchor
2
. The tightening force is the application of force to the body
4
by bringing wings
6
together. These hoop stresses take a substantial amount of the energy provided by moving the wings
6
together and store it in tension within the material of body
4
. As a result, a seriously reduced amount of energy is available for contacting the outer surface of the catheter to cause frictional contact with the catheter to hold it in place with respect to the anchor
2
.
Another problem occurs because anchor
2
is placed in a pocket
20
formed in tissue
18
in a patient's body. A problem with this anchor
2
is that it is difficult bring the wings
6
from their 180° opposed position to their pinched position in the small opening provided by in the pocket in the tissue
18
. This problem is exacerbated when the surgeon also has to open slit
10
and place the catheter
14
in the central channel
8
. This is often accomplished by bending wings
6
together on the opposite side of body
4
so that slit
10
opens. This requires a very dexterous maneuver in the small space presented by the pocket
20
in the tissue
18
. Often, it takes several tries to get the catheter
14
positioned within central channel
8
through slit
10
. This complicates the surgery with the concomitant chance or problems or complications.
SUMMARY OF THE INVENTION
The present invention provides an anchor for securely positioning a catheter intended to deliver drug or other medicaments to a desired position in tissue wherever found in the body or in epidural or intrathecal space of a spinal cord or brain. The present invention comprises, in the preferred embodiment, a generally tubular body for receiving the catheter and a pair of wings to assist in securing the device. The body has a slot that extends through the body between the wings. The wings and the slot cooperate so that the opposed edges of the slot just come together as the wings are brought into contact with each other. In this way, hoop forces are virtually eliminated so that all the stress produced by bringing the wings together is applied to the catheter to frictionally hold the catheter in position within the anchor. The wings interact with the slot to radially compress the catheter within the lumen of the tubular body to hold the catheter in a fixed relation to the tubular body.
In addition, the wings allow the device to be sutured to tissue to secure and fix the device to tissue. A first suture is placed around the base of the wings very near where the wings contact the body of the anchor. A second suture secures the wings together and affixes the anchor to the patient's tissue. This suture is placed through an eyelet in each of the wings. In this way, the normal stresses applied to the catheter by bringing the wings together are maximized.
In use the catheter is placed in the central channel of the anchor. The wings are brought together and sutured. The wings are then sutured to the patient's tissue.
It is an object of the present
Hankner Douglas O.
Pearson Robert M.
Yu Weiping
Banner & Witcoff , Ltd.
Casler Brian L.
Maynard Jennifer
Medtronic Inc.
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