Abstract:
A surgical tool arrangement for performing endoscopic surgical procedures which includes a powered handpiece and a cutting accessory which detachably connects to the handpiece and incorporates a cutting head configuration which provides both aggressive tissue resection and a smooth-cut finish on treated tissue.

Description:
CROSS REFERENCE TO RELATED APPLICATION 
       [0001]    This application claims the benefit of U.S. Provisional Application Ser. No. 61/783,436, filed Mar. 14, 2013, which is incorporated herein by reference in its entirety. 
     
    
     FIELD OF THE INVENTION 
       [0002]    This invention generally relates to a surgical tool arrangement useful for performing endoscopic surgical procedures which includes a powered handpiece and, more particularly, to a cutting accessory which detachably connects to the handpiece and incorporates a cutting head configuration which provides both aggressive tissue resection and a smooth-cut finish on treated tissue. 
       BACKGROUND OF THE INVENTION 
       [0003]    Endoscopic surgical procedures are routinely performed in order to accomplish various surgical tasks. In such a surgical procedure, small incisions or portals are made in the patient. An endoscope, which is a device that allows medical personnel to view the surgical site, is inserted into one of the portals. Surgical instruments used to perform other tasks are inserted into other portals. The surgeon views the surgical site through the endoscope to determine how to manipulate the surgical instruments in order to accomplish the desired procedure. An advantage of performing endoscopic surgery is that, since the portions of the body that are cut open are minimized, the portions of the body that need to heal after the surgery are likewise reduced. Moreover, during an endoscopic surgical procedure, only relatively small portions of the patient&#39;s internal organs and tissue are exposed to the open environment. This minimal opening of the patient&#39;s body lessens the extent to which a patient&#39;s organs and tissue are open to infection. 
         [0004]    The ability to perform endoscopic surgery is enhanced by the development of powered surgical tools especially designed to perform such procedures. Once such tool is sold by the Assignee hereof under the trademark FORMULA®. This tool is in the form of a cylindrical handpiece designed to be held in the hand of the surgeon. The handpiece has a front or distal end provided with a coupling assembly for releasably holding a cutting accessory, and a motor disposed within a handpiece housing which drives the accessory. One such cutting accessory, often termed a “shaver”, includes a hub which defines the proximal end of the accessory and is appropriately configured to cooperate with the coupling assembly of the handpiece to lock the accessory thereto, an elongated and tubular housing element having a proximal end fixed to the hub, and an elongated cutting element including a drive shaft disposed within the housing element. When the accessory is attached to the handpiece, the handpiece motor couples to the drive shaft of the accessory and moves same relative to the outer housing element. The handpiece motor is selectively actuable to drive the accessory drive shaft so as to cause a desired cutting action at the distal end of the accessory. The handpiece is associated with a control unit which controls the functioning thereof, and is actuated by the user via appropriate buttons provided on the handpiece itself, or alternatively directly at the control unit. 
         [0005]    In an endoscopic surgical procedure, irrigating fluid is introduced into the surgical site. This fluid serves as a transport media for removing tissue and debris from the surgical site. In order to remove the irrigating fluid and the material contained therein, the above handpiece and the various accessories which are usable therewith together define a suction conduit. A suction pump is connected to the handpiece to provide the suction force needed for drawing the fluid and material away from the surgical site. In order to control the suction flow through the accessory and the handpiece, the handpiece is provided with a manually operated valve which is manipulated by the surgeon to control suction of material away from the surgical site. 
         [0006]    Mechanical cutting accessories, such as the shaver discussed above, are commonly used in arthroscopic procedures, and allow for the resection of hard and soft bodily tissues, for example, those found within the knee, shoulder and other joints. In such a cutting accessory, the outer housing element defines a window or opening at the distal end, which window is defined by an edge of the wall of the outer housing element. The cutting element drive shaft at the distal end thereof also includes a cutting head having a window defined by an edge of the wall of the cutting head, and when the cutting head is disposed within the housing element, the cutting head window is positioned adjacent the window of the housing element. As the drive shaft is moved relative to the housing element by the handpiece motor, the cutting edge of the cutting head window and the opposed and facing cutting edge of the housing element window cause a cutting action which effectively severs tissue located within the housing element window and between the opposed cutting edges of the housing element and the cutting head. The configurations of these opposed edges allow for removal of particular tissue types, and a variety of different cutting window geometries are available to specifically address the type of cutting the accessory is to carry out. For example, providing the windows of both of the housing element and cutting head with straight cutting edges is useful for making fine or detailed cuts and removing areas of hard tissue, such as bone. This arrangement is often called a “straight-on-straight” cutting style or action. Alternatively, providing the windows of both the housing element and cutting head with toothed or serrated cutting edges achieves a more aggressive cut and is useful for removal of soft fibrous tissue, which arrangement is often called a “tooth-on-tooth” cutting style. A further arrangement involves providing the window of the housing element with a straight cutting edge and the window of the cutting head with a toothed cutting edge, which is often called a “tooth-on-straight” cutting style. Thus, a surgeon may often need to switch cutting accessories during a procedure in order to carry out the appropriate type or style of cut. 
         [0007]    While the above-described surgical accessories have proven useful, when a change in cutting is desired, these accessories require the user to remove the accessory currently in use from the patient, to remove the accessory from the handpiece, install a different accessory onto the handpiece, and then reinsert the new accessory into the surgical site. Further, the known arrangements require the purchase of a multitude of accessories, which results in higher costs and a larger number of surgical accessories which must be present in the operating room in order to carry out the desired surgical procedure. 
         [0008]    The predominant function of teeth provided on a cutting accessory, and specifically the teeth provided on the cutting head of the inner cutting element, is to pull tissue towards the cutting edge of the outer housing element, at which point the tissue is cut by means of a scissoring action between the two respective cutting edges. Even if the cutting edge of the window formed in the outer housing element is straight, the teeth of the cutting head of the inner cutting element can leave a jagged-cut finish on the tissue and/or can make grooves in the tissue. To create the cleanest finish on the tissue, the straight-on-straight scissoring or cutting style as mentioned above is typically required. However, this means that the ability of the inner cutting element to pull tissue to the cutting edge of the outer housing element is limited, which can significantly reduce the consumption rate of the surgical accessory. 
         [0009]    In order to obviate or at least minimize disadvantages of known arrangements, the surgical accessory according to the invention provides aggressive tissue resection while still providing a smooth-cut finish on tissue resected during surgery. In this regard, the cutting window or windows located at the distal end of the cutting accessory is/are provided with alternating toothed and straight cutting edges which facilitates both aggressive and smooth cutting in one surgical cutting accessory. 
         [0010]    Providing this type of blade geometry on a surgical accessory allows the surgeon, with a single surgical cutting accessory, to achieve a very smooth-cut finish on tissue while still being able to aggressively remove soft tissue. As such, the arrangement according to the invention reduces the number of surgical accessories that are needed during a surgery to achieve the desired result, and accordingly minimizes the need to remove the surgical accessory from the patient and then from the handpiece in order to replace same with another surgical accessory, all of which can save time during a procedure, promote safety during the procedure and reduce overall equipment costs. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0011]      FIG. 1  is a perspective view of the surgical tool arrangement according to the invention, including a handpiece with a surgical accessory attached thereto; 
           [0012]      FIG. 2  is an enlarged, fragmentary longitudinal cross-sectional view of the handpiece of  FIG. 1  with the surgical accessory attached thereto; 
           [0013]      FIG. 3  is an enlarged top and fragmentary view of the surgical accessory; 
           [0014]      FIG. 4  is an enlarged longitudinal cross-sectional and fragmentary view of the surgical accessory of  FIG. 3 , as seen generally along line IV-IV in  FIG. 3 ; 
           [0015]      FIG. 5  is an enlarged perspective and fragmentary view of a first embodiment of a cutting head of the surgical accessory in isolation; 
           [0016]      FIG. 6  is an enlarged top and fragmentary view of the cutting head of  FIG. 5 ; 
           [0017]      FIG. 7  is an enlarged cross-sectional view as seen generally along line VII-VII in  FIG. 5 ; 
           [0018]      FIG. 7A  is a cross-sectional view identical to  FIG. 7  but referencing additional features; 
           [0019]      FIG. 8  is an enlarged cross-sectional and fragmentary view as seen generally along line VIII-VIII in  FIG. 6 ; 
           [0020]      FIG. 9  is an enlarged cross-sectional and fragmentary view similar to  FIG. 8 , but illustrating an alternative edge configuration of the proximal edge portion of the cutting window of the cutting head of  FIG. 5 ; 
           [0021]      FIG. 10  is an enlarged bottom and fragmentary view of the cutting head of  FIG. 5 , rotated approximately 180 degrees from the view in  FIG. 6 ; 
           [0022]      FIG. 11  is an enlarged side and fragmentary view of the cutting head of  FIG. 5 ; 
           [0023]      FIG. 12  is an enlarged end view of the distal end of the cutting head of  FIG. 5 , as seen generally along line XII-XII in  FIG. 6 ; 
           [0024]      FIG. 13  is an enlarged, fragmentary and exploded top view of the of distal ends of the outer housing element and the cutting head of the inner cutting element of the surgical accessory of  FIG. 3 ; 
           [0025]      FIG. 14  is an enlarged and fragmentary top view of the distal end of the surgical accessory of  FIG. 3 ; 
           [0026]      FIG. 15  is an enlarged and fragmentary perspective view of a second embodiment of the cutting head of the surgical accessory in isolation; 
           [0027]      FIG. 16  is an enlarged and fragmentary top view of the cutting head of  FIG. 15 ; 
           [0028]      FIG. 17  is an enlarged cross-sectional view as seen generally along line XVII-XVII in  FIG. 15 ; 
           [0029]      FIG. 18  is an enlarged cross-sectional and fragmentary view as seen generally along line XVIII-XVIII in  FIG. 16 ; 
           [0030]      FIG. 18A  is an enlarged cross-sectional and fragmentary view similar to  FIG. 18  of an alternative edge configuration of the proximal edge portion of the cutting window of the cutting head of  FIG. 15 ; 
           [0031]      FIG. 19  is an enlarged side and fragmentary view of the cutting head of  FIG. 15 ; 
           [0032]      FIG. 20  is an enlarged end view of the distal end of the cutting head of  FIG. 15 , as seen generally along line XX-XX in  FIG. 16 ; 
           [0033]      FIG. 21  is an enlarged, fragmentary and exploded top view of the of distal ends of the outer housing element and the cutting head according to the second embodiment of  FIG. 15 ; 
           [0034]      FIG. 22  is an enlarged and fragmentary top view of the cutting head of the second embodiment of  FIG. 15  assembled within the distal end of the outer housing element; 
           [0035]      FIG. 23  is an enlarged and fragmentary top view of a third embodiment of the cutting head of the surgical accessory in isolation; and 
           [0036]      FIG. 24  is an enlarged and fragmentary perspective view of the cutting head of  FIG. 23 . 
       
    
    
       [0037]    Certain terminology will be used in the following description for convenience in reference only, and will not be limiting. For example, the words “upwardly”, “downwardly”, “rightwardly” and “leftwardly” will refer to directions in the drawings to which reference is made. The words “inwardly” and “outwardly” will refer to directions toward and away from, respectively, the geometric center of the arrangement and designated parts thereof. The words “forwardly” and “distally” will refer to the direction toward the end of the arrangement which is closest to the patient, and the words “rearwardly” and “proximally” will refer to the direction toward the end of the arrangement which is furthest from the patient. Said terminology will include the words specifically mentioned, derivatives thereof, and words of similar import. 
       DETAILED DESCRIPTION 
       [0038]    Referring to  FIGS. 1 and 2 , a surgical tool arrangement  10  according to the invention is illustrated. The arrangement  10  includes a handpiece  11 , which at its distal end mounts thereon a surgical accessory  12 . 
         [0039]    Handpiece  11  is a commercially available surgical handpiece manufactured by the Assignee hereof, under Model Nos. 375-704-500 and 375-701-500, and is accordingly only briefly described herein. Handpiece  11  includes an elongate outer housing  13  defining an elongate bore  14  therein. A motor  15  (shown diagrammatically only in  FIG. 1 ) is disposed within housing bore  14 . Motor  15  includes an output or drive shaft  16 , which drive shaft  16  mounts a drive pin  17  at the distal end thereof. A power cable  18  is coupled to the proximal end of handpiece  11  for supplying power to motor  15 . 
         [0040]    Handpiece housing  13  defines therein an elongate suction bore (not shown) extending generally parallel to and sidewardly of housing bore  14 . This suction bore communicates with a diagonally extending suction passage  20  defined in housing  13 , which passage  20  provides communication between the distal end of housing bore  14  and the suction bore. Suction is drawn through the handpiece  11  by a suction pump (not shown), which is connected to the handpiece  11  via a suction tube  21 . Suction flow through the handpiece  11  is regulated by an adjustable valve  22  having a valve stem (not shown) which is movably mounted in a valve bore  23  defined in housing  13 . The valve  22  is adjusted by the user via a movable handle or arm  24  connected to the valve stem. The above handpiece suction arrangement is described in detail in U.S. Pat. No. 7,682,333 issued on Mar. 23, 2010, which patent is owned by the same Assignee hereof and is hereby incorporated by reference herein in its entirety. 
         [0041]    The accessory  12  is removably attached to the distal end of the handpiece  11  by a coupling assembly  25  provided on the handpiece  11 . Coupling assembly  25  includes a generally ring-shaped collet  26  secured to the distal end of the handpiece housing  13 . A locking ring  27  is movably disposed in collet  26  and is biased to hold the accessory  12  within the housing bore  14  of handpiece  11 . A release button  28  is provided on locking ring  27 , and is used to release the locking ring  27  and allow removal of the accessory  12  from handpiece  11 . Further, a coil  30  is provided in collet  26 , which is used to facilitate inductive signal transfer to/from a radio-frequency identification device (RFID) disposed in the accessory  12  as discussed below. 
         [0042]    Referring to  FIGS. 2-4 , the accessory  12  will now be described. Accessory  12  includes an outer cannula or tubular housing element  32  and a cutting element  33  disposed within housing element  32 . Housing element  32  includes a hub  34  which defines the proximal end thereof. Hub  34  is defined by a generally tubular base body  35 , which defines therein a pair of generally rectangular and diametrically-opposed openings  36  adjacent the proximal end thereof. Base body  35  also has formed thereon a pair of outwardly-projecting, diametrically opposed and generally ramp-shaped ears  37  disposed distally of openings  36 . Ears  37  cooperate with coupling assembly  25  of handpiece  11  to secure accessory  12  therein. Hub  34  has a distal end defined by a head  39  or nose of a reduced diameter as compared to base body  35 . In the illustrated embodiment, a thread  40  extends about the circumference of head  39 , which thread  40  may be used to attach an operating cannula (not shown) over housing element  32 . Further, hub  34  defines therein a bore  41  which extends completely through the hub  34 , and with which openings  36  of base body  35  communicate. 
         [0043]    An annular seal  45  is disposed within the proximal end of bore  41  of hub  34 . Seal  45  is constructed of a resilient elastomeric material, and is defined by a main section  46  and axially-spaced proximal and distal sections  47  and  48  disposed at respective opposite ends of the main section  46 . Proximal section  47  defines thereon a pair of annular ribs  55  and  56 , which are disposed in sealing engagement with an inner annular surface of the collet  26  of the handpiece  11  when accessory  12  is coupled thereto, as shown in  FIG. 2 . Distal section  48  defines thereon a pair of outwardly projecting and diametrically-opposed lock tabs  57  which engage within the respective openings  36  of hub  34  to secure the seal  45  to the hub  34  and fix the axial position of seal  45  relative thereto. Distal section  48  additionally defines thereon a pair of inwardly projecting and diametrically-opposed stop tabs  58 , which are generally radially aligned with the respective lock tabs  57 . As shown in  FIGS. 2 and 4 , an RFID device  59  encapsulated within a ring structure is located within hub bore  41  distally from, and in axially-adjacent relationship with, the distal section  48  of seal  45 . 
         [0044]    The above-described coupling arrangement of handpiece  11  and the arrangement of the encapsulated RFID device  59  and coil  30  are disclosed in U.S. Pat. No. 7,887,559 issued on Feb. 15, 2011, which patent is owned by the same Assignee hereof and is hereby incorporated by reference herein in its entirety. 
         [0045]    Housing element  32  additionally includes an elongate housing tube  64  which projects distally from hub  34 . More specifically, housing tube  64  has a proximal end which is fixedly mounted within the distal portion of bore  41  of hub  34 . Housing tube  64  defines an elongate bore or conduit  65  therein, in which the cutting element  33  is disposed as discussed below. As best shown in  FIGS. 13 and 14 , housing tube  64  has a distal end  66  which is cut so as to define a window  67 , which window  67  in the illustrated embodiment opens generally sidewardly of the tube  64 , such that the distal end  66  is generally closed in the axial direction. The cutting of the housing tube  64  results in a ring-shaped edge of housing tube  64  which defines cutting window  67 , which edge has circumferentially-spaced, opposed and generally longitudinally-extending sides  70  and  71 . In the illustrated embodiment, both of these sides  70  and  71  are non-toothed. More specifically, the sides  70  and  71  of window  67 , as same extend longitudinally, have generally straight or linear central regions and curved end regions on opposite axial sides of the respective central region. 
         [0046]    Turning now to the cutting element  33 , same includes a hub  80  which defines the proximal end thereof. Hub  80  incorporates a motor-engaging drive element  81  defining a proximally opening bore  82  therein in which a coil spring  83  (shown only in  FIG. 2 ) is located, and a slot  84  which extends transversely to the longitudinal axis of the cutting element  33 . The hub  80  additionally includes a neck  85  which projects distally from drive element  81 . Neck  85  terminates at a head  86  which has an enlarged outer diameter as compared to the remainder of the neck  85 . In this regard, the outer diameter of the head  86  is slightly larger than the inward projection of the respective stop tabs  58  of seal  45 . A bore  87  extends through the neck  85  and the head  86 , in which an elongate and tubular drive shaft  88  is fixed. Drive shaft  88  defines therein a suction passage  89  which is in communication with a suction port  90  defined in the neck  85 , which suction port  90  is in turn in communication with the suction passage  20  of handpiece  11 . 
         [0047]    Drive shaft  88  has a distal end  91  which defines a cutting head  100  of the cutting element  33 . In the illustrated embodiment, the drive shaft  88  and the cutting head  100  are constructed as an integral or one-piece member formed from rigid metal, such as stainless steel. Alternatively, the drive shaft  88  and the cutting head  100  may be provided as separate components which are fixed to one another. In this regard, the drive shaft  88  may be constructed of a rigid plastic and then induction welded to the cutting head  100 , which may be constructed of rigid metal, such as stainless steel. 
         [0048]    With reference to  FIGS. 5-11 , the cutting head  100  defines a central longitudinal axis  99  and includes a tubular shaft  101 , which shaft  101  in the illustrated embodiment is coextensive with the drive shaft  88 . The shaft  101  is defined by a cylindrical wall  102  which encloses a hollow interior  103 . The shaft  101  has a distal end  105  defining a bearing wall  106  which extends transversely relative to the axis  99 . In the illustrated embodiment, the distal end  105  is cut so as to define a pair of windows or openings  107  and  108  which are located diametrically opposite one another along opposite sides of the cutting head  100 . The windows  107  and  108  open generally sidewardly of the cutting head  100 , and extend in the distal direction of the cutting head  100  up to the bearing wall  106 , which bearing wall  106  (as best shown in  FIG. 12 ) extends transversely between the windows  107  and  108  and defines the distal-most extent of each of the windows  107  and  108 . The bearing wall  106  as such partially closes off the distal end  105  of the drive shaft  88 . 
         [0049]    The cutting of the distal end  105  of the cutting head  100  results in a pair of ring-shaped edges  109  and  110  which respectively define the cutting windows  107  and  108 . The upper ring-shaped edge  109  of the cutting window  107  shown in  FIGS. 5 and 6  has circumferentially-spaced, opposed and generally longitudinally-extending sides  111  and  112 . The side  111  of the cutting window  107  is partially serrated or toothed, and in the illustrated embodiment includes a tooth  114 . The side  111  of cutting window  107  additionally includes a substantially straight-edged portion  115  disposed directly adjacent the tooth  114  and extending distally away therefrom towards the bearing wall  106 . The opposite side  112  of the window  107  is partially serrated or toothed, and similar to the side  111  includes a tooth  116  and a substantially straight-edged portion  117  disposed directly adjacent the tooth  116 . The ring-shaped edge  109  of cutting window  107  additionally includes a proximal portion  119  which extends between and interconnects the proximal regions of the sides  111  and  112 , and a distal portion  120  which extends between and interconnects the distal regions of the sides  111  and  112  and defines an upper edge of the bearing wall  106 . As best shown in  FIG. 6 , the tooth  114  and straight-edged portion  115  on one side  111  of the window  107  are respectively aligned (in a direction transverse to the axis  99 ) with the straight-edged portion  117  and the tooth  116  on the opposite side  112  of the window  107 . Further, in the illustrated embodiment, the straight-edged portions  115  and  117  are generally parallel with one another and with the axis  99 . 
         [0050]    With reference to  FIG. 10  which shows the opposite side of the cutting head  100  from that shown in  FIG. 6 , the lower ring-shaped edge  110  of the cutting window  108  is configured similarly to upper edge  109 . Specifically, the lower ring-shaped edge  110  has circumferentially-spaced, opposed and generally longitudinally-extending sides  130  and  131 . The side  130  of the cutting window  108  is partially serrated or toothed, and in the illustrated embodiment includes a tooth  132 . The side  130  of cutting window  108  additionally includes a substantially straight-edged portion  133  disposed directly adjacent the tooth  132  and extending proximally away therefrom. The opposite side  131  of the window  108  is partially serrated or toothed, and includes a tooth  134  and a substantially straight-edged portion  135  disposed directly adjacent the tooth  134 . The ring-shaped edge  110  of cutting window  108  additionally includes a proximal portion  140  which extends between and interconnects the proximal regions of the sides  130  and  131 , and a distal portion  141  which extends between and interconnects the distal regions of the sides  130  and  131  and defines a lower edge of the bearing wall  106 . With continued reference to  FIG. 10 , the tooth  132  and straight-edged portion  133  on one side  130  of the window  108  are respectively aligned (in a direction transverse to the axis  99 ) with the straight-edged portion  135  and the tooth  134  on the opposite side  131  of the window  108 . Further, in the illustrated embodiment, the straight-edged portions  133  and  135  are generally parallel with one another and with the axis  99 . Additionally, as shown in  FIGS. 6 and 10 , in this embodiment, the teeth  114  and  116  of upper cutting window  107  are respectively vertically aligned with the teeth  134  and  132  of the lower cutting window  108 . 
         [0051]    The upper and lower cutting windows  107  and  108  of the cutting element  33  are provided with geometries, and specifically shear angles, which maximize the cutting ability of the cutting element  33 . Shear angle in this context is intended to refer to the opening angle of the windows  107  and  108  which is determined during the cutting process which forms the windows  107  and  108 . In this regard, the ring-shaped edges  109  and  110  may be cut so as to provide some, or alternatively all, cutting edges with a negative internal shear angle which is less than zero degrees. This negative shear angle, when applied to cutting edges such as the teeth  114 ,  116 ,  132  and  134 , increases the likelihood that tissue will be scooped into the cutting windows  107  and  108 , thereby increasing the consumption rate of the cutting accessory. In the illustrated embodiment as shown in  FIG. 12 , at least the internal faces of the teeth  114 ,  116 ,  132  and  134  are provided with an internal shear angle A, which angle A is less than zero degrees. Further, as shown in  FIG. 7 , the internal faces of the respective straight-edged portions  115 ,  117 ,  133  and  135  in the illustrated embodiment have an internal shear angle B which is greater than or equal to zero degrees. However, as shown in dotted lines in  FIG. 7 , the internal faces of straight-edged portions  115 ,  117 ,  133  and  135  can alternatively be provided with an internal shear angle C which is negative, or less than zero degrees, similar to the teeth  114 ,  116 ,  132  and  134 . Providing the teeth and/or straight-edged portions with negative shear angles means that the internal cutting face of each of these components, when viewed in a direction normal to the axis  99 , angles inwardly as same projects towards the axis  99 . Additionally, the proximal internal faces of the proximal edges  119  and  140  of the windows  107  and  108  in the illustrated embodiment as shown in  FIG. 8  can be provided with a shear angle which is greater than or equal to zero degrees. Alternatively, the internal faces of the edges  119  and  140  can be provided with a negative shear angle D which is less than zero degrees, as shown in  FIG. 9 . Providing the proximal edges  119  and  140  with a negative shear angle reduces the likelihood that tissue will snag and cause the cutting accessory to clog. 
         [0052]    Additionally, the cutting head  100  utilizes small included edge angles on the cutting edges thereof. Included edge angle is the angle of the cutting edge as measured between a line tangential to the outer surface of the cutting head  100  and a line parallel with the internal face of the respective cutting edge. More specifically, as shown in  FIG. 7A , the included edge angle E of the teeth (only teeth  114  and  134  are shown in  FIG. 7A , but it is to be understood that the teeth  116  and  132  also have the included edge angle E), and the included edge angle F of the straight-edged portions (only straight-edged portions  117  and  133  are labeled in  FIG. 7A , but it is to be understood that straight-edged portions  115  and  135  also have the included edge angle F) of the windows  107  and  108  are each acute, or less than 90 degrees. The smaller the included edge angle, the more likely that tissue will be cut by the respective cutting edge. Creation of the internal shear angles and the included edge angles as discussed above in the illustrated embodiment is formed by a laser-cutting process. 
         [0053]    The cutting element  33  is assembled to the outer tubular housing element  32  by inserting the distal end  91  of the cutting element  33  into the bore  41  at the proximal end of the hub  34 . During this insertion, the enlarged head  86  of hub  80  expands the seal  45  and the head  86  pushes past the stop tabs  58 , at which point the seal  45  essentially resumes its original shape. The stop tabs  58 , while allowing some axial displacement of the cutting element  33  relative to housing element  32 , prevent the cutting element  33  from detaching or falling out of the housing element  32  due to gravitational forces. 
         [0054]    The assembled accessory  12  is secured to the handpiece  11  in a similar manner to that described in the &#39;559 patent referenced above, and will accordingly be only briefly described here. The accessory  12  is attached to the handpiece  11  by inserting the hubs  34  and  80  into the open distal end of collet  26 . The ears  37  of hub  34  seat within collet  26 , and the locking ring  27  serves to hold the accessory  12  within the handpiece  11 . The above securement of the accessory  12  to handpiece  11  causes the drive element  81  to engage the motor output shaft  16 . More specifically, the drive pin  17  of output shaft  16  seats within the slot  84  of drive element  81 , such that the rotational movement of the output shaft  16  is transferred to the cutting element  33 . The spring  83  of drive element  81  biases the cutting element  33  forwardly or in the distal direction, so as to maintain the distal end  91 , and specifically the bearing wall  106 , of cutting element  33  in bearing contact with the interior of the closed distal end  66  outer housing element  32 . 
         [0055]    In operation, the distal end of the tool  10  is inserted into the surgical site. If desirable or necessary, the distal end of the tool  10  can be inserted into the surgical site through a working portal defined by a conventional cannula or trocar (not shown). The cutting element  33  is controlled by a control unit (not shown) connected to the handpiece cable  18 , which control unit supplies electrical power to the motor  15  of the handpiece  11  in order to actuate the cutting element  33 . Control unit also controls the mode of operation of the cutting element  33 , for example by controlling motor  15  so as to drive cutting element  33  in a forward or reverse direction, or in an oscillating manner. If cutting of tissue is desired, then the motor  15  is activated so as to cause the cutting element  33  to rotate within and relative to the outer housing element  32 . In this regard, it will be appreciated that the control unit may include appropriate control buttons so as to allow the surgeon or operator to select the desired accessory operations. These control functions of the cutting element  33  may alternatively be performed directly from the handpiece  11  which would then include the appropriate control buttons thereon. Alternatively, the control unit may be associated with a switch, either through a suitable cable or wirelessly, to allow the surgeon to operate the controls remotely. Such a switch may be a footswitch or a hand switch. 
         [0056]    As shown in  FIG. 14 , with the cutting element  33  disposed within the housing element  32  and the accessory  12  secured to handpiece  11  as described above, when the cutting element  33  is rotated by the handpiece motor  15  in the direction indicated by the arrow in  FIG. 14 , the side  111  of the upper window  107  of cutting element  33  moves towards the side  70  of the housing tube window  67  and the tooth  114  grabs and pulls tissue into the window  67  and towards the side  70  thereof. This tissue is cut by the scissoring action between tooth  114  and the adjacent straight-edged portion  115  of the side  111  of upper window  107  and the opposed edge  70  of the housing tube window  67  as same closes. If the tooth  114  leaves a ragged edge and/or grooves the tissue in the area where cut, then with continued rotation in the direction of the arrow in  FIG. 14 , this ragged or grooved tissue adjacent the housing tube window  67  (as same opens again when the lower window  108  of the cutting element  33  aligns therewith) will be cut by the straight-edged portion  133  of the lower window  108  (see  FIG. 10 ) which will effectively clean up the ragged or grooved area of tissue so as to leave a smooth-finish cut. Thus, with a single rotation of the cutting element  33  through 360 degrees within the outer housing tube  32 , two types of cuts are provided, the first type of which occurs via the scissoring action between the tooth  114 /straight-edged portion  115  (of the window  107 ) and the opposed edge  70  after the tooth  114  grabs tissue and pulls same into the window  67 , and the second type of which occurs via the subsequent scissoring action between the straight-edged portion  133  (of the window  108 ) and the edge  70  which serves to provide a finishing or smoothing cut. Further, during rotation of the cutting element  33  in the direction indicated by the arrow in  FIG. 14 , the tooth  132  of the lower cutting window  108 , when the housing tube window  67  opens due to its alignment with lower cutting window  108 , will act in the same manner as described above with respect to tooth  114  and thus will pull tissue towards the edge  70  of the housing tube window  67 . Any grooving or raggedness left in the tissue by tooth  132  will thus be cleaned up or finished by the straight-edged portion  115  of the upper window  107  when same again aligns with housing tube window  67 . 
         [0057]    Of course, it is possible to rotate the inner cutting element  33  in a direction opposite to that indicated by the arrow in  FIG. 14 , meaning that the tooth  116  and straight-edged portion  117  of the window  107  would rotate towards the side  71  of the housing element  32  and, in cooperation with the straight-edged portion  135  and the tooth  134  of the window  108 , would cut and then smooth tissue in a similar manner as described above. 
         [0058]    Additionally, with the window configuration of the cutting element  33  as described above, the straight-edged portions  115 ,  117 ,  133  and  135  of upper and lower windows  107  and  108  are substantially greater in their axial or longitudinal dimensions as compared to the axial or longitudinal dimensions of the teeth  114 ,  116 ,  132  and  134 , the greatest longitudinal dimension of which would be at the root of the teeth. This means that, in this embodiment, there are significant lengths of straight-edged portions of the windows  107  and  108  of the cutting element  33  available to interact with the opposed straight sides or edges  70  and  71  of the outer housing tube window  67 . This arrangement, coupled with the smoothing or finishing action described above, thus allows the cutting accessory according to the invention to achieve or at least approximate a straight-on-straight cutting style, while still providing the tissue-grabbing ability associated with toothed cutting edge configurations. 
         [0059]    The cutting accessory  12  may be utilized in the forward or reverse mode, as described above, wherein the cutting element  33  rotates in either the forward direction or the reverse direction through continuous 360 degree cycles. The cutting accessory  12  may also be used in the oscillation mode, wherein the cutting element  33  is rotated a specified number of 360 degree cycles in a forward direction before reversing and rotating a specified number of 360 degree cycles in the opposite or reverse direction. In the oscillation mode, the tissue smoothing effect described above would provide a quicker clean-up of the targeted tissue at the surgical site due to the directional change in the cutting action which occurs in this mode. 
         [0060]    It will be appreciated that the number of teeth  114 ,  116 ,  132  and  134  provided on the windows  107  and  108  of the cutting element  33  as described herein is presented only by way of example, and thus a greater or lesser number of teeth may be provided within the scope of the invention. For example, the cutting head  100  of the cutting element  33  may only be provided with one tooth  114  located at the upper window  107 , and one tooth  132  located at the lower window  108  (so that the teeth  114 ,  132  are axially offset from one another). Alternatively, the cutting head  100  may be provided with one tooth  114  located at the upper window  107  and one tooth  134  located at the lower window  108  (so that the teeth  114 ,  134  are substantially vertically aligned with one another), so that there is an active tooth or tissue-grabbing ability in both the forward and reverse directions of rotation of the cutting head  100 . Further, it is within the scope of the invention to provide multiple teeth at the upper and lower windows  107  and  108 , which teeth can be provided in groups at the locations of the respective teeth shown in  FIGS. 5 and 10 . In the above-described embodiments, it is important that the tooth or teeth in one rotational direction of the cutting element  33 , which can be considered the leader tooth or teeth, be axially aligned with a straight-edged portion located at the lower window  108 , which straight-edged portion can be considered the follower straight-edged portion. 
         [0061]    If desirable or necessary, suction can be provided at the surgical site by manipulating the valve  22  on handpiece  11  to draw surgical debris from the surgical site through the window  67  of the housing element  32  and the window  107  or  108  of the cutting element  32  aligned therewith, into the drive shaft suction passage  89 , into the handpiece suction passage  20  and proximally through the handpiece  11  towards the suction pump. 
         [0062]    The accessory  12  according to the invention thus achieves or at least closely approximates the straight-on-straight cutting style of conventional surgical accessories, and at the same time incorporates the desirable tissue-grabbing function of a toothed surgical accessory. This arrangement thus effectively allows the combination of two different cutting actions or styles into one tool or accessory, which is advantageous in that the surgeon need not remove the accessory  12  from the surgical site in order to achieve a different cutting style or action, and can also reduce the costs associated with purchasing multiple surgical accessories. 
         [0063]      FIGS. 15-22  illustrate a second embodiment of the invention which will now be described. The second embodiment is generally similar to the first embodiment, the main difference being in that only a single cutting window is provided in the cutting head as compared to the dual cutting windows provided in the cutting head  100  of the prior embodiment. Components of this second embodiment which are similar or identical to components of the prior embodiment will include the same reference numbers as in the prior embodiment plus “100”, and a detailed description of all components will accordingly not be provided. The surgical accessory shown in  FIGS. 15-22  includes a cutting head  200  which defines a central longitudinal axis  199  and includes a tubular shaft  201  defined by a cylindrical wall  202  which encloses a hollow interior  203 . The shaft  201  has a distal end  205  defining a bearing wall  206 . In the illustrated embodiment, the distal end  205  is cut so as to define a window or opening  207  which opens generally sidewardly of the cutting head  200 , and extends in the distal direction of the cutting element  200  up to the bearing wall  206 , which bearing wall  206  closes off the distal end  205  of the drive shaft  88 . 
         [0064]    The cutting of the cutting head  200  results in a ring-shaped edge  209  which defines the cutting window  207 . The ring-shaped edge  209  of the cutting window  207  has circumferentially-spaced, opposed and generally longitudinally-extending sides  211  and  212 . The side  211  of the cutting window  207  is partially serrated or toothed, and in the illustrated embodiment includes a plurality of teeth  214 . The side  211  additionally includes a plurality of substantially straight-edged portions  215  located on opposite sides of each tooth  214  (except for the most distally-located tooth  214  adjacent bearing wall  206  which has only one straight-edged portion  215  disposed at the proximal side thereof). The opposite side  212  of the window  207  is also partially serrated or toothed, and similar to the side  211  includes a plurality of teeth  216  and a plurality of substantially straight-edged portions  217  disposed on opposite sides of each tooth  216  (again, except for the most distally-located tooth  216  located adjacent bearing wall  206 ). The ring-shaped edge  209  of cutting window  207  additionally includes a proximal portion  219  which extends between and interconnects the proximal regions of the sides  211  and  212 , and a distal portion  220  which extends between and interconnects the distal regions of the sides  211  and  212  and defines an upper edge of the bearing wall  206 . As best shown in  FIGS. 16 and 19 , each of the teeth  214  on one side  211  of the window  207  are respectively aligned (in a direction transverse to the axis  199 ) with a straight-edged portion  217  on the opposite side  212  of the window  207 , and each of the teeth  216  on the side  212  of the window  207  are respectively aligned with a straight-edged portions  215  on the opposite side  211  of the window  207 . Further, in the illustrated embodiment, the straight-edged portions  215  and  217  are generally parallel with one another and with the axis  199 . 
         [0065]    As shown in  FIG. 17 , the cutting window  207  of cutting head  200  is provided with a geometry which maximizes the cutting abilities or characteristics of the cutting element  133 . In this regard, the ring-shaped edge  209  is cut so as to provide the teeth  214  and  216  and the straight-edged portions  215  and  217  with respective included edge angles G and H which are acute. It will be appreciated that the teeth  214 ,  216  and/or the straight-edged portions  215 ,  217  may be provided with negative internal shear angles, as discussed above with respect to the first embodiment. Additionally, the internal face of the proximal edge  219  of the window  207  can be provided with a shear angle which is greater than or equal to zero degrees, as shown in  FIG. 18 . Alternatively, as shown in  FIG. 18A , the internal faces of the edge  219  can be provided with a negative shear angle I which is less than zero degrees. 
         [0066]      FIG. 22  shows the cutting head  200  disposed within the distal end  166  of housing element  132 . The cutting head  200  of this second embodiment as illustrated has a larger-sized cutting window  207  as compared to the sizes of the respective cutting windows  107  and  108  of the first embodiment. Further, the cutting head  200  includes a greater number of teeth  214  and  216  and larger-sized teeth  214  and  216  as compared to the first embodiment. The cutting head  200  is accordingly appropriate for use in situations where a more aggressive approach to tissue or bone removal is necessary and/or desirable, and as such the larger-sized window  207  allows a greater volume of tissue or bone to enter the window  207  for cutting. 
         [0067]    The cutting head  200  may be driven in forward and reverse modes. When the cutting element  133  is rotated by the handpiece motor  15  in the direction indicated by the arrow in  FIG. 22 , the side  211  of the window  207  of the cutting element  133  moves towards the side  170  of the housing tube window  167  and the teeth  214  grab and pull tissue into the window  167  and towards the side  170  thereof. This tissue is cut by the scissoring action between teeth  214  and the adjacent straight-edged portions  215  of the side  211  of the window  207  and the opposed edge  170  of housing tube window  167  as same closes. In the direction of rotation opposite from the arrow shown in  FIG. 22 , the side  212  of the window  207  of the cutting element  133  moves towards the side  171  of the housing tube window  167  and the teeth  216  grab and pull tissue into the window  167  and towards the side  171 , which causes cutting of tissue via the scissoring action between teeth  216  and the adjacent straight-edged portions  217  and the opposed edge  171  of housing tube window  167 . 
         [0068]    The cutting head  200  may also be driven in the oscillating mode which allows the surgeon to specify a number of forward cycles and a number of reverse cycles for the cutting head  200 . In this regard, due to the alignment of the teeth and straight-edged portions of the cutting head  200  as described above, when the cutting head  200  is first driven in the forward mode (for example as indicated by the directional arrow in  FIG. 22 ) for a specified number of rotational cycles, the teeth  214  may leave ragged or grooved tissue in the area(s) where cut. However, when the cutting head  200  is subsequently driven in the reverse mode (for example, in a direction opposite from the arrow in  FIG. 22 ), any ragged or grooved tissue areas adjacent the housing tube window  167  will be cut by the straight-edged portions  217  on the opposite side  212  of the window  207  which will effectively clean up and the ragged or grooved areas of tissue so as to leave a smooth-finish cut. 
         [0069]    Additionally, with the window configuration of the cutting head  200  as described above, the straight-edged portions  215  and  217  of the window  207  are substantially greater in their axial or longitudinal dimensions as compared to the axial or longitudinal dimensions of the teeth  214  and  216 , the greatest longitudinal dimension of which would be at the root or base of the teeth. As with the first embodiment, this means that there are significant lengths of straight-edged portions of the window  207  of the cutting head  200  available to interact with the opposed straight sides or edges  170  and  171  of the outer housing tube window  167 , even when the cutting element  133  is simply driven in one direction of rotation. This arrangement, coupled with the smoothing action described above when the cutting head  200  is driven in an oscillating mode, thus allows the cutting accessory according to the invention to achieve or at least closely approximate a straight-on-straight cutting style, while still providing the tissue-grabbing ability associated with toothed cutting edge configurations. 
         [0070]    It will be appreciated that the number of teeth  214  and  216  provided on the window  207  of the cutting element  133  as described herein is presented only by way of example, and thus a greater or lesser number of teeth may be provided within the scope of the invention, provided that the tooth or teeth located on one side of the window  207  of the cutting head  200  are aligned (in a direction transverse to the axis  199 ) with a straight-edged portion located on the opposite side of the window  207 . 
         [0071]    As with the prior embodiment, suction can be provided at the surgical site by manipulating the valve  22  on the handpiece  11  to draw surgical debris from the surgical site through the window  167  of housing element  132  and the window  207  of cutting head  200  aligned therewith, into drive shaft suction passage  89 , into the handpiece suction passage  20  and proximally through the handpiece  11  towards the suction pump. 
         [0072]      FIGS. 23 and 24  illustrate a third embodiment of the invention which will now be described. The third embodiment is generally similar to the first embodiment in that same includes dual cutting windows. Components of this third embodiment which are similar or identical to components of the first embodiment will include the same reference numbers as in the first embodiment plus “200”, and a detailed description of all components will accordingly not be provided. The surgical accessory shown in  FIGS. 23 and 24  includes a cutting head  300  which defines a central longitudinal axis  299  and includes a tubular shaft  301  defined by a cylindrical wall  302  which encloses a hollow interior  303 . The shaft  301  has a distal end  305  defining a bearing wall  306  which extends transversely relative to the axis  299 . In the illustrated embodiment, the distal end  305  is cut so as to define a pair of windows or openings  307  and  308  which are located generally diametrically opposite one another along opposite sides of the cutting head  300 , and which open generally sidewardly thereof. The windows  307  and  308  extend in the distal direction of the cutting element  300  up to the bearing wall  306 , which bearing wall  306  as in the first embodiment extends transversely between the windows  307  and  308  and defines the distal-most extent of each of the windows  307  and  308 . The bearing wall  306  as such partially closes off the distal end of the drive shaft  88 . 
         [0073]    The cutting of the distal end  305  of the cutting head  300  results in a pair of ring-shaped edges  309  and  310  which respectively define the upper and lower cutting windows  307  and  308 . The configuration of the edges  309  and  310  is similar to that of the first embodiment, except that additional teeth  314  are provided on one side  311  of the window  307 , which teeth  314  are separated by a substantially straight-edged portion  315 , and a further substantially straight-edged portion  315  is provided distally of distal-most tooth  314 . Additional teeth  316  are also provided on the opposite side  312  of the window  307 . The teeth  316  are separated by a substantially straight-edged portion  317 , and a further substantially straight-edged portion  317  is provided between the proximal-most tooth  316  and proximal edge portion  319  of the window  307 . As best shown in  FIG. 23 , each tooth  314  on one side  311  of the window  307  is aligned (in a direction transverse to the axis  299 ) with a straight-edged portion  317  on the opposite side  312  of the window  307 . Likewise, each tooth  316  on the side  312  is aligned with a straight-edged portion  315  on the opposite side  311  of the window  307 . Further, in the illustrated embodiment, the straight-edged portions  315  and  317  are generally parallel with one another and with the axis  299 . 
         [0074]    The lower window  308 , located on the opposite side of the cutting head  300  from the window  307 , on the side  330  has teeth  332  which are separated by a substantially straight-edged portion  333 . The side  330  of the cutting window  308  additionally includes a substantially straight-edged portion  333  disposed directly adjacent the proximal-most tooth  332  and the proximal portion  340 . The opposite side  331  of the window  308  includes teeth  334 , a substantially straight-edged portion  335  disposed directly between teeth  334 , and a further substantially straight-edged portion  335  located adjacent the bearing wall  306 . As best shown in  FIG. 23 , the teeth  314  and  316  of upper cutting window  307  are respectively vertically aligned with the teeth  334  and  333  of the lower cutting window  308 . 
         [0075]    As with the prior embodiments, the cutting windows  307  and  308  of cutting head  300  are provided with geometries which maximize the cutting characteristics of the cutting head  300 . Briefly, the teeth  314 ,  316 ,  332  and  334  and/or straight-edged portions  315 ,  317 ,  333  and  335  may be provided with acute included edge angles or with negative shear angles. Further, the proximal portions  319  and  340  of the windows  307  and  308  may be provided with negative shear angles. 
         [0076]    Although particular preferred embodiments of the invention are disclosed in detail for illustrative purposes, it will be recognized that variations or modifications of the disclosed apparatus, including the rearrangement of parts, lie within the scope of the present invention.