Abstract:
An inflow access cannula system for allowing an instrument to access a surgical site, the system including an inflow access cannula including distal and proximal ends and a central lumen extending therebetween, and an instrument adapter for releasable connection to the cannula, the adapter including a lumen communicating with the central lumen, the adapter further including a port and a fluid passageway connecting the port with the lumen of the adapter, and a spacer for spacing the proximal portion of the instrument from the distal end of the cannula, such that when the distal portion of an instrument extends within the central lumen and the proximal portion of the instrument is disposed in the lumen, in engagement with the spacer, fluid can flow into the port, along the fluid passageway, into the lumen and through the central lumen.

Description:
REFERENCE TO PENDING PRIOR PATENT APPLICATION 
     This patent application claims benefit of prior U.S. Provisional Patent Application Ser. No. 61/361,783, filed Jul. 6, 2010 by Jolene Cutts et al. for METHOD AND APPARATUS FOR ACCESSING THE INTERIOR OF A HIP JOINT, INCLUDING THE PROVISION AND USE OF A NOVEL INFLOW ACCESS CANNULA, which patent application is hereby incorporated herein by reference. 
    
    
     FIELD OF THE INVENTION 
     This invention relates to surgical methods and apparatus in general, and more particularly to methods and apparatus for treating the hip joint. 
     BACKGROUND OF THE INVENTION 
     The Hip Joint in General 
     The hip joint is a ball-and-socket joint which movably connects the leg to the torso. The hip joint is capable of a wide range of different motions, e.g., flexion and extension, abduction and adduction, medial and lateral rotation, etc. See  FIGS. 1A, 1B, 1C and 1D . 
     With the possible exception of the shoulder joint, the hip joint is perhaps the most mobile joint in the body. Significantly, and unlike the shoulder joint, the hip joint carries substantial weight loads during most of the day, in both static (e.g., standing and sitting) and dynamic (e.g., walking and running) conditions. 
     The hip joint is susceptible to a number of different pathologies. These pathologies can have both congenital and injury-related origins. In some cases, the pathology can be substantial at the outset. In other cases, the pathology may be minor at the outset but, if left untreated, may worsen over time. More particularly, in many cases, an existing pathology may be exacerbated by the dynamic nature of the hip joint and the substantial weight loads imposed on the hip joint. 
     The pathology may, either initially or thereafter, significantly interfere with patient comfort and lifestyle. In some cases, the pathology can be so severe as to require partial or total hip replacement. A number of procedures have been developed for treating hip pathologies short of partial or total hip replacement, but these procedures are generally limited in scope due to the significant difficulties associated with treating the hip joint. 
     A better understanding of various hip joint pathologies, and also the current limitations associated with their treatment, can be gained from a more thorough understanding of the anatomy of the hip joint. 
     Anatomy of the Hip Joint 
     The hip joint is formed at the junction of the leg and the hip. More particularly, and looking now at  FIG. 2 , the head of the femur is received in the acetabular cup of the hip, with a plurality of ligaments and other soft tissue serving to hold the bones in articulating condition. 
     More particularly, and looking now at  FIG. 3 , the femur is generally characterized by an elongated body terminating, at its top end, in an angled neck which supports a hemispherical head (also sometimes referred to as “the ball”). As seen in  FIGS. 3 and 4 , a large projection known as the greater trochanter protrudes laterally and posteriorly from the elongated body adjacent to the neck of the femur. A second, somewhat smaller projection known as the lesser trochanter protrudes medially and posteriorly from the elongated body adjacent to the neck. An intertrochanteric crest ( FIGS. 3 and 4 ) extends along the periphery of the femur, between the greater trochanter and the lesser trochanter. 
     Looking next at  FIG. 5 , the hip socket is made up of three constituent bones: the ilium, the ischium and the pubis. These three bones cooperate with one another (they typically ossify into a single “hip bone” structure by the age of 25 or so) in order to collectively form the acetabular cup. The acetabular cup receives the head of the femur. 
     Both the head of the femur and the acetabular cup are covered with a layer of articular cartilage which protects the underlying bone and facilitates motion. See  FIG. 6 . 
     Various ligaments and soft tissue serve to hold the ball of the femur in place within the acetabular cup. More particularly, and looking now at  FIGS. 7 and 8 , the ligamentum teres extends between the ball of the femur and the base of the acetabular cup. As seen in  FIGS. 8 and 9 , a labrum is disposed about the perimeter of the acetabular cup. The labrum serves to increase the depth of the acetabular cup and effectively establishes a suction seal between the ball of the femur and the rim of the acetabular cup, thereby helping to hold the head of the femur in the acetabular cup. In addition to the foregoing, and looking now at  FIG. 10 , a fibrous capsule extends between the neck of the femur and the rim of the acetabular cup, effectively sealing off the ball-and-socket members of the hip joint from the remainder of the body. The foregoing structures (i.e., the ligamentum teres, the labrum and the fibrous capsule) are encompassed and reinforced by a set of three main ligaments (i.e., the iliofemoral ligament, the ischiofemoral ligament and the pubofemoral ligament) which extend between the femur and the perimeter of the hip socket. See, for example,  FIGS. 11 and 12 , which show the iliofemoral ligament, with  FIG. 11  being an anterior view and  FIG. 12  being a posterior view. 
     Pathologies of the Hip Joint 
     As noted above, the hip joint is susceptible to a number of different pathologies. These pathologies can have both congenital and injury-related origins. 
     By way of example but not limitation, one important type of congenital pathology of the hip joint involves impingement between the neck of the femur and the rim of the acetabular cup. In some cases, and looking now at  FIG. 13 , this impingement can occur due to irregularities in the geometry of the femur. This type of impingement is sometimes referred to as cam-type femoroacetabular impingement (i.e., cam-type FAI). In other cases, and looking now at  FIG. 14 , the impingement can occur due to irregularities in the geometry of the acetabular cup. This latter type of impingement is sometimes referred to as pincer-type femoroacetabular impingement (i.e., pincer-type FAI). Impingement can result in a reduced range of motion, substantial pain and, in some cases, significant deterioration of the hip joint. 
     By way of further example but not limitation, another important type of congenital pathology of the hip joint involves defects in the articular surface of the ball and/or the articular surface of the acetabular cup. Defects of this type sometimes start out fairly small but often increase in size over time, generally due to the dynamic nature of the hip joint and also due to the weight-bearing nature of the hip joint. Articular defects can result in substantial pain, induce and/or exacerbate arthritic conditions and, in some cases, cause significant deterioration of the hip joint. 
     By way of further example but not limitation, one important type of injury-related pathology of the hip joint involves trauma to the labrum. More particularly, in many cases, an accident or sports-related injury can result in the labrum being torn away from the rim of the acetabular cup, typically with a tear running through the body of the labrum. See  FIG. 15 . These types of injuries can be very painful for the patient and, if left untreated, can lead to substantial deterioration of the hip joint. 
     The General Trend Toward Treating Joint Pathologies Using Minimally-Invasive, and Earlier, Interventions 
     The current trend in orthopedic surgery is to treat joint pathologies using minimally-invasive techniques. Such minimally-invasive, “keyhole” surgeries generally offer numerous advantages over traditional, “open” surgeries, including reduced trauma to tissue, less pain for the patient, faster recuperation times, etc. 
     By way of example but not limitation, it is common to re-attach ligaments in the shoulder joint using minimally-invasive, “keyhole” techniques which do not require laying open the capsule of the shoulder joint. By way of further example but not limitation, it is common to repair torn meniscal cartilage in the knee joint, and/or to replace ruptured ACL ligaments in the knee joint, using minimally-invasive techniques. 
     While such minimally-invasive approaches can require additional training on the part of the surgeon, such procedures generally offer substantial advantages for the patient and have now become the standard of care for many shoulder joint and knee joint pathologies. 
     In addition to the foregoing, in view of the inherent advantages and widespread availability of minimally-invasive approaches for treating pathologies of the shoulder joint and knee joint, the current trend is to provide such treatment much earlier in the lifecycle of the pathology, so as to address patient pain as soon as possible and so as to minimize any exacerbation of the pathology itself. This is in marked contrast to traditional surgical practices, which have generally dictated postponing surgical procedures as long as possible so as to spare the patient from the substantial trauma generally associated with invasive surgery. 
     Treatment for Pathologies of the Hip Joint 
     Unfortunately, minimally-invasive treatments for pathologies of the hip joint have lagged far behind minimally-invasive treatments for pathologies of the shoulder joint and the knee joint. This is generally due to (i) the constrained geometry of the hip joint itself, and (ii) the nature and location of the pathologies which must typically be addressed in the hip joint. 
     More particularly, the hip joint is generally considered to be a “tight” joint, in the sense that there is relatively little room to maneuver within the confines of the joint itself. This is in marked contrast to the shoulder joint and the knee joint, which are generally considered to be relatively “spacious” joints (at least when compared to the hip joint). As a result, it is relatively difficult for surgeons to perform minimally-invasive procedures on the hip joint. 
     Furthermore, the pathways for entering the interior of the hip joint (i.e., the natural pathways which exist between adjacent bones and/or delicate neurovascular structures) are generally much more constraining for the hip joint than for the shoulder joint or the knee joint. This limited access further complicates effectively performing minimally-invasive procedures on the hip joint. 
     In addition to the foregoing, the nature and location of the pathologies of the hip joint also complicate performing minimally-invasive procedures on the hip joint. By way of example but not limitation, consider a typical detachment of the labrum in the hip joint. In this situation, instruments must generally be introduced into the joint space using an angle of approach which is offset from the angle at which the instrument addresses the tissue. This makes drilling into bone, for example, significantly more complicated than where the angle of approach is effectively aligned with the angle at which the instrument addresses the tissue, such as is frequently the case in the shoulder joint. Furthermore, the working space within the hip joint is typically extremely limited, further complicating repairs where the angle of approach is not aligned with the angle at which the instrument addresses the tissue. 
     As a result of the foregoing, minimally-invasive hip joint procedures are still relatively difficult to perform and relatively uncommon in practice. Consequently, patients are typically forced to manage their hip pain for as long as possible, until a resurfacing procedure or a partial or total hip replacement procedure can no longer be avoided. These procedures are generally then performed as a highly-invasive, open procedure, with all of the disadvantages associated with highly-invasive, open procedures. 
     As a result, there is, in general, a pressing need for improved methods and apparatus for treating pathologies of the hip joint. 
     Arthroscopic Access to the Interior of the Hip Joint 
     Successful hip arthroscopy generally requires safe and effective access to the interior of the hip joint. More particularly, successful hip arthroscopy generally requires the creation of a plurality of access portals which extend from the surface of the skin, down through the intervening tissue, and then into the interior of the hip joint. Depending on the specific surgical site which is to be accessed within the interior of the hip joint, different anatomical pathways may be utilized for the access portals. By way of example but not limitation, one anatomical pathway may be used where a torn labrum is to be repaired, and another anatomical pathway may be used where the lesser trochanter must be addressed. And, in most cases, multiple access portals are generally required, with one access portal being used for visualization (i.e., to introduce an arthroscope into the interior of the hip joint), while other access portals are used to pass surgical instruments to and from the surgical site, etc. 
     Establishing these access portals typically involves forming an opening from the top surface of the skin down to the interior of the joint, and lining that opening with a tubular liner (sometimes referred to as an “access cannula”). This access cannula holds the incision open and provides a surgical pathway (or “corridor”) from the top surface of the skin down to the interior of the hip joint, thereby enabling keyhole surgery to be performed on the hip joint. 
     Prior Art Access Cannulas 
     Access cannulas of the sort discussed above are well known in the art. However, such prior art access cannulas are typically designed to serve a wide range of different purposes and, as a result, often perform certain specific tasks in a fairly mediocre manner, e.g., initial access creation and endoscope support. Furthermore, such prior art access cannulas typically have distal ends which can cause substantial trauma to tissue when they come into contact with tissue, e.g., during cannula insertion. In addition, such prior art access cannulas are typically relatively inefficient in their use of space, and hence cover a substantial portion of an instrument&#39;s length, thereby reducing access of the instrument to deep surgical sites within the joint space. 
     The Need for a New and Improved Access Cannula 
     On account of the foregoing, it will be appreciated that there is a need for a new and improved access cannula which can overcome the deficiencies of prior art access cannulas. 
     Among other things, there is a need for a new and improved access cannula which can perform certain specific tasks unusually well (e.g., initial access creation and endoscope support), has a distal end which is relatively atraumatic when it comes into contact with tissue, and which is highly efficient in its use of space so as to cover a reduced portion of an instrument&#39;s length, thereby increasing access of the instrument to deep surgical sites within the joint space. 
     SUMMARY OF THE INVENTION 
     These and other objects of the present invention are addressed by the provision and use of a new and improved inflow access cannula for accessing the interior of a hip joint or other interior body space. 
     Among other things, this new and improved inflow access cannula can perform certain specific tasks unusually well (e.g., initial access creation and endoscope support), has a distal end which is relatively atraumatic when it comes into contact with tissue, and which is highly efficient in its use of space so as to cover a reduced portion of an instrument&#39;s length, thereby increasing access of the instrument to deep surgical sites within the joint space. 
     In one form of the present invention, there is provided an inflow access cannula system for allowing an instrument to access a remote surgical site, wherein the instrument comprises a distal portion having a smaller diameter and a proximal portion having a larger diameter, the system comprising: 
     an inflow access cannula comprising a distal end, a proximal end and a central lumen extending therebetween, wherein the central lumen has a diameter larger than the distal portion of the instrument and smaller than the proximal portion of the instrument; and 
     an instrument adapter for releasable connection to the inflow access cannula, the instrument adapter comprising a lumen communicating with the central lumen of the inflow access cannula, the lumen having a diameter larger than the proximal portion of the instrument, the instrument adapter further comprising a port and a fluid passageway connecting the port with the lumen of the instrument adapter, and a spacer for spacing the proximal portion of the instrument from the distal end of the inflow access cannula, such that when an instrument is disposed in the inflow access cannula system so that the distal portion of the instrument extends within the central lumen of the inflow access cannula and the proximal portion of the instrument is disposed in the central lumen of the instrument adapter and is in engagement with the spacer, fluid can flow into the port of the instrument adapter, along the fluid passageway of the instrument adapter, into the lumen of the instrument adapter and through the lumen of the inflow access cannula. 
     In another form of the present invention, there is provided an inflow access cannula comprising: 
     an elongated body comprising a distal end, a proximal end and a lumen extending therebetween, the distal end of the elongated body comprising an atraumatic tip. 
     In another form of the present invention, there is provided a method for accessing a remote surgical site with an instrument, wherein the instrument comprises a distal portion having a smaller diameter and a proximal portion having a larger diameter, the method comprising: 
     providing an inflow access cannula system comprising:
         an inflow access cannula comprising a distal end, a proximal end and a central lumen extending therebetween, wherein the central lumen has a diameter larger than the distal portion of the instrument and smaller than the proximal portion of the instrument; and   an instrument adapter for releasable connection to the inflow access cannula, the instrument adapter comprising a lumen communicating with the central lumen of the inflow access cannula, the lumen having a diameter larger than the proximal portion of the instrument, the instrument adapter further comprising a port and a fluid passageway connecting the port with the lumen of the instrument adapter, and a spacer for spacing the proximal portion of the instrument from the distal end of the inflow access cannula, such that when an instrument is disposed in the inflow access cannula system so that the distal portion of the instrument extends within the central lumen of the inflow access cannula and the proximal portion of the instrument is disposed in the central lumen of the instrument adapter and is in engagement with the spacer, fluid can flow into the port of the instrument adapter, along the fluid passageway of the instrument adapter, into the lumen of the instrument adapter and through the lumen of the inflow access cannula;       

     advancing the inflow access cannula system through tissue to the surgical site; and 
     advancing the instrument into the inflow access cannula system. 
     In another form of the present invention, there is provided a method for accessing a remote surgical site with an instrument, wherein the instrument comprises a distal portion having a smaller diameter and a proximal portion having a larger diameter, the method comprising: 
     providing an inflow access cannula system comprising:
         an inflow access cannula comprising a distal end, a proximal end and a central lumen extending therebetween, wherein the central lumen has a diameter larger than the distal portion of the instrument and smaller than the proximal portion of the instrument; and   an instrument adapter for releasable connection to the inflow access cannula, the instrument adapter comprising a lumen communicating with the central lumen of the inflow access cannula, the lumen having a diameter larger than the proximal portion of the instrument, the instrument adapter further comprising a port and a fluid passageway connecting the port with the lumen of the instrument adapter, and a spacer for spacing the proximal portion of the instrument from the distal end of the inflow access cannula, such that when an instrument is disposed in the inflow access cannula system so that the distal portion of the instrument extends within the central lumen of the inflow access cannula and the proximal portion of the instrument is disposed in the central lumen of the instrument adapter and is in engagement with the spacer, fluid can flow into the port of the instrument adapter, along the fluid passageway of the instrument adapter, into the lumen of the instrument adapter and through the lumen of the inflow access cannula;       

     advancing the inflow access cannula through tissue to the surgical site; 
     mounting the instrument adapter to the instrument; and 
     advancing the instrument into the inflow access cannula so that the instrument adapter mounts to the inflow access cannula. 
     In another form of the present invention, there is provided an access cannula system for allowing an instrument to access a remote surgical site, the system comprising: 
     an access cannula; 
     an instrument adapter for releasable connection to the access cannula, the instrument adapter being adapted to mate with an instrument to be extended through the lumen of the access cannula; and 
     wherein the instrument adapter is releasably mounted to the access cannula by a bayonet mount. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       These and other objects and features of the present invention will be more fully disclosed or rendered obvious by the following detailed description of the preferred embodiments of the invention, which is to be considered together with the accompanying drawings wherein like numbers refer to like parts, and further wherein: 
         FIGS. 1A-1D  are schematic views showing various aspects of hip motion; 
         FIG. 2  is a schematic view showing the bone structure in the region of the hip joints; 
         FIG. 3  is a schematic view of the femur; 
         FIG. 4  is a schematic view of the top end of the femur; 
         FIG. 5  is a schematic view of the pelvis; 
         FIGS. 6-12  are schematic views showing the bone and soft tissue structure of the hip joint; 
         FIG. 13  is a schematic view showing cam-type femoroacetabular impingement (FAI); 
         FIG. 14  is a schematic view showing pincer-type femoroacetabular impingement (FAI); 
         FIG. 15  is a schematic view showing a labral tear; 
         FIGS. 16-26  are schematic views showing one preferred form of inflow access cannula system formed in accordance with the present invention; and 
         FIGS. 27-42  are schematic views showing another preferred form of inflow access cannula system formed in accordance with the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The present invention provides a new and improved inflow access cannula system for accessing the interior of a hip joint or other interior body space. 
     Among other things, this new and improved inflow access cannula can perform certain specific tasks unusually well (e.g., initial access creation and endoscope support), has a distal end which is relatively atraumatic when it comes into contact with tissue, and which is highly efficient in its use of space so as to cover a reduced portion of an instrument&#39;s length, thereby increasing access of the instrument to deep surgical sites within the joint space. 
     Looking now at  FIGS. 16-26 , there is shown an inflow access cannula system  5  which generally comprises an inflow access cannula  10  and an endoscope adapter  15 . 
     In accordance with the present invention, an obturator (not shown) is intended to be positioned within inflow access cannula  10 , and the inflow access cannula is intended to be inserted into the tissue of a patient so that the distal end of the inflow access cannula is disposed within the hip joint and the proximal end of the inflow access cannula is disposed at the surface of the skin. When inflow access cannula  10  has been properly positioned in the tissue of the patient, the obturator is removed, endoscope adapter  15  is positioned on the proximal end of inflow access cannula  10 , and an endoscope  20  is advanced through the central lumen of the endoscope adapter and the central lumen of the inflow access cannula, whereby to provide visualization of, and fluid flow to and/or from, a remote surgical site. Alternatively, endoscope adapter  15  may be mounted on endoscope  20  remote from inflow access cannula  10  and then the two elements (i.e., the endoscope and the endoscope adapter) advanced together as a unit so as to seat on inflow access cannula  10 . 
     More particularly, inflow access cannula  10  generally comprises an elongated tube  25  having a distal end  30 , a proximal end  35  and a central lumen  40  ( FIG. 21 ) extending therebetween. The shaft of elongated tube  25  is long enough so that it can extend between the outer surface of the patient&#39;s skin and the interior of the joint. Furthermore, the shaft of elongated tube  25  is preferably formed out of metal (e.g., stainless steel) so as to provide strength and rigidity during insertion of the inflow access cannula into the tissue of the patient and its subsequent use as a liner for the access corridor extending down to the remote surgical site. Alternatively, the shaft of elongated tube  25  may be a metal tube coaxial with a plastic tube, the metal tube being disposed either inside of, or outside of, the plastic tube. The outer surface of elongated tube  25  is preferably smooth so as to minimize trauma to tissue as inflow access cannula  10  is inserted in the tissue. 
     Distal end  30  of inflow access cannula  10  preferably comprises a soft, atraumatic distal tip  45  so as to also minimize tissue trauma during cannula insertion and use. 
     In one preferred form of the invention, at least the atraumatic distal tip  45  of inflow access cannula  10  comprises a polymer or other material which contains barium sulfate, preferably in the range of 5-30% (and preferably about 15%) by weight, so as to render the inflow access cannula visible under X-ray or fluoroscopy. This range (by weight) of barium sulfate is generally preferred since concentrations below 5% tend to be too low for good visualization in hip applications, whereas concentrations above 30% can lead to degradation of material properties. Alternatively, other opacifiers, at appropriate weight concentrations, may also be used to render the inflow access cannula visible under X-ray or fluoroscopy. Atraumatic distal tip  45  can be a thermoplastic which is over-molded onto the distal end of elongated tube  25  (see  FIGS. 16 and 17 ). 
     A mount  50  is secured to proximal end  35  of elongated tube  25 . Mount  50  includes a keyway  55  for receiving a corresponding key (not shown) of an obturator (also not shown), whereby to releasably rotatably lock the obturator to inflow access cannula  10 , e.g., so as to permit rotational driving deployment of the inflow access cannula into the tissue via the obturator. Mount  50  also includes a stem  60  ( FIG. 21 ) which protrudes upward from the floor  65  of mount  50 . Stem  60  includes a lumen  70  ( FIG. 26 ) which communicates with central lumen  40  ( FIG. 21 ) of elongated tube  25 . Stem  60  also includes an L-shaped keyway  75  ( FIG. 17 ) which receives corresponding keys  80  provided on endoscope adapter  15 , whereby to releasably axially lock endoscope adapter  15  to inflow access cannula  10 , as will hereinafter be discussed in further detail. 
     Endoscope adapter  15  comprises a body  85  which is adapted to mate with mount  50  of inflow access cannula  10 . More particularly, body  85  of endoscope adapter  15  is designed to seat over stem  60  of cannula mount  50  so that (i) an endoscope  20  can extend down lumen  70  ( FIG. 26 ) of endoscope adapter  15  and down central lumen  40  ( FIG. 21 ) of elongated tube  25 , and (ii) fluid introduced through ports  90  of endoscope adapter  15  can flow down to the surgical site through lumen  70  of endoscope adapter  15  and central lumen  40  of elongated tube  25  or, conversely, fluid at the surgical site can flow up through central lumen  40  of elongated tube  25  and lumen  70  of endoscope adapter  15 , and then out one of the ports  90 . Endoscope adapter  15  also includes keys  80  for mounting in keyways  75  of endoscope adapter  15  when endoscope adapter  15  is connected to, and seats into, inflow access cannula  10 . This engagement keeps endoscope adapter  15  connected to inflow access cannula  10  during surgical use. 
     More particularly, endoscope adapter  15  comprises an annular chamber  95  ( FIG. 23 ) which communicates with a plurality of radial passageways  100 , which in turn communicate with an annular opening  105  formed about the perimeter of stem  60 . Thus, fluid is able to pass into ports  90 , along annular chamber  95 , through radial passageways  100 , up annular opening  105 , down lumen  70  of stem  60  and then down lumen  40  of elongated tube  25 . Correspondingly, fluid is able to leave the surgical site by passing up lumen  40  of elongated tube  25 , through lumen  70  of stem  60 , down annular opening  105 , through radial passageways  100 , along annular chamber  95  and then out ports  90 . In this respect it will be appreciated that an O-ring  106  ensures a fluid seal between body  85  of endoscope adapter  15  and mount  50  of inflow access cannula  10 , and an O-ring  107  ensures a fluid seal between body  85  of endoscope adapter  15  and endoscope  20 —thus, when endoscope  20  is seated in assembled endoscope adapter  15 /inflow access cannula  10 , a closed flow path is established between ports  90  and lumen  40  of elongated tube  25 . Significantly, O-ring  107  also acts as a spacer to maintain a gap G ( FIG. 23 ) between the proximal end of the endoscope&#39;s body B and the mouth of lumen  70  of stem  60 , so that fluid can pass from annular opening  105 , through gap G and into lumen  70  of stem  60  (or from lumen  70  of stem  60 , through gap G and into annular opening  105 ). Thus it will be seen that with the foregoing construction, ports  90  are disposed distal to the proximal end of stem  60 . By virtue of the ports  90  being “below” (i.e., distal) to the top of stem  60 , the overall height of the assembled endoscope adapter  15 /inflow access cannula  10  is minimized. This provides for a significantly more compact design (in terms of length) which covers a reduced portion of an instrument&#39;s length, thereby increasing access of the instrument (e.g., endoscope  20 ) to deep surgical sites within the joint space. In other words, the compact design of the assembled endoscope adapter  15 /inflow access cannula  10  provides a more effective working length to the shaft of endoscope  20  (i.e., the length the endoscope shaft that extends distal to the distal surface of mount  50 ). Thus, while the flow path between ports  90  and the mouth of lumen  70  of stem  60  may be non-linear with the present invention, a more compact endoscope adapter/inflow access cannula design is obtained and the effective working length of an instrument (e.g., the endoscope) is increased. This is a significant advantage in the art. 
     Furthermore, keys  80  are preferably mounted on a rotating collar  110 . Rotating collar  110  is rotatably mounted to body  85  of endoscope adapter  15 , where it is fixed in the axial direction but can spin about the longitudinal axis of endoscope adapter  15 . Rotating collar  110  is spring-biased to force key  80  into the L-shaped keyway  75 . As such, when endoscope adaptor  15  is connected to inflow access cannula  10 , key  80  will be spring-biased into bottom corner  115  of L-shaped keyway  75 . To release, or disengage, endoscope adaptor  15  from inflow access cannula  10 , rotating collar  110  is rotated, which shifts key  80  out of bottom corner  115  to the vertical groove portion  120  of L-shaped keyway  75 ; this enables endoscope adaptor  15  to be moved axially away from inflow access cannula  10 . In  FIG. 26 , rotating collar  110  and straight key  80  (without additional components of endoscope adaptor  15 ) are illustrated to show engagement of key  80  into the L-shaped keyway  75  of mount  50  of inflow access cannula  10 . This design minimizes the length required to connect the endoscope adapter  15  and inflow access cannula  10 , hence providing for a more effective working length of the shaft of scope  20 . 
     Inflow access cannula system  5  may be used in various ways to provide access to the interior of a hip joint. Among other things, due to the smooth shaft of elongated tube  25  and the atraumatic distal tip  45  of the elongated tube, atraumatic cannula deployment can be achieved. Furthermore, the use of endoscope adapter  15  allows custom docking (secure seating and fluid flow) to be achieved when an endoscope is mounted in the inflow access cannula. And, significantly, the more compact design (in terms of length) of the assembled endoscope adapter/inflow access cannula covers a reduced portion of an instrument&#39;s length, thereby increasing access of the instrument (e.g., endoscope  20 ) to deep surgical sites within the joint space. 
     Looking next at  FIGS. 27-42 , there is shown another inflow access cannula system  125  which generally comprises an inflow access cannula  130 , an obturator  135  and an endoscope adapter  140 . Obturator  135  is intended to be positioned within an inflow access cannula  130  during insertion of the inflow access cannula into the tissue of the patient, as will hereinafter be discussed in further detail. As will also hereinafter be discussed in further detail, when the inflow access cannula  130  has been properly positioned in the tissue of the patient, obturator  135  is removed, endoscope adapter  140  is positioned on the proximal end of inflow access cannula  130 , and an endoscope  145  is advanced through the central lumen of the endoscope adapter and the inflow access cannula, whereby to provide visualization of, and fluid flow to and/or from, a remote surgical site. Alternatively, endoscope adapter  140  may be mounted on endoscope  145  remote from inflow access cannula  130  and then the two elements advanced together as a unit so as to seat on inflow access cannula  130 . 
     More particularly, inflow access cannula  130  generally comprises an elongated tube  150  having a distal end  155 , a proximal end  160  and a central lumen  165  ( FIG. 41 ) extending therebetween. The shaft of elongated tube  150  is long enough so that it can extend between the outer surface of the patient&#39;s skin and the inside of the joint. Furthermore, the shaft of elongated tube  150  is preferably formed out of metal so as to provide strength and rigidity during insertion of the cannula into the tissue of the patient and its subsequent use as a liner for the access corridor extending down to the remote surgical site. Alternatively, the shaft of elongated tube  150  may be a metal tube coaxial with a plastic tube, the metal tube being disposed either inside or outside of the plastic tube. The outer surface of elongated tube  150  is preferably smooth so as to minimize trauma to tissue as inflow access cannula  130  is inserted in the tissue. 
     Distal end  155  of inflow access cannula  130  preferably comprises a soft, atraumatic distal tip  170  ( FIG. 27 ) so as to also minimize tissue trauma during cannula insertion and use. 
     In one preferred form of the invention, at least the atraumatic distal tip  170  of inflow access cannula  130  comprises a polymer or other material which contains barium sulfate, preferably in the range of 5-30% (and preferably about 15%) by weight, so as to render the inflow access cannula visible under X-ray or fluoroscopy. This range (by weight) of barium sulfate is generally preferred since concentrations below 5% tend to be too low for good visualization in hip applications, whereas concentrations above 30% can lead to degradation of material properties. Alternatively, other opacifiers, at appropriate weight concentrations, may also be used to render the inflow access cannula visible under X-ray or fluoroscopy. 
     A mount  175  ( FIG. 27 ) is secured to the proximal end of elongated tube  150 . Mount  175  includes a keyway  180  ( FIG. 27 ) for receiving a key  185  ( FIG. 30 ) of obturator  135 , whereby to releasably rotatably lock obturator  135  to inflow access cannula  130 . Mount  175  also includes one or more keys  190  ( FIG. 37 ) for receipt in corresponding keyways  195  ( FIG. 38 ) in endoscope adapter  140 , whereby to releasably rotatably lock endoscope adapter  140  to inflow access cannula  130 . Mount  175  also includes a stem  200  ( FIG. 37 ) which protrudes upward from the floor  205  of mount  175 . Stem  200  includes a lumen  210  ( FIG. 37 ) which communicates with central lumen  165  ( FIG. 41 ) of elongated tube  150 . 
     Obturator  135  generally comprises a shaft  215  ( FIG. 30 ) terminating in a blunt distal end  220  and a proximal handle  225 . Handle  225  includes a key  185  for receipt in the aforementioned keyway  180  ( FIG. 27 ) of mount  175 , whereby to releasably rotatably lock obturator  135  to inflow access cannula  130 . As seen in  FIG. 32 , the distal end  220  of obturator shaft  215  protrudes from atraumatic tip  170  of cannula tube  150  when obturator key  185  is seated in cannula keyway  180 , so that the blunt distal end  220  of obturator  135  leads the assembly and prevents tissue coring by inflow access cannula  130  when the inflow access cannula is advanced through tissue. 
     Endoscope adapter  140  comprises a body  230  ( FIG. 41 ) which mates with mount  175  of inflow access cannula  130 . More particularly, body  230  of endoscope adapter  140  is designed to seat over stem  200  of cannula mount  175  so that (i) an endoscope  145  can extend down lumen  210  ( FIG. 37 ) of endoscope adapter  140  and down central lumen  165  of elongated tube  150 , and (ii) fluid introduced through ports  235  ( FIG. 42 ) of endoscope adapter  140  can flow down to the surgical site through central lumen  165  of elongated tube  150  or, conversely, fluid at the surgical site can flow up through central lumen  165  of elongated tube  150  and then out one of the ports  235 . As noted above, cannula mount  175  also includes keys  190  ( FIG. 37 ) for mating with keyways  195  ( FIG. 38 ) of endoscope adapter  140 , so that proper alignment of inflow access cannula  130  and endoscope adapter  140  can be ensured. Cannula mount  175  also includes a keyway  240  ( FIG. 27 ) for mating with flexure key  245  ( FIG. 29 ) of endoscope adapter  140 . Flexure key  245  comprises a locking tab  250  which engages notch  255  ( FIG. 27 ) when endoscope adapter  140  is connected to, and seats into, inflow access cannula  130 . This engagement keeps endoscope adapter  140  connected to inflow access cannula  130  during surgical use. Flexure key  245  can be compressed and moved radially inwardly (i.e., toward the center axis of endoscope adapter  140 ) to disengage locking tab  250  from notch  255  and thus allow endoscope adapter  140  to be disconnected from inflow access cannula  130 . 
     Inflow access cannula system  125  may be used in various ways to provide access to the interior of a hip joint. Among other things, due to the smooth shaft of elongated tube  150  and the atraumatic distal tip  170  of the elongated tube, atraumatic cannula deployment can be achieved. Furthermore, the use of endoscope adapter  140  allows custom docking (secure seating and fluid flow) to be achieved when an endoscope is mounted in the inflow access cannula. And, significantly, the more compact design (in terms of length) of the assembled endoscope adapter/inflow access cannula covers a reduced portion of an instrument&#39;s length, thereby increasing access of the instrument (e.g., endoscope  20 ) to deep surgical sites within the joint space. 
     Use of the Inflow Access Cannula for Other Applications 
     It should be appreciated that the novel inflow access cannula of the present invention may be used for accessing joints other than the hip joint (e.g., the inflow access cannula may be used to access the interior of a shoulder joint), and/or for accessing other interior body spaces (e.g., the abdominal cavity). 
     Modifications of the Preferred Embodiments 
     It should be understood that many additional changes in the details, materials, steps and arrangements of parts, which have been herein described and illustrated in order to explain the nature of the present invention, may be made by those skilled in the art while still remaining within the principles and scope of the invention.