Abstract:
An instrument for performing a medical procedure includes a drive shaft, a holding clutch, a drive clutch, and an actuator. The holding clutch only allows advancement of the drive shaft, while the drive clutch transfers an advancement force from the actuator to the drive shaft. The dual clutch system allows a lever to be used as the actuator so that a user can generate large actuation forces manually (and optionally remotely) without significant physical effort. This capability can beneficially improve the usability and effectiveness of percutaneous surgical systems, such as those for vertebroplasty or kyphoplasty.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation of U.S. patent application Ser. No. 12/512,929, filed on Jul. 30, 2009, which is incorporated herein by reference, in its entirety. 
    
    
     FIELD OF THE INVENTION 
     The invention relates to a system and method for performing a surgical procedure, and in particular, to a system for efficiently generating high pressures in a surgical instrument. 
     BACKGROUND OF THE INVENTION 
     For many individuals in our aging world population, undiagnosed and/or untreatable bone strength losses have weakened these individuals&#39; bones to a point that even normal daily activities pose a significant threat of fracture. In one common scenario, when the bones of the spine are sufficiently weakened, the compressive forces in the spine can cause fracture and/or deformation of the vertebral bodies. For sufficiently weakened bone, even normal daily activities like walking down steps or carrying groceries can cause a collapse of one or more spinal bones. A fracture of the vertebral body in this manner is typically referred to as a vertebral compression fracture. Other commonly occurring fractures resulting from weakened bones can include hip, wrist, knee and ankle fractures, to name a few. 
     Fractures such as vertebral compression fractures often result in episodes of pain that are chronic and intense. Aside from the pain caused by the fracture itself, the involvement of the spinal column can result in pinched and/or damaged nerves, causing paralysis, loss of function, and intense pain which radiates throughout the patient&#39;s body. Even where nerves are not affected, however, the intense pain associated with all types of fractures is debilitating, resulting in a great deal of stress, impaired mobility and other long-term consequences. For example, progressive spinal fractures can, over time, cause serious deformation of the spine (“kyphosis”), giving an individual a hunched-back appearance, and can also result in significantly reduced lung capacity and increased mortality. 
     Until recently, treatment options for vertebral compression fractures, as well as other serious fractures arid/or losses in bone strength, were extremely limited—mainly pain management with strong oral or intravenous medications, reduced activity, bracing and/or radiation therapy, all with mediocre results. Because patients with these problems are typically older, and often suffer from various other significant health complications, many of these individuals are unable to tolerate invasive surgery. In addition, to curb further loss of bone strength, many patients are given hormones and/or vitamin/mineral supplements—again with mediocre results and often with significant side effects. 
     In an effort to more effectively and directly treat vertebral compression fractures, minimally invasive techniques such as vertebroplasty and, subsequently, kyphoplasty, have been developed. Both techniques involves the percutaneous injection of a flowable reinforcing material, usually polymethylmethacrylate (PMMA—commonly known as bone cement), into a fractured, weakened, or diseased vertebral body. Shortly after injection, the liquid filling material hardens or polymerizes, desirably supporting the vertebral body internally, alleviating pain and preventing further collapse of the injected vertebral body. 
     In a vertebroplasty procedure, a needle is inserted directly into a vertebral body, and the bone cement is dispensed from the needle. Because the liquid bone cement naturally follows the path of least resistance within bone, and because the small-diameter needles used to deliver bone cement in vertebroplasty procedure typically require either high delivery pressures to ensure that the bone cement remains within the already compromised vertebral body is a significant concern in vertebroplasty procedures. 
     Kyphoplasty addresses this issue by first creating a cavity within the vertebral body (e.g., with an inflatable balloon to enable the procedure to be performed percutaneously) and then filling that cavity with bone filler material. The cavity provides a natural containment region that minimizes the risk of bone filler material escape from the vertebral body. An additional benefit of kyphoplasty is that the creation of the cavity can also restore the original height of the vertebral body, further enhancing the benefit of the procedure. 
     In both vertebroplasty and kyphoplasty procedures (as in any procedure in which filler material is delivered percutaneously to a target location in a body), the ability to apply higher pressures to the filler material can beneficially enhance the safety, efficacy, and/or flexibility of the procedure. For example, the use of higher viscosity bone cements can reduce the likelihood of extravasation, and the use of smaller diameter delivery tools (e.g., cement delivery needles or nozzles) can minimize trauma to the patient and provide greater placement flexibility. 
     Accordingly, it is desirable to provide surgical tools and techniques that can generate high pressures for use in surgical procedures. 
     SUMMARY OF THE INVENTION 
     By incorporating a lever-actuated drive clutch and a holding clutch into a mechanism for advancing a plunger or piston, high pressures for surgical material delivery can be generated by a surgeon without significant physical exertion. 
     In one embodiment, a surgical instrument includes a shaft that effectuates the action of the surgical instrument (e.g., drives a plunger in a syringe to dispense a flowable material or deploys a manipulation structure for a body part). A housing for the shaft also includes a holding clutch mounted on the shaft, a drive clutch mounted on the shaft, and a lever for applying a translation force to the drive clutch. 
     The holding clutch is configured such that it allows advancement of the shaft (i.e., movement of the shaft in a proximal direction relative to the housing), but does not allow movement in the opposite direction (i.e., does not allow retraction of the shaft). The drive clutch is configured such that it exhibits a range of motion relative to the housing, but only engages with the shaft when being driven in the proximal direction by the lever. 
     Thus, when the lever is actuated, it drives the drive clutch in a proximal direction. The drive clutch engages with the shaft, thereby advancing the shaft as it moves. The holding clutch allows this proximal motion of the shaft, but once the advancement force being applied by the lever is removed, the holding clutch prevents any reverse motion of the shaft (retraction). Meanwhile, the drive clutch disengages from the shaft and returns to its original position within the housing. The lever can then be actuated again to repeat the process and continue to advance the shaft. 
     In various embodiments, the drive clutch and/or the holding clutch can include binding plates to provide controllable engagement/disengagement capabilities with the shaft. The binding plates can simply comprise plates with apertures slightly larger than the shaft dimensions, such that if either plate is substantially perpendicular to the shaft, the shaft can move freely with respect to the plate, but if the binding plate is canted with respect to the shaft, relative motion between the plate and shaft is prevented. In various embodiments, the binding plates and/or shaft can include features that enhance the binding functionality. 
     In one embodiment, the holding clutch includes a binding plate and a bias spring, and the drive clutch includes a binding plate and a return spring. The bias spring in the holding clutch causes the binding plate in the holding clutch to assume a normally canted orientation (i.e., engaged) with respect to the shaft, thereby preventing shaft retraction. Advancement of the shaft overcomes the bias spring and presses the binding plate against a surface(s) or feature(s) of the housing that cause the binding plate to become oriented substantially perpendicularly (i.e., disengaged) with respect to the shaft. When the advancement of the shaft ceases, the bias spring returns the binding plate to its canted orientation, thereby locking the shaft in place. 
     Meanwhile, the return spring in the drive clutch biases the binding plate in the drive clutch towards a perpendicular orientation (disengaged) with respect to the shaft and towards a baseline position within the housing. The binding plate in the drive clutch is further configured to receive off-axis loading from the lever that causes canting (engagement) with respect to the shaft, thereby resulting in any advancement loading from the shaft lever being transferred to the shaft. 
     Thus, as the lever is actuated to apply an advancement force to the binding plate in the drive clutch, that binding plate engages with the shaft to begin advancing the shaft. The shaft advancement causes the binding plate in the holding clutch to disengage from the shaft to allow further advancement of the shaft. When the lever is released, the advancement of the shaft stops, the binding plate in the holding clutch is re-engaged with the shaft by the bias spring to prevent retraction, and the binding plate in the drive clutch disengages from the shaft and is returned to its baseline position by the return spring. The lever can then be re-actuated to further advance the shaft. 
     As will be realized by those of skilled in the art, many different embodiments of a surgical instrument, kit, and/or methods of using a surgical instrument incorporating a dual-clutch mechanism for enabling high force generation are possible. Additional uses, advantages, and features of the invention are set forth in the illustrative embodiments discussed in the detailed description herein and will become more apparent to those skilled in the art upon examination of the following. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a diagram of a surgical instrument that includes a dual clutch system for efficiently generating large internal forces/pressures. 
         FIG. 1A  is a diagram of an alternative surgical instrument incorporating the dual clutch system of  FIG. 1 . 
         FIG. 1B  is a diagram of an alternative surgical instrument that provides remote actuation capabilities in combination with the dual clutch mechanism of  FIG. 1 . 
         FIGS. 2-3  show an exemplary actuation of the surgical instrument of  FIG. 1   
         FIG. 4  is a flow diagram for the use of the surgical instrument of  FIG. 1   
         FIG. 5  is a block diagram of a kit that includes the surgical instrument of  FIG. 1 . 
     
    
    
     DETAILED DESCRIPTION 
     By incorporating a lever-actuated drive clutch and a holding clutch into a mechanism for advancing a plunger or piston, high pressures/forces for surgical procedures can be generated by a surgeon without significant physical exertion. 
       FIG. 1  shows a block diagram of a surgical instrument  190  that includes high force advancement mechanism  100  incorporating a dual-clutch mechanism for applying and maintaining a large force within the surgical instrument. Mechanism  100  includes a housing  101  that houses a holding clutch  130  and a drive clutch  140 , both mounted on a shaft  110 . Holding clutch  130  and drive clutch  140  enable the advancement of shaft  110  with great force to effectuate the surgical procedure being performed by surgical instrument  190 . 
     Holding clutch  130  can be any mechanism that allows shaft  110  to be moved in one direction and resists motion of shaft  110  in the opposite direction (e.g., a ratchet). Drive clutch  140  can be any mechanism that controllably engages and disengages shaft  110  (e.g., a chuck or clamp, among others). When an actuator such as a lever  120  mounted on housing  101  applies a force to drive clutch  140 , drive clutch  140  engages and advances shaft  110 . When lever  120  is released, holding clutch  130  maintains the position of shaft  110  while drive clutch  140  disengages from shaft  110  and returns to its original position. In this manner, the force multiplication provided by the action of lever  120  is directly converted to advancement of shaft  110 . 
     For exemplary purposes, surgical instrument  100  is depicted in  FIG. 1  as a syringe  102  for performing vertebroplasty or kyphoplasty. A plunger tip  111  at the end of shaft  110  drives bone filler material  103  (e.g., bone cement) from syringe  102  through a delivery path  104  (e.g., a flexible tube and delivery needle/nozzle) into a vertebral body  105 . The large force generated by mechanism  100  allows a high viscosity bone filler material  103  to be delivered during the procedure, thereby minimizing extravasation risks. 
     Note that in various other embodiments, surgical instrument  100  can be any type of surgical system in which the generation of large forces would be beneficial. For example,  FIG. 1A  shows an alternative embodiment of surgical instrument  100 A in which shaft  110  includes an expandable element  111 A that can be used for percutaneous bone manipulation (e.g., cavity creation within cancellous bone or restoring vertebral endplate position after a fracture has occurred). As shaft  110  is advanced through a sheath  102 A, expandable element  111 A is compressed against a solid tip  102 B of sheath  102 A, and expands outwards in response. The large forces that can be applied to shaft  110  enable the use of a robust expandable element  111 A, which in turn can enable more effective bone manipulation during surgical procedures. Various other embodiments of surgical instruments incorporating a dual clutch system will be readily apparent. 
     Returning to  FIG. 1 , holding clutch  130  can be any mechanism that allows shaft  110  to be moved in one direction and resists motion of shaft  110  in the opposite direction (e.g., a ratchet or other type of restraining mechanism). Drive clutch  140  can be any mechanism that controllably engages and disengages shaft  110  (e.g., a chuck or clamp, among others). In one embodiment, holding clutch  130  and drive clutch  140  can include binding plates  131  and  141 , respectively. 
     Binding plates  131  and  141  include apertures  135  and  145 , respectively, through which shaft  110  is passed. The relative angle of binding plates  131  and  141  relative to shaft  110  determines whether holding clutch  130  and drive clutch  140 , respectively, are engaged with or disengaged from shaft  110 . For example, when binding plate  131  is substantially perpendicular to shaft  110 , holding clutch  130  is disengaged from shaft  110 , and shaft  110  can freely move with respect to holding clutch  130 . However, when binding plate  131  is sufficiently canted with respect to shaft  110  (i.e., is sufficiently non-parallel to shaft  110 ), holding clutch  130  is engaged with shaft  110  and no relative motion is possible. 
     Likewise, when binding plate  141  is substantially perpendicular to shaft  110 , drive clutch  140  is disengaged from shaft  110  and can move freely with respect to shaft  110 . However, when binding plate  141  is sufficiently canted with respect to shaft  110 , drive clutch  140  is engaged with shaft  110 , and any force (and motion) applied to drive clutch  140  is also applied to shaft  110 . 
     Note that binding plates  131  and  141 , along with shaft  110 , can take any configuration that enables the above-described operation wherein canted orientation relative to the shaft results in engagement (binding), and perpendicular orientation relative to the shaft results in disengagement (release). For example, shaft  110  can include grooves, ridges, or other features that enhance engagement with the edges of apertures  135  and  145 . Shaft  110  could be round, square, rectangular, or any other shape (e.g., a rectangular shaft  110  within slot-shaped apertures  135  and  145  could provide a larger engagement area when either holding clutch  130  or drive clutch  140  is engaged. Various other embodiments will be readily apparent. 
     Holding clutch  130  further includes a bias spring  132  that forces binding plate  131  against a surface S 1  of housing  101 . Surface S 1  causes binding plate  131  to orient itself in a canted position relative to shaft  110 , thereby engaging shaft  110 . In various embodiments, surface S 1  can be a continuous surface that is angled with respect to a plane perpendicular to shaft  110 , multiple surfaces or features that cause binding plate  131  to align in a non-perpendicular position (with respect to shaft  110 ), or any other suitably orienting structure. In this manner, bias spring  132  creates a default engaged condition for holding clutch  130  that resists retraction of shaft  110 . 
     Meanwhile, drive clutch  140  further includes a return spring  142  that places binding plate  141  in a perpendicular position relative to shaft  110  and moves binding plate  141  into a baseline position within housing  101 . Note that while a single spring is depicted for clarity, return spring  142  can include any number of spring or elastomeric elements that tend to orient binding plate  141  substantially perpendicularly with respect to shaft  110 . In this manner, return spring  142  acts to return binding plate  141  back to a default position without requiring motion of shaft  110 . 
     To advance shaft  110 , lever  120  is rotated rearward (proximally), which causes drive element  121  at the end of lever  120  to push forward (distally) against one portion of binding plate  141 , as shown in  FIG. 2 . Note that although a simple lever is depicted for clarity, in various embodiments, lever  120  can take any shape or any combination of elements. For example, in one embodiment, drive element  121  of lever  120  can be a cam that applies force to the same location on binding plate  141  as lever  120  is rotated. In various other embodiments, lever  120  can incorporate a linkage, geared, or threaded mechanism. 
     However, regardless of the particular configuration of lever  120 , because the force applied by drive element  121  is applied unevenly around aperture  145  (i.e., force is not evenly distributed about aperture  145 ), actuation causes binding plate  141  to become canted with respect to shaft  110 . Consequently, actuation of lever  120  quickly engages binding plate  141  with shaft  110 , such that any subsequent force applied to binding plate  141  by drive element  121  is transmitted to shaft  110  as well. 
     Note that the sensitivity of this binding action can be controlled in various ways, such as increasing the width of binding plate  141  and/or sizing aperture  145  to be only slightly larger than the dimensions of shaft  110  (e.g., dimensioning aperture  145  to provide a slip fit hole for a round shaft  110 ). Typically, it is desirable to have binding plate  141  quickly engage with shaft  110 , although if less engagement sensitivity is desired, the dimensions of aperture  145  could be increased or the width of binding plate  141  could be decreased. 
     As drive element  121  continues to apply force to binding plate  141  (now engaged with shaft  110 ), shaft  110  begins to advance (proximally) within housing  101 . At the onset of this advancement, binding plate  131  is engaged with shaft  110 , and advances along with shaft  110 . However, binding plate  131  quickly comes into contact with surface S 2  of housing  101 . Surface S 2  is configured such that it orients binding plate  131  substantially perpendicularly with respect to shaft  110 , thereby disengaging binding plate  110  from shaft  110 . Note that surface  82  can be a continuous surface, or multiple surfaces or features that cause binding plate  131  to be positioned perpendicularly with respect to shaft  110 . 
     Once binding plate  131  is disengaged from shaft  110 , any further loading of binding plate  141  by drive element  121  results in advancement of shaft  110  relative to binding plate  131 . Then, as shown in  FIG. 3 , when lever  120  is released, the advancement of shaft  110  stops, and so bias spring  132  pushes binding plate  131  back against surface S 1 , thereby re-engaging binding plate  131  with shaft  110  and preventing any retraction (i.e., movement in the proximal direction) of shaft  110 . Meanwhile, return spring  142  presses against binding plate  141 , orienting binding plate  141  substantially perpendicularly with respect to shaft  110 . As a result, binding plate  141  is disengaged from shaft  110  and returned to its base position (along with lever  120 ). 
     In this manner, each actuation of lever  120  advances shaft  110  and holds shaft  110  in that new position. The operation described above with respect to  FIGS. 1-3  can be repeated to advance shaft  110  a desired distance with respect to housing  101 . The force multiplication provided by this lever-based actuation allows shaft  110  to be advanced with significant force compared to the actuation force the user applies to lever  120 . Consequently, mechanism  100  can be incorporated into any surgical instrument  190  that would benefit from the ability to generate large internal pressures/forces. 
     For example, because lever  120  does not require a large actuation force to produce large advancement forces on shaft  110 , mechanism  100  is conducive to remote operation.  FIG. 1B  shows an embodiment of surgical instrument  190  in which lever  120  is connected to a remote controller  182  by a push-pull cable  181 . The sheath (casing)  181 -S of push-pull cable  181  is connected to housing  101 , and core  181 -C of push-pull cable  181  is connected to lever  120 . Controller  182  can move core  181 -C relative to sheath  181 - 3 , thereby allowing lever  120  to be actuated remotely from surgical instrument  190 . This in turn, can beneficially allow the user to be removed from any radiation field in which surgical instrument  190  is being used. Various other remote operation mechanisms will be readily apparent, such as flexible cable-based, solenoid-based, motor-based, and pulley-based mechanisms, among others. 
       FIG. 4  shows a flow diagram of the mechanical operation described above with respect to  FIGS. 1-3 . In a DEPRESS ACTUATOR step  410 , an actuation mechanism (e.g., lever  120 ) is actuated. In response, in an ENGAGE DRIVE CLUTCH step  421 , a first clutch engages a drive shaft of a surgical instrument (e.g., binding plate  141  of drive clutch  140  being canted with respect to shaft  110 ). Roughly concurrently, in a RELEASE HOLDING CLUTCH step  422 , a second clutch is disengaged from the drive shaft (e.g., binding plate  131  of holding clutch  130  coming in to contact with surface S 2  and being oriented substantially perpendicularly to drive shaft  110 ), and in an ADVANCE SHAFT step  423 , the drive shaft is advanced (i.e., moved proximally) in response to a drive force applied to the second clutch (e.g., drive element  121  continuing to apply force to binding plate  141 ). The shaft movement enables performance of a desired surgical procedure (e.g., delivery of bone filler material  103  as shown in  FIGS. 1-3 , or the expansion of a cavity creation device for bone such as expandable element  111 A shown in  FIG. 1A ) in an EFFECT FUNCTION step  430 . 
     Then, the actuation mechanism is released in a RELEASE ACTUATOR step  440 , which causes the second clutch to re-engage with the drive shaft in an ENGAGE HOLDING CLUTCH step  451 , while disengaging the first clutch from the drive shaft in a RELEASE DRIVE CLUTCH step  452 , and returning the first clutch to a baseline position (e.g., return spring  142  pushing binding plate  141  back to its baseline position) in a RESET DRIVE CLUTCH step  453 . Finally, in a REPEAT AS NECESSARY step  460 , the sequence of steps  410 - 453  is repeated until the a desired amount of drive shaft advancement and/or force exertion by the drive shaft is reached (e.g., a desired amount of bone filler material  103  is dispensed at a desired pressure or an expandable element  111 A is expanded to a desired size or applies a desired pressure on surrounding bone). 
     Note that while steps  421 - 423  and steps  451 - 453  are described as occurring relatively concurrently for explanatory purposes, in various other embodiments, steps  421 - 423  can occur in any sequence, as can steps  451 - 453 . For example, as described above with respect to  FIGS. 1-3 , binding plate  141  engages shaft  110  (step  421 ) and begins to advance shaft  110  (step  423 ) slightly before binding plate  131  disengages from shaft  110  (step  422 ). However, various other embodiments of drive clutch  140  and holding clutch  130  may produce a slightly different ordering of steps  421 - 423  and  451 - 453 . 
       FIG. 5  shows a diagram of a kit  500  for use in performing a surgical procedure. Kit  500  includes a surgical instrument  190  (e.g., surgical instrument  190  or  190 A as shown in  FIGS. 1 and 1A , respectively) that includes a high force advancement mechanism  100  (as described with respect to  FIGS. 1-3 ). Kit  500  further includes optional additional instruments  504  and optional directions for use  505  that provide instructions for using surgical instrument  190  and optional additional instruments  504  (e.g., instructions for performing a vertebroplasty or kyphoplasty procedure using surgical instrument  190  and optional additional instruments  504 ). 
     For example, kit  500  could be a kit for use in a kyphoplasty procedure, and surgical instrument  190  could be a system for delivering bone filler material (e.g., as described with respect to  FIGS. 1-3 ), in which case optional additional instruments  504  could be tools for creating a void in cancellous bone. Alternatively, kit  500  could be a kit for use in a kyphoplasty procedure in which surgical instrument  190  is a cavity creation system (e.g., as described with respect to  FIG. 1A ), in which case optional additional instruments  504  could be tools for delivering bone filler material to the void created by surgical instrument  190 . Various other additional instruments  504  will be readily apparent for various other surgical procedures. 
     While various embodiments of the invention have been described above, it should be understood that they have been presented by way of example only, and not limitation, Where methods and steps described above indicate certain events occurring in certain order, those of ordinary skill in the art having the benefit of this disclosure would recognize that the ordering of certain steps may be modified and that such modifications are in accordance with the variations of the invention. Additionally, certain steps may be performed concurrently in a parallel process when possible, as well as performed sequentially as described above. Thus, the breadth and scope of the invention should not be limited by any of the above-described embodiments, but should be defined only in accordance with the following claims and their equivalents. While the invention has been particularly shown and described with reference to specific embodiments thereof, it will be understood that various changes in form and details may be made.