1. Field of Invention
This invention relates to medical retrieval devices for removing objects from a body, particularly calculi from the urinary and biliary systems.
2. 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 gallstones, 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 device. Typically, such instruments consist of 2 or more flexible elements that are joined at their proximal ends and may or may not be joined at their distal ends. The flexible elements are formed in the shape of a basket, cage, grasper, or other entrapping configuration. This basket is attached to a drive wire that passes through the lumen of a small diameter (typically 2.3 mm (7.0 Fr) or less) flexible sheath, which is usually greater than 50 cm in length. The proximal ends of the sheath and drive wire are attached to a multi-part handle, normally constructed of thermoplastic materials, which can typically be operated by the user with a single hand. By manipulating the handle, the drive wire can be pulled back relative to the sheath, collapsing the basket as it retracts into the sheath. In this closed position, the sheath can be passed through the working channel of an endoscope to the proximity of the object to be removed within the patient's body. The basket is expanded to the open position by manipulating the handle, which remains outside the endoscope and the patient's body. The device is then manipulated using the handle until the object becomes enclosed within the basket. This manipulation may include advancing, withdrawing and/or rotating the basket in order to get the object to pass between the flexible elements that comprise the basket. When the object has been successfully engaged within the basket, the endoscope and the retrieval device containing the object are then simultaneously removed from the body.
A number of designs for the handle of medical retrieval devices are in use. Typically, these handles consist of two main elements, a handle base and an actuation mechanism. The sheath is attached to one of these elements, and the drive wire is attached to the other. By moving the actuation mechanism relative to the handle base, the basket can be retracted into the sheath and extended from it. The handle design that appears to be preferred, based on actual current use and sales volumes, is of a thumb slide design. This design features a main handle base that remains stationary and a thumb slide actuator that slides along a portion of the handle body and has a thumb pad. This handle is held in one hand by wrapping the four fingers of the hand partially around the handle base. The thumb of the same hand is placed on the thumb pad. The device is actuated in one direction by moving the thumb pad away from the proximal end of the handle base, and in the other direction by moving the thumb pad toward the proximal end of the handle base. This type of handle can normally be held in such a way that the range of motion of the thumb required to fully actuate the device is located in a natural and comfortable area near the thumb's resting position. Since considerable skill and dexterity can be required of the user in order to retrieve an object, user comfort is of primary importance.
There are many variations of the thumb slide handle in use. However, these and other prior art handle designs do not have a mechanism for rotating the basket to facilitate capturing the object. Rotation can only be accomplished by rotating the entire handle. This method has a number of disadvantages. By rotating the entire handle, the user must accordingly rotate their hand. Since the hand would initially be placed in a natural position, the position of the hand after rotation would not necessarily be comfortable for further manipulation of the handle. Again, user comfort is significant due to the considerable skill and dexterity needed to successfully complete a stone retrieval procedure. Additionally, since the entire handle must be rotated in order to rotate the basket, the sheath must rotate as well as the drive wire. This is a disadvantage because the friction between the sheath and the endoscope's working channel can prevent a smooth 1:1 torque ratio between the handle and the basket. This is particularly relevant when the endoscope is flexible and is in an articulated position. Lack of precise rotational control can increase the difficulty of engaging the object in the basket, thereby lengthening the procedure.
Certain handle designs have been used which allow rotation of the basket without rotating the entire handle and thus the sheath as well. U.S. Pat. No. 4,046,150 (1977) to Schwartz et al. discloses a retrieval basket with such a handle. This handle has a first member that is attached to the sheath. A second member, which is attached to the drive wire, is located at the proximal end of the first member. The device is actuated by sliding the second member into and out of the first member, which is held stationary. The basket is rotated relative to the sheath by rotating the second member relative to the first member. However, this handle is not of the preferred thumb slide style, and requires the use of two hands to actuate. Also, the actuational and rotational controls are not independent of each other.
U.S. Pat. No. 5,957,932 (1999) to Bates et al. discloses a retrieval basket with yet another type of handle. This handle is of a pistol grip style, with a control knob located at the proximal end of the handle. The sheath is attached to the main body of the handle, and the drive wire is attached to the control knob. The device is actuated by pulling the control knob out from the main body of the handle and pushing it in. The control knob can also be rotated to rotate the basket. When the trigger portion of the handle is squeezed, mechanical advantage is applied to the actuation of the device. This design has several disadvantages. It requires two hands for normal actuation. And since the control knob is used for both actuation and rotation of the basket, the actuation and rotation are not independent of each other. It also uses a larger number of parts than other handle designs and is therefore is more complex and more expensive to manufacture. The above patents to Schwartz and Bates are incorporated herein by reference.
Another type of prior art handle, which is not referenced in any patents, is shown in FIGS. 7 and 8. A handle assembly 190 consists of a stationary portion or handle base 110 and a thumb slide 130 with a thumb pad 131. Handle base 110 has a distal end 181, a proximal end 182, and a length 180. Thumb slide 130 fits partially within handle base 110 and extends out from distal end 181, with thumb pad 131 remaining beyond distal end 181. A hollow tube or sheath 150 has a working length 186 and is attached to thumb slide 130. A drive wire (not shown) passes through the lumen of sheath 150 attaches at the proximal end to handle base 110 and at the distal end to a basket 160. To operate this device, handle base 110 is held in one hand with the four fingers of the hand. The thumb of the same hand is placed on thumb pad 131. When the thumb is extended away from the hand, thumb slide 130 slides out from distal end 181 of handle base 110. This results in the device being in the closed position, as shown in FIG. 7. When the thumb is pulled back toward the hand, thumb pad 131 slides toward distal end 181 of handle base 110. This results in sheath 150 being pulled back to expose basket 160. When thumb pad 131 is pulled back completely to handle base 110, the device is in the open position, as shown in FIG. 8. To rotate basket 160, handle base 110 is rotated relative to thumb slide 130. This design has the disadvantage that the actuation mechanism and the rotation mechanism are not independent. Both actuation and rotation are achieved by movement of the thumb slide and the handle base relative to each other. This design also has the disadvantage that the thumb pad is located beyond the distal end of the stationary handle base. This is a disadvantage because manipulation of the thumb slide is done with the user's thumb extended away from the hand in a somewhat awkward position, which results in less than ideal tactile control over the actuation of the device.
The prior art handle designs that do allow rotation of the basket without rotating the entire handle have the disadvantage that the rotation mechanism and actuation mechanism are not independent. As a result, while the basket is being rotated, it may be inadvertently and undesirably expanded or retracted, or while it is being expanded or retracted, it may be inadvertently and undesirably rotated. The retrieval of an object from within a patient's body using an endoscope and a retrieval device is a precise and delicate procedure that requires considerable user skill and dexterity. Since the user's control of the basket is limited by the handle of the device, it is desirable that the handle allows precise and independent control of both the actuation and rotation of the basket, and is comfortable to use.