Abstract:
Disclosed is an infinitely adjustable depth stop for a laparoscopic instrument having a shaft, the depth stop including a first component having a first annular space adapted to allow the shaft to be fitted therethrough. The first annular space has a reducible diameter and an interference surface against which the shaft may be fitted. Upon reduction of the reducible diameter, the interference surface frictionally engages the shaft to arrest relative movement of the depth stop along the shaft. The frictional engagement may be along a curve, a spiral curve, or an area. Means are also provided to reopen the reducible diameter to release the depth stop.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    The present invention relates to laparoscopic instrument depth stops, particularly morcellator depth stops. 
         [0002]    Morcellating devices are conventionally utilized for removing tissue from patients during a laparoscopic procedure. Examples of such tissue may be uterine fibroids or even an entire uterus. In some instances, it is desirable to limit the depth of penetration of the morcellating device beneath the skin of a patient to prevent insertion of the mocellating portion of the device beyond the compromised tissue and into healthy tissue below. 
         [0003]    One known method of limiting the depth of penetration is to provide a sliding collar that may be slid up and down the shaft of a morcellating device and locked into place with a locking set screw. Another method includes spacers placed in series on the shaft of the morcellating device. In these devices, the sliding collar or spacers abuts the exterior skin of a patient and serve to restrict the depth in which the shaft may penetrate the body. 
       BRIEF SUMMARY OF THE INVENTION 
       [0004]    Although well received, these methods have proven to be insufficient for the delicate equipment and in the modern operating arena. In the sliding collar example, the locking screw has proven to be difficult to secure with a gloved hand. Moreover, torqueing of the screw creates a point load that can easily damage the morcellator shaft. In the stacked spacer example, depth adjustability is naturally limited by the number and dimensions of the spacers available. It is therefore very difficult to provide a stop at precisely the necessary depth for a particular patient. 
         [0005]    The present invention provides for laparoscopic depth stops that are attachable to a laparoscopic instrument shaft, such as a morcellator shaft, where the depth stops can be adjusted and securely positioned on the shaft to enable infinitely variable positioning with heretofore unknown ease of use. The laparoscopic depth stops described herein also provide the capability of being secured to the morcellator without damaging the morcellator shaft. Principally, the shaft is protected from damage because the forces acted upon it by the inventive devices are non-point load forces, and instead act along a curve, spiral curve, or area. 
         [0006]    In accordance with one embodiment of the invention, there is provided a depth stop for a laparoscopic instrument having a shaft, where the depth stop comprises a first component having a first annular space adapted to allow the shaft to be fitted therethrough, and a second component adapted to be connected to the first component, the second component having a second annular space adapted to allow the shaft to be fitted therethrough. The first annular space and the second annular space form a combined annular space having a first cross sectional area. When the first component is moved relative to the second component the combined annular space reduces to a second cross sectional area less than the first cross sectional area to impart a force on the shaft, the force capable of arresting relative movement of the depth stop along the shaft. 
         [0007]    The movement may be by rotation. 
         [0008]    The reduction in combined annular space may be created by eccentric alignment of the first annular space and second annular space relative to each other. If so provided, the first component may comprise a handle with a cylindrical portion extending therefrom, the cylindrical portion having an exterior recess. The second component may include a cylindrical well adapted to accept the cylindrical portion of the first component, the cylindrical well having an interior extension adapted to fit within the recess when the first component and the second component are connected. 
         [0009]    The reduction in annular space may be created by tapering of the first annular space. If so provided, the first component may comprise a tapered section and the second component may comprise a collet that conforms to the geometry of the tapered section. The first component and the second component may be threaded together with threads, whereby rotation of the first component and second component relative to each other moves the collet with respect to the tapered section. 
         [0010]    The reduction in annular space may be created by rotation of a stop lever about a point outside the cross sectional area of the shaft. The depth stop may further comprise a spring, the spring imparting a force on the stop lever. The stop lever includes a cylindrical section between a first tab and second tab. 
         [0011]    The second component may be a helical coil. The first component may further comprise a series of recesses, the depth stop further comprising a third component, the third component including a ramp adapted to ratchet with the series of recesses. The depth stop may further comprise a release button adapted to release the ramp from the series of recesses. 
         [0012]    In accordance with a further embodiment, there is provided a depth stop for a laparoscopic instrument having a shaft, where the depth stop comprises a first component having a first annular space with a first cross sectional area adapted to allow the shaft to be fitted therethrough, and a second component adapted to be fitted over portions of the first component to reduce the first annular space to a second cross sectional area less than the first cross sectional area. 
         [0013]    The second component may be fitted over the first component by moving the second component a direction perpendicular to the longitudinal axis of the shaft. 
         [0014]    The second component may be a clip having first and second legs connected by a connector member. 
         [0015]    In accordance with a further embodiment of the invention, there is provided a depth stop for a laparoscopic instrument having a shaft, where the depth stop comprises a first component having a first annular space adapted to allow the shaft to be fitted therethrough. The first annular space has a reducible diameter and an interference surface against which the shaft may be fitted. Upon reduction of the reducible diameter, the interference surface frictionally engages the shaft to arrest relative movement of the depth stop along the shaft. 
         [0016]    The frictional engagement may be along a curve. The curve may be a spiral curve. 
         [0017]    The frictional engagement may form an area. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0018]    The subject matter regarded as the invention is particularly pointed out and distinctly claimed in the concluding portion of the specification. The invention, however, both as to organization and method of operation, together with features, objects, and advantages thereof, will be or become apparent to one with skill in the art upon reference to the following detailed description when read with the accompanying drawings. It is intended that any additional organizations, methods of operation, features, objects or advantages ascertained by one skilled in the art be included within this description, be within the scope of the present invention, and be protected by the accompanying claims. 
           [0019]    With respect to the drawings, 
           [0020]      FIG. 1A  depicts a conventional depth stop in use on a surgical morcellating device; 
           [0021]      FIG. 1B  depicts an alternate embodiment of a conventional depth stop; 
           [0022]      FIG. 2A  depicts a perspective view of a depth stop in accordance with a first embodiment of the present invention; 
           [0023]      FIG. 2B  depicts a second perspective view of the depth stop of  FIG. 2A ; 
           [0024]      FIG. 2C  depicts a bottom view of the male component forming a portion of the depth stop of  FIG. 2A ; 
           [0025]      FIG. 2D  depicts a top view of the female component forming a portion of the depth stop of  FIG. 2A ; 
           [0026]      FIG. 2E  depicts a perspective view of the male component of  FIG. 2C ; 
           [0027]      FIG. 2F  depicts a perspective view of the female component of  FIG. 2D ; 
           [0028]      FIG. 3A  depicts a depth stop in accordance with a second embodiment of the present invention; 
           [0029]      FIG. 3B  depicts a perspective view of the outer component of the depth stop of  FIG. 3A ; 
           [0030]      FIG. 3C  depicts a perspective view of the inner component of the depth stop of  FIG. 3A ; 
           [0031]      FIG. 4A  depicts a perspective view of a depth stop in accordance with a third embodiment of the present invention; 
           [0032]      FIG. 4B  depicts a perspective view of a first section of the depth stop of  FIG. 4A ; 
           [0033]      FIG. 4C  depicts a perspective view of the second section of the depth stop of  FIG. 4A ; 
           [0034]      FIG. 4D  depicts a perspective view of select components of the second section of the depth stop of  FIG. 4A ; 
           [0035]      FIG. 5A  depicts a perspective view of a depth stop in accordance with a fourth embodiment of the present invention; 
           [0036]      FIG. 5B  depicts a perspective view of the base component of the depth stop of  FIG. 5A ; 
           [0037]      FIG. 5C  depicts a cross sectional view of the depth stop of  FIG. 5A ; 
           [0038]      FIG. 6A  depicts a perspective view of a depth stop in accordance with a fifth embodiment of the present invention; 
           [0039]      FIG. 6B  depicts a perspective view of the inner portion and helical gripper of the depth stop of  FIG. 6A ; 
           [0040]      FIG. 6C  depicts a second perspective view of the inner portion and helical gripper of the depth stop of  FIG. 6A ; 
           [0041]      FIG. 6D  depicts a perspective view of the outer portion and helical gripper of the depth stop of  FIG. 6A ; and 
           [0042]      FIG. 6E  depicts a perspective view of the outer portion of the depth stop of  FIG. 6A . 
       
    
    
     DETAILED DESCRIPTION 
       [0043]    In the following are described the preferred embodiments of the laparoscopic instrument depth stop of the present invention. In describing the embodiments illustrated in the drawings, specific terminology will be used for the sake of clarity. However, the invention is not intended to be limited to the specific terms so selected, and it is to be understood that each specific term includes all technical equivalents that operate in a similar manner to accomplish a similar purpose. Where like elements have been depicted in multiple embodiments, identical reference numerals have been used in the multiple embodiments for ease of understanding. 
         [0044]    As discussed above, the invention features laparoscopic depth stops that are attachable to laparoscopic devices. For ease of discussion, a morcellator will be used as a representative device. However, other laparoscopic devices are to be considered within the context of this disclosure. 
         [0045]    The present disclosure therefore provides for depth stops for a morcellator having a shaft, where the depth stops can be adjusted with infinitely variable positioning and then secured to the shaft. The laparoscopic depth stops described herein also provide the capability of being secured to the morcellator without damaging its shaft by applying force to the shaft in a form other than a point load. For example, the forces applied may be along a curve, spiral, or within an area. 
         [0046]    As discussed above, conventional depth stops are known.  FIG. 1A  discloses one such conventional depth stop  600 A generally comprising a sliding collar  602  that may slide along the shaft  604  of a morcellator  606 , or other laparoscopic device. The sliding collar  602  includes a locking screw  608  that may be tightened to lock the sliding collar against the shaft  604 . Thus, when the shaft  604  of the morcellator  606  is inserted through the skin S of a patient, its end  610  may be prevented from extending beyond compromised tissue CT to be removed and into healthy tissue HT. 
         [0047]    In so locking the device of  FIG. 1A , it will be appreciated that the forces acting on the shaft  604  by virtue of the locking screw  608  are point forces. No matter how much care is taken by the surgeon in securing the sliding collar  602 , these point forces may damage the delicate shaft  604  of the surgical tool. 
         [0048]      FIG. 1B  depicts an alternative conventional system. Here, the depth stop  100 B generally comprises a series of spacers  612 ,  614 ,  616  that may be stacked to limit the excursion of the shaft  604  into the skin S. The number of spacers and the size of the spacers may be varied as required. Nevertheless, there are only a reasonable number of different size spacers to choose from, and the depth stop is therefore not infinitely variable. 
         [0049]    Generally speaking, the depth stops of the present invention provide for curve, spiral, or area contact between portions of the depth stop and the morcellator shaft rather than point contact. These configurations help to equalize or counteract forces acting on the morcellator shaft while also minimizing the impact of such forces resulting in both improved functionality and reduced risk of damaging the morcellator shaft. Additionally, the depth stops of the present invention provide infinitely variable depth control by being adjustable in an infinite number of positions. 
         [0050]    In accordance with one embodiment, presented initially in a first perspective view in  FIG. 2A , a depth stop  100  comprises a male component  102  and a female component  104 . As will be discussed, the male component  102  and female component  104  engage each other and may be turned relative to each other to offset eccentric lumens that engage the shaft of a morcellator to lock the depth stop  100  in place. 
         [0051]    The male component  102  comprises a handle  106  which in the embodiment shown is generally formed in the shape of a mushroom. Other configurations that easily fit within the grasp of a gloved surgeon are also contemplated. Moreover, the handle may be knurled or may include depressions  108 , as shown, to aid in tactile feel and grip. 
         [0052]    Extending from a central location of the bottom portion  110  of the handle  106  is a male connector  112 . The male connector  112  is configured as an open cylindrical structure with an annular wall  114  forming an annular space  115 . Formed in the generally smooth outer portions  116  of the annular wall  114  are a pair of recesses  118 ,  120 . As best shown in  FIG. 2A  with respect to recess  118 , the recesses  118 ,  120  each include a first portion  122  extending through the annular wall  114  to the termination  124  thereof. In turn, the first portion  122  extends in the opposite direction into a second portion  126  generally configured transverse to the first portion and extending partially around the central axis  128  of the male component  102  and particularly the male connector  112 . 
         [0053]      FIG. 2B  depicts the depth stop  100  in a second perspective view highlighting the female component  104 . As shown, the female component  104  is generally configured as a circular component forming an annular ring  130 . The annular ring  130  forms a well, is generally smooth on its interior portion  132 , and may be knurled or otherwise shaped on its outer portion  134  to facilitate handling by a gloved surgeon. As shown in  FIG. 2B , the outer portion  134  is preferably scalloped. Extending from the interior portion  132  into the annular space  136  provided by the annular ring  130  are a pair of extensions  138 ,  140 . The extensions  138 ,  140  may be formed as part of the female component  104  or may be formed as separate pins that are fitted in apertures of the female component and affixed therein. 
         [0054]    In the embodiment shown, the extensions  138 ,  140  are tubular but it will be appreciated that the extensions may be configured as other shapes and configurations provided that such shapes or configurations are adapted to fit within the recess  118  of the male connector  112 . It will also be appreciated that the male component  102  and female component  104  may be fitted together by positioning the extensions  138 ,  140  first into the first portions  122  (and the other corresponding first portion) of the recesses  118 ,  120  and then into the second portions  126  (and the other corresponding second portion). Upon rotation of the male component  102  relative to the female component, the extensions  138 ,  140  will travel through the second portions  126  (and the other corresponding second portion) to lock the two components together. 
         [0055]      FIG. 2C  depicts a bottom view of the male component  102 . Highlighted for reference are the bottom portion  110  of the handle  106  and male connector  112 . From this view, it will be appreciated that the geometric centerline  142  of the annular wall is offset from the geometric centerline  144  of the outer portion  116  of the male connector  112  by a distance “d.” Distance “d” is preferably 0.20″ and the exact tolerance would depend on the materials used and the tolerance range of the instrument. This offset creates a first eccentricity. 
         [0056]    A second eccentricity is shown in  FIG. 2D , a top view of the female component  104 . The eccentricity can be seen by examination of the apertures formed by the top portion  146  of the annular ring  120 , which is also shown in  FIG. 2B , versus the bottom wall  148  within the annular space  136 . Here, the geometric centerline  150  of the top portion  146  (and the outer portion  134 ) is offset a distance “d2” from the geometric centerline  152  of the bottom wall  148 . Notably, the female component  104  includes a notch  154  on its our wall aligning with the smaller annual diameter of the female component while the male component also includes a similar notch  156  ( FIG. 2C ) aligning with the smaller annual diameter thereof. When the two notches  154 ,  156  are aligned, so too are the extensions  138 ,  140  and the recesses  118 ,  120 . 
         [0057]    A morcellator shaft may be positioned through the annular space  115  of the male component and the annular space  136  of the female component  104  with the two components connected and the notches  154 ,  156  aligned. The depth stop  100  may then be moved up or down the morcellator shaft to a desired position, whereby the surgeon may rotate one or both of the male component  102  and female component  104  to provide for a shift in the two annular spaces  115 ,  136 . This shift reduces the overall cross sectional area of the combined annular space. It will be appreciated that the annular spaces  115 ,  136  are sized such that this shift and reduction in size locks the depth stop  100  against the morcellator shaft by virtue of friction alone. To unsecure the depth stop  100 , the surgeon merely has to rotate the two components in the opposite direction. If it is desired to take the two components apart, the surgeon rotates in the opposite direction the full excursion permitted and pulls the components apart as the extensions  138 ,  140  are removed from the recesses  118 ,  120 . 
         [0058]    For clarity,  FIGS. 2E and 2F  are also provided, with  FIG. 2E  being a further perspective view of the male component  102  and  FIG. 2F  being a further perspective view of the female component  104 . 
         [0059]    A second embodiment of the invention is provided in  FIG. 3A  in the form of depth stop  200 . Depth stop  200  comprises two major components, an outer component  202  and an inner component  204 . As shown in  FIG. 3A , the inner component and outer component may be fitted together. 
         [0060]    A perspective view of the outer component  102  is shown in  FIG. 3B . As shown, the outer component comprises a gripping portion  206  and a base portion  208 . The base portion  208  is generally round while the gripping portion  206  extends outwardly therefrom with a series of fins  210 . The fins  210  are separated by scalloped sections  212  to enable the gloved hand of a surgeon to interact with the outer component  202 . Of course, other configurations are possible. 
         [0061]    Extending through a central portion of the outer component  202  is a lumen  214  having an inner wall  216 . The inner wall  216  of the lumen includes threads  218 . It will be appreciated that the inner wall  216  of the lumen  214  tapers from a first diameter near the base  208  to a smaller second diameter near the upper extent of the fins  210 . 
         [0062]      FIG. 3C  depicts a perspective view of the inner component  204  of the depth stop  200 . The inner component  204  comprises a handle section  220  and a collet section  222 . The handle section  220  is configured with arrayed fins  224  separated by scalloped sections  226  to aid with a surgeon&#39;s grasping of the depth stop  202 . 
         [0063]    The collet section  222  extends outwardly from the base  226  of the handle section  220  toward a collet section terminus  228 . It will be appreciated that the collet section  222  is sized and configured to fit within the lumen  214  of the outer component  202  and includes threads  230  for mating with the threads  218  of the outer section. When so engaged, the outer component  202  and inner component  204  may be rotated relative to each other to advance the inner component, and specifically the collet section  222 , further into the lumen  214  of the outer component. 
         [0064]    The collet section is tubular and includes a lumen  229  therethrough. At the terminus  228  of the collet section  222  are collets  232   a ,  232   b ,  232   c ,  232   d . Although four such collets are shown, there may be as few as one or more than four. As the collet section  222  is advanced through the lumen  214  of the outer component  202 , the collets  232   a ,  232   b ,  232   c ,  232   d  are squeezed together into the spaces  234   a ,  234   b ,  234   c ,  234   d  there between by virtue of the tapered inner wall  216   
         [0065]    It will be appreciated that when the lumen  214  of the outer component  202  and the lumen  229  of the collet section  222  of the inner component  204  are threaded through the shaft of a morcellator, the components are free to slide up and down thereon. The inner and outer components  202 ,  204  are sized and configured such that when the inner component is threaded into the outer component, and the two components are rotated relative to each other, the collets  232   a ,  232   b ,  232   c ,  232   d  will squeeze together by virtue of the tapered inner wall  216  of the lumen  214  to squeeze the morcellator shaft and affix the depth stop  200  thereon. Relative rotation in the opposite direction serves to unfix the two depth stop  200  from the shaft by releasing the collets  232   a ,  232   b ,  232   c ,  232   d.    
         [0066]    It will be appreciated that the depth stop  200  may be sized and configured such that the collets  232   a ,  232   b ,  232   c ,  232   d  provide effective force on the morcellator shaft without damaging the shaft. Also, the thread pitch may be engineered to limit the rotation necessary to achieve such effective force, or may be engineered to permit finer control by requiring a greater degree of rotation to achieve the effective force. 
         [0067]    A third embodiment of the invention is first depicted in  FIG. 4A  as depth stop  300 . Depth stop  300  comprises a first section  302  and a second section  304 . The first section  302  is generally mushroom-shaped and includes a mushroom cap  306  and base section  308 . The second section  304  is generally cylindrical and connects with the base section  308  of the first section  302 . 
         [0068]    The first section  302  is shown in greater detail in  FIG. 4B . Here, it can be seen that the base section  308  comprises a plurality of separate sections, including an open cylindrical section  310 . The open cylindrical section  310  includes a partial cylinder section  312  with an open section  314 . Opposite the open section  314  is a plug  316  extending from the exterior wall  318  of the open cylindrical section  310 . Lastly, the open cylindrical section also includes a plurality of apertures  320 . 
         [0069]      FIG. 4C  depicts a top perspective view of the second section  304 . The second section  304  comprises several components, including a stop lever  322 , actuator slide  324 , spring  326 , and a cylindrical body  328 . The cylindrical body  328  generally comprises a base  330  and a cylindrical upstanding wall  332  extending therefrom. The cylindrical upstanding wall  332  includes an annular space  334  within its confines. It will also be appreciated that the base  330  includes an aperture  336 . 
         [0070]    The upstanding wall  332  includes an open section  338  adjacent to which is the actuator slide  324 . The actuator slide  324  includes an opening  340  facing inward relative to the second section  304  and ribs  342  facing outward. The ribs  342  facilitate tactical feel of a gloved surgeon. 
         [0071]    The stop lever  322  extends across the upstanding wall  332  from a portion opposite the open section  338 , where it connects to spring  326 , to the open section  338 . In turn, the spring  326  connects between the stop lever  322  and the base  330  of the cylindrical body  328 . 
         [0072]    The configuration of the stop lever  322 , spring  326 , and slide  324  are shown in  FIG. 4D . In  FIG. 4D , it is shown that the stop lever  322  includes a spring tab  342  on a first side for connecting to the spring  326  and a slide tab  344  on a second side for connecting to the slide  324 . Between the spring tab  342  and the slide tab  344  is a cylindrical section  346 . In the standard configuration, it will be appreciated that the stop lever  322  is parallel to the base  330  of the cylindrical body  328  such that the lumen  348  of the cylindrical section  346  presents its greatest cross sectional area to a morcellator shaft extending through the cylindrical body. The connection between the spring tab  342  and spring  326  may be a pressure fit within an aperture (not shown) of the  342 , or other means. The connection between the slide tab  344  and slide  324  is preferably by way of a pin  325 . 
         [0073]    It is also noted that the cylindrical body  332  includes a plurality of apertures  350 , generally corresponding to the size and configuration of the apertures  320  of the first section  302 . Thus, when the first section  302  and second section  304  of the depth stop  300  are brought together, pins (not shown) may be driven through the aligned apertures  320 ,  350  to connect the two members. So connected, it will be appreciated that a shaft of a morcellator may be threaded through the aperture of the first member (not shown, but configured at the upper extremity of the mushroom head  306 ), the stop lever  322 , and the aperture  336  of the base  330 . In the standard configuration, the depth stop  300  is free to slide up and down the morcellator shaft. However, upon positioning in a location where it is desired that the depth stop  300  be secured, the surgeon merely shifts the slide  324  from a first position, upward within the open section  338  toward the plug  316  which fits within the open section. This action tends to rotate the stop lever  322  about its intersection with the spring  326 , outside the cross sectional area of the shaft, and effectively reduces the cross sectional area presented to the shaft by the cylindrical section  346  of the stop lever  322 . As such, it will be appreciated that a line force is imposed around a portion of the circumference of the shaft by the stop lever  322 , effectively securing the depth stop  300 . 
         [0074]    A fourth embodiment of the invention is provided starting with  FIG. 5A , which depicts depth stop  400 . Depth stop  400  comprises two components, a base  402  and clamp  404 . 
         [0075]    AS shown in  FIG. 5B , the base  402  comprises a domed upper portion  406  with a lumen  408  extending through its central portion. Opposite of the domed upper portion  406  is a circular foot  410 . Connecting the domed upper portion  406  and the foot  410  is a split strap  412 . It will be appreciated that the lumen  408  extends through the split strap  412  and the foot  410 . 
         [0076]    The split strap  412  comprises an anchor  414  which provides the actual connection between the domed upper portion  406  and the foot  410 . Extending from the anchor  414  are two arms  416 ,  418  ( 418  is most clearly shown in  FIG. 5C ). 
         [0077]      FIG. 5C  is a cross sectional view of the depth stop  400 . As shown in  FIG. 5C , the arms  416 ,  418  are created as opposing arches  420 ,  422  forming a portion of the lumen  408 . The arches  420 ,  422  begin at the anchor  414  and terminate with tabs  424 ,  426  which are spaced apart to leave a gap  428 . As will be discussed later, the arches  420 ,  422  may flex at the anchor to open or close the gap  428 . Approximately midway along their respective lengths, the tabs  424 ,  426  include bulges  430 ,  432 . 
         [0078]    Also shown in  FIG. 5C  is the clamp  404 . Clamp  404  is generally shaped as a horse shoe with a pair of open arms  432 ,  434  and a connector  436 . The open arms  432 ,  434  and connector  436  form an inner surface  438  with cams  440 ,  442  at its end opposite the connector  436 . At the connector  436 , the clamp  404  also comprises an aperture  444 . 
         [0079]    It will be appreciated that in operation, the clamp  404  may be grasped by a gloved surgeon at recesses  446 ,  448  located approximately centrally on its arms  432 ,  434 . The open end (at the arms  432 ,  434 , opposite the connector  436 ) of the clamp  404  may then be slid against the outer walls  446 ,  448  of the arches  420 ,  422  of the split strap  412 , simultaneously spreading the arms  432 ,  434  of the clamp and squeezing the gap  428  of the split strap. To aid in holding the base  402 , the anchor includes grasping regions  445 ,  447 . Continuing pressure on the recesses  446 ,  448  further cams open the clamp  404  by action of the cams  440 ,  442  against the outer walls  446 ,  448  of the arches  420 ,  422 . Upon sufficient excursion of the clamp  404  around the split strap  412 , when the cams  440 ,  442  reach the decreasing radius of the split strap  412 , the clamp will “pop” into place forcing the tabs  424 ,  426  to enter the aperture  444  at the connector  436 . The inner walls of the recess  450 ,  452  cooperate with the bulges  430 ,  432  to effectively close the gap  428 , or at least reduce its size. This decreases the diameter of the lumen  408  in the area of the split strap  412 . 
         [0080]    In this regard, the base  402  of the depth stop  400  may be placed on the shaft of a surgical instrument, such as a morcellator, by threading the shaft through the lumen  408 . The base  402  may then be moved up or down the shaft to a desired stop location. At that location, a surgeon may connect the clamp  404  to the base  402  as discussed above to reduce the diameter of the lumen  408  at the split strap  412  and effectively lock the split strap against the shaft. When it is desired to move the depth stop  400 , the surgeon simply removes the clamp  400  by pulling back on the recesses  446 ,  448  in a manner opposite to assembly while supporting the base at the grasping regions  445 ,  447 . 
         [0081]    The fifth embodiment of the present invention is shown initially in  FIG. 6A , a perspective view of the depth stop  500 . Depth stop  500  comprises three components, an inner portion  502 , outer portion  504 , and helical gripper  506  (best shown in  FIG. 6B ). 
         [0082]    The inner portion  502  begins, opposite its connection with the outer portion  504 , with a mushroom head  506 . Although shown in  FIG. 6A  only at its exit at the outer portion  504 , the mushroom head  506  includes a lumen  508  through its central axis  510 . The lumen is sized and configured to accept a shaft of a surgical instrument, such as a morcellator. Tapering down from the base  512  of the mushroom head  506  is a cylindrical portion  514 . As shown in  FIG. 6B , a perspective view of the underside of the inner portion  502 , the cylindrical portion  514  ends with a series of sloped recesses  515  around its perimeter. It will be appreciated that these sloped recesses  515  form a portion of a ratchet, as will be discussed. 
         [0083]    Also shown in  FIG. 6B  is the lumen  508  of the inner portion  502 . Within the lumen  508  is the helical gripper  506 , which includes at one end a first bent tab  516  and at its second end a second bent tab  518 . The second bent tab  518  is fitted within a recess  520 , best shown in  FIG. 6C , of the lumen  508  of the inner portion  502 . 
         [0084]      FIG. 6D  depicts a perspective view of the outer portion  504  with helical gripper  506  protruding therefrom. The outer portion  504  is generally cylindrical with a cutout  522  near its upper end  524 . At the lower end  526  of the outer portion  504 , there is a chamfered edge  528 . The lumen  508  passes through the cylindrical outer portion  204  from the lower end  526  to the upper end  524 . 
         [0085]    Within the cutout  522  is a cantilevered release button  530 . As suggested, the release button  530  is cantilevered from an inner wall  532  of the cutout  522  by a pliable arm  534 . 
         [0086]      FIG. 6E  depicts a top perspective view of the outer portion  504 . Here, the release button  530  can be seen from its rear  536 . On the rear section  536  is mounted a ramp  538 . It will be appreciated that when assembled with the inner portion  502 , this ramp  538  fits within the one of the series of recesses  515 . By virtue of the ramped shape of the ramp  538 , and the slope of the recesses  515 , the outer portion  504  may rotate relative to the inner portion  502  in the direction of arrow R while the cantilevered release button  530  ratchets from one recess  515  to the next. 
         [0087]    Also shown is slot  540 . Upon assembly of the depth stop  500 , the first bent tab  516  is fitted within the slot  540 . Recall that the second bent tab  518  is fitted within recess  520  of the inner portion  502 . As the outer portion  504  is rotated relative to the inner portion  502  in the direction of arrow R, the helical gripper  506  is tightened such that its relative cross sectional area is reduced. In the meantime, the outer portion  504  is prevented from rotating in the direction opposite of arrow R by virtue of the ratcheting of the release button  530 , and specifically action of the ramp  538  fitting within the one of the series of recesses  515 . When it is desired to permit rotation of outer portion  504  in the direction opposite of arrow R, the release button  530  may be lifted to pull the ramp  538  away from, and out of interaction with, the recesses  515 . This serves to increase the relative diameter of the helical gripper  506 . 
         [0088]    It will therefore be appreciated that in use, the depth stop  500  may be fitted on a shaft of a surgical instrument, such as a morcellator. When the depth stop  500  is in a position where it is desired to be affixed, a surgeon may rotate the outer component  504  relative to the inner component  502  in the direction of arrow R to tighten the helical gripper  506  around the shaft. Ratchet action of the ramp  538  and recesses  515  will prevent loosening until such time that the release button  530  is lifted. 
         [0089]    Each of the components described in the various embodiments may be configured from a variety of materials. Preferably, such materials are suitable for the surgical arena and have engineering properties suitable for their use. For example, the materials should be capable of repeated use and heat sterilization. Such materials include various metals, polymers, and the like. Items such as spring  326  are preferably metal. Other components, such as the helical gripper  506 , may be configured from silicone. 
         [0090]    Although the invention herein has been described with reference to particular embodiments, it is to be understood that these embodiments are merely illustrative of the principles and applications of the present invention. It is therefore to understood that numerous modifications may be made to the illustrative embodiments and that other arrangements may be devised without departing from the spirit and scope of the present invention as defined by the appended claims.