Trocar with retractable cutting surface

A trocar having a cutting shaft with a cutting surface at a distal end. The cutting shaft moves longitudinally with respect to an obturator such that in one position the cutting surface is in an exposed position suitable for application of a piercing force. Upon interruption of the piercing force to the cutting surface, the cutting surface moves longitudinally with respect to the obturator such that the cutting surface is in a retracted position within the obturator. The trocar may include a first spring urging the cutting surface to an exposed position and a second spring urging the cutting surface to a retracted position. The second spring has a slightly stronger biasing force than the first spring to bias the cutting surface to the retracted position.

The present invention relates to a trocar and in particular to a trocar that has a retractable cutting surface such as a retractable cutting blade.

Trocars are surgical instruments that are used to puncture tissue to gain access to body cavities. Generally, a cannula surrounds at least a portion of the trocar so that after the tissue is punctured, the cannula can provide access to the body cavity for endoscopic instruments and the like. Common to many trocars is that sharp tip used to puncture the tissue is withdrawn or covered after the tissue is punctured and the trocar is removed from the site of the puncture.

One such example is shown in U.S. Pat. No. 5,474,539 where an obturator having an attached piercing tip is movable from a protected position within the cannula to an advanced or operative position distally of the cannula. After piercing the tissue, the obturator and attached tip are automatically withdrawn to a retracted position within the cannula. A disadvantage to this type of system is that there must be an operative connection between the obturator and the cannula, which complicates the system and increases its cost.

Another proposed solution provides a safety shield that covers the blade. The problem with this solution is that the incision must be sufficiently large so that the shield can cover the blade. In addition, the friction between the shield and the tissue must be reduced or eliminated; otherwise, the movement of the shield to cover the blade may be too slow.

Therefore, it would be beneficial to provide a trocar that does not rely on an operative connection with the cannula and does not need a cannula within which to withdraw the cutting surface in order to position the cutting surface in a safety position. The trocar according to the present invention solves that problem.

SUMMARY

According to the present invention a trocar is provided with a cutting surface, blade, or tip that is retractable within the obturator. Advantageously, the cutting surface will automatically retract into the obturator after the cutting surface penetrates through the tissue and the corresponding presence of pressure against the cutting surface is reduced or removed. The cutting surface quickly retracts so that contact or damage any internal organs is reduced or avoided

In accordance with one embodiment of the present invention, a trocar is provided that comprises an outer housing, an inner housing, an obturator, a cutting shaft with a cutting surface at a distal end, and a spring that biases the cutting surface to an exposed position. The obturator is hollow with an open distal end and defines a longitudinal axis. The obturator surrounds the cutting shaft and cutting surface. The inner housing cooperates with the cutting shaft such that in a first position the cutting surface is retracted within the obturator and upon rotation of the inner housing from the first position, the cutting surface moves longitudinally with respect to the obturator to a second position wherein the cutting surface is exposed with the cutting surface located beyond the distal end of the obturator.

The cutting surface may have any known or suitable shape as is well known in the art or can be contemplated. In one embodiment, the cutting surface is removable from the cutting shaft. As a result, the cutting surface can be varied in its length, shape, or other features. Moreover, if the cutting surface is removable from the cutting shaft, a sharp surface can be provided as desired or needed.

Advantageously, the obturator is reusable, simple in construction, easy to clean, sterilize and maintain. Moreover, a cannula is not necessary for operation of the trocar so that the cannula is used to provide access for instrument insertion after penetration of the tissue.

DESCRIPTION

Turning now toFIGS. 1 and 2, a trocar10of the present invention is shown. The trocar10includes an outer housing20, an inner housing40, a cutting shaft120that carries a cutting surface130, an obturator140that surrounds the cutting shaft120and from which the cutting surface130extends, a first spring160, and a second spring170. The trocar10may be described as being aligned along a longitudinal axis12and having a proximal end14and a distal end16. The proximal end14is the end of the trocar10defined by the outer housing20and the distal end16is the end of the trocar10from which the cutting surface130extends from the obturator140.

The outer housing20has an outer surface22and an inner surface28. The outer surface22may have any shape suitable for grasping. Accordingly, the outer housing20as shown inFIG. 1has a convex top portion24with a tapered sidewall26. The outer housing20can be made of any material suitable for a sterile environment. The inner surface of the outer housing20is cylindrical and has a diameter slightly larger than at least a portion of the outer surface42of the inner housing so that the outer housing20can surround the inner housing40.

A flange34extends from an inner portion of the outer housing20and contains threads36on its periphery that will threadably engage threads154provided on the inner portion of the proximal end146of the obturator. As will become clear from the discussion below, the flange34also receives one end162of a spring160.

As best seen inFIG. 2, the inner housing40is desirably cylindrically shaped and has an outer surface42, an inner surface58, a first (or proximal) end46, and a second (distal) end50. The inner housing50may be formed of two pieces, an inner piece48and an outer piece52. When formed of two pieces, each piece may be formed of a single material or of differing materials. In addition, when formed of two pieces the pieces are securely joined or attached such that movement of the outer piece52results in movement of the inner piece48and vice versa. Alternatively, the inner housing50may be formed of a single piece.

In one embodiment, at least a portion of the outer surface42adjacent the second end50defines a flange56. The distal end32of the outer housing20may abut the flange56. The outer surface of the second end50of the inner housing desirably has a gripping surface54so that the inner housing40can be grasped and rotated. The gripping surface54can have any suitable form or material. For example, the gripping surface54may be in the form of scalloping.

The inner surface58of the inner housing40has a groove60that circumscribes the inner surface58of the inner housing40. The groove60is located adjacent the proximal end46of the inner housing. The groove60receives a spring170, desirably a torsion spring such as a radial torsion spring. Therefore, the groove60has a width62that is about the same size as the width of the torsion spring. In addition, an aperture64is provided and it receives one end172of the spring.

The inner housing40cooperates with the cutting shaft120such that when the inner housing40is in a first position, the cutting surface130is retracted and when the inner housing40rotates to a second position, the cutting shaft120and the cutting surface130move laterally such that the cutting surface130is exposed. Referring back toFIG. 2, the cutting shaft120has a proximal end122and a distal end128. The distal end128carries a cutting surface130. The cutting surface130may have any known or suitable shape as is well known in the art or can be contemplated. In one embodiment, the cutting surface130is removable from the cutting shaft120. As a result, the cutting surface130can be varied in its length, shape, or other features. The proximal end122has a flange124that surrounds the outer surface of the cutting shaft. Desirably, the flange includes a pin126that is received within a cam slot80provided on the inner housing40as described below.

The cam slot80is located adjacent the distal end50of the inner housing40. The cam slot80is provided on the inner surface58of the inner housing40. Although the cam slot80can extend from the inner surface58to the outer surface42, it is desired that the cam slot80does not extend through to the outer surface because it will reduce the amount of surface that can become dirty or contaminated or caught by the operator.

The cam slot80has at least two portions82,92defining two positions, e.g., a first position where the cutting surface130is retracted, i.e., not exposed and a second position where the cutting surface130is exposed. In one embodiment, the cam slot80has three portions82,92,98defining three positions. The first82and second portions92are the same as described above. The third portion98defines a position when pressure is exerted in a proximal direction against the cutting surface130.

As better seen inFIGS. 5-7, in one embodiment of the trocar10of the present invention, the cam slot80has a first portion82, a second portion92, and a third portion98. The first portion82has a first end84, a second end86, a proximal surface88, a distal surface90, and is angled from the longitudinal axis12such that when the pin126is at the first end84of the first portion82, the cutting shaft120is in the furthest proximal position. In this, the first position, the cutting surface130is retracted into the obturator140as shown inFIG. 5. The first portion82may have any suitable angle from the longitudinal axis depending on the force desired to return the cutting surface to the first position.

The second portion92has a first end (a proximal position)94, a second end (a distal position)96. The second end96is open at the distal end50of the inner housing40so that the pin126can engage the cam slot80. In other words, in order to assemble the trocar10, the second end96of the second portion92is open so that the pin126can slide into the cam slot80. In use, despite the fact that the second or distal end96of the second portion92is open, the cutting shaft120is stopped from distal movement when the flange124on the cutting shaft120contacts an inner flange156on the obturator140. When the pin126is in the distal end96of the second portion, the cutting surface130is exposed, i.e., the cutting surface130extends from the distal end142of the obturator140as best seen inFIG. 6, which is referred to as the second position.

The third portion98of the cam slot80connects the first portion82with the second portion92and is aligned normal to the longitudinal axis12. The third portion98has a stop100that is adjacent the distal end86of the proximal surface88of the first portion82. When the pin126is in the second position, the cutting surface130is exposed and pressure has been applied to the cutting surface130in a proximal direction such as by, for example, tissue or tissue body that the cutting surface130is penetrating. As a result, the pin126has traveled from the second portion92to the third portion98and is held by the stop100so that the cutting surface130can penetrate or cut the tissue or other material, as best seen inFIG. 7, which is referred to as the third position.

An obturator140surrounds the cutting shaft120and, when the cutting shaft120is in the first position, the cutting surface130is completely withdrawn inside the obturator140. The obturator140has a distal end142, from which the cutting surface130extends, and a proximal end146, which cooperates with the proximal end122of the cutting shaft120and the inner housing40. At least one longitudinal slot148is provided at the proximal end146of the obturator140. Desirably, a first longitudinal slot148and a second longitudinal slot150are provided at the proximal end146of the obturator140. The second slot150may be provided at any suitable location relative to the first slot148. In some embodiments, the second slot150is opposite the first slot148.

The first slot148receives the pin126provided on the cutting shaft120and the pin extends outwardly from the obturator140. The first longitudinal slot148extends from the proximal end146of the obturator140toward the distal end142of the obturator140. The first longitudinal slot148extends a distance such that when the pin126abuts the distal end of the slot148, the cutting surface130is exposed a desired distance from the distal end142of the obturator140.

The second longitudinal slot150receives one end174of the second spring170. The second longitudinal slot150extends from the proximal end146of the obturator140toward the distal end142of the obturator.

A flange152is provided adjacent the proximal end146of the obturator140. The flange152may act as a stop for the inner housing40and to limit the distance the inner housing40can slide in a distal direction.

As noted above, a first spring160is provided and it is desirably a coil spring having a first end162and a second end164. The first end162is received within the flange34provided on the inner surface28of the outer housing20opposite the top of the outer housing24. The second end164abuts the flange124provided on the cutting shaft120to bias the cutting shaft120in a distal direction, i.e., in a direction such that the cutting surface130will be in an exposed position. If desired, the second end164may be fixed to the flange124on the cutting shaft120.

The trocar10also has a second spring170, desirably in the form of a torsion spring, such as a radial torsion spring. The second spring170has a first end172that extends outward from the spring170and is received in an aperture64provided in the groove60of the inner surface58of the inner housing40. The second end174extends inward from the spring170and is received in the at least one of the longitudinal slots148,150of the obturator140. Desirably, the second end174extends into the second longitudinal slot150.

It will be understood by one of skill in the art that because the first172and second174ends of the second spring170are retained in a position relative to each other that the inner housing40will be biased to a first position. In addition, rotation of the inner housing40will act against the spring tension or force of the second spring170. The second spring can be manufactured to provide a suitable force or torque. In one embodiment, the spring provides a torque at 90° in the range from about 20 to about 40 N·mm, suitably in the range from about 24 to about 31 N·mm.

Operation of the trocar10will now be described.FIG. 5shows the safety position of the trocar10with the cutting surface130disposed within the obturator140. In this position, the cutting shaft120is retracted to its most proximal position and the pin126is at the first end84of the first portion82of the cam slot80. In a desired embodiment, the tension or spring force of the second spring170is greater than the spring force of the first spring160. Because the force of second spring170overcomes the force of the first spring160, which biases the cutting surface130to an exposed position, the inner housing40is biased to the position shown inFIG. 5. In addition, because the inner housing40is biased to the position shown inFIG. 5, the pin126is at the first end84of the first portion82of the cam slot80and thus, the cutting shaft120is at its most proximal position.

To actuate and expose the cutting surface130from the distal end142of the obturator140, the inner housing40is rotated to the position shown inFIG. 6. As a result, the pin126travels downwardly in the first portion82of the cam slot80, across the third portion98and into the second portion92of the cam slot80. Although the second spring170acts to bias the inner housing40to the position shown inFIG. 5, the wall of the second portion92of the slot80prevents the inner housing40from rotating. In this position, the first spring force160biases the cutting surface130to an exposed position with the cutting surface130extending beyond the distal end142of the obturator140. The cutting surface130will distally extend a distance dictated by either the length of the first spring160, the flange152provided on the obturator140, or a combination of both.

The cutting surface130is now ready to be used. When the cutting surface130contacts, for example, the tissue body of the abdominal wall, pressure is exerted in a proximal direction against the cutting surface130. The spring force of the first spring160is such that it is less than the pressure required to penetrate the tissue body and is such that the pin126moves to the proximal position94of the second portion92of the cam slot80. In this position, the inner housing40is not constrained from rotational movement by the pin126in the third portion98of the cam slot80and therefore, the inner housing40rotates in a direction such that the pin126moves toward the first portion82of the cam slot80. The pin126moves along the third portion98of the cam slot80until it contacts the stop100. The pin126, cutting shaft120, and cutting surface130remain in this position until the pressure against the cutting surface130is reduced to a degree or by an amount such that it is less than the distally biasing force of the first spring160or is removed.

As noted above, the angle of the first portion82of the cam slot80will determine the amount of force that the second spring170must provide to overcome the biasing force of the first spring160and move the cutting shaft120and pin126to the proximal end84of the cam slot80. In other words, the greater the angle of the first portion82, the greater the force that the second spring170must provide. Likewise, the smaller the angle of the first portion82, the lower the force that the second spring170must provide.

When the pressure against the cutting surface130is reduced to a degree or by an amount such that it is less than the distally biasing force of the first spring160or is removed (e.g. when the cutting surface130completely penetrates the tissue), the first spring160biases the cutting shaft120(and thus the pin126) in a distal direction. As a result, the pin126is moved from the stop100and, because the force of the second spring170is greater than the force of the first spring160, the inner housing40rotates such that the pin126travels in a proximal direction along the first portion82of the cam slot80as best seen inFIG. 8until the pin126reaches the proximal position84of the first portion82of the cam slot80, as best seen inFIG. 5. The cutting surface130is then in its fully retracted position (the safety position). Thus, the cutting surface quickly retracts so that the cutting surface does not contact or damage any internal organs, blood vessels, or unintended areas.

It will be appreciated that during operation of the trocar10that the inner housing40rotates but does not move laterally and that the cutting shaft120moves laterally but does not rotate. In addition, the trocar10of the present invention provides a cutting surface130that immediately and automatically retracts after the cutting surface130has penetrated the tissue body. In other words, after the manual actuation of the cutting surface130to expose the cutting surface130to a use position (the second position), the retraction of the cutting surface130to a retracted or safety position is immediate and automatic.

Turning now toFIG. 9another embodiment of the present invention is illustrated. In describing this embodiment like reference numerals will be used to identify like parts. As with the previously described embodiment, the trocar10is provided with an outer housing220, an inner housing240, a cutting shaft120that carries a cutting surface130, an obturator140that surrounds the cutting shaft120. In addition, the trocar includes an actuation ring200and a return spring210. As with the previously described embodiment, the cutting shaft120, the obturator140, the first spring160and the second spring170in this embodiment function in the same manner as the previously described embodiment. In this embodiment, the outer housing220has a top portion222and a sidewall224extending from the top portion. The top portion222and sidewall224may be separate pieces or may be a single unitary piece. The sidewall224is provided with a slot226that is preferably substantially laterally oriented (best seen inFIG. 12). Adjacent the slot226, icons228may be located to provide a visual indication of the state of the cutting surface130. In other words, the icons228may indicate whether the cutting surface130is in an extended or a retracted position.

The inner housing240has a first or proximal end242and a second or distal end244. The distal end244of the inner housing is contiguous with the flange152of the obturator140. As with the inner housing of the other embodiments, the inner surface246of the inner housing240has a groove (not shown) that circumscribes the inner surface246of the inner housing240to receive the second spring170in the same manner as with the inner housing40.

The inner housing240is provided with a cam slot80located adjacent the distal end244of the inner housing240. The cam slot80is provided on the inner surface of the inner housing40. Although the cam slot80can extend through the entire wall of the inner housing, it is not necessary that the cam slot80does so. Accordingly, the cam slot80may be provided only on the inner surface246of the inner housing, which will reduce the amount of surface that can become dirty or contaminated or caught by the operator. Alternatively, the actuation ring200can be located so that the actuation ring200covers the cam slot80.

The cam slot80has at least two portions82,92defining two positions, e.g., a first position where the cutting surface130is retracted, i.e., not exposed and a second position where the cutting surface130is exposed. In one embodiment, the cam slot80has three portions82,92,98defining three positions. The first82and third portions98are the same as described above. The second portion92in the inner housing240is angled. Desirably, the angle is in a direction opposite that of the travel of the pin126as the pin travels from the cutting surface extended position to the cutting surface retracted position.

The inner housing240is also provided with a first radially extending pin250and a second radially extending pin252spaced from the first radially extending pin. The first radially extending pin engages a slot202provided in the inner surface202of the actuation ring200to drivingly connect the actuation ring200to the inner housing240. The slot204extends around a portion of the inner surface202of the actuation ring200, the purpose of which will become clear from the following text. Alternatively, the pin may be dispensed with and the actuation ring200may be drivingly connected to the inner housing in another conventional manner. Or, the actuation ring and the inner ring may be formed as a single piece.

The second radially extending pin252extends through the slot226of the side wall224of the outer housing220. The second radially extending pin252can therefore provide a visual indication whether the cutting surface130is in an extended or a retracted position. It will be understood by those of skill in the art, that the second radially extending pin252in conjunction with the icons228can provide an enhanced visual indication.

As noted above, a return spring210is provided. The return spring is provided with a first end212and a second end214. The first end212engages a cavity206formed on the bottom208of the actuation ring200. The second end214engages a cavity158formed on the flange152of the obturator140. When the first end212and the second end214are received in their respective cavities, the actuation ring200will be biased toward a rest position. In practice, the actuation ring200is drivingly connected to the inner housing240by the engagement of the pin250in the slot204so that the shaft120and thus the cutting surface130will be in the retracted position (indicated with the icon228“safe” inFIG. 12).

To actuate and expose the cutting surface130from the distal end142of the obturator140, the actuation ring200is rotated to drivingly rotate the inner housing240such that the pin is in the second portion92of the cam slot80. In other words, as the actuation ring200is rotated, one end wall (not shown) of the slot204contacts the first radially extending pin250to drivingly rotate the inner housing240. The second radially extending pin moves from one end of the slot226(indicated with the icon228“safe” inFIG. 12) to the other end of the slot (indicated with the icon228“armed” inFIG. 12). The cutting surface130is then exposed. When the force rotating the actuation ring200is released, the actuation ring200is biasingly moved to its rest position, while the inner housing240remains in position because the slot204rides over the pin250without moving the inner housing240.

Referring toFIG. 13, another embodiment of a portion of the trocar of the present invention is shown. InFIG. 13, a portion of the inner housing240is shown with an intermediate member300surrounding the inner housing240. The intermediate member300may be integrally formed as or with the actuation ring (not shown) or it may be separate from the actuation ring. When the intermediate member300is separate from the actuation ring, the actuation ring may be fixed to the intermediate member in any suitable manner such as by press fitting or the like.

As with the inner housing240of the other embodiments, the inner surface of the inner housing has a groove (not shown) that circumscribes the inner surface of the inner housing to receive the second spring170in the same manner as with the other inner housings. In addition, the inner housing is provided with a cam slot (not shown) as described in connection with the other inner housings.

The intermediate member300surrounds the inner housing and in general surrounds the distal portion of the inner housing. The intermediate member300has a radially extending pin310that rides in the slot204of the actuation ring200. The intermediate member radially extending pin310is also attached to the inner housing240in any suitable manner so that movement of the intermediate member300causes corresponding movement of the inner housing240.

The intermediate member300is provided with a peripheral groove330about a portion of the outer periphery320. In addition, the bottom302of the intermediate member300is provided with a slot304that extends about a portion of the circumference of the bottom302of the intermediate member300. The slot has a first end306and a second end308. A traveling pin340has a first end342extending in the groove and a second end344that extends through the slot304and engages the cavity158formed on the flange152of the obturator140.

The traveling pin340is biased to a position adjacent the first end306of the slot304by a biasing member360. The biasing member360can have one end362attached to the traveling pin340and a second end364attached to a portion of the intermediate member300. As shown inFIG. 13, a stationary pin370is provided to secure a second end364of the biasing member360. The biasing member360can have any suitable form and is shown as a coil spring inFIG. 13.

The first end342of the traveling pin340may be provided with a first346and a second shoulder348that will aid in the travel of the traveling pin340in the groove330. In this regard, the first shoulder346may be adjacent one wall332of the groove and the second shoulder348may be adjacent the opposite wall334of the groove. Where a first346and second348shoulder is provided, one end362of the biasing member360may be attached to the traveling pin340in the area between the first346and second348shoulder.

When the second end344of the traveling pin340is received in the cavity158, the actuation ring200will be biased toward a rest position. In practice, the actuation ring200is drivingly connected to the inner housing240by the engagement of the intermediate member radially extending pin310with the inner housing240and with the slot204of the actuation ring200so that the shaft120and thus the cutting surface130will be in the retracted position (indicated with the icon228“safe” inFIG. 12).

To actuate and expose the cutting surface130from the distal end142of the obturator140, the actuation ring200is rotated to drivingly rotate the inner housing240such that the pin126is in the second portion92of the cam slot80. In other words, as the actuation ring200is rotated, one end wall (not shown) of the slot204contacts the intermediate member radially extending pin310to drivingly rotate the inner housing240. When the force rotating the actuation ring200is released, the actuation ring200is biasingly moved to its rest position by the biasing member360, while the inner housing240remains in position because the slot204rides over the intermediate member radially extending pin310without moving the inner housing240.

It is to be understood that, while the invention has been described above in conjunction with the specific embodiments, the description is intended to illustrate and to limit the scope of the present invention, which is defined by the scope of the claims. For example, while several or the parts have been described as being formed as separate parts, it is possible to form them as a single piece. Advantageously, one of skill in the art will understand that the trocar10of the present invention will operate independently of a cannula, although the use of a cannula with the trocar10is contemplated. The cannula may surround the proximal end of obturator and, after penetration of the tissue body (e.g., the abdominal wall), the cutting surface will retract into the obturator (but not into the cannula), the cannula can be placed, and the trocar can be withdrawn from the cannula to provide an access port, as is known in the art.