Abstract:
A method, apparatus, and system for cutting anatomic members, such as ligaments, in surgical procedures such as carpal tunnel release, plantar fasciotomy, gastroc release, cubital tunnel release, and tarsal tunnel release is disclosed. The apparatus includes a guide tool for guiding a knife and a scope during surgery which may be employed with a translating knife. Relevant features include a knife stop for preventing the knife from inadvertently raising out of the knife channel, indicia viewable to show the proper orientation for the guide tool, a self dilating tip and channel design on the guide tool, a cover piece and/or pivotable panel system for preventing ligaments and other anatomy from getting caught in the guide tool, a pivot pin and groove system for stabilizing the knife and also assuring that the knife blade is not inadvertently raised out of the channel, and a use indicator employable to prevent re-use of the device.

Description:
[0001]    This application is a Continuation in Part Application to U.S. patent application Ser. No. 13/183,020 filed on Jul. 14, 2011, which claims the benefit of U.S. Provisional Application No. 61/364,128 filed on Jul. 14, 2010, both of which are fully incorporated herein by reference. 
     
    
     FIELD OF INVENTION 
       [0002]    The invention pertains to methods, apparatus, and systems for performing endoscopic ligament release surgery, such as carpal tunnel release, plantar fasciotomy, gastroc release, cubital tunnel release, and tarsal tunnel release surgery, and similar surgical procedures on anatomic members. 
       BACKGROUND 
       [0003]    Carpal tunnel syndrome occurs when the median nerve is squeezed where it passes through the carpal tunnel, thereby causing insanguination of the nerve, which leads to numbness, a cold feeling, and/or pain in the hand and fingers. The carpal tunnel is an anatomic passageway at the base of the wrist through which the median nerve and the flexor tendons for the fingers of the hand pass. It is defined by the carpal bones of the hand and the transverse carpal ligament. Carpal tunnel syndrome is commonly caused by highly repetitive hand motions over a number of years. For instance, carpal tunnel syndrome is common in certain professionals such as secretaries and other professionals who type on a keyboard regularly, carpenters, dentists or anyone who performs the same hand motions repeatedly and regularly. 
         [0004]    The current standard of care for alleviating carpal tunnel syndrome is to incise the transverse carpal ligament to open up the carpal tunnel and release the pressure on the median nerve. With few exceptions, most people can manage daily activities with a severed transverse carpal ligament with almost no adverse effects. 
         [0005]    The particular current procedure for carpal tunnel release is an endoscopic or arthroscopic procedure in which an incision is made in the wrist proximal of the carpal tunnel. An endoscope with a camera is inserted into the incision and through the carpal tunnel to allow the surgeon to visualize the carpal tunnel, and, particularly, the transverse carpal ligament, and then a knife is inserted alongside the endoscope to cut the transverse carpal ligament. 
       SUMMARY OF INVENTION 
       [0006]    The invention pertains to a method, apparatus, and system for cutting anatomic members, such as ligaments, in surgical procedures such as carpal tunnel release, plantar fasciotomy, gastroc release, cubital tunnel release, and tarsal tunnel release. The apparatus includes a retrograde knife and a guide tool for guiding the knife and a scope during surgery. Relevant features include a knife stop for preventing the knife from inadvertently raising out of the knife channel, indicators showing the proper orientation for the guide tool, a self dilating tip and channel design on the guide tool, a cover piece and/or pivotable panel system for preventing ligaments and other anatomy from getting caught in the guide tool, a pivot pin and groove system for stabilizing the knife and also assuring that the knife blade is not inadvertently raised out of the channel, and a use indicator for preventing re-use of a single use device. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0007]      FIG. 1  is a diagram illustrating use of one particular endoscopic carpal tunnel release apparatus and method in accordance with the prior art. 
           [0008]      FIG. 2  is a perspective view of a guide in accordance with one particular embodiment of the invention. 
           [0009]      FIG. 3  is a close up view of the distal end of the guide of  FIG. 2 . 
           [0010]      FIG. 4A  is a perspective view of a guide in accordance with a second embodiment of the invention viewed from a first perspective. 
           [0011]      FIG. 4B  is a perspective view the guide in accordance with the second embodiment of the invention viewed from a second perspective. 
           [0012]      FIG. 4C  depicts a mode of the device in a view similar to that of  4 A showing a shorter version without the extending handle portions at the proximal end. 
           [0013]      FIG. 4D  depicts a mode of the device in a view similar to that of  4 B showing a shorter version without the extending handle portions at the proximal end. 
           [0014]      FIG. 5  is a perspective view of the distal portion of a guide in accordance with a third embodiment of the invention. 
           [0015]      FIG. 6A  is a perspective view of a guide in a first condition in accordance with a fourth embodiment of the invention. 
           [0016]      FIG. 6B  is a perspective view of the guide of the fourth embodiment in a second condition. 
           [0017]      FIG. 7A  is a cross sectional side view of the longitudinal member of a guide in a first condition in accordance with a fifth embodiment of the invention. 
           [0018]      FIG. 7B  is a cross sectional side view of a distal longitudinal member of a guide in a second condition in accordance with the fifth embodiment of the invention. 
           [0019]      FIGS. 8A and 8B  show a cover member and guide, respectively, in accordance with a sixth embodiment of the invention. 
           [0020]      FIG. 9A  is a transverse cross-section of a guide in accordance with a seventh embodiment of the invention. 
           [0021]      FIG. 9B  is a side view of a knife in accordance with the seventh embodiment of the invention 
           [0022]      FIG. 9C  is a top view of the guide and knife of  FIGS. 10A and 10B  assembled. 
           [0023]      FIG. 10A  is a perspective view of a knife prior to sterilization in accordance with an eighth embodiment of the invention. 
           [0024]      FIG. 10B  is a close up perspective view of the proximal end of the knife in accordance with the eighth embodiment. 
       
    
    
     DETAILED DESCRIPTION OF THE EMBODIMENTS 
       [0025]    Referring to  FIG. 1 , one system available on the market today is the SEG-Way system offered by Core Essence Orthopedics, Inc. of Fort Washington, Pa., USA. The SEG-Way system comprises, among other things, a guide  10  and a retrograde knife  12 . As seen in  FIG. 1 , the guide  10  compromises a longitudinal member  14 , containing a channel  16 . The channel  16  is for receiving the endoscope  20  and the knife  12  side-by-side. A key feature of the SEG-Way system is that the endoscope and knife are entirely independently manipulable. The guide further comprises a transverse member  19  at its proximal end comprising two wings  21  and  22  extending in opposition transverse directions from the proximal end  23  of the longitudinal member  14 . The wings  21 ,  22  provide a place for the surgeon to hold the guide as well as some stability against rotation about the longitudinal axis  24  of the longitudinal member because the wings essentially rest upon the forearm  26  of the person after the guide has been inserted through the incision  25 . 
         [0026]    In use, the incision  25  is made in the wrist proximal to the carpal tunnel  27  and the longitudinal member  14  of the guide  10  is advanced distally into and through the carpal tunnel, thereby dilating the carpal tunnel. Once the guide  10  is fully inserted and through the carpal tunnel  27 , the endoscope  20  is advanced through the first channel  16  to allow the surgeon to see the carpal tunnel, and particularly, the transverse carpal ligament  30 . Then, the knife  12  is advanced distally within the channel  16 . As can be seen in  FIG. 1 , the knife comprises a handle  34  and a distal segment  36  disposed at an angle  38  to each other and has a hooked, retrograde blade  29  at the distal end of the distal segment  36  that faces proximally and cuts when the knife is pulled back in the proximal direction. The angled junction  38  between the handle  34  and the distal segment  36  of the knife  12  generally defines a pivot point about which the knife will be rotated after insertion and prior to cutting. More particularly, the knife  12  is inserted into the channel  16  with the distal segment  36  lying flat in the channel  16  and flush against the bottom of the channel with the blade  29  concealed inside the channel  16  until it is past the transverse carpal ligament so as not to contact any anatomy. This inherently means that the handle segment  34  will be angled upwardly. Then, the surgeon pushes down on the handle to cause the distal segment, and particularly, the retrograde blade to rise up out of the channel  16  so that it can engage the distal edge  30   a  of the transverse carpal ligament  30  and cut it by drawing the knife  12  back in the proximal direction. 
         [0027]      FIG. 2  is a perspective view looking substantially from the proximal end of a guide member in accordance with a first embodiment of the present invention.  FIG. 3  is a close up view of the distal end of the guide member of  FIG. 2 . The guide  100  comprises a longitudinal member  101  and a transverse member  102 . The transverse member comprising two wings  103  and  105  extended laterally from the proximal end  104  of the longitudinal member  101 . The longitudinal member  101  defines two channels  107  and  109  separated by a partition, such as a ridge  106  in a surface of the longitudinal member for accepting a scope, such as an endoscope or arthroscope, and a knife, respectively. 
         [0028]    One issue of which surgeons must be aware when using carpal tunnel release surgical systems of the type shown in  FIGS. 1 and 2  is the fact that the cutting tip of the knife should remain concealed within the knife channel  109  so as not to accidentally engage anatomy when the knife is being inserted distally through the carpal tunnel. This, of course, is achieved by holding the knife handle at an angle to the longitudinal axis  108  so that the distal segment of the knife lays flat on the bottom surface  113  of the channel  109  as described above in connection with  FIG. 1 . However, if the knife is advanced distally far enough into the channel to engage the endwall or distal wall  115  of the channel  109 , if that wall is at an obtuse angle to the longitudinal axis  108  of the guide, the wall may divert some of the distally directed advancing force on the knife upwardly, thereby deflecting the distal end of the knife, i.e., the blade to exit the safe area inside the channel  109  and possibly cut anatomy inadvertently. 
         [0029]    Thus, in accordance with this embodiment of the invention, the end wall  115  of the channel  109  forms an angle  118  with the bottom  113  of the channel  109  that is substantial enough that any distally-directed advancing force on the knife is not easily redirected upwardly so as to cause the distal end of the knife to rise up out of the channel  109 . This angle  118  may be a right angle (90°). However, it can be an acute angle so that engagement of the end of the knife with the wall  115  actually applies a downward force on the distal end of the knife. Generally, no downward motion of the distal end of the knife will actually occur because the distal segment of the knife already should be flush against the bottom  113  of the channel  109 . However, if the surgeon is holding the knife at an incorrect angle so that the distal end of the knife is not flush against the bottom of the channel, the engagement with the end wall  115  may actually help by pushing the distal end of the knife down into the channel until it is flush with the bottom surface  113 . 
         [0030]    In other embodiments, the angle may even be slightly greater than 90°. Specifically, since there will be some friction between the knife and the wall  115  such that contact between the end of the knife and the wall under reasonably expected loads still would not result in the knife sliding upward along the end wall  115  and rising out of the channel. 
         [0031]    Additionally, the ridge  106  between the endoscope channel  107  and the knife channel  109  helps prevent the endoscope and knife from inadvertently interfering with each other. Specifically, in prior devices having a single channel for containing both the endoscope and the knife, the scope and knife would often cross over into each other&#39;s spaces within the single channel, sometimes causing difficulty in individually advancing, withdrawing, tilting, turning, or otherwise moving the endoscope and/or knife. The present design with two channels  107 ,  109  separated by a ridge  106  essentially keep each of the endoscope and knife from crossing over into the channel of the other instrument and interfering with it. 
         [0032]      FIGS. 4A and 4B  are right-side and left-side perspective views of a second embodiment of the guide  200  illustrating another feature. Particularly, with respect to the human body, medical personnel generally adhere to certain semantic conventions for clarity. For instance, the term “medial” is generally used to describe a direction towards the center of the body, and the term “lateral” is generally used to describe a direction away from the center of the body. However, with respect to the hands, this language is not sufficiently definite because a person can hold one&#39;s hand in different orientations, e.g., with the palm facing towards the sky or with the palm facing towards the ground. Accordingly, the terms medial and lateral are indefinite with respect to hands. Hence, with respect to the hand, the terms “ulnar” and “radial” often are used instead. Ulnar refers to the direction from the center of the hand towards the ulnar nerve. The ulnar nerve runs along the length of the hand on the pinky side of the hand. Accordingly, the ulnar direction is the direction transverse the length of the hand facing from the center of the hand towards the pinky as illustrated by arrow  13  in  FIG. 1 . Radial, of course, is the opposite direction, as illustrated by arrow  15  in  FIG. 1 . 
         [0033]      FIGS. 4C and 4D  are right-side and left-side perspective views of the device in similar configuration to that of  FIGS. 4A and 4B  but showing a shorter version without the two wing type projections at the proximal end in a mode which might be employed on other parts of the body such as the feet. 
         [0034]    When performing endoscopic carpal tunnel release surgery using a guide such as any of guides  10 ,  100 , and  200 , it is desirable to have the camera on the radial side and the knife on the ulnar side because the guide is inserted to the ulnar side of the medial nerve. This places the endoscope against the medial nerve, which is preferred because it separates the medial nerve from the knife for extra safety in avoiding accidental nicking of the medial nerve with the knife. Accordingly, it is desirable to provide different guides for the right hand and the left hand. Therefore, to help avoid confusion, the two guides should be clearly marked, such as with an L and an R for the left-hand and right-hand guides, respectively.  FIGS. 4A and 4B , for instance, illustrate the left hand guide and, it can be seen that there is a prominent L printed on one of the transverse wings. 
         [0035]    Nevertheless, there still tends to be confusion during surgery as to the proper choice and orientation of the guide. Accordingly, in addition to clearly marking the guide as left or right, each guide member is also marked to indicate which side of the guide  200  should be facing towards the radial direction and the ulnar direction. This may be accomplished, for instance, by printing the words “radial”  202  and/or “ulnar”  204  on the sidewall of the channels as shown in  FIGS. 4A and 4B . 
         [0036]      FIG. 5  is a perspective view of the distal end of a guide  300  according to a third embodiment. Particularly, as previously described, the distal tip of the guide leads the guide into and through the carpal tunnel. The carpal tunnel is rather tightly packed with flexor tendons and the median nerve. Accordingly, tip  301  is shaped to better assist in dilating the carpal tunnel and spreading the various flexor tendons and radial nerve to create room for the guide to pass through the carpal tunnel. 
         [0037]    More specifically, the distal tip  301  of the guide  300  is prow shaped in order to ease the insertion of the distal tip of the guide into the carpal tunnel and to assist in the dilation of the carpal tunnel and the spreading of the flexor tendons and the medial nerve to allow the longitudinal member  302  of the guide to pass through the carpal tunnel. As can be seen, the distal tip is shaped like the prow of a boat. Particularly, it is pointy without being sharp and it is curved upward slightly. 
         [0038]      FIGS. 6A and 6B  illustrate an alternative embodiment of the longitudinal portion  401  of a guide  400  designed to even further ease insertion of the longitudinal portion  401  of the guide into the carpal tunnel and to more efficiently dilate the tunnel. In accordance with this embodiment, the longitudinal portion  401  of the guide  400  actually comprises two longitudinal members  404 ,  406  that are collapsible and expandable in the transverse dimension  402  relative to each other. In this manner, the longitudinal portion  401  of the guide  400  can be initially inserted into and through the carpal tunnel while in the collapsed condition shown in  FIG. 6A  in order to ease insertion by virtue of having a smaller profile in the transverse dimension (the ulnar/medial direction) and be expandable to the expanded condition shown in  FIG. 6B  to further dilate the carpal tunnel and provide the necessary room for the endoscope and knife within the longitudinal portion  401 . In the exemplary embodiment illustrated in  FIGS. 6A and 6B , the first longitudinal member  404  defines the endoscope channel  408  and the second longitudinal member  406  defines the knife channel  405 . The second longitudinal member  406  is a transversely translatable L-shaped member. In the closed position, the bottom leg  407  of the L-shaped second longitudinal member  406  slides into a groove (not shown) under the endoscope channel  408  of the first longitudinal member  404  so that the vertical leg  409  of the L-shaped second longitudinal member  406  butts up against the ulnar-side wall  411  of the endoscope channel  408 . This essentially collapses the knife channel  405  to nothing and reduces the cross-section of the guide portion  404 . The longitudinal portion  404  of the guide  400  can be initially inserted into and through the carpal tunnel in the collapsed condition shown in  FIG. 6A . Then, after initial insertion and, perhaps, after waiting a designated period of time to allow the carpal tunnel to dilate and adjust to accommodate the collapsed longitudinal portion  401 , the L-shaped second longitudinal member  406  can then be slid transversely outwardly into the expanded condition illustrated in  FIG. 6B , with the bottom leg  407  of the L-shaped member  406  sliding out from under the first longitudinal member  404  to open the knife channel  405 . 
         [0039]    The mechanism for permitting the longitudinal member to be collapsible and expandable may take many forms. One such mechanism comprises transverse grooves in the bottom leg  407  of the L-shaped member  406  that mate with pegs protruding from underneath the endoscope channel  408 . The transverse grooves can slide laterally relative to the pegs. The transverse grooves may have detents at two positions to provide a higher resistance to transverse sliding when in the fully collapsed position and the fully opened position. The movement between the collapsed position and open position can be actuated by any number of mechanisms. For instance, a turnbuckle-type screw runs through a longitudinal channel underneath the endoscope channel  408 , the proximal half of the screw being right-hand threaded and the distal half of the screw being left-hand threaded. Each half of the screw bears a matingly threaded wedge-shaped nut that sits within a mating cut out in the bottom leg  407  of the L-shaped member  406 . The proximal end of the screw protrudes from the proximal end of the longitudinal member and has a thumb wheel to allow the surgeon to turn it by hand. Instead of a thumb wheel, the screw may have a contoured head that mates with an instrument, such as a screwdriver, to turn the screw. When the screw is turned in one direction, the mating threads in the wedges and on the screw cause the wedges  437 ,  438  to move toward each other; causing the edges of the wedges to travel along the adjacent edges of the cutouts, thus pushing the L-shaped member  406  transversely outward. 
         [0040]    This exposes (or creates) the knife channel  405 , which is defined by the inner surface  409   a  of upper leg  409  of the L-shaped second longitudinal member  406 , the upper surface  407   a  of the bottom leg  407  of the L-shaped second longitudinal member  406 , and the ulnar-side outer surface  411   a  of the first longitudinal member  404 . The endoscope and knife can then be advanced into their respective channels  408  and  405  and the procedure performed. After the procedure is performed and the knife and endoscope are withdrawn from their channels, the screw may be turned in the opposition direction. The force of the wedge pushing the L-shaped second longitudinal member transversely outward is thus released and the surrounding forces of the flexor tendons, median nerve, and other anatomy in the carpal tunnel on the outer surface  409   b  of upper leg  405  of the L-shaped member  406  will push the L-shaped member  406  back to the collapsed position shown in  FIG. 6A . The guide  400  may then be withdrawn while in this collapsed state. If desired, the edges of the wedge nuts can be provided with pegs that fit within further grooves in the adjacent edges of the triangular cutouts so that the pegs cannot escape from the grooves, but can only travel within the grooves. In this manner, turning the screw in the opposite direction will actually draw the L-shaped member back inwardly in and of itself without the need to rely on any external forces from the tendons and/or medial nerve in the carpal tunnel. 
         [0041]      FIGS. 7A and 7B  illustrate a fifth embodiment of a guide  500 . Particularly,  FIGS. 7A and 7B  are transverse cross-sectional slices of the longitudinal member  501  of the guide  500  in accordance with this embodiment.  FIG. 7A  illustrates the closed position and  FIG. 7B  illustrates the open position. In this embodiment, the outer walls  545 ,  547  of the endoscope and knife channels  507 ,  509  bear panels  551 ,  553  that are rotatable on pins  555 ,  557  between a first position as illustrated in  FIG. 7A  and a second position as illustrated in  FIG. 7B . 
         [0042]    Initially and throughout most of the procedure, the panels remain in the first position and simply form part of the walls  545 ,  547  of the two channels  507 ,  509 . However, after the ligament has been cut and the guide  500  is to be withdrawn from the carpal tunnel, the panels  551 ,  553  may be flipped into the closed position illustrated in  FIG. 7B  to help prevent pieces of the cut ligament or other anatomy from falling into the channels  507 ,  509 . 
         [0043]    Particularly, it is not uncommon for pieces of the cut ligament to hang down into the channels of the longitudinal member  501  of the guide  500  and potentially be pulled by the guide  500  as it is withdrawn, which would cause unnecessary pain and possible damage to the patient. In accordance with this embodiment, the panels  551 ,  553  can be rotated into the second position shown in  FIG. 7B . As can be seen in  FIG. 7B , in this position, the panels  551 ,  553  block off a significant portion of the channels  507 ,  509 . As they are rotated up, the panels would tend to push out any ligament that has fallen into the channel. Furthermore, as the guide  500  is withdrawn from the carpal tunnel, the panels will substantially prevent ligament strands and other anatomy from falling into the channel and potentially getting caught in the channels. 
         [0044]    In the illustrated embodiment, the panels  551 ,  553  do not fully close off the channels  507 ,  509 . This is acceptable because the ligaments tend to get caught on the edges of the channels rather than in the middles of the channels. However, if desired, the panels  551 ,  553  can be made wide enough to meet each other in the second position to completely close off all of the channels. Preferably, the panels  551 ,  553  run the entire length of the channels, but shorter lengths that leave a small portion of the channels exposed at either the proximal or distal end of the channels would be acceptable. 
         [0045]    The mechanism for rotating the panels between the first and second positions can take many forms. In the illustrated embodiment, the panels are fixedly mounted on longitudinal pins  555 ,  557  that run in holes  561 ,  563  the full length of the channels  507 ,  509 . The proximal ends of those pins  555 ,  557  protrude from the proximal end of the longitudinal member and bear thumb wheels for allowing the surgeon to rotate the pins  555 ,  557 . The panels  551 ,  553  can be fixable in any position, not just the first and second positions. For instance, at least the proximal ends of the pins can be threaded and nuts  565 ,  567  can be provided near the proximal end of each pin and so that the nuts can be rotated on the pins as desired to abut the proximal end of the longitudinal member  501  and thereby lock the pins/panels in any desired orientation. 
         [0046]    The panels  551 ,  553  also may be rotated and locked in the second positions to close off the channels during initial insertion of the guide  500  into and through the carpal tunnel. Particularly, although less common, it is possible for the transverse carpal ligament, flexor tendons, medial nerve or other anatomy to get caught in one of the channels  507 ,  509  during insertion too. Accordingly, it may be desirable to flip up the panels during both insertion and withdrawal of the guide from the carpal tunnel or other anatomical passageway. 
         [0047]      FIGS. 8A and 8B  illustrate aspects of a sixth embodiment of the invention having some of the same advantages as the fifth embodiment described above in connection with  FIGS. 7A and 7B . 
         [0048]    More particularly, in this embodiment, a cover piece  680  illustrated in  FIG. 8A  is provided to completely cover the channels  607 ,  609  in the longitudinal member  601  of the guide  600  (illustrated in  FIG. 8B ) during insertion into and/or withdrawal. In this embodiment, the cover  607  piece comprises two members  681 ,  683 , one shaped to exactly fill the endoscope channel  607  and the other shaped to exactly fill the knife channel  609 . The two members  681 ,  683  are joined to each other through a proximal end piece  685 . The cover piece is inserted simply by pushing it distally into the longitudinal member from the proximal end openings  607   a ,  609   a  of the channels  607 ,  609 . The cover piece  680  fully fills both channels  607 ,  609 . 
         [0049]    In use, the cover piece  680  is inserted into the longitudinal member  601  prior to insertion of the guide  600  into the carpal tunnel. The cover piece  680  serves the purpose of closing off the channels, thereby preventing ligaments and other fibers from getting caught in the channels as the guide is advanced into and through the carpal tunnel. Once the guide  600  is inserted, the cover member  680  can be withdrawn proximally to expose the channels  607 ,  609  so that the endoscope and knife can be inserted into their respective channels. If desired, after the procedure is performed, the cover member  680  may be reinserted into the channels  607 ,  609  prior to withdrawing the guide  600  from the carpal tunnel in order to again close off the channels and prevent ligament strands and other fibers from getting caught in the channels as the guide is pulled out. 
         [0050]      FIGS. 9A, 9B, and 9C  illustrate a seventh embodiment of the invention.  FIG. 9A  is a transverse cross-section view through the guide of this embodiment.  FIG. 9B  is a side view of the knife in accordance with the seventh embodiment.  FIG. 9C  is a top view of the knife in accordance with the seventh embodiment. In this embodiment, two pin grooves  711 ,  712  are provided in the knife channel  709  of the longitudinal member  701  of the guide  700 , the pin grooves  711 ,  712  are open to the proximal end of the guide. Mating pins  713 ,  714  for sliding in the grooves  711 ,  712  are provided on the body of the retrograde knife  770 . Hence, the height of the pin grooves  711 ,  712  within the knife channel  709  and the position of the pins  713 ,  714  on the knife  770  are selected so that, when the knife is inserted into the channel with the longitudinal dimension of the distal portion  771  of the knife  770  parallel to the channel  709  and concealed within the channel  709 , the pins  713 ,  714  meet the grooves  711 ,  712  and can ride within the grooves in the longitudinal direction, thereby allowing the knife  770  to slide freely in the knife channel  709  in the longitudinal direction, but fixing the height of the knife in the channel at the location of the pins. The mating grooves  711 ,  712  and pins  713 ,  714  provide a defined position about which the knife can be pivoted to raise the retrograde blade out of the channel for cutting the ligament. More particularly, the height of the pivot point is fixed by the height of the grooves  711 ,  712 . However, while the pivot pins  713 ,  714  define the precise axis about which the knife can be pivoted, the longitudinal position of those pins within the grooves is freely and fully adjustable within the grooves. 
         [0051]    The combination of the pivot pins  713 ,  714  and the pivot grooves  711 ,  712  also provides increased stability to the knife  770  during distal advancement of the knife into the channel  709  insofar as the height of the knife is vertically fixed in the channel at the point where the pivot pins are positioned on the knife. As long as the surgeon maintains a neutral or upward force on the handle  772  of the knife, the distal segment  771  of the knife will remain entirely in the knife channel  709 . On the other hand, in the absence of the pivot pins and grooves, the surgeon would need to be much more careful when inserting the knife to assure that the entire distal segment  771  of the knife  770  remained in the channel  709 . Even further, the pivot pins/grooves combination also provides greater knife stability against roll (see arrow  747 ) about the longitudinal axis  749  of the distal segment  771  of the knife  770 . 
         [0052]    The pivot pins  713 ,  714  should be positioned on the knife  770  at an axis around which it is most desirable to pivot the knife. This will usually be at or very near the point  781  defining the base of the angle between the handle portion  772  of the knife and the distal portion  771  of the knife. The diameter of the pivot pins  713 ,  714  should be very close to the height, h, of the pivot pin grooves  711 ,  712  so that there is very little vertical play between the pivot pins and the pivot pin grooves, but should allow the pins to slide freely in the grooves. The grooves may run the entire length of the knife channel so that the knife can be advanced into the channel to any desired distance. However, in accordance with another embodiment, the groove may have a defined length, I, from the proximal end of the knife channel  709  so that the knife  770  cannot advance distally past the point where the pins  713 ,  714  on the knife hit the ends of the grooves  711 ,  712 . This length, for instance, may be selected to prevent the distal end  773  of the knife from hitting the distal wall of the knife channel  709 . This would be another potential mechanism for preventing the end of the knife from hitting the end wall of the channel and potentially being damaged and/or accidentally riding up the end wall  710  and out of the channel  709  inadvertently, as discussed above in connection with the embodiment of  FIGS. 2 and 3 . 
         [0053]    Although the various features disclosed herein have been described in connection with different embodiments of a guide, it should be understood that any and all of the features of each embodiment may be combined in the same instrument in virtually any permutation. 
         [0054]    In accordance with another aspect of the invention and with reference to  FIGS. 10A and 10B , a portion  802  of the knife  800 , preferably on the handle  801  is composed of a material different than the rest of the knife, which material cannot survive an autoclaving process intact.  FIGS. 10A and 10B  show the knife prior to sterilization. This is a desirable feature because it will provide an easily identifiable visual cue that the knife has been autoclaved. More particularly, in accordance with at least one embodiment, the entire system, including the guide, knife, and any other related instruments, such as a ligament rasp or a probe, are single-use surgical instruments, i.e., they can only be used once and then should be discarded. However, it is not uncommon for either medical staff or medical equipment resellers to inadvertently or even intentionally attempt to re-use or re-sell medical equipment that is intended only for a single use. In order to reuse any surgical instrument, it must be sterilized after the first use, which usually involves an autoclaving process. Accordingly, providing a portion  802  of the knife that is made of a material that cannot survive autoclaving, can provide a easy visual reference that the device has been previously used, and therefore should not be used again. In the embodiment illustrated in  FIGS. 10A and 10B , the portion is a circular medallion  802  near the proximal end of the handle  801 . The knife  800  generally will be made of a biocompatible metal, such as titanium or nitinol. The medallion, however, may be made of a polymer that will melt or otherwise degrade when subjected to a conventional autoclaving process (or any other process that might be used to re-sterilize a medical instrument). 
         [0055]    In one embodiment, the medallion may run through the entire width, w, of the handle so that, after autoclaving, a hole will be left in the handle. However, in another embodiment, the button may only comprise a surface layer of material which, when destroyed reveals an underlying non-degradable material, such as the same material that the rest of the knife is made of, bearing a warning indicator indicating that the device has been used and should be not re-used, such as the words “Warning, this instrument has been used and should be discarded” or simply “Discard”. 
         [0056]    Having thus described a few particular embodiments of the invention, various alterations, modifications, and improvements will readily occur to those skilled in the art. Such alterations, modifications, and improvements as are made obvious by this disclosure are intended to be part of this description though not expressly stated herein, and are intended to be within the spirit and scope of the invention. Accordingly, the foregoing description is by way of example only, and not limiting. The invention is limited only as defined in the following claims and equivalents thereto.