Abstract:
A differential dissecting instrument for differentially dissecting complex tissue comprising is disclosed. The differential dissecting instrument comprises a rotary drive train having a central, longitudinal axis, a distal end, and a proximal end. The differential dissecting instrument also comprises at least one differential dissecting bluntwheel, wherein the at least one differential dissecting bluntwheel is rotatably associated with the distal end of the rotary drive train, has at least one axis of rotation substantially transverse to the central, longitudinal axis of the rotary drive train, and is rotated by the rotary drive train. The bluntwheel may comprise projections that are configured to differentially dissect a complex tissue when the differential dissecting instrument is in operation.

Description:
PRIORITY APPLICATIONS 
       [0001]    The present application claims priority to U.S. Provisional Patent Application No. 61/982,633 entitled “Instruments, Devices, and Related Methods for Soft Tissue Dissection,” filed on Apr. 22, 2014, which is incorporated herein by reference in its entirety. 
         [0002]    The present application also claims priority to co-pending U.S. patent application Ser. No. 14/065,191, entitled “Instruments, Devices, and Related Methods for Soft Tissue Dissection,” filed on Oct. 28, 2013, which in turn is a continuation-in-part application of, and claims priority to, co-pending U.S. patent application Ser. No. 13/872,766 entitled “Instruments, Devices, and Related Methods for Soft Tissue Dissection,” filed Apr. 29, 2013, which in turn claims priority to the following three Provisional applications: U.S. Provisional Patent Application No. 61/783,834, entitled “Instruments, Devices, and Related Methods for Soft Tissue Dissection,” filed on Mar. 14, 2013; U.S. Provisional Patent Application No. 61/744,936, entitled “Instrument for Soft Tissue Dissection,” filed on Oct. 6, 2012; and U.S. Provisional Patent Application No. 61/687,587, entitled “Instrument for Soft Tissue Dissection,” filed on Apr. 28, 2012, all of which are incorporated herein by reference in their entireties. 
         [0003]    The present application also claims priority to PCT Patent Application No. PCT/US15/26466, entitled “Methods and Devices for Soft Tissue Dissection,” filed on Apr. 17, 2015, which in turn claims priority to U.S. Provisional Patent Application No. 61/981,556, entitled “Methods and Devices for Soft tissue Dissection,” filed on Apr. 18, 2014, both of which are incorporated herein by reference in their entireties. 
     
    
     BACKGROUND 
       [0004]    Field of the Disclosure 
         [0005]    The field of the disclosure relates to methods or devices used to dissect tissue during surgery or other medical procedures. 
         [0006]    Technical Background 
         [0007]    Surgeons sever or separate patients&#39; tissues as a major component of most surgical procedures. Called “dissection,” this is how surgeons tunnel from an accessible region of a patient to reach a target within. The two dominant dissection techniques are: (1) “sharp dissection,” where surgeons sever tissues with either scissors, scalpels, electrosurgical devices, and other cutting instruments; and (2) “blunt dissection,” consisting of separating tissues by controlled tearing of one tissue from another. 
         [0008]    The advantage of sharp dissection is that the cutting instrument easily cuts through any tissue. The cut itself is indiscriminate, slicing through all tissues to which the instrument is applied. This is also the disadvantage of sharp dissection, especially when trying to isolate a first tissue without damaging it, when the first tissue is embedded in, and is obscured by, a second tissue, or more commonly, is enveloped in many tissues. Accidental cutting of a blood vessel, a nerve, or bowel, for example, is a constant threat for even the most experienced surgeons and can rapidly lead to serious, even life-threatening, intra-operative complications, with prolonged consequences for the patient. When employing minimally invasive procedures, for example laparoscopy or the use of a surgical robot, the chances of surgical error increase. 
         [0009]    Isolation of a first tissue embedded in other tissues is therefore frequently performed by blunt dissection. In blunt dissection, a blunt instrument is used to force through a tissue, to force apart two tissues, or to otherwise separate tissues by tearing rather than cutting. Almost all surgeries require blunt dissection of tissues to expose target structures, such as blood vessels to be ligated, or nerve bundles to be avoided. Examples in thoracic surgery include isolation of blood vessels during hilar dissection for lobectomy and exposure of lymph nodes. In plastic surgery, blunt dissection comprises the lion&#39;s share of many procedures, consisting of undermining very large areas of the patient&#39;s skin, where poor blunt dissection can result in hematomas, dermal punctures, and necrosis of the skin. 
         [0010]    Blunt dissection includes a range of maneuvers, including various ways to tease apart or tear soft tissues, such as the insertion of blunt probes or instruments, inverted action (i.e., spreading) of forceps, and pulling of tissues with forceps or by rubbing with a “swab dissector” (e.g., surgical gauze held in a forceps, or a purpose-built, disposable swab stick such as a Kitner). When needed, sharp dissection is used judiciously to cut tissues that resist tearing during blunt dissection. 
         [0011]    The general goal of blunt dissection is to tear or otherwise disrupt occluding tissue, such as membranes and mesenteries, away from the target structure without tearing or disrupting either the target structure or critical structures such as nearby vessels or nerves. The surgeon capitalizes on the different mechanical behaviors of tissues, such as the different stiffness of adjacent tissues, or the existence of planes of softer tissue between firmer tissues. Frequently, the surgeon&#39;s goal is to isolate a target tissue that is mechanically firm, being composed of more tightly packed fibrous components, and is embedded in a tissue that is mechanically soft, being composed of more loosely packed fibrous components (for example, loose networks of collagen, reticulin, or elastin). More tightly packed fibrous tissues include tissues composed of tightly packed collagen and other fibrous connective tissues, usually having highly organized anisotropic distributions of fibrous components, often with hierarchical composition. Examples include blood vessels, nerve sheaths, muscles, fascia, bladders, and tendons. More loosely packed fibrous tissues have a much lower number of fibers per unit volume or are composed of less well organized materials such as fat and mesenteries. Fibrous components include fibers, fibrils, filaments, and other filamentous components. When a tissue is referred to as “fibrous”, the reference is typically to extracellular filamentous components, such as collagen and elastin—proteins that polymerize into linear structures of varying and diverse complexity to form the extracellular matrix. As mentioned in the previous paragraph, the density, orientation, and organization of fibrous components greatly determine the tissue&#39;s mechanical behavior. Sometimes, tissues are referred to as “tough, fibrous tissues” indicating that the fibrous or filamentous components are densely packed, organized, and comprise a significant fraction of the bulk of the tissue. However, all tissues are fibrous, to one extent or another, with fibers and other filamentous extracellular components being present in virtually every tissue. 
         [0012]    What is important to the present discussion is that softer tissues tear more easily than firmer tissues, so blunt dissection attempts to proceed by exerting sufficient force to tear softer tissue but not firmer tissue. 
         [0013]    Blunt dissection can be difficult, tedious, dangerous, and is often time-consuming. Judging the force to tear a soft tissue, but not a closely apposed firm tissue, is not easy. Thus, blood vessels can be torn. Nerves can be stretched or torn. In response, surgeons attempt judicious sharp dissection, but blood vessels, nerves, and airways can be cut, especially the smaller side branches, which become exponentially more common at smaller scales. This all leads to long, tedious dissections and increased risk of complications, like bleeding, air leaks from the lungs, and nerve damage. Complications of blunt dissection are common, as are repairs. 
         [0014]    Surgeons frequently use forceps for blunt dissection. Forceps include finger engagers, a pivot, and two jaws for clamping together on tissues, but surgeons often employ forceps in a spreading mode, forcing the jaws apart in an attempt to tear or rend two adjacent tissues apart. This secondary use of forceps is common, but forceps are far from ideal for blunt dissection. 
         [0015]    Laparoscopic and thoracoscopic (collectively referred here as “endoscopic”) instruments use a similar action, albeit at the distal end of a very long shaft piercing the patient&#39;s body wall through a trocar. This arrangement imposes even more challenges, making laparoscopic blunt dissection more difficult, lengthening the time of procedures, and increasing the chances of intraoperative complications. 
         [0016]    For either instrument, forceps  10  or endoscopic forceps  10 , a surgeon performs blunt dissection by closing the forceps, pushing the closed forceps into a tissue and then, optionally, opening the forceps inside the tissue, using the force applied by opening of the jaws of the forceps to tear the tissue apart. A surgeon thus proceeds to dissect a tissue by a combination of pushing into the tissue and opening the jaws of the forceps. 
         [0017]    Blunt dissection is commonly used for wet and slick tissues, and the smooth, passive surfaces of most surgical instruments slide easily along the tissue, impairing the instrument&#39;s ability to gain purchase and separate the tissue. Furthermore, the surgeon has only limited control, being able only to jab, move sideways, or separate. An improved instrument for blunt dissection that could differentially separate soft tissues while not disrupting firm tissues would greatly facilitate many surgeries. Of further utility would be an improved instrument that was as simple as possible, getting the job done with as few moving parts as can be achieved, whilst increasing both safety and speed. 
       SUMMARY OF THE DETAILED DESCRIPTION 
       [0018]    Embodiments disclosed herein include methods and devices for blunt dissection, which differentially disrupt soft tissues while not disrupting firm tissues. In particular, in one embodiment, components for simplified tissue engaging surfaces and a drive mechanism for a powered differential dissecting instrument for differentially dissecting complex tissue are disclosed. The differential dissection instrument may be handheld, or may form a portion of a surgical machine, such as a laparoscopic instrument or a teleoperated surgical robot. 
         [0019]    In one embodiment, a differential dissecting instrument for differentially dissecting complex tissue comprising is disclosed. The differential dissecting instrument comprises a rotary drive train having a central, longitudinal axis, a distal end, and a proximal end. The differential dissecting instrument also comprises at least one differential dissecting bluntwheel, wherein the at least one differential dissecting bluntwheel is rotatably associated with the distal end of the rotary drive train, has at least one axis of rotation substantially transverse to the central, longitudinal axis of the rotary drive train, and is rotated by the rotary drive train. The bluntwheel may comprise projections that are configured to differentially dissect a complex tissue when the differential dissecting instrument is in operation. 
         [0020]    In another embodiment, the tissue-engaging surfaces disclosed herein comprise two sets of blunt, differentially dissecting, tissue-engaging projections configured to pass one another in close approximation and in opposite directions. The tissue to be differentially dissected can be presented with these twin sets of tissue engaging projections via opposed linear motions or opposed rotational motions, in a concentrated point or along an edge, or by a self-supporting set of tissue engaging projections, or by an exposed portion of tissue engaging projections otherwise covered by a shroud or housing. The two sets of passing projections to be presented to a complex tissue might be achieved by locating a linear series of the blunt, differentially dissecting, tissue-engaging projections along an edge of an object, for example along a pair of rods, bars, or other linear forms possessing an edge, or, if continuous cyclic passage of the blunt, differentially dissecting, tissue-engaging projections is desired, a pair of belts. As it is desirable to keep a surgical instrument small and simple, it is advantageous to locate the blunt, differentially dissecting, tissue-engaging projections along the edge of, or form the edge of, a small wheel, disk, or other rotatable form. Hereinafter, a wheel or disk that sports blunt, differentially dissecting, tissue-engaging projections along or forming its edge or margin is referred to as a “bluntwheel.” 
         [0021]    One embodiment of the distal-most, tissue-contacting tip of a differential dissection instrument may comprise two such bluntwheels. The bluntwheels may be roughly planar, situated parallel to one another, and coaxially rotatable about a common axis transverse to, or at least not parallel to, a long axis of the surgical instrument. The bluntwheels may also be substantially apposed or even in contact, such that when the first wheel is rotated clockwise about the common axis while simultaneously the second wheel is rotated counterclockwise, the twin sets of blunt, differentially dissecting, tissue-engaging projections pass closely in opposing directions, thus differentially dissecting a complex tissue. The bluntwheels herein can be constructed of a high-modulus material, like steel, or PEEK, having a Young&#39;s modulus greater than one gigapascal. Alternatively, the bluntwheels can be made of a polymeric elastomer, like a polyurethane, and possess a Young&#39;s modulus of less than one megapascal, depending on the surgical procedure involved, the type of tissue to be dissected, or the relative dimensions of the surgical instrument and the anatomical structure of interest. 
         [0022]    Another embodiment of the distal-most, tissue-contacting tip of a differential dissection instrument may include a flexible bluntwheel. The tip may comprise one roughly planar, flexible, deformable, elastic bluntwheel rotatable about an axis, where the axis can be coaxial and coincident with a driveshaft upon which the bluntwheel is firmly affixed. Further, the differential dissecting instrument may be configured to spin the driveshaft (and thus the associated flexible bluntwheel) while intentionally interfering with the free rotation in space of the edge of, margin of, outer limb of, or similar substantial portions of the roughly planar, natural disk or wheel-like form of the flexible, deformable, elastic bluntwheel. 
         [0023]    In one embodiment, of the device is configured so that, in operation, the edge or margin of the freely spinning flexible, deformable, elastic bluntwheel is impinged upon, distorted, deformed, flexed, folded, stressed, strained, re-directed, bent, or otherwise driven out of its unstressed, roughly planar, disk-like state by another portion of the differential dissecting instrument. For example, an associated fixed, nonrotating shroud or other form of housing, cowling, case, cover, wall, sheet, lid, beam, frame, or other structure may be configured to continuously resist the free passage of at least a portion of the rotating margin of the flexible, deformable, elastic bluntwheel. Thus the impingement of the nonrotating shroud onto the spinning bluntwheel causes the flexible, elastic bluntwheel to dynamically and continuously assume a non-disk-like shape, the form of which persists in fixed position to the nonrotating shroud even while the flexible, deformable, elastic bluntwheel is itself spinning. The continuous, spatially fixed deformation of the edge of a spinning flexible, elastic bluntwheel is not unlike a standing wave, where the speed of a passing medium exactly equals the wave propagation speed in that medium. In this fashion, any desired stable deformation of a flexible, deformable, elastic bluntwheel can be achieved and maintained. 
         [0024]    In one embodiment of a differential dissecting instrument employing a nonrotating shroud to create a stable deformation in a substantially transverse, driveshaft-mounted, spinning flexible, deformable, elastic bluntwheel, the nonrotating shroud is configured to deform the flexible bluntwheel into a substantially folded shape, where the opposite edges of a flexible bluntwheel continuously come together in a substantial apposed fashion. This configuration resembles a soft taco, where the flexible circular sheet is gently folded. This stable, continuous deformation by the nonrotating shroud of a spinning elastic bluntwheel ensures that the two opposed, and apposed, edges of the bluntwheel sporting differentially dissecting tissue engaging projections that are exposed distally by the nonrotating shroud are passing in opposite directions in a manner not unlike that of the exposed portions of two apposed bluntwheels counter-rotating about a common axis. 
         [0025]    In either case, whether employing two counter-rotating bluntwheels or employing one folded, spinning bluntwheel, the complex tissue to be dissected encounters the distal-most edges of twin counter-rotating bluntwheels, each edge featuring tissue-engaging projections, which differentially dissect the complex tissue. 
         [0026]    In another embodiment, the achievement of distally exposing twin edges of tissue engaging projections is created by employing twin bent bluntwheels, that is, bluntwheels which deviate slightly from a planar form, and whose centers of rotation are roughly similar, but whose axes of rotation are not parallel. These apposed, bent bluntwheels also sport crown gears on their apposed faces and these can be engaged by a bevel pinion gear atop a drive shaft passing from a proximal location (such as the handle of the differential dissection instrument, or the surgical robot) distally to a location between the apposed bent bluntwheels. When the drive shaft rotates, one bent bluntwheel is rotated clockwise about its axis of rotation, while simultaneously the second, apposed bent bluntwheel is rotated counterclockwise, so that twin sets of blunt, differentially dissecting, tissue-engaging projections pass closely in opposing directions, thus differentially dissecting a complex tissue when impinged upon it. 
     
    
     
       BRIEF DESCRIPTION OF THE FIGURES 
         [0027]      FIG. 1  shows the form of an exemplary bluntwheel for a differential dissecting instrument for dissecting complex tissue, the bluntwheel possessing tissue-engaging projections about its edge, the bluntwheel here viewed along the bluntwheel&#39;s rotational axis. 
           [0028]      FIG. 2  shows a cross-sectional side view of the bluntwheel, illustrating its curved and flat faces. 
           [0029]      FIG. 3  shows an exterior side view of the bluntwheel, illustrating its curved and flat faces. 
           [0030]      FIGS. 4 and 5  each show the forms of each half of a bluntwheel pair, and each viewed along its rotational axis; these two bluntwheels can each rotate about their centers. 
           [0031]      FIG. 6  shows a view of the bluntwheels from both  FIG. 4  and  FIG. 5 , here shown together and apposed, rotating in counter-rotating fashion about a substantially common axis. 
           [0032]      FIG. 7  depicts a cross-sectional side view of the two bluntwheels shown in  FIG. 6 , including the direction of motion of the mass of each bluntwheel closest to the viewer as the pair of bluntwheels counter-rotate about a substantially common axis. 
           [0033]      FIG. 8  shows an external side view of the two bluntwheels shown in  FIG. 6  and  FIG. 7 , including the direction of motion of the mass of each bluntwheel closest to the viewer as the pair of bluntwheels counter-rotate about a substantially common axis. 
           [0034]      FIG. 9  shows a cross-sectional view of an embodiment of the distal portion of a differential dissection instrument, depicting an assembly of two bluntwheels in apposition and configured to counter-rotate about a common axis. 
           [0035]      FIG. 10  shows an external view of the differential dissector embodiment depicted in  FIG. 9 . 
           [0036]      FIG. 11  shows an axial view of a rotatable, flexible, elastic bluntwheel mounted on a drive shaft. 
           [0037]      FIG. 12  shows a cross-sectional, side view of the rotatable, flexible, elastic bluntwheel mounted on a drive shaft; 
           [0038]      FIG. 13  shows an external, side view of the rotatable, flexible bluntwheel mounted to the drive shaft. 
           [0039]      FIG. 14  shows an external side view of the driveshaft-mounted, rotatable, flexible, elastic bluntwheel before it is deformed. 
           [0040]      FIG. 15  shows an external side view of the same rotatable, flexible bluntwheel as it is deformed. 
           [0041]      FIG. 16  illustrates in external side view the driveshaft-mounted, rotatable, flexible, elastic bluntwheel as it is forced by a shroud to fold while spinning. 
           [0042]      FIG. 17  depicts in cross-sectional, side view the internal structures of the driveshaft-mounted, rotatable, flexible, elastic bluntwheel as illustrated in  FIG. 16 , where the bluntwheel is forced to fold while spinning inside a shroud. 
           [0043]      FIG. 18  depicts in external front view the driveshaft-mounted, rotatable, flexible, elastic bluntwheel as it is forced by a shroud to fold while spinning as illustrated in  FIG. 16 . 
           [0044]      FIG. 19  shows in cross-sectional view the internal structures of the driveshaft-mounted, rotatable, flexible, elastic bluntwheel in  FIG. 18 , where the bluntwheel is forced to fold while spinning inside a shroud. 
           [0045]      FIG. 20  shows the form of a driveshaft-mounted, rotatable, hollow, flexible, elastic bluntcone when viewed proximally along its rotational axis. 
           [0046]      FIG. 21  depicts an external side view of the driveshaft-mounted, rotatable, flexible, elastic bluntcone before the bluntcone is deformed. 
           [0047]      FIG. 22  shows an external view of the rotatable, hollow, flexible bluntcone after it is deformed by folding the flexible, elastic bluntcone until the opposite edges of the flexible, elastic bluntcone substantially meet in apposition. 
           [0048]      FIG. 23  depicts a cross-sectional side view of a driveshaft-mounted, rotatable, hollow, flexible, elastic bluntcone, where the bluntcone is forced to fold by a nonrotatable rigid shroud of non-circular cross-section. 
           [0049]      FIG. 24  shows an external front view of the driveshaft-mounted, rotatable, hollow, flexible, elastic bluntcone in  FIG. 23 , where the bluntcone is forced to fold by a nonrotatable rigid shroud of non-circular cross-section. 
           [0050]      FIG. 25  illustrates an internal front view of the driveshaft-mounted, rotatable, hollow, flexible, elastic bluntcone in  FIG. 24 , where the bluntcone is forced to fold by a nonrotatable rigid shroud of non-circular cross-section. 
           [0051]      FIG. 26  shows a front view of two bent bluntwheels counter-rotating with respect to one another, with their axes of rotation near each other but not parallel to each other. 
           [0052]      FIG. 27  shows a cross-sectional side view of one embodiment of a bent bluntwheel assembly comprising the pair of bent bluntwheels from  FIG. 26  connected by their apposed faces to a driveshaft possessing a bevel pinion gear. 
           [0053]      FIG. 28  depicts a cross-sectional front view of the bent bluntwheel assembly depicted in  FIG. 27 , here also showing a nonrotating shroud, input motion and output motion. 
           [0054]      FIG. 29  shows an external view of the bent bluntwheel assembly of  FIG. 28 . 
           [0055]      FIG. 30  depicts an oblique, external view of a driveshaft-mounted, rotatable, hollow, flexible, elastic bluntcone, with differentially dissecting projections along its edge, with the axis of rotation of the bluntcone coaxial with the long axis of the drive shaft. 
           [0056]      FIG. 31  shows an oblique, external view of one embodiment of the distal portion of a powered differential dissection instrument for achieving safe blunt dissection. 
       
    
    
     DETAILED DESCRIPTION 
       [0057]      FIGS. 1 through 3  show views of an exemplary bluntwheel  100  for a differential dissecting instrument for dissecting complex tissue.  FIG. 1  shows a front view of the form of a bluntwheel  100  when viewed along a rotational axis  102 . The bluntwheel  100  has a body  101  and an edge  103  comprising or substantially formed by a plurality of tissue-engaging projections  104  extending radially outward from the center  102 . The bluntwheel  100  is rotatable about the rotational axis  102  in one embodiment. 
         [0058]      FIG. 2  shows a cross-section of the bluntwheel  100 , illustrating its roughly flattened, planar form. In  FIG. 2 , the body  101  of the bluntwheel  100  posseses a curved face  106  and a flat face  105 , an axis of rotation  102  oriented parallel to the plane of the page, and tissue engaging projections  104  extending radially from an edge  103 . 
         [0059]      FIG. 3  shows an exterior side view of the bluntwheel  100 , with its body  101 , a curved face  106  and a flat face  105 , an axis of rotation  102  parallel to the plane of the page, and a plurality of tissue engaging projections  104 . Some embodiments of the bluntwheel  100  can be formed out of a high-modulus material, for example possessing a Young&#39;s modulus of one gigapascal or more, for example, stainless steel or medical-grade PEEK, whereas other embodiments of the bluntwheel  100  are preferably formed out a low-modulus material, for example possessing a Young&#39;s modulus of one megapascal or less, for example polyurethane elastomer. The orientation of the roughly planar bluntwheel  100  with respect to the rest of the differential dissection instrument depends on each embodiment, as we disclose below. 
         [0060]      FIGS. 4 and 5  each show the form of a first half of a bluntwheel pair  110  and the form of a second half of a bluntwheel pair  120 , respectively, where each is viewed along its rotational axis  102  and is rotatable. Each half  110  and  120  possesses a body  101  and an edge  103  comprising or substantially formed by a plurality of tissue-engaging projections  104  extending radially outward from the center  102 . Together these two bluntwheels comprise a pair of apposed bluntwheels  110  and  120  that can each rotate about an axis of rotation  102 , where the two rotational axes can be substantially coaxial. The orientation of the axes of rotation  102  with respect to the long axis  398  of the differential dissection instrument depends on the configuration of the embodiment, as disclosed below. 
         [0061]      FIG. 6  shows a view of an embodiment  130  of a differential dissecting device, comprising the bluntwheels  110  and  120  from  FIG. 4  and  FIG. 5 , here shown with the axes of rotation  102  pointing out of the plane of the page. In  FIG. 6  the bluntwheels  110  and  120  are shown together with their flat sides apposed, rotating in counter-rotating fashion about a substantially common axis  102 , where the bluntwheel  110  from  FIG. 4  is shown closer to the viewer and rotating clockwise (arrow  150 ) about the common axis  102 , while the bluntwheel  120  from  FIG. 5  is shown farther from the viewer and rotating counterclockwise (arrow  151 ) about the common axis  102 . The substantially common axis  102  is, in this embodiment, oriented at 90° to a long axis  398  of the differential dissection instrument, and the plurality of tissue engaging projections  104  are being carried along with their respective bluntwheel, thereby presenting a differential dissecting action to the complex tissue to be dissected. The long axis  398  further possesses a proximal end  501  directed at the user or surgical machine, which can be motorized, and a distal end  502  directed at the complex tissue to be dissected. This embodiment, when activated, thus presents the two opposed passing sets of tissue engaging projections  104  distally to the complex tissue to be dissected, differentially dissecting the complex tissue, enabling safer and faster blunt dissection during surgical procedures. 
         [0062]      FIG. 7  depicts a cross-sectional side view of the embodiment  130  of the two bluntwheels  110  and  120  shown in  FIG. 6 , with the long axis  398  of the surgical instrument shown oriented vertically, forming a 90° angle with respect to the (in this view, transverse) axis of rotation  102 . In  FIG. 7 , it can be seen that the flat faces  105  of the bluntwheels are apposed, leaving the curved faces  106  facing away from each other. The bluntwheels  110  and  120  are rotatably associated and are configured to rotate about a substantially common axis of rotation  102 .  FIG. 7  also shows that the clockwise rotation  150  of the bluntwheel  110  is directly opposite the counterclockwise rotation  151  of the bluntwheel  120 , thus carrying each bluntwheel&#39;s plurality of tissue engaging projections  104  past the other plurality of tissue engaging projections  104 , thereby presenting a differential dissecting action to the complex tissue to be dissected. The long axis  398  possesses a proximal end  501  directed at the user and a distal end  502  directed at the complex tissue to be dissected. At the top of  FIG. 7 , it can be seen that the two sets of tissue engaging projections  104  pass either out of (for bluntwheel  110 ) or into (for bluntwheel  120 ) the plane of the page, thus presenting two opposed passing sets of tissue engaging projections  104  distally to the complex tissue to be dissected, differentially dissecting the complex tissue. 
         [0063]      FIG. 8  shows an external side view of the embodiment  130  comprising the two rotatably associated bluntwheels  110  and  120  shown in and  FIG. 7 , again showing that their opposing flat faces  105  are directly apposed, with their curved faces  106  facing away from one another, and depicting the direction of motion of each bluntwheel ( 150  for bluntwheel  110 , and  151  for bluntwheel  120 ) as the pair of bluntwheels counter-rotate about a substantially common axis  102 , which is itself perpendicular to the long axis  398  of a surgical instrument located near the proximal end  501 . The surgical instrument may be motorized, such that when operated it presents to the distal end  502  a plurality of tissue engaging projections  104  to the complex tissue to be dissected. 
         [0064]      FIG. 9  shows a cross-sectional view of an embodiment of the distal portion of a differential dissection instrument, depicting an assembly  140  of two bluntwheels  110  and  120  with their flat faces  105  in apposition and configured to counter-rotate (black arrows  150  and  151 ) about a substantially coaxial, common axis of rotation  102 . The axis of rotation  102  is oriented substantially transversely to a long axis  398  of a differential dissection instrument. The long axis  398  further possesses a proximal end  501  directed at a user or surgical machine, which may be motorized, and a distal end  502  directed at a complex tissue to be dissected. The two bluntwheels  110  and  120  each possess a plurality of tissue engaging projections  104 . Each bluntwheel further comprises an affixed crown gear  109  that is located on each bluntwheel&#39;s flat face  105  and is coaxial to each bluntwheel&#39;s axis of rotation  102 . The assembly  140  further comprises a drive shaft  107  substantially aligned with the long axis  398  and rotatable about it. The driveshaft  107  further may be rotatably associated with the surgical machine near the proximal end  501  of the long axis  398 , and further may possess a pinion bevel gear  108  affixed to its distal-most end and meshing with the two crown gears  109  on the flat faces  105  of the bluntwheels  110  and  120 . The pinion bevel gear  108  is configured so that when the drive shaft  107  rotates (black arrow  149 ), it drives the affixed pinion bevel gear  108 , and so drives the counter-rotation (black arrows  150  and  151 ) of the bluntwheels  110  and  120 , thus presenting to the complex tissue to be dissected two opposed passing sets of tissue engaging projections  104  distally, thus differentially dissecting the complex tissue. The assembly further comprises a shroud  170  which covers and protects the differential dissection instrument  130  from the patient&#39;s tissues and vice versa, and can provide support for locating the bluntwheels  110  and  120  and drive shaft  107 . 
         [0065]      FIG. 10  is an external view of the embodiment depicted in  FIG. 9 , also showing the rotary input  149  of the drive shaft  107  and the resulting counter-rotational outputs ( 150  and  151 ) of the bluntwheels  110  and  120 . It is clear that the shroud  170  can cover most of the assembly  140  while leaving just the distal portion of the counter-rotating bluntwheels to effect differential dissection of the complex tissue to be dissected. 
         [0066]      FIG. 11  through  FIG. 13  show the form of a driveshaft-mounted, flexible, elastic bluntwheel  200 , possessing a roughly disk-like, planar body  101 C shown oriented perpendicular to a long axis  398  of a surgical instrument. The bluntwheel  200  also comprises a curved face  106  here facing proximally, a flat face  105  facing distally, an edge  103  comprised of a plurality of radially extending tissue engaging projections  104 , a drive shaft  107 , and a means  102 A to affix the body  101 C to the drive shaft  107 . The bluntwheel  200  shares an axis of rotation  102  with the drive shaft  107 . Note that as long as the elastic, roughly disk-like, planar body  101 C is unstressed, it will remain substantially planar, at rest, unloaded, until acted upon. Long axis  398  comprises a proximal end directed at a user or surgical machine, which may be motorized, and a distal end directed at a complex tissue to be dissected. 
         [0067]      FIG. 11  shows the axial view of the driveshaft-mounted, flexible, elastic bluntwheel  200 . 
         [0068]      FIG. 12  shows a cross-sectional, side view of the driveshaft-mounted, flexible, elastic bluntwheel  200 , showing that the axis of rotation  102  is coincident with the long axis  398 , so that this embodiment rotates transversely about the long axis  398 .  FIG. 13  shows an external, side view of the driveshaft-mounted, flexible, elastic bluntwheel  200 . The embodiment  200  further comprises a long axis  398 , which itself has a proximal end  501  directed proximally toward a user or surgical machine, which may be motorized, and a distal end  502  directed at the complex tissue to be dissected. The bluntwheel  200  has a body  101 C, here formed of flexible, elastic material, which may be of a low Young&#39;s modulus, for example roughly one megapascal, and can be a polyurethane elastomer or any other medically appropriate material. It is important to note that the flexible, elastic bluntwheel  200  is non-rigid and so can be deflected out-of-plane, that is, this bluntwheel  200  can be deformed, folded, stressed, strained, or otherwise deflected by anything that impinges strongly enough upon it. This folding can be due to a static load, or it can be due to a dynamic load, or it can be of arbitrary form, as desired by the designer. Thus the folding can be an intentional, configurable outcome of the various embodiments described below. As before, the edges  103  of such bluntwheels  200  possess a series of tissue engaging projections  104  configured for the differential dissection of a complex tissue brought into contact with it by the surgeon. 
         [0069]      FIG. 14  is identical to  FIG. 13 , save for the labeled presence of first, distally directed, impinging forces  299 , which can act to deflect the elastic, flexible body  101 C of bluntwheel  200 , and second, diametrically opposite portions  105 A and  105 B of the distally directed, flat face  105 . The impinging forces  299  are shown in this view as incipient, and not yet deflecting the body  101 C of bluntwheel  200 . 
         [0070]      FIG. 15  illustrates that the impinging forces  299  have now acted to fold the body  101 C of the driveshaft-mounted, flexible, elastic bluntwheel  200  distally until the diametrically opposite portions  105 A and  105 B of the distally directed, flat face  105  have now contacted one another, and are thus substantially apposed. Since the now folded body  101 C is elastic, the curved face  106  is now stretched, while flat face  105  is now compressed, and the body  101 C of the bluntwheel  200  is thus elastically loaded, like a spring, storing the energy from the impinging forces  299 , and so the body  101 C would immediately recoil back to a flat shape if released. 
         [0071]    Together,  FIG. 14  and  FIG. 15  depict two stages in the deformation of the body  101 C of the driveshaft-mounted, flexible, elastic bluntwheel  200 . Thus,  FIG. 14  shows an external side view of the driveshaft-mounted flexible, elastic, disk-like, roughly planar bluntwheel  200  before it is deformed, and  FIG. 15  shows an external side view of the same flexible, elastic bluntwheel  200  while it is deformed by the impinging forces  299 , here folding the flexible, elastic bluntwheel  200  distally like a taco until the diametrically opposed flat faces  105 A and  105 B of opposite edges of the flexible, elastic bluntwheel substantially meet, thus placing two sets of a plurality of tissue engaging projections  104  in apposition, distally, directed toward  502  and so the complex tissue to be dissected. 
         [0072]      FIG. 16  illustrates in external side view another embodiment of a bluntwheel assembly  201 .  FIG. 16  is identical to  FIG. 15 , save for the inclusion of a nonrotating, non-circular shroud  170 , which, given its placement as seen in this view, is the source of the impinging forces  299  in  FIG. 15 . Thus the shroud  170  loads the elastic body  101 C, and so brings into distal apposition the diametrically opposed faces  105 A and  105 B of the flat face  105  of the driveshaft-mounted, flexible, elastic bluntwheel  201 . Thus the bluntwheel  201  is folded as shown in  FIG. 15  and is protected, so is forced to deform by folding, and supported in folded form by an encompassing rigid shroud  170 . In cutaway fashion, it is shown where the drive shaft (shown vertical in this view) resides within the non-circular shroud  170 , which in this view is narrow. 
         [0073]      FIG. 17  depicts in cross-sectional, side view the internal structures of the driveshaft-mounted, flexible, elastic bluntwheel  201  as illustrated in  FIG. 16 . In  FIG. 17 , the flexible, elastic bluntwheel  201  is shown similarly folded, and here is further shown protected, forced to deform by folding, and supported in folded form by a rigid shroud  170  of non-circular cross-section (narrow in this view). In  FIG. 17 , there is also depicted an internal support  173  in the form of a curved plate located proximal to the body  101 C of the flexible, elastic bluntwheel. The internal support  173  assists the shroud  170  in maintaining the distally folded form of the body  101 C of the flexible, elastic bluntwheel and through which the driveshaft  107  passes via orifice  174 . The drive shaft  107  is also shown vertical and exposed, and showing its rotation  149  about the long axis  398  and where the resulting motion (black arrows  155 A and  155 B) of the associated driveshaft-mounted flexible, elastic bluntwheel  201  is clearly seen. The resulting apposed, opposed, counter-rotating motions  155 A and  155 B of the projections  104  on the two edges of the flexible, elastic bluntwheel that have been brought into apposition by the presence of the non-circular shroud  170 , display exposed behavior, not unlike the distal-most effects of the two counter-rotating bluntwheels  110  and  120  depicted in  FIG. 9  and  FIG. 10 . 
         [0074]      FIG. 18  depicts the embodiment shown in  FIG. 16 , in external view and with the driveshaft  107  oriented vertically within the plane of the page. In  FIG. 18 , the driveshaft  107  is shown parallel and perpendicular to  FIG. 16 , so that the non-circular shroud  170  appears wide. In  FIG. 18 , the body  101 C of the flexible, elastic bluntwheel is shown protected, forced to deform by folding, and supported in folded form by the non-circular shroud  170  and also by the shroud edge  172 . 
         [0075]      FIG. 19  shows  201 , the driveshaft-mounted, flexible, elastic bluntwheel as illustrated in  FIG. 18 , in cross-sectional, internal view.  FIG. 19  shows the body  101 C of the flexible, elastic bluntwheel  201  shown protected, forced to deform distally by folding, and supported in distally folded form by the rigid shroud  170  of non-circular cross-section.  FIG. 19  also depicts an internal support in the form of a curved plane  173  that is proximally assisting the shroud  170  in maintaining the distally folded form of the flexible, elastic bluntwheel  101 C and a hole  174  through which the driveshaft  107  passes. In  FIG. 19  the driveshaft  107  is also shown vertical and exposed, and showing its rotation  149  about its long axis  398  and the resulting motion  155 A and  155 B of the associated driveshaft-mounted flexible, elastic bluntwheel is clearly seen, including the resulting distally apposed, counter-rotating motions  155 A and  155 B of the projections  104  on the two edges  103  of the flexible, elastic bluntwheel that have been brought into apposition by the presence of the non-circular shroud  170 , with exposed behavior not unlike the distal-most effects of the two counter-rotating bluntwheels  110  and  120  depicted in  FIG. 9  and  FIG. 10 . 
         [0076]    Referring now to  FIG. 20  through  FIG. 25 , these depict embodiments  300  and  301  of driveshaft-mounted, hollow, rotatable, flexible, deformable, elastic cones bearing tissue-engaging projections  104  along their distal-most edges, and caused to deform into a twin set of distally, externally counter-rotating differentially dissecting edges by a nonrotating shroud  170 . Hereinafter, a cone similar to the cones referred to in the above sentence and shown in  FIG. 20  through  FIG. 25  is referred to as a “bluntcone.” 
         [0077]    First,  FIG. 20  shows the form  300  of the driveshaft-mounted, hollow, flexible, elastic bluntcone when viewed proximally, along its rotational axis  102 , toward the user, handle, or surgical machine. The device  300  here has a long axis  398 , which itself has a user direction  501  directed proximally, and a tissue direction  502 , directed distally toward a complex tissue to be dissected. The bluntcone  300  has a body  101 D, possessing a center  102  where it joins affixed at  102 A proximally with a drive shaft  107 , and an edge  103 , located distal to where the body  101 D of the bluntcone  300  joins the drive shaft  300 . The edge of the bluntcone  300  possesses a series of tissue engaging projections  104  configured for the differential dissection of a complex tissue brought into contact with it by the surgeon. The bluntcone  300  also has an interior surface  105 D directed distally. 
         [0078]      FIG. 21  and  FIG. 22  depict two stages in the deformation of a hollow, flexible, elastic bluntcone  300  mounted on a drive shaft  107  (oriented vertically in these two FIGS.) and sharing an axis of rotation  102  with the drive shaft. In the first stage,  FIG. 21  shows an external side view of the driveshaft-mounted flexible, elastic bluntcone  300  before it is deformed. In the second stage,  FIG. 22  shows an external view of the same flexible bluntcone  300  after it is deformed, here, by folding the body  101 D of the flexible, elastic bluntcone  300  until the opposite interior faces  105 D of opposite edges of the flexible, elastic bluntcone  300  substantially meet in apposition. In both  FIG. 21  and  FIG. 22 , the drive shaft  107  is oriented vertically and parallel to the plane of the page. 
         [0079]      FIG. 23  depicts a cross-sectional side view of a driveshaft-mounted, hollow, flexible, elastic bluntcone  301 , where the drive shaft  107  is oriented vertically in this image. The bluntcone  300  shares an axis of rotation  102  with the drive shaft. The body  101 D of the bluntcone  301  is protected, forced to deform by folding, and supported in folded form by a rigid shroud  170  of non-circular cross-section. Interior face  105 D has collapsed into apposition, folding flat, causing tissue engaging projections  104  to form two rows distally. 
         [0080]      FIG. 24  shows an external view of the hollow, flexible, elastic bluntcone  301  in a shroud  170  of  FIG. 23 , with the drive shaft  107  still oriented vertically, but perpendicular to that view, with an orientation similar to  FIG. 22 .  FIG. 24  shows that the body  101 D of the bluntcone  301  is forced to deform by folding, and supported in folded form by a rigid shroud  170  of non-circular cross-section. 
         [0081]      FIG. 25  illustrates an external view of the hollow, flexible, elastic bluntcone  301  in a shroud  170  of  FIG. 24 , with the drive shaft  107  still oriented vertically and distally directed distally  502  at a complex tissue to be dissected. In  FIG. 25 , the vertical driveshaft  107  is shown exposed.  FIG. 25  shows the rotation  149  of the driveshaft  107  about its long axis  398 , with the resulting induced motion  155 A and  155 B of the associated driveshaft-mounted flexible, elastic bluntcone  301 . Also seen in  FIG. 25  is the resulting distally apposed, counter-rotating motions  155 A and  155 B of the projections  104  on the two edges of the flexible, elastic bluntcone  301  that have been brought into apposition by the presence of the non-circular rigid shroud  170 . The exposed behavior of this embodiment is not unlike the distal-most behavior of the two counter-rotating bluntwheels depicted in  FIGS. 9, 10, and 19 . 
         [0082]      FIG. 26  shows embodiment  400 , depicting two bent bluntwheels  101 AE and  101 BE counter-rotating (black arrows  150  and  151 ) with respect to one another; while their axes of rotation  102 E are near each other, the axes of rotation  102 E of bent bluntwheels  101 AE and  101 BE may not be parallel, and neither of the bent bluntwheels  101 AE and  101 BE is a flat disk. 
         [0083]      FIG. 27  shows an exposed cross-sectional side view of one embodiment of a bent bluntwheel assembly  401  comprising the pair of bent bluntwheels  101 AE and  101 BE from  FIG. 26 , clearly showing their bent form. It can be seen in  FIG. 27  that neither of the bent bluntwheels  101 AE and  101 BE is a flat disk, and that their rotational axes  102 E are nonparallel with one another.  FIG. 27  also illustrates that this embodiment of a bent bluntwheel assembly  401  includes a vertical drive shaft  107  with a distally located bevel pinion gear  108 E, and how this bevel pinion gear  108  can engage a pair of bevel crown gears  105 E located on the roughly apposed faces of the two apposed bent bluntwheels  101 AE and  101 BE; this image also shows the input rotation  149  of the (here, vertical) drive shaft  107  causes the counter-rotating output action (black arrows  150  and  151 ) of the two apposed bent bluntwheels  101 AE and  101 BE, thus distally offering a twin set of passing projections  104  to the complex tissue to be dissected, thus performing differential dissection there. 
         [0084]      FIG. 28  depicts an embodiment  402  in cross-sectional side view of the bent bluntwheels  101 AE and  101 BE depicted in  FIG. 27 , clearly showing the (here, vertical) drive shaft  107  with distally mounted bevel pinion gear  108 E engaging crown bevel gears  109 E on the apposed faces  105 E of two bent bluntwheels  101 AE and  101 BE. The rotational input  149  of the drive shaft  107  is seen, and it is clear that the drive shaft input  149  results in a counter-rotating action (black arrows  150  and  151 ) of the two bent bluntwheels  101 AE and  101 BE. This offers a differential dissection effect at the distal-most portion of the differential dissection instrument, thus differentially dissecting a complex tissue when brought into contact with same. 
         [0085]      FIG. 29  shows an external view of  FIG. 28 , again clearly illustrating how the drive shaft&#39;s  107  rotational input  149  results in counter-rotational output  150  and  151  at the exposed projections  104  of the bent bluntwheels  101 AE and  101 BE, thus differentially dissecting a complex tissue in contact thereof. 
         [0086]      FIG. 30  depicts an oblique, external view of a driveshaft-mounted, hollow, flexible, elastic bluntcone  300 , complete with differentially dissecting projections  104  along its edge  103 , with the axis of rotation  102  of the bluntcone coaxial with the long axis  398  of the drive shaft  107 . 
         [0087]      FIG. 31  shows an oblique, external view of one embodiment  500  of the distal portion of a powered differential dissection instrument for achieving safe blunt dissection. In  FIG. 31 , two counter-rotating, passing edges  555  sporting projections  104  configured for blunt dissection are presented to a complex tissue to be dissected. The projections  104  are configured to differentially dissect a complex tissue on contact when the device is operative. Achieving differential dissection is effected by impinging the two sets  555  of passing projections  104  to the complex tissue to be dissected, regardless of the internal mechanism creating the two sets of passing projections. In one embodiment, the two sets of passing projections can be attained internally by employing twin counter-rotating bluntwheels as shown in  FIGS. 1 through 10 . In another embodiment, the two sets of passing projections can be attained internally by employing twin counter-rotating bent bluntwheels as depicted in  FIGS. 26 through 29 . In yet another embodiment, the two sets of passing projections can internally be created by employing one driveshaft-mounted, flexible, folded elastic bluntwheel as shown in  FIGS. 11 through 19 . In still another embodiment, the two sets of passing projections can be produced by internally using one driveshaft-mounted, hollow, flexible, flattened elastic bluntcones as illustrated in  FIGS. 20 through 25 . 
         [0088]    One normally skilled in the art will appreciate that many variations and combinations of the devices and components herein are possible without violating the spirit of the invention. The many variations and combinations of the devices and components herein are therefore included.