Abstract:
A safety needle comprising a handle; a hollow needle; a trigger carriage; an obturator; a spring; a trigger; a first latch and a second latch; the first latch, second latch and trigger being configured so that when the trigger carriage is in a distal position and the first latch set, and the trigger is thereafter pulled proximally, the first latch is released and the trigger carriage moves proximally into a proximal position, and thereafter releasing the trigger causes the trigger carriage to move into an intermediate position and set the second latch; and further wherein, when the trigger carriage is in its intermediate position and the distal end of the obturator engages tissue, the trigger carriage is moved proximally so as to release the second latch.

Description:
REFERENCE TO PENDING PRIOR PATENT APPLICATION 
       [0001]    This patent application claims benefit of pending prior U.S. Provisional Patent Application Ser. No. 60/993,615, filed Sep. 13, 2007 by Julian Nikolchev et al. for SAFETY NEEDLE FOR ACCESSING THE INTERIOR OF A HIP JOINT (Attorney&#39;s Docket No. FIAN-7 PROV), which patent application is hereby incorporated herein by reference. 
     
    
     FIELD OF THE INVENTION 
       [0002]    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 
       [0003]    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 ,  1 B,  1 C and  1 D. 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. 
         [0004]    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. 
         [0005]    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. 
         [0006]    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 
       [0007]    The hip joint is formed at the junction of the femur and the hip. More particularly, and looking now at  FIG. 2 , the ball 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. 
         [0008]    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. 
         [0009]    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 around the age of 25 or so) so as to collectively form the acetabular cup. The acetabular cup receives the head of the femur. 
         [0010]    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 . 
         [0011]    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  FIG. 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  FIGS. 11 and 12 . 
       Pathologies of the Hip Joint 
       [0012]    As noted above, the hip joint is susceptible to a number of different pathologies. These pathologies can have both congenital and injury-related origins. 
         [0013]    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 a cam-type femoroacetabular impingement (i.e., a 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 a pincer-type femoroacetabular impingement (i.e., a pincer-type FAI). Impingement can result in a reduced range of motion, substantial pain and, in some cases, significant deterioration of the hip joint. 
         [0014]    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 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. 
         [0015]    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 
       [0016]    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 the patient&#39;s tissue, less pain for the patient, faster recuperation times, etc. 
         [0017]    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. 
         [0018]    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. 
         [0019]    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 
       [0020]    Unfortunately, minimally-invasive treatments for pathologies of the hip joint have lagged far behind minimally-invasive treatments for pathologies of the shoulder joint and 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. 
         [0021]    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 when compared to the hip joint. As a result, it is relatively difficult for surgeons to perform minimally-invasive procedures on the hip joint. 
         [0022]    Furthermore, the pathways for entering the interior of the hip joint (i.e., the pathways which exist between adjacent bones) 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. 
         [0023]    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 set at approximately a right angle to the angle of re-attachment. This makes drilling into bone, for example, much more complicated than where the angle of approach is effectively aligned with the angle of re-attachment, 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 of re-attachment. 
         [0024]    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. 
         [0025]    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 
       [0026]    Successful hip arthroscopy generally requires safe and reliable 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, through the underlying muscle tissue, through the capsule of the joint, and then down to the specific surgical site within 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 deploy an arthroscope), another access portal being used for irrigation, another access portal being used to pass surgical instruments to and from the surgical site, etc. 
         [0027]    However, the creation of access portals can be problematic. For one thing, the patient&#39;s anatomy (e.g., bone, blood vessels, nerves, etc.) can greatly restrict the possible portal locations. Furthermore, some hip structures (e.g., the articular cartilage on the femoral head, the articular cartilage on the acetabular cup, etc.) can be quite delicate, thereby requiring great precision when forming the access portal so as to avoid damaging delicate structures. Additionally, some of the intervening tissue (e.g., the joint capsule) can be quite tough, thus requiring substantial force to penetrate the tissue, and thereby raising the danger of accidental plunging as an access tool “breaks through” the intervening tissue. Such accidental plunging increases the risk of inadvertently damaging delicate joint structures (e.g. articular cartilage) located on the far side of the intervening tissue. 
         [0028]    Due to the numerous difficulties and concerns associated with forming an access portal, surgeons have traditionally resorted to a multi-step procedure for forming an access portal. 
         [0029]    More particularly, surgeons have traditionally first passed a small needle (sometimes referred to as an access needle) down to the interior of the hip joint. This is generally done by first using external anatomical landmarks and tactile feedback for needle guidance; then, as the sharp tip of the access needle enters the capsule of the joint and approaches delicate structures (e.g. articular cartilage), fluoroscopy is used to carefully direct final needle placement. Inexperienced surgeons, or experienced surgeons dealing with particularly problematic cases, may also use fluoroscopy during the earlier stages of needle placement. 
         [0030]    Once the access needle has been positioned, the tissue surrounding the access needle is opened laterally by passing a series of tissue dilators over the access needle. These tissue dilators progressively increase in diameter so as to dilate the intervening tissue disposed between the skin and the interior of the joint. 
         [0031]    After the intervening tissue has been laterally dilated, a tubular liner (sometimes referred to as an access cannula) is inserted over the access needle. This access cannula holds the incision open and provides a surgical pathway down to the interior of the hip joint, thereby enabling keyhole surgery to be performed on the hip joint. 
         [0032]    Once the access cannula has been emplaced, the access needle may be withdrawn, leaving the full diameter of the access cannula available for passing instruments and the like down to the surgical site. Alternatively, in many cases, the access needle may be left in place and thereafter used as a guidewire for directing instruments down to the surgical site. 
       The Need for an Improved Access Needle 
       [0033]    As noted above, arthroscopic access to the interior of the hip joint generally requires the creation of an access portal into the interior of the hip joint and, as further noted above, the creation of an access portal into the interior of the hip joint in turn typically requires passing an access needle from the surface of the skin down to the interior of the hip joint. Due to the sharpness of the access needle and the delicate structures of the hip joint, passing the access needle down to the interior of the hip joint is often an anxious and time-consuming procedure for the surgeon, even where fluoroscopy is used, and even where the surgeon is experienced. By way of example but not limitation, there is considerable concern as the needle is passed through the capsule. This is because high push forces are needed to penetrate through the tough fibers of the capsule, but the delicate articular cartilage of the femoral head and/or the acetabular cup lie just beneath the capsule, so any uncontrolled plunging of the access needle can cause serious injury to the patient&#39;s anatomy. As a result of these concerns, needle placement typically proceeds relatively slowly, even with experienced surgeons, and there is typically substantial use of fluoroscopy during needle placement. Such use of fluoroscopy during needle placement tends to slow down the procedure and exposes the patient to additional radiation. 
         [0034]    On account of the foregoing, there is a substantial need for a safer and more convenient approach for creating an access portal to the interior of the hip joint. 
         [0035]    More particularly there is a substantial need for a new safety needle for accessing the interior of the hip joint. 
       SUMMARY OF THE INVENTION 
       [0036]    The present invention provides a safer and more convenient approach for creating an access portal to the interior of the hip joint. 
         [0037]    More particularly, the present invention comprises the provision and use of a novel safety needle for accessing the interior of the hip joint. This safety needle provides a safer, more controlled and more convenient approach for creating access to the interior of the hip joint. 
         [0038]    In one preferred form of the invention, there is provided a safety needle comprising: 
         [0039]    a handle; 
         [0040]    a hollow needle mounted to the handle, the hollow needle having a sharp distal end; 
         [0041]    a trigger carriage slidably mounted to the handle for movement between a distal position and a proximal position; 
         [0042]    an obturator mounted to the trigger carriage and slidably received within the hollow needle, the obturator having a distal end, and the obturator being sized such that (i) when the trigger carriage is in its distal position, the distal end of the obturator extends beyond the distal end of the needle, and (ii) when the trigger carriage is in its proximal position, the distal end of the obturator is received within the distal end of the needle; 
         [0043]    a spring for urging the trigger carriage into its distal position; 
         [0044]    a trigger mounted to the trigger carriage for urging the trigger carriage towards its proximal position; 
         [0045]    a first latch for releasably locking the trigger carriage in its distal position; 
         [0046]    a second latch for releasably locking the trigger carriage in an intermediate position located between the distal position and the proximal position, wherein the distal end of the obturator partially emerges from the hollow needle; 
         [0047]    the first latch, second latch and trigger being configured so that when the trigger carriage is in its distal position and the first latch set, and the trigger is thereafter pulled proximally, the first latch is released and the trigger carriage moves proximally into its proximal position, and thereafter releasing the trigger causes the trigger carriage to move into its intermediate position and set the second latch; 
         [0048]    and further wherein, when the trigger carriage is in its intermediate position and the distal end of the obturator engages tissue, the trigger carriage is moved proximally so as to release the second latch. 
         [0049]    In another form of the present invention, there is provided a method for accessing the interior of a hip joint, the method comprising: 
         [0050]    providing a safety needle comprising:
       a handle;   a hollow needle mounted to the handle, the hollow needle having a sharp distal end;   a trigger carriage slidably mounted to the handle for movement between a distal position and a proximal position;   an obturator mounted to the trigger carriage and slidably received within the hollow needle, the obturator having a distal end, and the obturator being sized such that (i) when the trigger carriage is in its distal position, the distal end of the obturator extends beyond the distal end of the needle, and (ii) when the trigger carriage is in its proximal position, the distal end of the obturator is received within the distal end of the needle;   a spring for urging the trigger carriage into its distal position;   a trigger mounted to the trigger carriage for urging the trigger carriage towards its proximal position;   a first latch for releasably locking the trigger carriage in its distal position;   a second latch for releasably locking the trigger carriage in an intermediate position located between the distal position and the proximal position, wherein the distal end of the obturator partially emerges from the hollow needle;   the first latch, second latch and trigger being configured so that when the trigger carriage is in its distal position and the first latch set, and the trigger is thereafter pulled proximally, the first latch is released and the trigger carriage moves proximally into its proximal position, and thereafter releasing the trigger causes the trigger carriage to move into its intermediate position and set the second latch;   and further wherein, when the trigger carriage is in its intermediate position and the distal end of the obturator engages tissue, the trigger carriage is moved proximally so as to release the second latch;       
 
         [0061]    configuring the safety needle so that the trigger carriage is in its distal position and the first latch set; 
         [0062]    moving the trigger so that the first latch is released and the trigger carriage moves proximally into its proximal position; 
         [0063]    releasing the trigger so as to cause the trigger carriage to move into its intermediate position and set the second latch; and 
         [0064]    advancing the safety needle so that the distal end of the needle and the distal end of the obturator engage tissue. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0065]    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: 
           [0066]      FIGS. 1A-1D  are schematic views showing various aspects of hip motion; 
           [0067]      FIG. 2  is a schematic view showing the bone structure in the region of the hip joints; 
           [0068]      FIG. 3  is a schematic view of the femur; 
           [0069]      FIG. 4  is a schematic view of the top end of the femur; 
           [0070]      FIG. 5  is a schematic view of the pelvis; 
           [0071]      FIGS. 6-12  are schematic views showing the bone and soft tissue structure of the hip joint; 
           [0072]      FIG. 13  is a schematic view showing cam-type femoroacetabular impingement (FAI); 
           [0073]      FIG. 14  is a schematic view showing pincer-type femoroacetabular impingement (FAI); 
           [0074]      FIG. 15  is a schematic view showing a labral tear; 
           [0075]      FIG. 16  is a schematic view showing a novel safety needle formed in accordance with the present invention; 
           [0076]      FIGS. 17 and 18  are schematic views showing various aspects of the safety needle shown in  FIG. 16 ; 
           [0077]      FIGS. 19 and 20  are schematic views showing the safety needle of  FIG. 16  after assembly and prior to use; 
           [0078]      FIGS. 21-24  are schematic views showing the safety needle of  FIG. 16  being placed into its “cocked” condition, with the trigger being pulled a first step so as to put the safety needle in a first, partially-cocked condition ( FIGS. 21 and 22 ) and with the trigger thereafter being pulled a second step so as to put the safety needle into a second, fully-cocked condition ( FIGS. 23 and 24 ); 
           [0079]      FIGS. 25 and 26  are schematic views showing the condition of the safety needle as it is advanced through tissue; and 
           [0080]      FIGS. 27 and 28  are schematic views showing the condition of the safety needle immediately after the distal end of the safety needle passes through intervening tissue and enters the interior of the joint. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0081]    Looking next at  FIG. 16 , there is shown a safety needle  3  formed in accordance with the present invention. Safety needle  3  generally comprises a handle assembly  100 , a needle assembly  200  and an obturator  300 . In general, and as will hereinafter be discussed in further detail, during use, needle assembly  200  is mounted to handle assembly  100 , and obturator  300  extends through handle assembly  100  and needle assembly  200 , in substantially the manner shown in  FIG. 16 . 
         [0082]    More particularly, and looking now at  FIGS. 17 and 18 , handle assembly  100  generally comprises a tubular housing  103  having a distal end  106 , a proximal end  109  and a central lumen  112  extending therebetween. An annular wall  115  is formed intermediate the length of tubular housing  103 . A side port  116  ( FIG. 17 ) extends through the side wall of tubular housing  103 , proximal to distal end  106  and distal to annular wall  115 . A trigger opening  118  extends through the side wall of tubular housing  103 , distal to proximal end  109  and proximal to annular wall  115 . 
         [0083]    A fluid conduit  121  is captured within tubular housing  103  between a mount  124  and a front cap  127 . O-rings  130  are disposed on either end of fluid conduit  121  so as to form (i) a watertight seal between fluid conduit  121  and mount  124  and (ii) a watertight seal between fluid conduit  121  and front cap  127 . Leaf springs  133  bias mount  124  against annular wall  115 . A thumb lever  136  permits mount  124  to be urged distally toward front cap  127 , thereby shortening the chamber holding fluid conduit  121  and O-rings  130 , whereby to radially expand O-rings  130  and thereby cause the O-rings to seal against obturator  300 . As a result, when thumb lever  136  urges mount  124  toward front cap  127 , obturator  300  will be secured to handle assembly  100 . Conversely, thumb lever  136  may be released, so that leaf springs  133  urge mount  124  proximally against annular wall  115 , whereby to ease the compression of O-rings  130  and thereby release the aforementioned seal on obturator  300 . As a result, when thumb lever  136  is released, obturator  300  is no longer secured to handle assembly  100  and may be removed from the handle assembly. 
         [0084]    Front cap  127  comprises a longitudinal bore  137  for receiving needle assembly  200 , and a transverse bore  139  for receiving a locking pin  142 . More particularly, transverse bore  139  includes an annular flange  145 , and locking pin  142  includes a locking nut  148 , whereby leaf spring  151  can yieldably bias locking nut  148  against annular flange  145 . A longitudinal bore  154  extends through locking pin  142  so that when the head of locking pin  142  is pressed inwardly, against the bias of leaf spring  151 , longitudinal bore  154  of locking pin  142  can be aligned with longitudinal bore  137  of front cap  127 ; conversely, when the inward force on the head of locking pin  142  is released, leaf spring  151  causes the locking pin&#39;s longitudinal bore  154  to move out of alignment with the front cap&#39;s longitudinal bore  137 . In this way, locking pin  142  can be used to selectively capture needle assembly  200  to handle assembly  100 . 
         [0085]    A trigger carriage  157  ( FIG. 18 ) is slidably disposed within tubular housing  103 , between annular wall  115  ( FIG. 17 ) and proximal end  109  ( FIG. 18 ). A trigger  160  is pivotally mounted to trigger carriage  157 , with a spring  163  biasing trigger  160  in a distal direction. A finger  166  ( FIG. 18 ) is pivotally mounted to trigger carriage  157 , so as to selectively engage a notch  301  formed in obturator  300 . A release button  172  ( FIG. 18 ), having a peripheral flange  175 , is captured between trigger carriage  157  and an end cap  178 . More particularly, a spring  181  biases trigger carriage  157  and peripheral flange  175  away from one another. 
       Assembly 
       [0086]    Safety needle  3  may be assembled as follows. 
         [0087]    First, trigger  160  is pinned to trigger carriage  157 , with trigger spring  163  in place, and then the components are inserted into tubular housing  103  until the trigger&#39;s finger  184  ( FIG. 18 ) extends out the bottom of trigger opening  118 . 
         [0088]    Next, spring  181  and release button  172  are introduced into the back of tubular housing  103 , and then end cap  178  is screwed into place. 
         [0089]    Then mount  124  ( FIG. 17 ), fluid conduit  121  and O-rings  130  are inserted into the distal end of tubular housing  103 , and thereafter secured in place using front cap  127 . 
         [0090]    Next, locking pin  142  is pressed inwardly so that its longitudinal bore  154  is moved into alignment with the front cap&#39;s longitudinal bore  137 . Then needle assembly  200  is inserted into longitudinal bore  137  of front cap  127  and through longitudinal bore  154  of locking pin  142 . Then locking pin  142  is released, thereby locking needle assembly  200  to handle assembly  100 , with the interior of needle assembly  200  communicating with the interior of tubular housing  103  via an opening  179  formed in the proximal end of cap  127 . 
         [0091]    Finally, obturator  300  is advanced through (i) an opening  180  formed in release button  172 , (ii) an opening  182  formed in the proximal end of finger  166 , (iii) an opening  183  formed in trigger carriage  157 , (iv) the interior of tubular housing  103 , (v) an opening  185  formed in mount  124 , (vi) the proximal O-ring  130 , (vii) the interior of fluid conduit  121 , (viii) the distal O-ring  130 , (ix) opening  179  formed in the proximal end of front cap  127 , and (x) needle assembly  200 , until notch  301  ( FIG. 18 ) is engaged by finger  166 , whereby to releasably secure obturator  300  to handle assembly  100 . 
         [0092]    At this point, safety needle  3  is disposed in the condition shown in  FIGS. 19 and 20 . More particularly, the trigger&#39;s proximal arm  186  is in engagement with the proximal end  187  of trigger opening  118  ( FIG. 19 ), and obturator  300  is in its extended position ( FIG. 20 ), whereupon the sharp distal tip  201  of needle assembly  200  is proximal to, and shielded by, the projecting distal tip  302  of the extended obturator  300 . 
         [0093]    The safety needle may now be sterilized and packaged for shipping. 
       Operation 
       [0094]    During use, safety needle  3  is first removed from its sterile package. 
         [0095]    Then end cap  178  ( FIG. 18 ) is screwed towards or away from tubular housing  103  so as to set the appropriate tension on trigger carriage  157  via spring  181 . 
         [0096]    Next, safety needle  3  is “cocked” by pulling trigger finger  184  proximally, so as to rotate the complete trigger  160  in a clockwise direction. As this occurs, trigger finger  184  is first disposed intermediate trigger opening  118 , with the trigger&#39;s proximal arm  186  and distal arm  188  substantially parallel to obturator  300 , and with distal tip  302  of obturator  300  approximately aligned with distal tip  201  of needle assembly  200  (see  FIGS. 21 and 22 ). Trigger finger  184  is pulled further back until the safety needle is placed into its “cocked” position ( FIGS. 23 and 24 ), with distal arm  188  of trigger finger  184  engaging the distal end  189  of trigger opening  118 , and with distal tip  302  of obturator  300  residing just proximal to, yet protruding slightly out of, distal tip  201  of needle assembly  200 . 
         [0097]    With safety needle  300  in this condition, the safety needle is advanced into the patient. As the safety needle is forced through the tissue of the patient, obturator  300  is urged proximally, further into needle assembly  200 , by virtue of the engagement of the distal tip of the obturator with the tissue. At the same time, trigger carriage  157  is urged proximally due to the engagement of finger  166  with notch  301  of obturator  300 . This action causes the trigger&#39;s distal arm  188  to pivot counterclockwise, releasing distal arm  188  from its engagement with the distal end  189  of trigger opening  118  (see  FIGS. 25 and 26 ). 
         [0098]    The safety needle is held in this equilibrium condition as the safety needle is advanced through the tissue, by virtue of the proximally-directed force imposed on the advancing obturator by the intervening tissue. 
         [0099]    As soon as safety needle  3  penetrates through the tissue, so that there is no longer a proximally-directed force acting on distal tip  302  of obturator  300 , trigger carriage  157  “pops” forward, carrying obturator  300  with it by virtue of the engagement of finger  166  with notch  301 . Trigger carriage  157  and obturator  300  move forward as a unit until the trigger&#39;s distal arm  188  encounters annular wall  115 , whereupon obturator  300  will project out the distal end of needle assembly  200  ( FIGS. 27 and 28 ). As this occurs, the trigger&#39;s proximal arm  186  rotates counterclockwise to engage proximal end  187  of trigger opening  118  ( FIG. 27 ). This action locks obturator  300  in its extended position ( FIG. 28 ), whereupon sharp distal tip  201  of needle assembly  200  resides proximal to blunt distal tip  302  of obturator  300 , and is as such prevented from engaging tissue due to the shielding tip of obturator  300 . 
         [0100]    It will be appreciated that, at this point, safety needle  3  will have returned to the “starting position” shown in  FIGS. 19 and 20 , i.e., the condition it was in when it was removed from the sterile packaging. 
         [0101]    At this point, needle assembly  200  can be disassembled from handle assembly  100  (i.e., by depressing locking pin  142 ), and then handle assembly  100  and obturator  300  can be removed from the surgical site, thereby leaving needle assembly  200  extending from a point outside the body down to the surgical site. Tissue dilators may then deployed over needle assembly  200  so as to dilate the tissue disposed between the skin and the interior of the joint. Then an access cannula may be inserted over needle assembly  200 . Thereafter, the needle assembly  200  may be withdrawn, leaving the access cannula available for passing instruments and the like down to the surgical site. 
       Use of the Safety Needle in Conjunction with Fluids 
       [0102]    During hip surgery, it can be helpful to introduce fluids into the interior of the hip joint and/or to remove fluids from the interior of the hip joint. By way of example but not limitation, a saline flush can be used at the surgical site to improve visibility (e.g., to remove blood) and to flush away particles (e.g., surgical debris). Furthermore, fluids can be used to administer therapeutic agents (e.g., pharmaceuticals, growth factors, etc.) to the surgical site. In addition, fluids can be used to help “break” the suction seal which normally exists between the ball of the femur and the acetabular cup. 
         [0103]    Safety needle  3  is constructed so as to facilitate (i) the delivery of fluids into the interior of the hip joint and/or (ii) the withdrawal of fluids from the interior of the hip joint. 
         [0104]    More particularly, obturator  300  is preferably formed so that it has an interior lumen  305  ( FIG. 17 ). Lumen  305  extends between (i) an opening  310  ( FIG. 26 ) formed just proximal to distal tip  302  of obturator  300 , and (ii) the proximal end  320  ( FIG. 16 ) of obturator  300 . As a result, fluid can be passed to and from the surgical site via the proximal end  320  of obturator  300 . In this respect it should also be appreciated that, by forming the obturator&#39;s distal tip  302  with a “closed wall” configuration, and by positioning opening  310  in the sidewall of the obturator just proximal to distal tip  302  of the obturator, tissue coring during safety needle insertion will be prevented while still preserving fluid access to and from the surgical site. 
         [0105]    In addition to the foregoing, and looking now at  FIG. 17 , obturator  300  preferably is also provided with one or more sidewall openings  325 . Sidewall openings  325  communicate with openings  190  formed in the sidewall of fluid conduit  121 . As a result, fluid from the interior of lumen  305  communicates (via sidewall openings  325  and openings  190 ) with the chamber formed between annular wall  115  and front cap  127 . Side port  116  ( FIG. 17 ), equipped with a removable closure, is formed in the sidewall of tubular housing  103  so as to permit fluid to be selectively passed to and from the surgical site via side port  116 , openings  190  in fluid conduit  121 , sidewall openings  325  in obturator  300  and lumen  305  in obturator  300 . O-rings  130  prevent any fluid within the interior of fluid conduit  121  from escaping along the exterior of obturator  300 . 
       Combining Obturator Function with Guidewire Function 
       [0106]    In many situations, surgical instruments and/or implants may be introduced to, and/or removed from, the surgical site by (i) forming the surgical instruments and/or implants with a cannulated construction, and (ii) running the cannulated instruments and/or implants coaxially down a guidewire to the surgical site. By way of example but not limitation, such an approach is commonly used in many minimally-invasive surgical procedures. 
         [0107]    In accordance with the present invention, obturator  300  can be formed and utilized so as to provide both obturator function and guidewire function. 
         [0108]    More particularly, in one form of the present invention, after safety needle  3  has been introduced into the interior of the hip joint, handle assembly  100  and needle assembly  200  may be withdrawn (preferably as a unit) over the distal end of obturator  300 , thereby leaving obturator  300  extending from a point outside of the body down to the surgical site. Cannulated surgical instruments and/or cannulated surgical implants may then be introduced to, and/or removed from, the surgical site by running those cannulated devices coaxially over obturator  300 . 
         [0109]    Thus, for the purposes of the present invention, obturator  300  may be considered to be a guidewire as well as an obturator. 
       Use of the Safety Needle for Other Joints, Etc 
       [0110]    It should be appreciated that safety needle  3  may also be used for accessing joints in addition to the hip joint, e.g., safety needle  3  may be used to access the knee joint, the shoulder joint, etc. Furthermore, safety needle  3  may also be used to access other interior bodily spaces, e.g., regions around the spine, the abdominal cavity, the chest cavity, etc. In essence, safety needle  3  may be used in any circumstance where it is desired to safely advance a sharp needle into the body through intervening tissue. 
       Modifications of the Preferred Embodiments 
       [0111]    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.