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. There remains a further need for a puncture device that locks in a preloaded state for improved ease of use. 
       SUMMARY 
       [0004]    A puncture device mitigates over-puncture with a bias spring that biases a leading, cutting edge in the opposite direction of an anticipated over-puncture. An associated locking mechanism is configured to release the force of the bias spring when a puncture event releases the tension force of a target surface such as tissue against the cutting edge. A preload lock secures the cutting edge in a loaded state until an initial engagement with the target surface. When the cutting edge initially engages tissue with an applied force, the preload lock releases, and when an opening in the tissue forms, the locking mechanism for the cutting edge also releases so that the cutting edge can move opposite to the direction of puncture 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. 
           [0017]      FIG. 12  is a flowchart of a method for puncture access with a tool that provides preload locking. 
           [0018]      FIG. 13  is a functional diagram of a puncture device with a preload lock. 
           [0019]      FIG. 14  illustrates a step in a puncture operation. 
           [0020]      FIG. 15  illustrates a step in a puncture operation. 
           [0021]      FIG. 16  illustrates a step in a puncture operation. 
           [0022]      FIG. 17  illustrates a step in a puncture operation. 
           [0023]      FIG. 18  is a functional diagram of a barrel-loading puncture device. 
           [0024]      FIG. 19  illustrates operation of a barrel-loading puncture device. 
           [0025]      FIG. 20  illustrates operation of a barrel-loading puncture device. 
           [0026]      FIG. 21  illustrates operation of a barrel-loading puncture device. 
           [0027]      FIG. 22  illustrates a puncture device with a bistable preload lock. 
           [0028]      FIG. 23  illustrates a puncture device with a bistable preload lock. 
           [0029]      FIG. 24  illustrates a puncture device with a bistable preload lock. 
           [0030]      FIG. 25  illustrates a puncture device with a preload lock. 
           [0031]      FIG. 26  illustrates the puncture device of  FIG. 25  in a preloaded state. 
           [0032]      FIG. 27  illustrates a puncture device with a compliance mechanism. 
           [0033]      FIG. 28  illustrates a puncture device with a compliance mechanism. 
           [0034]      FIG. 29  illustrates a puncture device with an angled preload locking mechanism. 
       
    
    
     DETAILED DESCRIPTION 
       [0035]    All documents mentioned herein are hereby incorporated in their entirety by reference. References to items in the singular should be understood to include items in the plural, and vice versa, unless explicitly stated otherwise or clear from the text. Grammatical conjunctions are intended to express any and all disjunctive and conjunctive combinations of conjoined clauses, sentences, words, and the like, unless otherwise stated or clear from the context. Thus the term “or” should generally be understood to mean “and/or” and so forth. 
         [0036]    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, a cranial drill, and a lung puncture device to correct a collapsed lung. 
         [0037]    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 benefit from 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. 
         [0038]      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. 
         [0039]      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 . 
         [0040]    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 . 
         [0041]    The instrument  204  may be slideably 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 slideably 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 ). 
         [0042]    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. 
         [0043]    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 . 
         [0044]    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. 
         [0045]    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. 
         [0046]    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. 
         [0047]      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 . 
         [0048]    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. 
         [0049]    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 . 
         [0050]    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. 
         [0051]    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. 
         [0052]    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. 
         [0053]      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 . 
         [0054]      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. 
         [0055]    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. 
         [0056]    Operation of a surgical puncture access device is now described in greater detail with reference to a puncture operation. 
         [0057]      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. 
         [0058]      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 that the functional tip  606  remains forcibly engaged with the target surface. 
         [0059]      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. 
         [0060]      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. 
         [0061]      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. 
         [0062]      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. 
         [0063]    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. 
         [0064]    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. 
         [0065]    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 . 
         [0066]    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. 
         [0067]    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. 
         [0068]    A surgical puncture access tool as described above may in general be improved by a preload lock that secures a blade or other functional tip in a deployed position until ready for use. This may simplify operation of the tool so that the device can be preloaded, e.g., with a plunger or the like, and then pressed against a target surface for application of a puncture force. The axial force from initially pressing the tool against the target surface may first release the preload lock so that the tool is in a state as generally described above for application of a puncture force. Systems and methods for preload locking are now described in greater detail. 
         [0069]      FIG. 12  is a flowchart of a method for puncture access with a tool that provides preload locking. In general, a preload lock secures a tool in a deployed position with a preloaded bias force to retract a functional tip upon subsequent occurrence of a puncture event. It will be appreciated that while the following method  1200  is described with reference to a blade, the method may be readily adapted to any instrument with a functional tip (e.g., a drill or an awl) that is used with a puncture force. 
         [0070]    As shown in step  1202 , the method  1200  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 to move the blade from a first position within the housing to a second, deployed position extending from the housing. The bias may be achieved for example with a coil spring, flexural spring element, or any other suitable spring, elastic or other compliance mechanism, or any combination of the foregoing that can provide sufficient biasing force to retract the blade or other functional tip as contemplated herein. 
         [0071]    As shown in step  1204 , the method  1200  may include locking the blade in the deployed position. This may be accomplished, e.g., by any of the preload locking mechanisms described below. In this preloaded state, the blade is deployed in a position protruding from the housing for use in a puncture procedure, and does not require a sustained deployment force to remain in this state. At the same time, the biasing force to return the blade to the retracted position is maintained by the preload lock, which mechanically engages the blade in this deployed, pre-biased position. 
         [0072]    As shown in step  1206 , the deployment force, e.g., the force applied to a plunger, slider, or the like to deploy the blade, may be released and the device can remain secured in this preloaded state by the preload lock. 
         [0073]    As shown in step  1208 , the method  1200  may include pressing the blade against a target surface while in the deployed position, thereby creating a force against the blade, e.g., an axial force normal to the target surface and toward the housing. 
         [0074]    As shown in step  1210 , the method  1200  may include converting the axial force into forces for a number of different functions. In one aspect, the axial force may be converted into a first force to release the preload lock, and the corresponding preload locking force. While this might free the blade to move in response to the biasing force within the device, the axial force may also be converted, e.g., substantially concurrently, into a second force normal to an interior surface of the housing to establish a friction fit against the interior surface proportional to the force against the blade. It will be understood that the second force need not be exclusively normal to the interior surface. Instead, the second force may have any normal component that increases in proportion to the axial loading on the blade such that the blade can be retained in the deployed position under an increasing applied force to achieve a puncture. A variety of mechanisms for providing the first force and second force are described with reference to the figures below. 
         [0075]    In general, the second force may be created using mechanisms such as those described above to achieve locking of the blade under sustained force by the blade against the target surface. This locking may maintain the blade 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, provided that an axial force is maintained on the blade. 
         [0076]    As shown in step  1212 , a puncture force may be applied to the housing. This puncture force, which may be any suitable puncture action or technique that maintains (and presumably increases) a force of the blade against the target surface, may drive the blade through the target surface. 
         [0077]    As shown in step  1214 , when a puncture event occurs, the blade may be released from its locked position. That is, when the axial force on the blade decreases due to puncture of the target surface, the corresponding forces that frictionally engage the blade within the housing are concurrently released so that the blade is free to slide within the housing. In this state, 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  1202  and the method  1200  may be repeated. 
         [0078]      FIG. 13  is a functional diagram of a puncture device with a preload lock. In general, the preload lock  1302  may include an engagement feature  1304  such as a flange, notch, or hook, clasp, or beveled surface on a compliance structure  1306  such as a cantilevered arm that permits the engagement feature  1304  to move laterally within a housing  1308  into and out of engagement with a corresponding engagement feature  1310  of an instrument  1312  that moves within the housing  1308 . In general operation, the engagement feature  1304  is positioned to engage and secure the corresponding engagement feature  1310  of the instrument  1312  when the instrument  1312  is in a deployed position extending from the housing. In this deployed state, the biasing force of a spring or other biasing mechanism  1314  can retain a preloading force that, when released as discussed below, will tend to retract the instrument  1312  from its deployed position and back into an undeployed position (as generally depicted in  FIG. 13 ) with the instrument  1312  disposed within the housing  1308 . 
         [0079]      FIG. 14  illustrates a step in a puncture operation. In  FIG. 14 , a deployment force has been applied to extend an instrument outside of a housing. A preload lock  1402  is engaged to secure the instrument in the deployed position. 
         [0080]      FIG. 15  illustrates a step in a puncture operation. In  FIG. 15 , the instrument is partially through a target surface such as an abdominal wall of a patient. An axial force on an instrument laterally displaces an interior surface  1502  of the housing, such as a cantilevered arm or other compliant mechanism. This lateral displacement results from an outward force from the locking mechanism of the instrument that converts the axial force on the instrument to a force that is substantially normal to the interior surface  1502 , which latter force frictionally engages the instrument against the interior surface  1502  to secure the instrument in place during a puncture operation. At substantially the same time, the lateral displacement can release the preload lock by moving an engagement feature on the interior surface away from a corresponding engagement feature of the instrument, or more generally, any plunger or other activation mechanism coupled to or otherwise integrated with the instrument. 
         [0081]    It will be appreciated that the normal force created against the interior surface  1502  need not be an exclusively normal force. Rather, as used in this context, “substantially normal” is intended to mean having a sufficiently great normal component to frictionally engaged the instrument in a deployed position with enough tenacity to secure the instrument against axial movement into the housing when a contrary puncture force is applied to the housing in a puncture operation. In general, a range of contact angles for the locking arms of the instrument against the interior surface  1502  may provide sufficient normal force, although a more normal contact angle will in general provide a greater normal contact force, and in practice a substantially normal, or slightly less than normal (as illustrated in  FIG. 15 ) contact angle will provide satisfactory results. 
         [0082]    The interior surface may further include a preload lock clearing mechanism  1504 . This may for example include a spring loaded or compliance driven latch or hook that secures the engagement feature of the preload lock, e.g., on a cantilevered arm as depicted, laterally away from the corresponding engagement feature of the instrument. When the locking mechanism for the blade applies a normal force, e.g., to the cantilevered arm, this may laterally displace the cantilevered arm until the preload lock is secured by the preload lock clearing mechanism  1504 . In this manner, the preload lock is held out of the way of the instrument and a return path for the instrument into the housing, thus removing or reducing any timing requirements for the preload lock relative to the locking mechanism when an axial force is removed. 
         [0083]      FIG. 16  illustrates a step in a puncture operation. In  FIG. 16 , a puncture is completed, thus releasing the axial force on the instrument. This in turn releases the normal forces applied by the blade locking mechanism so that the only force acting on the instrument is the spring bias for the preloaded biasing mechanism. 
         [0084]      FIG. 17  illustrates a step in a puncture operation. As shown in  FIG. 17 , with the axial load removed and the locking mechanism released, the instrument may return into the housing in response to the retraction force applied by the biasing mechanism, e.g., a coil spring or the like. 
         [0085]      FIG. 18  is a functional diagram of a barrel-loading puncture device. In general, the device  1800  may provide a locking and preload locking system as contemplated above. However, the device  1800  is generally adapted for use with a drill or other tool that cannot (or generally is not) axially manipulated during use. In order to facilitate preloading and use, an outside barrel is provided that can be operated in pump-action fashion to bias a retraction biasing mechanism and move a cutting instrument into a deployed and preloaded state. A first end  1802  of the device may, for example, be shaped and sized for use in a chuck of a drill, and the housing  1804  may be a cylindrical housing constructed about the internal components and slideably coupled to the instrument  1806 , which may for example be a drill bit or other rotary cutting instrument. 
         [0086]      FIG. 19  illustrates operation of a barrel-loading puncture device. By grasping and moving the barrel  1902  of the housing axially forward (downward in the orientation of  FIG. 19 , as indicated by an arrow  1903 ), a biasing mechanism  1904 , e.g., a spring, can be loaded, and the instrument can be secured against the resulting biasing force with a preload lock  1906  such as any of the preload locks described above. In the configuration of  FIGS. 18-21 , the cantilevered arms for the instrument locking mechanism and the preload lock extend from the end of the housing distal to the functional tip of the instrument. This permits the exterior of the barrel to move without (necessarily) shifting the various components of the locking mechanisms relative to one another. 
         [0087]      FIG. 20  illustrates operation of a barrel-loading puncture device. With the preload lock engaged, the instrument may in general be secured against axial movement. The housing may then be moved toward a first end  2002  of the device to expose the instrument while the housing moves. When an axial force is applied to the instrument, e.g., when the exposed drill bit is placed against a surface for use, the locking mechanism may be expanded against the interior surface(s) of the housing, e.g., the cantilevered arms. This force can laterally displace the cantilevered arms to release the preload lock, thus preparing the instrument to retract when the axial force is released. 
         [0088]      FIG. 21  illustrates operation of a barrel-loading puncture device. As illustrated, when the axial force is released from the instrument, e.g., when a puncture event occurs, the instrument may retract into the housing under force from the biasing mechanism. 
         [0089]    It will be understood that numerous adaptations may be made for use in rotary tools. For example, while complementary left and right locking mechanisms are depicted, the device may use any number of radially distributed preload locks and locking mechanisms. Further, the device may use a different number of preload locks and locking mechanisms, provided that the resulting configuration permits the preload locks to be released substantially at the same time that the locking mechanism engages. It will also be understood that drills may rotate at hundreds or thousands of revolutions per minute, creating significant centripetal forces on various compliance features such as cantilevered arms or springs. A variety of techniques may be employed to account for such rotationally induced forces so that the device remains locked when axially loaded and becomes released when the axial load is removed. In another aspect, the axial locking mechanism and/or preload lock may be mechanically isolated from the drill-to-drill bit coupling, e.g., with one or more thrust bearings and axial sliders, to permit rotational isolation of the locking mechanisms from the drill. 
         [0090]      FIG. 22  illustrates a puncture device with a bistable preload lock. In general, a bistable mechanism  2202  may have two stable states under axial loading, and a center state where two opposing arms are collinear. When a force is applied, e.g., to a plunger, the bistable mechanism  2202  may pass through the center state and then drive an instrument out of the housing to a deployed position. 
         [0091]      FIG. 23  illustrates a puncture device with a bistable preload lock. With the instrument deployed, the bistable mechanism  2302  may, upon a return path induced by a biasing mechanism, frictionally engage an interior surface  2304  of a housing, such as the cantilevered arms described above. In this state, the biasing force is converted into substantially normal forces by the arms of the bistable mechanism against the interior surface  2304  of the housing, thus locking the instrument in a preloaded state with the instrument deployed and a biasing return force retained by the preload lock. 
         [0092]      FIG. 24  illustrates a puncture device with a bistable preload lock. As illustrated, when an axial load is applied to the deployed instrument, a locking mechanism displaces the interior surface of the housing to lock the instrument in a deployed position. This lateral displacement of the interior surface may also release the axial loading on the bistable preload lock, thus permitting the preload lock to move to a second bistable state where the bistable preload lock can move axially upward within the housing. 
         [0093]      FIG. 25  illustrates a puncture device with a preload lock. The device  2500  may advantageously be constructed from a small number of parts using a variety of techniques. For example, a functional interior surface may be provided by one or more cantilevered arms  2502  integrated into the housing  2504 . 
         [0094]    In one aspect, the instrument  2506  may include one or more notches  2508  or the like to receive one or more corresponding arms  2510  of a plunger  2512 . This arrangement may provide certain structural advantages such as permitting the arms  2510  to pivot within the notches  2508 , while securely coupling the plunger  2512  to the instrument  2506  against axial displacement. 
         [0095]      FIG. 26  illustrates the puncture device of  FIG. 25  in a preloaded state. In particular, one or more engagement features of the plunger are secured to corresponding engagement features of the cantilevered arms within the housing. In this secure relationship, the bias on a spring  2602  or the like can be maintained for use in retracting the instrument after a puncture event. 
         [0096]      FIG. 27  illustrates a puncture device with a compliance mechanism for a preload lock. The compliance mechanism  2702  may, for example, be integrated into the plunger  2704 , and may include any other spring(s) or other biasing mechanism(s) that are flexible, but tend to bias a first end  2703  of the plunger  2704  to move to a predetermined distance from a second end  2705  of the plunger  2704 . The compliance mechanism  2702  can effectively spring-load the preload lock so that when the preload lock is released—that is, when an axial load is applied to the deployed instrument—the engagement features of the preload lock can spring axially away from corresponding engagement features of the interior of the housing. This configuration can advantageously reduce the chances of the preload lock re-engaging. For example, where there is some latency between release of the locking mechanism for the instrument and axial movement due to the preload bias, the cantilevered arms or other interior surfaces may move to an unloaded position where the preload lock is intended to engage. By moving the engagement features of the preload lock axially away from one another immediately upon release of the preload lock, any resulting, unintended engagement with the preload lock can be avoided. 
         [0097]    It will also be noted that where cantilevered arms are used, the cantilevered arms may include one or more relief features such as notches as illustrated to preferentially engage an instrument locking mechanism at one or more locations. This may include functional engagement such as axial locking of the instrument for a puncture operation, or to provide tactile feedback to a user concerning state changes such as initial movement of a plunger or preload locking. 
         [0098]    It will be understood that while a flexural compliance mechanism is illustrated, axial compliance sufficient to separate preload lock engagement features may be achieved with a variety of compliance techniques including without limitation any spring, flexural element, resilient material and the like, as well as combinations of the foregoing. 
         [0099]    Other techniques may also or instead be used to prevent the preload lock from reengaging when the locking mechanism for a functional tip is released. For example, a viscoelastic damper such as a foam or similar material may couple the cantilevered arms to the interior walls of the housing, or the cantilevered arms may be wholly or partially formed of a viscoelastic material that returns slowly to an unloaded state. In this manner, the cantilevered arms or any similar structure can be fabricated in a manner that will not snap quickly back into an undeformed shape, e.g., where the preload lock engagement features might prevent axial movement of the instrument within the housing. 
         [0100]      FIG. 28  illustrates a puncture device with a compliance mechanism. As shown in the drawing, when an instrument is locked in a deployed position by an axial load, a spring bias to clear the preload lock may be provided by the same biasing mechanism that provides the force to retract the instrument after a puncture event. The plunger and locking mechanism may be fabricated as a three-part assembly with a first part  2802 , a second part  2804  and a third part  2806  (rigidly coupled to an instrument). In this configuration, the first part  2802 , which is coupled to a plunger, can move relative to the second part  2804  and the third part  2806 . When the cantilevered arms  2808  are laterally displaced such that the preload locking features  2810  are not engaged, the first part  2802  can move axially due to the force of the biasing mechanism  2812  so that the respective features are moved axially out of alignment as illustrated. In this state, there is no opportunity for the preload locking features  2810  to engage around the time when a locking mechanism for the instrument is released. 
         [0101]    It will also be noted that the second part  2804  includes arms that rest in corresponding notches of the third part  2806 . This permits the arms to rotate as indicated by an arrow  2814  so that when the instrument is deployed and an axial force is applied to the instrument, the arms will tend to laterally displace the cantilevered arms as increasing axial force is applied to provide a locking mechanism as described above. 
         [0102]      FIG. 29  shows a puncture device with an angled preload locking mechanism. The preload locking mechanism  2902  of the puncture device  2904  is shown in an expanded view  2906  in an engaged state. In general, when an instrument is deployed, the movement of components within the puncture device  2902  may apply normal forces to one or more cantilevered arms to laterally displace the arms. This tends to move the cantilevered arms out of alignment with the primary axis of the puncture device  2904 , and diminishes the effectiveness of preload locking mechanisms that rely on normal contact forces for frictional engagement. In order to mitigate this effect, the preload locking engagement features may be pre-angled as illustrated in the figure so that they are substantially parallel to one another when locked in the preloaded stated. It will be understood that the actual angle will depend on the amount of deflection in the cantilevered arm, and may vary significantly from design to design. Thus the angled preload locking features depicted in  FIG. 29  are by way of example only, and should in general be understood to include any angle or angles that maintain substantially parallel surfaces for complementary engagement features, or more generally any angle that improves the tenacity of engagement between such complementary engagement features. 
         [0103]    The method steps of the invention(s) described herein are intended to include any suitable method of causing such method steps to be performed, consistent with the patentability of the following claims, unless a different meaning is expressly provided or otherwise clear from the context. So for example performing the step of X includes any suitable method for causing another party, device, or system, such as a remote user or a remote processing resource (e.g., a server or cloud computer) to perform the step of X. Similarly, performing steps X, Y and Z may include any method of directing or controlling any combination of such other individuals, devices, systems or other resources to perform steps X, Y and Z to obtain the benefit of such steps. 
         [0104]    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.