Abstract:
A surgical device mitigates over-puncture with a bias spring that biases a leading, cutting edge in the opposite direction of the anticipated over-puncture. An associated locking mechanism is configured to release the force of the bias spring in a direction counter to the direction of insertion when the tension force of tissue against the cutting edge is released. Thus, when an opening in the tissue forms, the tension is released and the cutting edge can move opposite to the direction of insertion of the surgical device at the same time that an applied force drives the instrument in the direction of insertion. In this manner, the spring and locking mechanism cooperate to move the cutting edge opposite to the direction of insertion as soon as an incision is made.

Description:
BACKGROUND 
       [0001]    In minimally invasive surgical procedures, one or more tissue layers must sometimes be punctured without direct visualization of an instrument tip in order to gain access to a body cavity, duct, or the like. The instruments for such procedures are generally long and slender with high axial stiffness. In use, a surgeon or other user applies sufficient axial force so that the instrument can penetrate into the tissue by cutting, tearing or separating tissue fibers. 
         [0002]    At the point of puncture, or the instant when the tissue opens at the tip of the instrument, the force applied to the instrument by tissue tension goes to zero while the force applied by the user remains as a net force accelerating the instrument into the surgical site. Device designers have attempted to improve instruments to mitigate this forward driving force and subsequent acceleration by offering dynamic blade covers, blunt-tipped devices, and other features that indirectly address the problem of over-puncture by seeking to reduce the harmful effects when an over-puncture occurs. 
         [0003]    There remains a need for puncture devices that reduce or eliminate the over-puncture event, rather than addressing consequences of an over-puncture after it occurs. 
       SUMMARY 
       [0004]    A surgical device mitigates over-puncture with a bias spring that biases a leading, cutting edge in the opposite direction of the anticipated over-puncture. An associated locking mechanism is configured to release the force of the bias spring in a direction counter to the direction of insertion when the tension force of tissue against the cutting edge is released. Thus, when an opening in the tissue forms, the tension is released and the cutting edge can move opposite to the direction of insertion of the surgical device at the same time that an applied force drives the instrument in the direction of insertion. In this manner, the spring and locking mechanism cooperate to move the cutting edge opposite to the direction of insertion as soon as an incision is made. 
     
    
     
       DRAWINGS 
         [0005]    The invention may be more fully understood with reference to the accompanying drawings wherein: 
           [0006]      FIG. 1  is a perspective view of a device for surgical puncture access. 
           [0007]      FIG. 2  is a cut-away perspective view of a device for surgical puncture access. 
           [0008]      FIG. 3  is a cross-sectional view of a device for surgical puncture access. 
           [0009]      FIG. 4  is a cross-sectional view of a device for surgical puncture access. 
           [0010]      FIG. 5  is a cross-sectional view of a device for surgical puncture access. 
           [0011]      FIG. 6  depicts spring loading of a device. 
           [0012]      FIG. 7  depicts locking of a spring-loaded device. 
           [0013]      FIG. 8  depicts initiation of a puncture with a spring-loaded device. 
           [0014]      FIG. 9  depicts completion of a puncture with a spring-loaded device. 
           [0015]      FIG. 10  depicts retraction of a blade of spring-loaded device. 
           [0016]      FIG. 11  is a flow chart of a method for surgical puncture access. 
       
    
    
     DETAILED DESCRIPTION 
       [0017]    Disclosed herein are systems and methods for surgical puncture access, and in particular, puncture access using a retraction mechanism that retracts a blade in a direction opposite to a puncture force when a puncture is achieved and the resistive force of intervening tissue is removed. Although the disclosed retraction mechanisms are intended for a trocar in a surgical procedure, the principles of the invention have wide applicability. In a surgical context, any puncture-access device may employ similar techniques to prevent over-puncture, including a Veress needle, a venous access needle for catheter placement, an epidural or spinal tap needle, and a lung puncture device to correct a collapsed lung. 
         [0018]    More generally, the phenomenon of over-puncture appears in areas outside medicine and the principles of the invention may be applied in numerous non-medical contexts. For example, in certain manufacturing processes, a hole is drilled through a wall or vehicle body behind which lies a pipe, electrical conduit, gas tank, or other fragile or dangerous object. A power drill may be adapted to use the principles of the invention in order to drill only through the wall and no further, retracting a drill bit or the like when a complete puncture has been achieved. In similar fashion, a drill press can be adapted to prevent a user from drilling through a part and into a drilling table or chuck. Much larger industrial drilling applications through rock or soil could similarly use these mechanisms to prevent damage due to over-drilling. All such variations that would be apparent to one of ordinary skill in the art are intended to fall within the scope of this disclosure. 
         [0019]      FIG. 1  is a perspective view of a device for surgical puncture access. In general, the device  100  may include a housing  102  with an axis  104  oriented through the housing  102  in a direction of applied force as described below. As depicted, the device  100  is in a deployed position where a functional tip  106  of an instrument such as a cutting edge of a surgical blade extends outside the housing where it can be used in a cutting procedure or the like. 
         [0020]      FIG. 2  is a cut-away perspective view of a device for surgical puncture access. In general, the device  200 , which may be the device  100  described above, may include a housing  202 , an instrument  204 , a mechanical control  206 , a locking mechanism  208 , and a biasing mechanism  210 . 
         [0021]    The housing  202  may be formed of any suitable material such as biocompatible plastic or surgical stainless steel, and may enclose various components of the device  200 . The housing  202  may be a trocar shaped and sized for use in a laparoscopic procedure. More generally, the housing  202  may be of any other shape and size suitable for a particular medical or industrial application as contemplated herein. The housing has an interior  212  that contains various components of the device  200 . 
         [0022]    The instrument  204  may be slidably retained within the housing so that it can move axially (i.e., along the axis  104  depicted in  FIG. 1 ) during use. More specifically, the instrument  204  may be slidably retained within the housing  202  and movable along the axis between a first position where a functional tip of the instrument  204  extends outside the housing  202  (as depicted in  FIG. 1 ) and a second position where the functional tip rests within the housing  202  (as depicted in  FIG. 2 ). 
         [0023]    The instrument  204  may include a blade  214  such as an off-the-shelf symmetrical scalpel blade or any other blade or cutting instrument, or more generally any functional tip such as a drill bit, an awl or other piercing instrument, or the like. The instrument  204  may also include a shaft  216  that mechanically couples the blade  212  to other components of the device  200 . The shaft  216  may be coupled to the blade  214  with a pin, dowel, or any other permanent or removable/replaceable attachment fixture. In  FIG. 2 , the instrument  204  is depicted in a retracted position where the blade  204  is disposed within the housing  202 . In this position, the tip of the blade  214  is shielded within an insertion end  216  of the housing that has a rounded or blunt tip so that the device  200 , with the blade  214  in this retracted position does not have an exposed cutting surface. The blade  214  may be fully enclosed by a second half of the housing that is not shown here. 
         [0024]    The mechanical control  206  may be coupled (e.g., through the locking mechanism  208 ) to the instrument  204  and provides a manual control to move the instrument from the second (retracted) position to the first (deployed) position. This may, for example, include a plunger as depicted or any similarly operable device such as a slide or tab on a side of the housing  202  that permits axial movement of the instrument  204  into the deployed position by a user. Thus, the mechanical control  206  may be generally operable at a first end  216  of the housing  202  distal from a second end  218  of the housing where a functional tip of the instrument  204  deploys from the housing  202 . 
         [0025]    The locking mechanism  208  may be generally configured to secure the instrument against movement toward the second (retracted) position when the instrument is in the first (deployed) position and a force is applied to the blade  214  of the instrument  204  along the axis of the housing  202  and toward the interior  212  of the housing  202 , or toward the first end  216  of the housing  202  opposite the second end  216  (the insertion end). The locking mechanism  208  may also release the instrument  204  to move toward the second (retracted) position when the force applied to the blade  214  is removed. 
         [0026]    The biasing mechanism  210  generally biases the instrument  204  toward the second position where the instrument  204 , or more specifically the blade  214  or other function tip of the instrument is enclosed within the housing  202 . The biasing mechanism may, for example, include a coil spring or other spring configuration coupled between the mechanical control  206  (e.g., a plunger) and the housing  202 , or any other suitable spring mechanism, elastic mechanism, or the like. 
         [0027]    The cooperation of the locking mechanism  208  and the accompanying biasing mechanism  210  is discussed below, and generally facilitates retraction of the instrument  204  in a direction opposite to the direction of puncture when the loading force on the instrument  204  decreases, e.g., after a puncture is achieved. 
         [0028]      FIG. 3  is a cross-sectional view of a device for surgical puncture access. The device  300  may include a housing  302 , which may be any of the housings described above, with an interior wall  304 . A locking mechanism as described above may be formed of a first plurality of members  306  and a second plurality of members  308 . 
         [0029]    The first plurality of members  306  may be coupled to a plunger  310  or other mechanical control through a base plate or the like, which may include one or more hinges  312  to permit rotation of the first plurality of members  306  during use. In general, the first plurality of members may be oriented substantially parallel to the interior wall  304  of the housing  302 . In this orientation, the plunger  310  can apply a force to move an instrument connected to a shaft  314  from a retracted position inside the housing  302  to a deployed position outside the housing  302 . It will be understood that being oriented substantially parallel to the interior wall  304  does not require strict mathematical parallelism. Rather, each of the first plurality of members  306  may be generally closer to parallel than normal, or otherwise oriented sufficiently close to parallel to deliver an axial force from the plunger  310  against a biasing spring or the like to move the shaft  314  forward (or downward, in  FIG. 3 ) and deploy an instrument. By orienting the first plurality of members  306  nearly parallel to the interior wall  304 , a force applied to the plunger  310  creates a relatively small normal force against the interior wall  304  and prevents the locking mechanism from locking by friction against the interior wall  304  of the housing. 
         [0030]    The second plurality of members  306  may be hingeably coupled on a first end  316  to the first plurality of members, and coupled to the instrument (e.g., through the shaft  314 ) on a second end  318 . The second plurality of members  306  may be oriented substantially normal to the interior wall  304  of the housing. In this orientation, the first end  316  of each of the second plurality of members  306  can apply a normal force to frictionally engage the interior wall  304  of the housing  302  in a non-sliding mechanical relationship when a load is applied to the blade or other functional tip of an instrument coupled to the shaft  314 . More specifically a force applied in a direction from the deployed position to the retracted position along the axis of the housing  302  is converted through the linkages of the locking mechanism into a relatively large normal force into the interior wall  304  at the ends  316  of the second plurality of members  308 . 
         [0031]    For the second plurality of members  308 , being oriented substantially normal to the interior wall  304  does not require strict mathematical orthogonality. Rather, each of the second plurality of members  308  may be generally closer to normal than parallel, or otherwise oriented sufficiently close to normal to deliver a normal force to the interior wall  304  so that the first end  316  of each of the second plurality of members  308  can frictionally engage the interior wall  304  and secure the shaft  314  against further movement toward a retracted position. This arrangement advantageously increases the locking effect of the frictional engagement as the retraction load on the shaft  314  increases. 
         [0032]    In operation, the locking mechanism may secure an instrument against moving from a first position outside the housing  302  to a second position within the housing  302  by frictionally engaging the interior wall  304  of the housing  302  with a force proportional to a load applied to the functional tip in a direction from the first position to the second position along the axis of the housing  302 . When the load is removed, the complementary normal forces against the interior wall  304  are similarly removed, and the spring or other biasing mechanism can return the instrument to the second (retracted) position. 
         [0033]    It will be understood that while two pairs of members are shown, any number of members may be used. For example, the locking mechanism may use three or more pairs of members in a radial configuration within a cylindrical housing interior. Similarly, the principles of the locking mechanism may be usefully adapted to employ a single first and second member in an asymmetrical configuration. Thus, the arrangement of components in the locking mechanism of  FIG. 3  is provided by way of example only, and is not intended to limit the scope of the invention. 
         [0034]      FIG. 4  is a cross-sectional view of a device for surgical puncture access. In an alternative configuration of the device  400 , the first and second plurality of members may be formed of a monolithic piece of material with flexural hinges  402  such as corner-filleted hinging elements in place of the pin-based hinge elements depicted in  FIG. 3 . Operation of this device  400  is otherwise similar to the device  300  depicted in  FIG. 3 . 
         [0035]      FIG. 5  is a cross-sectional view of a device for surgical puncture access. In an alternative configuration of the device  500 , the locking mechanism may be formed of curved elements  502  that generally reproduce the loading schemes discussed above without use of hinges or discrete structural members. 
         [0036]    The device  500  may include a mechanical stop  504  positioned to prevent collapse of the locking mechanism and comprise of the locking function under large loads. In general, the mechanical stop  504  prevents a lower portion of the integral locking mechanism—that portion that extends substantially normal to the interior wall of the housing—from moving past a normal or ninety degree orientation where further displacement of the shaft will not provide additional frictional force against the interior wall. It will be appreciated that the mechanical stop  504  may be usefully incorporated into any of the embodiments described above. For example, in the embodiment of  FIG. 3 , the mechanical stop  504  may be positioned to prevent the second plurality of members from hinging beyond a predetermined angle relative to the interior wall of the housing, such as beyond ninety degrees where increased force would no longer yield increased frictional loading against the interior wall. 
         [0037]    Operation of a surgical puncture access device is now described in greater detail with reference to a puncture operation. 
         [0038]      FIG. 6  depicts spring loading of a device. In an initial step, a plunger  602  or other mechanical control is depressed to create a bias force against a spring  604 . In this state, a functional tip  606  is deployed, but there is no force independent of the plunger  602  maintaining the functional tip  606  in this position. 
         [0039]      FIG. 7  depicts locking of a spring-loaded device. In this step, the device is pressed against a target surface such as an abdominal wall  608  of a surgical patient. Thus the force applied to the functional tip  606  may be created by applying an axial force to the housing of the device (as indicated by arrows  610 ) while the cutting edge or other functional tip  606  engages a tissue layer of a patient. While an abdominal wall  608  is depicted, it will be understood that this tissue layer may also or instead include skin, muscle, peritoneum, or any other superficial layer of tissue, depending on whether and to what extent skin and other layers are surgically exposed prior to use of the device. The axial force may be obtained by a user gripping the device in any suitable manner and applying an axial load toward the target surface. It will be noted that at the moment of engagement with the target surface, two complementary forces—a first force applied to the plunger and a second force applied to the functional tip  606 —are used to secure the instrument in the deployed position. These two complementary forces create the outward or normal force on the interior wall of the housing that frictionally engages the locking mechanism. However, once so engaged, the force on the functional tip  606  can sustain the locking effect and the force applied to the plunger may be removed, thus permitting free manipulation of the housing by a user, provided the functional tip  606  remains forcibly engaged with the target surface. 
         [0040]      FIG. 8  depicts initiation of a puncture with a spring-loaded device. In this step, the housing may be manually driven into the target surface so that the cutting edge of the instrument can puncture the surface. The force manually applied to the housing is directly translated to the functional tip  606  to obtain this cutting action. 
         [0041]      FIG. 9  depicts completion of a puncture with a spring-loaded device. In this step, the functional tip  606  has been driven through the surface. When the cutting edge of the functional tip  606  punctures the target surface (e.g., peritoneum of a patient), the force against the functional tip  606  is removed, and so is the resulting normal force against the housing. Without this normal force to secure frictional engagement with the housing, the locking mechanism can separate from the interior wall of the housing. This is illustrated as a small gap between the locking mechanism and the interior wall of the housing, however, physical separation of the surfaces is not required. The desired reduction in frictional engagement may be achieved while the two surfaces remain in contact, albeit under a reduced normal force. 
         [0042]      FIG. 10  depicts retraction of a blade of spring-loaded device. When the frictional engagement of the locking mechanism to the interior wall is reduced or removed, the spring  604  can operate to retract the functional tip  606  in a direction opposite to the driving force  614  on the housing, thereby retracting the functional tip  606  at the moment of puncture and mitigating the over-puncture event. 
         [0043]      FIG. 11  is a flow chart of a method for surgical puncture access. The method  1100  may be performed using any of the devices described above. 
         [0044]    As shown in step  1102 , the method  1100  may begin with applying a deployment force to spring load a blade in a deployed position exposed outside a housing with a bias to return to a retracted position within the housing. This may, for example, include depressing a plunger or other control mechanism on the housing of the device. The bias may be achieved for example with a coil spring or any other suitable spring or elastic mechanism, or any combination of the foregoing that can provide sufficient biasing force to retract the blade or other functional tip as contemplated herein. 
         [0045]    As shown in step  1104 , the method  1100  may include pressing the blade against a target surface while in the deployed position, thereby creating a force against the blade. 
         [0046]    As shown in step  1106 , the method  1100  may include locking the blade in the deployed position by directing the force against the blade normally against an interior wall of the housing to establish a friction fit proportional to the force. This locking step is performed mechanically by the components of the device in response to the user-controlled steps of spring loading as in step  1102  and engagement with a target surface as in step  1104 . 
         [0047]    As shown in step  1108 , the method may include releasing the deployment force on the plunger or other control mechanism. With the locking obtained in step  1106  and sustained force of the blade against a target surface, the blade can remain locked in the deployed position notwithstanding a driving force (e.g., by the hand of a user) of the housing and blade into the target surface. Thus, the hands of a user are free to manipulate the deployed blade to obtain a puncture of the target surface in any desire manner. 
         [0048]    As shown in step  1110 , a puncture force may be applied to the housing. This puncture force, which may be any suitable surgical puncture action or technique that maintains a force of the blade against the target surface, may drive the blade through the target surface. As a result, the force against the blade is released and the bias in the spring or other biasing mechanism can withdraw the blade into the retracted position. A similar effect may be achieved by simply removing the blade from the target surface, which would also remove the force against the blade, release the locking mechanism, and cause the spring to retract the blade into the housing. In order to resume the procedure from this state, the blade can once again be deployed with a deployment force as described in step  1102  and the method  1100  may be repeated. 
         [0049]    It will be appreciated that the methods and systems described above are set forth by way of example and not of limitation. Numerous variations, additions, omissions, and other modifications will be apparent to one of ordinary skill in the art. While particular embodiments of the present invention have been shown and described, it will be apparent to those skilled in the art that various changes and modifications in form and details may be made without departing from the spirit and scope of the invention as defined by the following claims. The claims that follow are intended to include all such variations and modifications that might fall within their scope, and should be interpreted in the broadest sense allowable by law.