Injection tool and method of its use

Details Injection tool and method of its use Injection tool and method of its use

1995-03-13

1998-10-27

Coggins, Wynn Wood

Surgery

Means for introducing or removing material from body for...

Treating material introduced into or removed from body...

604158, 604164, 604165, 604187, 604218, A61M 500

Patent

active

058272364

DESCRIPTION:

BRIEF SUMMARY
TECHNICAL FIELD

This invention relates to an injection tool for administering drugs at sites of a very small size that are located comparatively deep in the body and develop comparatively high internal pressure.


BACKGROUND ART

A known technique for injecting chymopapain for purposes such as the treatment of herniated intervertebral disks in dogs is depicted by rough sketch in FIG. 8 and comprises the following steps: an injection needle 52 that has an inner needle (mandolin) 51 inserted therein is allowed to pierce through the skin 61 and then muscle 62 so that its distal end reaches the vertebral pulp 64 in an intervertebral disk 63 (FIG. 8A); then, the inner needle 51 is withdrawn and a connector 53 at the basal end of the injection needle 52 is filled with part of the drug to be injected; a lure lock 55 at the distal end of the injection barrel 54 into which the drug has been aspirated is coupled to the connector 53; and the piston 56 is pushed, thereby injecting the drug into the vertebral pulp 64 (FIG. 8B) (see "Kachiku Chiryo (Domestic Treatment)", No. 1, Treatment of Herniated Intervertebral Disks in Dogs by Chymopapain Injection, compiled under the supervision of Masashige Nakayama, published by Inters Videotape Co., Ltd., 1992).
Stated more specifically, the vertebral pulp 64 in the intervertebral disk 63 is a closed space surrounded with a fibrous ring 66 and is located at a comparatively deep site in the body; hence, in order to assure penetration through the skin 61, muscle 62 and even the fibrous ring 66, the injection needle 52 must have a reasonable thickness and, at the same time, it is necessary to use the inner needle 51 so that the injection needle 52 will neither bend nor undergo obstruction by tissue fragments during piercing.
To this end, the injection needle 52 is a separate member from the injection barrel 54 in the current method and when the needle tip has reached the intended site, the inner needle 51 is withdrawn and the injection barrel 54 is connected. However, with the current means of coupling the lure lock 55 to the drug filled connector 53, it is impossible to avoid inaccuracy in the injected dose of the drug. What is more, complete exclusion of air is difficult to achieve by the means of connecting the injection barrel after the connector 53 is filled with the drug and any residual air will cause further inaccuracy in the injected dose of the drug.
In addition, when the injection needle 52 is pulled out after injection, a considerably large piercing hole remains in the fibrous ring 66 due to the injection needle 52, and the drug that has been injected into the vertebral pulp 64, developing high internal pressure, is prone to flow out of the piercing hole, thus introducing inaccuracy in the drug dosage and also damaging the surrounding tissue by the drug outflow.
Therefore, even if one attempts to employ the aforementioned technique for administering drugs at sites of a very small size that are located comparatively deep in the body and develop comparatively high internal pressure not only in the treatment of herniated intervertebral disks in dogs but also in the treatment of similar diseases such as herniated intervertebral disks in humans, difficulty is involved in accurately administering predetermined doses and, at the same time, a considerably large piercing hole remains, requiring a long time for it to close, during which time not only the drug but also blood and other body fluids can potentially flow out in large quantities.
The problem to be solved by the present invention is that there has not been available any injection-based drug administering means by which predetermined doses of drugs can be administered in an accurate manner at sites of a very small size that are located comparatively deep in the body and develop comparatively high internal pressure, and which yet will not leave a large piercing hole open at the intended site.


DISCLOSURE OF INVENTION

The present invention provides (1) an injection tool comprising an injection device comprising an inje

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