Surgery – Instruments – Means for concretion removal
Reexamination Certificate
1999-11-05
2001-02-20
Thaler, Michael H. (Department: 3731)
Surgery
Instruments
Means for concretion removal
Reexamination Certificate
active
06190394
ABSTRACT:
BACKGROUND FIELD OF THE INVENTION
This invention relates to medical retrieval baskets for removing objects from a body, particularly calculi from the urinary and biliary systems.
BACKGROUND DESCRIPTION OF PRIOR ART
Medical instruments are currently in use which reduce the invasiveness and potential trauma previously associated with various medical procedures. One such procedure is the removal of objects, such as kidney stones and gall stones, from the body. Various surgical devices are available which allow objects to be removed from the body without requiring major surgery. One type of surgical device is a mechanical retrieval basket. Typically, such instruments consist of 3 or more flexible elements joined at their distal and proximal ends and formed in the shape of a basket, or cage. This cage is attached to an actuation wire or cable which passes through the lumen of a small diameter flexible tube. By manually manipulating the actuation cable at the proximal end of the tube, the cage can be retracted into the tube. This adjustment is normally accomplished using a sliding multi-part handle attached to the proximal ends of the tube and actuation cable. In this closed position, the tube can be passed through the working channel of an endoscope to the proximity of the object to be removed. The cage is extended to the open position by manipulating the actuation cable in the opposite direction. The device is then manipulated until the object becomes enclosed within the cage. The endoscope and the retrieval basket containing the object are then simultaneously removed from the body.
A number of designs for the medical retrieval baskets are in use. U.S. Pat. No. 2,943,626 (1960) to Dormia discloses a retrieval basket which has a cage made of flexible elements which may extend in radial planes which pass through the axis of the tube, or may take the shape of a helix. The flexible elements are constructed of wires or narrow bands.
U.S. Pat. No. 4,590,938 (1986) to Segura et al. discloses a retrieval basket with a cage defined by a multiplicity of spaced apart flat spring strips which are outwardly bowed and extend generally axially of the tube. The cage has a generally bulbous form at its distal end.
These and other similar prior art designs have a configuration in which the flexible elements which comprise the cage are equiangularly spaced about the cage. These designs all have certain disadvantages. When the cage comprises a small number of flexible elements (typically 3 or 4), the object to be captured passes fairly easily into the cage. However, because of the small number of flexible elements and thus large spaces between them, the object can be difficult to maintain within the cage, particularly when the object is small. Conversely, when the cage comprises a larger number of flexible elements (typically 5 or more), the object can be maintained within the cage more easily. However, because of the large number of flexible elements and thus smaller spaces between them, the object can be difficult to capture within the cage.
Certain prior art retrieval baskets have attempted to provide a cage configuration which facilitated both capturing and maintaining the object within the basket. U.S. Pat. No. 4,347,846 (1982) to Dormia discloses a cage configuration similar to that of U.S. Pat. No. 2,943,626, except that the flexible elements are disposed in pairs, one element of each pair spiraled in a clockwise direction and the other element spiraled in a counter-clockwise direction. The flexible elements of each pair are arranged so that they intersect each other in the distal half of the cage. The intent of this design is that the object can be captured in the proximal portion of the cage, and the intersecting elements in the distal portion of the cage will facilitate maintaining the object within the cage when it is partially closed. However, this configuration has certain disadvantages, which may explain why it is not currently marketed in the U.S. When the cage is in the completely retracted position within the tube, its cross-sectional area is much larger than that of a cage with the same number of similarly sized, non-intersecting elements. Very small tube diameters (typically 1 millimeter or less) are clearly desirable to allow passage through the working channels of small diameter endoscopes. In order to have a tube of the desired size with a cage having intersecting elements, the elements themselves would have to be significantly smaller than with other prior art designs. This would result in the elements exerting less dilating force on the tissue surrounding the object when the cage is expanded. In some applications, the elements might not exert enough force to open the cage completely, thus hindering the capture of the object. This design has the further disadvantage of being difficult to manufacture.
U.S. Pat. No. 5,496,330 (1996) to Bates et al. discloses a configuration in which a plurality of generally widely spaced strands form a helical shaped cage. Each of the strands consists of a plurality of elements which are closely angularly spaced throughout the length of the cage. Typical embodiments of this design are three or four strands, each of which consist of two elements. This does increase the number of contact points the basket has with the object without decreasing the size of the of the spacing between strands. However, there are certain disadvantages with this design. When three strands are used, the spacing between the strands is still rather large, allowing objects to slip through between the strands. And when four strands are used, a total of eight flexible elements are needed, more than are typically used in the other prior art baskets. In order to fit inside the same size tube, the diameter of the individual flexible elements must be reduced, which reduces their strength.
Additionally, all of the prior art baskets have a further disadvantage. Frequently, the objects to be retrieved are of irregular shape, such as urinary or biliary calculi. It is not uncommon that a particular object is difficult to secure with one type of basket, while another type of basket readily secures the same object. For example, a particular portion of an irregularly shaped object may be readily secured with two closely spaced elements of a basket. Other geometries exist in which a single element is more effective. The prior art retrieval baskets all have the limitation that each of the flexible elements presents the same configuration to the object. If a particular difficult to grasp area of the object is not effectively secured by one part of the cage, rotating the cage to use another part will have little effect, since each area of the cage presents a similar configuration.
OBJECTS AND ADVANTAGES
Accordingly, several objects and advantages of the present invention are:
(a) to provide a novel medical retrieval basket which facilitates both the capture of an object and maintaining the object within the basket;
(b) to provide a novel medical retrieval basket which is capable, by means of rotation, of presenting differing configurations of flexible elements to a given portion of the object to be retrieved;
(c) to provide a novel medical retrieval basket which optimizes the combination of the number of flexible elements and the size, spacing and cross sectional shape of the elements; and
(d) to provide a novel medical retrieval basket which can effectively dilate tissue surrounding the object to be captured in order to facilitate capture of the object.
Further objects and advantages are to provide a medical retrieval basket of the type described herein which is of simple design, is simple and inexpensive to manufacture, and is easy to use. Still further objects and advantages will become apparent from a consideration of the ensuing description and drawings.
REFERENCES:
patent: 2918919 (1959-12-01), Wallace
patent: 2943626 (1960-07-01), Dormia
patent: 3008467 (1961-11-01), Morris
patent: 4046149 (1977-09-01), Komiya
patent: 4046150 (1977-09-01), Schwartz et al.
patent: 4198960 (1980-04-0
Karels Eugene C.
Lind Stuart J.
Annex Medical, Inc.
Thaler Michael H.
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