Surgery – Instruments – Means for removing tonsils – adenoids or polyps
Reexamination Certificate
2000-02-02
2003-02-11
Robert, Eduardo C. (Department: 3732)
Surgery
Instruments
Means for removing tonsils, adenoids or polyps
Reexamination Certificate
active
06517550
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates generally to the field of medical instruments for retrieving foreign articles from patients. More particularly, it concerns an apparatus for use as a snare or foreign body retrieval device that is guidewire-compatible and includes a continuously-adjustable, laterally-oriented loop.
2. Description of Related Art
During medical procedures which utilize catheters, guidewires, pacemaker leads, or other medical devices, a portion of the device can sometimes break off and be left within the patient. The detached portion may then travel within the patient's vascular system and come to rest in a luminal organ, vein or artery, and usually at a branching point or in the heart. Leaving these foreign bodies within the patient can be quite harmful, and may result in complications like sepsis, perforation, thrombosis, arrhythmias, myocardial necrosis, or even death. Therefore, it is necessary and urgent to remove the foreign body from the patient.
Similarly, several interventional radiological procedures involve implantation of different devices within the body. Recently, embolization coils, stents and vena cava filters, among others, have been frequently used. Misplacement and/or dislodgment of these devices may result in serious consequences and necessitate their removal (Galal et al.,
Eur. Heart J
., 1997; Ing and Bierman,
Cardiovasc. Intervent. Radiol
., 1995; Siegel and Robertson,
JVIR
, 1993; Lipton,
JVIR
, 1995).
The percutaneous removal of foreign bodies or devices has become acceptable because it is relatively easy and safe. However, current devices possess certain shortcomings that inhibit their ease and range of use.
The Amplatz “Goose Neck” snare, commercially available from Microvena Corporation of White Bear Lake, MN, is currently the most popular snare. Described in U.S. Pat. No. 5,171,233 to Amplatz et al. (1992), the Amplatz snare consists of a superelastic wire that is bent in half. The two wire segments created as a result of the bend are bonded together to eliminate the possibility of moving the segments relative to each other. A loop is fashioned at the location of the bend. The loop is bent at its proximal end (i.e., the end of the loop closest to the operator) such that the loop is oriented at an angle to the bonded wire segments. Because the wire segments are bonded together to prevent the relative movement of either, the size of the loop is fixed.
In order to operate the Amplatz snare, the loop is constrained (pinched) and inserted into a catheter. Once positioned in the patient, to utilize the loop, the position of the catheter is maintained, and the folded wire is pushed until the loop is fully extended beyond the tip of the catheter. It then returns to its unconstrained configuration. Prior to being completely extended beyond the tip of the catheter, the loop will remained constrained and useless.
After the loop is formed, the Amplatz snare may be manipulated until the loop passes over the foreign body to be retrieved. Then, by maintaining the position of the folded wire, the catheter may be advanced over the bonded segments and the loop until the foreign body is firmly wedged between the distal end of the loop and the catheter. This process may also be achieved by holding the catheter steady and withdrawing the bonded wire segments, or both may be manipulated at once. The snare may then be removed from the patient along with the laterally-oriented foreign body.
A purported advantage of the bonded wire segments and fixed loop of the Amplatz snare is that the operator need only utilize one hand to form the loop, in contrast to other snares in which the relative movement of the two wire halves may be required in order to form a useful loop. (See, e.g., the snare disclosed in Bett et al.,
Med. J Aust
., 1971)
The fixed nature of the loop of the Amplatz snare, however, poses certain shortcomings. For example, because the loop is fixed, having only one or two snare sizes may not be feasible to efficiently remove foreign bodies of all sizes in the least disruptive manner to the patient. Obviously, while having a snare with a relatively large loop may be useful for retrieving correspondingly large foreign bodies in sufficiently sized vessels or structures, a patient could be traumatized by retrieving a more diminutively-sized foreign body with the same snare. Specifically, it would not be beneficial to the patient to retrieve a small foreign body lodged in a small vessel or structure with an Amplatz snare having a loop that is larger than the size of the vessel. The vessel or structure could be traumatized by the pressure the loop would exert on the wall thereof during the procedure. As a result, it is not possible to feasibly utilize one or two Amplatz snares for the retrieval of foreign bodies of virtually all sizes.
Further, as a result of the fixed nature of the loop and the fact that it must be extended beyond the tip of the catheter before it is formed and operational, if a foreign body were positioned in a way that made it more feasible to surround it by withdrawing the loop toward the operator rather than by advancing the loop away from him or her, the tip of the catheter would need to be positioned distally of the distal end of the foreign body prior to forming the loop. As a result, the vessel or structure would need to possess a sufficient amount of space distal of the foreign body in which the constrained loop could be extended during its formation. If such space did not exist, such as at a branch or bifurcation, the Amplatz snare would be useless in that application.
Another shortcoming of the Amplatz snare is that prior to removing it, the foreign body must be pinched or wedged between the distal end of the loop and the distal tip of the catheter. As a result, in cases in which the foreign body is straight or slightly bent, the foreign body will be oriented transversely to the catheter as it is being withdrawn. Consequently, the wall of the vessel or structure from which it is removed may be traumatized by the laterally-oriented foreign body scraping against it as the foreign body is extracted. For the same reason, negotiating tortuous passageways may be difficult, and the foreign body may become caught or wedged in a passageway and require surgical removal.
Yet another shortcoming of the Amplatz snare is that it is not guidewire compatible. The use of a guidewire is neither disclosed nor suggested by the Amplatz patent. Thus, the catheter in which the folded wire is housed must be used to guide the snare to its desired location. Further, the use of a guidewire with the Amplatz snare would only add to its bulk since a larger delivery catheter would be needed in order to accommodate the two twisted wire segments bonded together and the guidewire.
The surgical snare disclosed in U.S. Pat. No. 5,342,371 to Welter et al. (1994) (commercially available from Cook Inc., Bloomington, Ind.) (the “Welter snare”) suffers from some of the same shortcomings as the Amplatz snare, but addresses one of them. The Welter consists of an elongated member in which two longitudinally spaced-apart ports are provided. A stainless steel wire is threaded out of one of the ports, helically wrapped around the elongated member, and threaded back into the member through the other port, thereby forming a collapsed, stainless steel helical snare loop external of the member. The distal end of the stainless steel wire is attached to the distal end of the member. The stainless steel helical snare loop may be opened and closed by manipulating a sliding handle affixed to the proximal end of the member. By attaching the distal end of the stainless steel wire to the distal end of the elongated member, the Welter snare addresses the problem recognized in the Amplatz patent of having to move one end of the stainless steel wire forming the helical snare loop relative to the other by fixing the position of the distal end of the wire, instead of by bending the wire and bonding the two wire segments. As a r
Kónya András
Wright Kenneth C.
Board of Regents , The University of Texas System
Fulbright & Jaworski L.L.P.
Robert Eduardo C.
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