Patent Application
20060135887
This invention relates to medical devices.
The human uterine cavity is approximately triangular in shape and relatively flat, much like an envelope. The cavity is entered via the endocervical canal. The proximal end of the canal, the external cervical os, opens to the vagina while the distal end, the internal cervical os, opens to the uterine cavity. The tip of the triangular-shaped uterine cavity is located at the internal cervical os, while the base is defined by the openings that lead to the fallopian tubes, the tubal ostia. Sounding the uterus, i.e., determining the length of the uterus, is usually a blind procedure. A physician inserts a uterine sound transcervically and advances the sound until it reaches the top, or fundus of the uterine cavity, i.e., the base of the triangle between the tubal ostia. The length from the interior fundus to the external cervical os can be measured directly using graduations stamped on the shaft of the sound. The physician relies upon tactile feedback to determine when the sound has touched the fundus.
Sounding the uterus can lead to perforation of the uterine wall by the uterine sound, reportedly in as many as 1% to 3% of all intrauterine procedures. The risk of perforation increases when locating the fundus is difficult, especially if the uterine cavity is severely anteverted or retroverted, if intrauterine pathology (e.g., polyps, fibroids) is present, or if the cervix is stenotic. In the latter case, the cervix is difficult to dilate to a diameter sufficient to facilitate easy passage of the sound. A tight cervix can create friction against the sound, requiring more force to be exerted by the physician in order to advance the sound to the fundus. Increased insertion force, uncertain geometry and intracavitary pathology all contribute to increased incidence of perforation.
Conventional uterine sounds are constructed from a malleable metal material, approximately 3.5 mm in diameter with a working length of roughly 25 cm, and have a flattened handle portion the physician can grasp. The uterine sound necessarily is substantially rigid in the axial direction and somewhat flexible out of plane, transverse to its axis, in order to reach the fundus and provide the physician the tactile sensation of touching the fundus. The small diameter and axially rigid construction of the conventional uterine sound makes it relatively easy to perforate the uterine wall. Additionally, the physician cannot easily discern the difference between resistance due to the uterine wall and that due to a tight cervix, further increasing the risk of perforation.
In general, in one aspect, the invention features a uterine sounding device including an elongate member having a longitudinal axis, distal and proximal ends. The elongate member, being configured for insertion into a uterus, includes an end cap connected to the distal end of the elongate member. The end cap is in a closed position when the elongate member is inserted into the uterus, subsequently switching into an open position when a force applied to a distal tip of the end cap by the uterus exceeds a threshold force. A surface area of the end cap projected onto a plane substantially perpendicular to the longitudinal axis of the elongate member is enlarged in the open position as compared to in the closed position. The open position resists penetration of the end cap into a wall of the uterus.
Implementations of the invention can include one or more of the following features. The elongate member of the device can be substantially rigid compressively between the distal and proximal ends, and substantially flexible out of the plane of the longitudinal axis. The elongate member of the device can include graduations marked on at least a portion of a length of the elongate member for measuring a length of the uterus.
The end cap of the device can include one or more fin members, where the fin members are positioned along a longitudinal axis of the elongate member when the end cap is in the closed position and deploy laterally from the longitudinal axis when switching into the open position. Each of the one or more fin members of the device can include of a first fin link and a second fin link. Furthermore, when in the open position, the first fin link, the second fin link and a portion of the elongate member can approximately form a triangle. The first fin link of the device can be deployed at substantially 90 degrees to the longitudinal axis of the elongate member and the second fin link can be deployed at substantially 30 degrees to the longitudinal axis of the elongate member. For each fin member of the device, the first fin link and the second fin link can be a unitary element and can be separated by a portion having decreased thickness comprising a living hinge. In one embodiment, the first link can be substantially 0.25 centimeters to 1 centimeter in length and the second fin link can be substantially 0.75 centimeters to 3 centimeters in length. In another embodiment, the first fin link can be substantially 0.7 centimeters in length and the second fin link can be substantially 2.1 centimeters in length.
The device can include a deployment mechanism, configured to switch the end cap from the closed position to the open position upon a force on the distal tip of the end cap exceeding the threshold force. In one implementation, the deployment mechanism can include a spring positioned about the elongate member, wherein the spring is preloaded to exert the threshold force on a first face of a retainer connected to the rod. The threshold force exerted by the spring prevents the rod from translating in a direction away from the end cap, and the retainer includes a second face abutting a housing preventing translation of the rod in a direction toward the end cap. When a force on the distal end of the end cap exceeds the threshold force, the rod translates axially compressing the spring. The distal end of the end cap translates causing the one or more fin members to deploy laterally switching the end cap into the open position. The rod can be attached to a hardstop configured to limit translational movement of the rod in a direction away from the end cap. The device can further include a handle attached to the elongate member substantially near the proximal end of the elongate member, and the deployment mechanism can be housed within the handle.
The distal tip of the end cap of the device can be configured to be atraumatic. For example, the distal tip of the end cap can be a full radius tip, a chamfered tip, or a convex tip.
The device can include a handle attached to the elongate member substantially near the proximal end. The device can further include an indicator configured to provide an indication to a user when the end cap has switched from the closed to the open position. The indication can include at least one or more of the following: a tactile, visual, electric or audible signal. In one implementation, the indicator can be a member that protrudes from the handle when the end cap is in the open position.
In general, in another aspect, the invention features a uterine sounding device including an elongate member having distal and proximal ends. The elongate member is configured for insertion into a uterus and include graduations marked on at least a portion of a length of the elongate member for measuring a length of the uterus. The device further includes an end cap connected to the distal end of the elongate member. The end cap is in a closed position when the elongate member is inserted into the uterus, and switches into an open position when a force applied to a distal tip of the end cap by the uterus exceeds a threshold force. A surface area of the end cap projected onto a plane substantially perpendicular to the longitudinal axis of the elongate member is enlarged in the open position as compared to in the closed position. The open position can resist penetration of the end cap into a wall of the uterus. The device further includes a handle connected to the elongate member substantially near the proximal end. The handle houses a deployment mechanism configured to switch the end cap from the closed position into the open position when the force applied to the distal tip of the end cap exceeds the threshold force.
Implementations of the invention can include one or more of the following features. The end cap can include one or more fin members, where the fin members are positioned along a longitudinal axis of the elongate member when the end cap is in a closed position and deploy laterally from the longitudinal axis when switching into the open position.
The elongate member can include a rod connected to the distal tip of the end cap, wherein the deployment mechanism includes a spring positioned about the elongate member. The spring can be preloaded to exert the threshold force on a first face of a retainer connected to the rod, where the threshold force exerted by the spring prevents the rod from translating in a direction away from the end cap. The retainer includes a second face abutting an inner wall of the handle preventing translation of the rod in a direction toward the end cap. When a force on the distal end of the end cap exceeds the threshold force, the rod translates axially compressing the spring and thereby translating the distal end of the end cap causing the one or more fin members to deploy laterally switching the end cap into the open position.
Aspects of the invention may include one or more of the following advantageous features. When there is no risk of perforating a uterine wall, the uterine sound operates in a closed position, maintains a small insertion profile and is substantially axially rigid. When a force exerted by a uterine wall on the distal tip of the uterine sound exceeds a threshold force, the surface area of the distal tip substantially increases (the open position) and resists perforation of the uterine wall. However, in the closed position, friction on the shaft of the uterine sound from a tight cervix or other conditions does not trigger a switch to the open position, allowing the uterine sound to function without interference in the absence of a risk of perforation.
From the perspective of a user, the uterine sound generally can be used in the same way as a conventional uterine sound, and can therefore easily replace a conventional uterine sound, while providing the benefit of the safer end cap.
The end cap of the uterine sound can include fins having shorter and longer links deployable outwardly, with the shorter links coming to a stop at approximately 90 degrees to the long axis of the elongate member and the longer links stopping at approximately 30 degrees to the long axis. When in the open position, this geometry presents the maximum surface area possible to the uterine wall on the short links, yet creates a rigid, stable triangular configuration that can withstand a substantial load without buckling.
An atraumatic design of the distal tip can prevent scraping the uterine walls and function to resist perforation. Under typical operating conditions, the uterine sound pushes against the distal wall of the uterine cavity in a direction substantially perpendicular to the wall. Intravascular catheters and the like include tips useful in preventing scraping and resisting perforation. However, these are ill suited for use in the current application, as the primary function of the uterine sound is to measure a length and long, flexible tips tend to deflect or buckle, leading to erroneous measurements. The uterine sound includes an atraumatic tip designed to resist perforation in a direction normal to tissue. For example, when the distal tip of the uterine sound is configured as a convex tip, an axial load applied to the end cap generates compressive stress in the central region of the tip. The resulting compressed short column of tissue therein tends not to divide. In order for the tip to perforate, the tissue must be sheared around the outer perimeter, while the central region is compressed which requires much higher axial loads.
The details of one or more embodiments of the invention are set forth in the accompanying drawings and the description below. Other features, objects, and advantages of the invention will be apparent from the description and drawings, and from the claims.
Like reference symbols in the various drawings indicate like elements.
A uterine sound is configured having an open and a closed position. Under normal operating conditions, the uterine sound is in the closed position for insertion into a uterus to measure the length of the uterus. Under conditions where there is a risk of the uterine sound perforating a uterine wall, the uterine sound switches into an open position. The open position provides an enlarged surface area of a distal end of the uterine sound that is in contact with a uterine wall and resists perforation by the uterine sound of the uterine wall.
Referring to
In the embodiment depicted, the uterine sound 100 includes an elongate member 101 having distal and proximal ends, where the elongate member 101 is configured for insertion into a uterus. Similar to a conventional uterine sound, the elongate member 101 is generally rigid axially yet flexible and/or malleable non-axially. As such, the elongate member 101 is rigid in the compressive direction with respect to the elongate member's distal and proximal ends, and flexible out of a longitudinal axis of the elongate member 101. The elongate member can be rigid in the compressive direction such that a user is provided a tactile sensation when the fundus of the uterus is engaged. The general configuration of the uterine sound 100 permits the same general procedure for measuring the length of the uterus as a conventional uterine sound.
In one embodiment, the uterine sound 100 is disposable and made of injection molded thermoplastic. The elongate member 101 of the uterine sound 100 can be molded to include a curvature suitable for easing passage of the elongate member 101 through the uterus. The curvature of the elongate member can be configured in any number of shapes and degrees of curvature, including but not limited to for example, the average curvature of the uterus. In another embodiment, the uterine sound 100 is disposable and made of injection molded thermoplastic and a malleable metal. In this embodiment, the elongate member 101 can optionally be molded to include a desired curvature and/or be manipulated by a user to provide a desired curvature.
As shown in
Referring also to
Referring to
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The shorter links 201 and longer links 202 of the fins 200 can be injection molded links, pinned rigid links, resilient wire or other suitable formed links. When the end cap fins 200 are injection molded, the end cap 102 can have one or more slots 205 defining fin 200 width and one or more holes 203 in the slot 205. The holes 203 are configured to define shorter link 201 and longer link 202 length, and provide an area of increased bending stress, thereby providing a “living hinge” at the ends of the fins 200. A living hinge can be, for example, a molded thin flexible bridge of material (e.g., polypropylene or polyethylene) that joins two substantially rigid bodies together. Additional one or more holes 204 in the end cap 102 located adjacent to the one or more slots 205, can be configured to enhance the living hinge separating the shorter links 201 and longer links 202.
The uterine sound 100 includes a feature to sense when to switch from a closed to an open position, and a feature to deploy into the open position. In the embodiment shown, a mechanical deployment mechanism both senses when a threshold force is exceeded and automatically deploys the fins 200 into the open position. Referring again to
An orientation indicator can be provided to indicate to a user the proper orientation of the uterine sound 100 relative to the uterus. For example, where the fins 200 of the uterine sound 100 deploy in a plane, the proper orientation substantially aligns the plane with the plane of the substantially flat uterus to ensure safe deployment of the fins 200. The orientation indicator can be positioned substantially near the proximal end of the uterine sound 100. The orientation indicator can be a marking on the surface, or a tactile indicator at the proximal end of the uterine sound 100. In one embodiment, the proximal end of the handle 400 can include an orientation indicator in the form of a flattened planar side that coincides with the plane of deployment of the fins 200. In one embodiment, the plane of handle 400 itself can indicate the plane of deployment of the fins 200.
In the embodiment shown in
When the uterine sound 100 is inserted into a uterus and the distal tip 500 of the end cap 102 presses against a uterine wall, a resistance force exerted by the uterine wall 600 (see
Under certain circumstances, e.g., through inadvertence, accident, anatomical divergence or stenosis of the uterus, the measuring process can result in forces on the uterine wall 600 that could result in perforation of the uterus with the uterine sound 100. For example, in the case of stenosis of the uterus, passing the uterine sound 100 through the cervix may be difficult and lead to an abrupt entry into the uterus. Once a force approaching, but substantially lower than a force capable of perforating the uterine wall 600, i.e., the threshold force, is transmitted to the retainer 404, the force preloaded in the spring 406, i.e., the threshold force, begins to compress the spring 406. As the spring 406 compresses, the retainer 404 moves away from the adjacent handle wall 403b and translates the rod 300 through the journals 402. The rod's translation is limited by the hardstop 405 contacting the boss 407. The translation of the rod 300 relative to the shaft 103 draws the distal tip 500 of the end cap 102 toward the handle 400, thereby deploying the fins 200 (see
After deployment, the fins 200 of the uterine sound 100 can be returned to the undeployed state by e.g., physically pushing the proximal end of the rod 300 to the undeployed position in the elongate member 101, thereby returning the distal tip 500 of the endcap 102 and accordingly the fins 200 to their undeployed positions. Alternatively, in the embodiment depicted, once the force on the distal tip 500 of the end cap 102 is released, i.e., is less than the threshold force, the spring 406 expands and automatically contracts the fins 200. Once returned to the undeployed position, the uterine sound 100 can safely be removed or used again.
Referring again to
Referring to FIGS. 5A-C and 6A-C, the end cap 102 includes a distal tip 500. The distal tip 500 can include an atraumatic geometry configured to resist perforation of the uterine wall 600 by reducing stress on the uterine wall 600. Examples of atraumatic geometry are shown in FIGS. 5A-C, including a full radius tip 501, a chamfered tip 502 or a convex tip 503 respectively.
As shown in FIGS. 6A-C, different atraumatic distal tip geometries produce different axial loads P on the uterine wall 600.
A number of embodiments of the invention have been described. Nevertheless, it will be understood that various modifications may be made without departing from the spirit and scope of the invention. Accordingly, other embodiments are within the scope of the following claims.
