Abstract:
A method for creating space in a joint, the method comprising:
       applying force to a body part so as to distract the joint and create an intrajoint space;   inserting an expandable member into the intrajoint space while the expandable member is in a contracted condition;   expanding the expandable member within the intrajoint space; and   reducing the force applied to the body part so that the joint is supported on the expandable member.

Description:
REFERENCE TO PENDING PRIOR PATENT APPLICATIONS 
       [0001]    This patent application claims benefit of: 
         [0002]    (i) pending prior U.S. Provisional Patent Application Ser. No. 61/210,315, filed Mar. 17, 2009 by Julian Nikolchev et al. for JOINT SPACING BALLOON CATHETER (Attorney&#39;s Docket No. FIAN-28 PROV); 
         [0003]    (ii) pending prior U.S. Provisional Patent Application Ser. No. 61/268,340, filed Jun. 11, 2009 by Julian Nikolchev et al. for METHOD AND APPARATUS FOR DISTRACTING A JOINT, INCLUDING THE PROVISION AND USE OF A NOVEL JOINT-SPACING BALLOON CATHETER AND A NOVEL INFLATABLE PERINEAL POST (Attorney&#39;s Docket No. FIAN-42 PROV); 
         [0004]    (iii) pending prior U.S. Provisional Patent Application Ser. No. 61/278,744, filed Oct. 9, 2009 by Julian Nikolchev et al. for METHOD AND APPARATUS FOR DISTRACTING A JOINT, INCLUDING THE PROVISION AND USE OF A NOVEL JOINT-SPACING BALLOON CATHETER AND A NOVEL INFLATABLE PERINEAL POST (Attorney&#39;s Docket No. FIAN-49 PROV); and 
         [0005]    (iv) pending prior U.S. Provisional Patent Application Ser. No. 61/336,284, filed Jan. 20, 2010 by Julian Nikolchev et al. for METHOD AND APPARATUS FOR DISTRACTING A JOINT, INCLUDING THE PROVISION AND USE OF A NOVEL JOINT-SPACING BALLOON CATHETER AND A NOVEL INFLATABLE PERINEAL POST (Attorney&#39;s Docket No. FIAN-53 PROV). 
         [0006]    The four (4) above-identified patent applications are hereby incorporated herein by reference. 
     
    
     FIELD OF THE INVENTION 
       [0007]    This invention relates to surgical methods and apparatus in general, and more particularly to methods and apparatus for treating a hip joint. 
       BACKGROUND OF THE INVENTION 
     The Hip Joint in General 
       [0008]    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. 
         [0009]    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. 
         [0010]    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. 
         [0011]    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. 
         [0012]    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 
       [0013]    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. 
         [0014]    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. 
         [0015]    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. 
         [0016]    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 . 
         [0017]    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 
       [0018]    As noted above, the hip joint is susceptible to a number of different pathologies. These pathologies can have both congenital and injury-related origins. 
         [0019]    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. 
         [0020]    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. 
         [0021]    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 
       [0022]    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. 
         [0023]    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. 
         [0024]    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. 
         [0025]    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 
       [0026]    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. 
         [0027]    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. 
         [0028]    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. 
         [0029]    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. 
         [0030]    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. 
         [0031]    As a result, there is, in general, a pressing need for improved methods and apparatus for treating pathologies of the hip joint. 
       Current Approaches for Hip Joint Distraction 
       [0032]    During arthroscopic hip surgery, it is common to distract the hip joint so as to provide increased workspace within the joint. More particularly, during arthroscopic hip surgery, it is common to unseat the ball of the femur from the socket of the acetabular cup so as to provide (i) improved access to the interior of the joint, (ii) additional workspace within the interior of the joint, and (iii) increased visibility for the surgeon during the procedure. This hip joint distraction is normally accomplished in the same manner that the hip joint is distracted during a total hip replacement procedure, e.g., by gripping the lower end of the patient&#39;s leg near the ankle and then pulling the leg distally with substantial force so as to unseat the ball of the femur from the acetabular cup. 
         [0033]    However, since the distracting force is applied to the lower end of the patient&#39;s leg, this approach necessitates that the distracting force be applied across substantially the entire length of the leg. As a result, the intervening tissue (i.e., the tissue located between where the distracting force is applied and the ball of the femur) must bear the distracting load for the entire time that the hip joint is distracted. 
         [0034]    In practice, it has been found that the longer the distracting load is maintained on the leg, the greater the trauma imposed on the intervening tissue. Specifically, it has been found that temporary or even permanent neurological damage can occur if the leg is distracted for too long using conventional distraction techniques. 
         [0035]    As a result, the standard of care in the field is for the surgeon to limit the duration of distraction during arthroscopic hip surgery to 90 minutes or less in order to minimize damage to the intervening tissue due to joint distraction. In some situations, this can mean that desirable therapeutic procedures may be curtailed, or even eliminated entirely, in order to keep the duration of the distraction to 90 minutes or less. And even where the duration of the distraction is kept to 90 minutes or less, significant complications can nonetheless occur for many patients. 
         [0036]    In addition to the foregoing, in current hip distraction, it is common to use a perineal post to facilitate hip distraction. More particularly, and looking now at  FIG. 16 , a perineal post is generally positioned between the legs of the patient so that the medial side of the femur which is to be distracted lies against the perineal post. After the patient&#39;s leg is pulled distally (i.e., in the direction of the pulling vector V P ), the leg is adducted so as to lever the leg against the perineal post, which moves the neck and ball of the femur in the direction of the lateral vector V L ; the combination of these two displacements is V D  (i.e., the resultant vector of the vectors of V L  and V P ). This ensures that the ball of the femur is unseated from the acetabular cup in the desired direction (i.e., in the direction of the resultant vector V D ). 
         [0037]    Unfortunately, it has been found that the use of a perineal post can contribute to the damage done to the intervening tissue when the leg is distracted too long. This is because the perineal post can press against the pudendal nerve and/or the sciatic nerve (as well as other anatomy) when distraction occurs. Thus, if the distraction is held too long, neurological damage can occur. This is another reason that the standard of care in the field is for the surgeon to limit the duration of distraction during arthroscopic hip surgery to 90 minutes or less. Additionally, the perineal post can exert pressure on the blood vessels in the leg, and it has been shown that blood flow in these vessels (e.g., the femoral vein, etc.) can be reduced, or in some cases completely occluded, while the hip is in distraction, thus placing the patient in danger of forming deep vein thrombosis or developing other complications. 
         [0038]    Additionally, current hip distraction limits the extent to which the leg can be manipulated under distraction during hip arthroscopy, since a substantial pulling force must be maintained on the distal end of the leg throughout the duration of the distraction. Due to this, and due to the fact that there are typically only 2-4 portals available for surgical access into the interior of the hip joint, visualization and access to hip joint pathology and anatomy is frequently hindered. This can limit the extent of surgical procedures available to the surgeon, and can prevent some procedures from being attempted altogether. Procedures such as mosaicplasty and autologous cartilage injection are examples of procedures which require access to extensive areas of the articular surfaces of the femoral head, but which are typically not performed arthroscopically because of the aforementioned access limitations due to leg distraction. 
         [0039]    Thus, there is a need for a new and improved approach for distracting the hip joint which addresses the foregoing problems. 
       SUMMARY OF THE INVENTION 
       [0040]    These and other objects of the present invention are addressed by the provision and use of a new method and apparatus for distracting a joint. 
         [0041]    Among other things, the present invention provides a novel method for distracting a joint and for maintaining distraction of a joint, wherein the novel method minimizes damage to intervening tissue while maintaining distraction of the joint. In addition, the novel method allows visualization of areas in the hip joint that were not previously visible using a conventional hip distraction approach. 
         [0042]    The present invention also provides novel apparatus for distracting a joint and for maintaining distraction of a joint, wherein the novel apparatus comprises a novel joint-spacing balloon catheter for maintaining the distraction of a joint. In addition, the novel apparatus preferably includes a novel inflatable perineal post for use in distracting the joint. 
         [0043]    In one preferred form of the invention, there is provided a method for creating space in a joint, the method comprising: 
         [0044]    applying force to a body part so as to distract the joint and create an intrajoint space; 
         [0045]    inserting an expandable member into the intrajoint space while the expandable member is in a contracted condition; 
         [0046]    expanding the expandable member within the intrajoint space; and reducing the force applied to the body part so that the joint is supported on the expandable member. 
         [0047]    In another preferred form of the invention, there is provided a method for creating space in a joint, the method comprising: 
         [0048]    inserting a first expandable member into the interior of the joint while the expandable member is in a contracted condition; 
         [0049]    expanding the first expandable member within the joint so as to create a first intrajoint space; 
         [0050]    inserting a second expandable member into the first intrajoint space while the second expandable member is in a contracted condition; and 
         [0051]    expanding the second expandable member within the first intrajoint space so as to create a second intrajoint space. 
         [0052]    In another preferred form of the invention, there is provided a joint-spacing balloon catheter comprising: 
         [0053]    a shaft having a distal end and a proximal end; an expandable member attached to the distal end of the shaft, the expandable member being capable of supporting opposing bones of a previously-distracted joint when the distraction force is reduced; and a handle attached to the proximal end of the shaft. 
         [0054]    In another preferred form of the invention, there is provided a perineal post comprising a balloon. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0055]    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: 
           [0056]      FIGS. 1A-1D  are schematic views showing various aspects of hip motion; 
           [0057]      FIG. 2  is a schematic view showing the bone structure in the region of the hip joints; 
           [0058]      FIG. 3  is a schematic anterior view of the femur; 
           [0059]      FIG. 4  is a schematic posterior view of the top end of the femur; 
           [0060]      FIG. 5  is a schematic view of the pelvis; 
           [0061]      FIGS. 6-12  are schematic views showing the bone and soft tissue structure of the hip joint; 
           [0062]      FIG. 13  is a schematic view showing cam-type femoroacetabular impingement (FAI); 
           [0063]      FIG. 14  is a schematic view showing pincer-type femoroacetabular impingement (FAI); 
           [0064]      FIG. 15  is a schematic view showing a labral tear; 
           [0065]      FIG. 16  is a schematic view showing how a perineal post is used to distract the hip joint in a conventional hip distraction; 
           [0066]      FIGS. 17-19  are schematic views showing a novel joint-spacing balloon catheter formed in accordance with the present invention; 
           [0067]      FIG. 20  is a schematic flowchart showing one novel aspect of a novel method for distracting a joint; 
           [0068]      FIG. 21  is a schematic view showing the novel joint-spacing balloon catheter of  FIGS. 17-19  being deployed within a hip joint; 
           [0069]      FIG. 22  is a schematic flowchart showing another novel aspect of a novel method for distracting a joint; 
           [0070]      FIG. 23  is a schematic view showing how the leg of a patient may be manipulated once the ball of the femur is being supported on the inflated balloon of the joint-spacing balloon catheter, and once the external distracting force previously applied to the distal end of the leg has been released; 
           [0071]      FIGS. 23A-23D  are schematic views showing an outer guiding member which may be used to deploy the joint-spacing balloon catheter within the joint; 
           [0072]      FIGS. 24-28  are schematic views showing how one or more expandable elements may be used to tether the joint-spacing balloon catheter to the capsule of the joint; 
           [0073]      FIG. 28A  is a schematic view showing another means for stabilizing the joint-spacing balloon catheter within a joint; 
           [0074]      FIGS. 29 and 30  are schematic views showing how additional lumens may be provided in the elongated shaft of the joint-spacing balloon catheter in order to accommodate additional structures, e.g., guidewires, obturators, working instruments, optical fibers, etc.; 
           [0075]      FIGS. 31-35  are schematic views showing alternative configurations for the balloon of the joint-spacing balloon catheter; 
           [0076]      FIGS. 36-38  are schematic views showing additional alternative configurations for the balloon of the joint-spacing balloon catheter; 
           [0077]      FIGS. 39-52  are schematic views showing that the joint-spacing balloon catheter may comprise multiple balloons, with those multiple balloons being arranged in a variety of configurations; 
           [0078]      FIGS. 53-55  are schematic views showing how a balloon of the joint-spacing balloon catheter may comprise a plurality of separate chambers, with those chambers being arranged in a variety of configurations; 
           [0079]      FIGS. 56-60  and  60 A- 60 D are schematic views showing how a balloon of the joint-spacing balloon catheter may incorporate puncture protection within its structure; 
           [0080]      FIGS. 61-63  are schematic views showing how a associated structure may be used in conjunction with the joint-spacing balloon catheter so as to provide puncture protection for a balloon of the joint-spacing balloon catheter; 
           [0081]      FIGS. 64-72  are schematic views showing how a supplemental structure may be provided within a balloon of the joint-spacing balloon catheter so as to provide fail-safe support in the event that the balloon should lose its integrity; 
           [0082]      FIGS. 73-78  are schematic views showing additional mechanisms for expanding a balloon of the joint-spacing balloon catheter; 
           [0083]      FIGS. 79 and 80  are schematic views showing an inflatable perineal post provided in accordance with the present invention; and 
           [0084]      FIGS. 81 and 82  are schematic views showing another inflatable perineal post provided in accordance with the present invention. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Novel Joint-Spacing Balloon Catheter 
       [0085]    In one form of the present invention, there is provided a novel joint-spacing balloon catheter for use in distracting a joint, and particularly for maintaining the distraction of a joint, as will hereinafter be discussed in detail. 
         [0086]    More particularly, in this form of the invention, and looking next at  FIGS. 17-19 , there is shown a novel joint-spacing balloon catheter  5  formed in accordance with the present invention. Novel joint-spacing balloon catheter  5  generally comprises an elongated shaft  10  having a balloon  15  disposed at its distal end and a handle  20  disposed at its proximal end. 
         [0087]    Elongated shaft  10  is preferably flexible, and preferably includes an internal stiffener  25  extending along at least a portion of its length so as to facilitate proper positioning of balloon  15  during use. Internal stiffener  25  could comprise a round or rectangular wire (e.g., such as shown in  FIG. 19 ), and be made out of a metal (e.g., stainless steel, Nitinol, etc.) or plastic. If internal stiffener  25  comprises a rectangular wire, the short axis of the wire can provide flexibility (e.g., to enable the distal end of the joint-spacing balloon catheter  5  to navigate around the curvature of the femoral head); whereas, the long axis can provide stiffness to better control the position of the balloon in the joint space. If desired, elongated shaft  10  may also include a rigid overshaft  30  adjacent to handle  20  so as to further stiffen the proximal end of elongated shaft  10 , whereby to provide better control for the positioning of balloon  15 . Rigid overshaft  30  can be a stainless steel tube. Rigid overshaft  30  can be about 10 cm to about 30 cm in length, but is preferably about 12.5 cm to about 22.5 cm in length. A steering cable  35  is provided for steering the direction of balloon  15 . More particularly, steering cable  35  extends through elongated shaft  10  between the distal end of elongated shaft  10  and a steering control mechanism  40  provided on handle  20 . By manipulating steering control mechanism  40 , the user is able to steer the direction of balloon  15 , e.g., in the manner shown in  FIG. 18 . More particularly, steering control mechanism  40  and steering cable  35  are adapted to cause shaft  10  to arc. This arc can be a radius of about 5 mm to about 10 cm, but is preferably a radius of about 1 cm to about 5 cm. 
         [0088]    Balloon  15  is preferably selectively inflatable/deflatable via an inflation/deflation lumen  45  extending through elongated shaft  10  and handle  20 . An inflation/deflation control mechanism  50  is interposed between inflation/deflation lumen  45  and a supply port  55  which is connected to an appropriate fluid reservoir (not shown). By manipulating inflation/deflation control mechanism  50 , the user is able to inflate/deflate balloon  15  as desired. Inflation/deflation control mechanism  50  may comprise a stopcock, a valve, a pump and/or other fluid control mechanisms. Balloon  15  preferably includes an atraumatic tip  60  at its distal end. 
         [0089]    On account of the foregoing, joint-spacing balloon catheter  5  may have its balloon  15  set to its deflated state via inflation/deflation control mechanism  50 , the deflated balloon may be advanced to a remote site using handle  20  and steering control mechanism  40 , and then balloon catheter  5  may have its balloon set to its inflated state by further manipulating inflation/deflation control mechanism  50 , whereby to support tissue and maintain the distraction of a joint, as will hereinafter be discussed in detail. 
       Novel Method for Distracting a Joint 
       [0090]    In another form of the present invention, there is provided a novel method for distracting a joint, preferably the hip joint, and preferably using novel joint-spacing balloon catheter  5 . 
         [0091]    More particularly, in this form of the invention, and looking now at  FIG. 20 , the hip joint is first distracted using a standard leg distraction technique, e.g., by positioning a perineal post between the patient&#39;s legs, pulling on the distal end of the leg with a substantial force, and then adducting the leg so as to unseat the ball of the femur from the acetabular cup, in the manner described above and shown in  FIG. 16 . 
         [0092]    Next, joint-spacing balloon catheter  5 , with balloon  15  set in its deflated state, is inserted into the space created between the ball of the femur and the acetabular cup. This may be done under direct visualization (i.e., using an endoscope inserted into the distracted joint), or under fluoroscopy, or both. 
         [0093]    Then balloon  15  is inflated. See  FIG. 21 . 
         [0094]    Next, the distal force which was previously applied to the distal end of the leg is partially or fully released. Release of the full distraction force has the beneficial effect of completely eliminating the tension load imposed on the intervening tissue, whereas a partial release of the distraction force only partially eliminates the tension load imposed on the intervening tissue—however, even such partial release of the distraction force can still meaningfully reduce the tension load imposed on the intervening tissue, and it provides a safeguard in the event that balloon  15  should prematurely deflate, e.g., mid-procedure. The aforementioned partial or full release of the external distraction force allows the ball of the femur to seat itself on the inflated balloon, with the balloon acting as a spacer so as to maintain a desired spacing between the ball of the femur and the acetabular cup. Thus, joint distraction is maintained even though a substantial distraction force is no longer being applied to the distal end of the leg. Since joint distraction can be reliably maintained without the risk of damage to the intervening tissue from a substantial externally-applied distraction force, the traditional concern to complete procedures in 90 minutes or less is substantially diminished, and complications from joint distraction are greatly reduced. This is a very significant improvement over the prior art. 
         [0095]    With the joint so distracted, the arthroscopic surgery can then proceed in the normal fashion. 
         [0096]    Significantly, and in accordance with another novel aspect of the invention (see  FIG. 22 ), the use of joint-spacing balloon catheter  5  can enable the leg to be manipulated while the joint is in a distracted state. More particularly, it has been discovered that, once balloon  15  has been inflated within the joint and the pulling force applied to the distal end of the leg has been partially or fully released, so that the head of the femur is resting on the balloon, the leg can be moved about (i.e., pivoted) on the balloon. Manipulation can include flexion and extension, adduction and abduction, as well as internal and external rotation. See, for example,  FIG. 23 . This manipulation of the leg while the joint is in a distracted, balloon-supported state enables more of the joint anatomy and pathology to be visualized and accessed, for superior surgical results. By contrast, a patient&#39;s leg cannot be manipulated in this manner when the leg is being distracted in a conventional manner, i.e., by a pulling force applied to the distal end of the leg. Therefore, procedures can be performed using the present invention which cannot be performed using conventional distraction techniques. This is a very significant improvement over the prior art. 
         [0097]    Additionally, some procedures which would normally require the creation of an additional portal to access pathology can be accomplished without the creation of the additional portal, thereby reducing the visible scar and potential morbidity of the additional portal. This is also a significant improvement over the prior art. 
         [0098]    At the conclusion of the arthoscopic surgery, a distal force is re-applied to the distal end of the leg so as to take the load off the inflated balloon, the balloon is deflated, and then the joint-spacing balloon catheter is removed from the interior of the joint. 
         [0099]    Finally, the distal force applied to the distal end of the leg is released, so as to allow the ball of the femur to re-seat itself in its normal position within the acetabular cup. 
         [0100]    With respect to the foregoing method of the present invention, it should be appreciated that joint-spacing balloon catheter  5  can be specifically located in the joint space so as to preferentially bias the position of the femoral head relative to the acetabulum when the pulling force on the distal end of the leg is relaxed and the ball of the femur transfers its load to (i.e., is seated on) the inflated balloon. For example, positioning joint-spacing balloon catheter  5  so that balloon  15  is more posterior in the joint causes the femoral head to settle in a more anterior position, which can improve visualization and access to the posterior acetabular rim. 
         [0101]    With respect to the foregoing method of the present invention, it should also be appreciated that joint-spacing balloon catheter  5  can be placed in the joint space so as to provide better visualization and access to the peripheral compartment of the hip. 
         [0102]    Thus it will be seen that the present invention provides a safe and simple way to significantly reduce trauma to intervening tissue in the leg when practicing leg distraction, since a substantial distally-directed force only needs to be applied to the distal end of the patient&#39;s leg long enough for the deflated balloon to be positioned in the distracted joint and for the balloon to thereafter be inflated—the distally-directed distraction force does not need to be maintained on the distal end of the patient&#39;s leg during the surgery itself. As a result, trauma to the intervening tissue is greatly reduced, and the surgeon no longer needs to limit the duration of distraction to 90 minutes or less in order to avoid damage to the intervening tissue. This is a very significant improvement over the prior art. 
         [0103]    In addition, the use of the present invention enables more of the joint anatomy and pathology to be visualized and accessed, since supporting the ball of the femur on an inflated balloon allows the initial external distraction to be relaxed, and allows the leg to be manipulated on the inflated balloon while the joint is in a distracted state. By contrast, the leg cannot be manipulated in this manner while the leg is being distracted in a conventional manner, i.e., by a pulling force applied to the distal end of the leg. Therefore, arthroscopic procedures can be performed using the present invention which cannot be performed using conventional distraction techniques. This is a very significant improvement over the prior art. 
         [0104]    Additionally, some procedures which would normally require the creation of an additional portal to access pathology can be accomplished without the creation of the additional portal, thereby reducing the visible scar and potential morbidity of the additional portal. This is also a significant improvement over the prior art. 
       Further Details of the Joint-Spacing Balloon Catheter 
       [0105]    It will be appreciated that balloon  15  preferably serves as a both a spacer and as a pivot support to allow the manipulation of the femur while the joint is distracted. Balloon  15  is constructed so as to be atraumatic in order to avoid damaging the anatomy, including the cartilage surfaces of the joint. At the same time, and as will hereinafter be discussed in further detail, balloon  15  may be appropriately textured and/or sculpted in order to maintain its position within the joint, preferentially to either one of the acetabulum or femur, while still allowing the opposing bone to move smoothly over the balloon surface. 
         [0106]    In one preferred form of the invention, elongated shaft  10  has an outer diameter of about 0.040″ (or less) to about 0.250″ (or more). An outer diameter of approximately 0.120″ to 0.200″ is preferred for many hip applications. 
         [0107]    If desired, a retractable sheath (not shown) may be provided over shaft  10  in order to cover balloon  15  prior to inflation. 
         [0108]    And if desired, the distal end of shaft  10  can be pre-shaped with a bend so as to give joint-spacing balloon catheter  5  a directional bias at its distal end. 
         [0109]    Furthermore, if desired, and looking now at  FIGS. 23A-23D , an outer guiding member  57  may be provided for directing joint-spacing balloon catheter  5  to a location within the joint. More particularly, in this form of the invention, outer guiding member  57  comprises a central lumen  58  sized to receive joint-spacing balloon catheter  5 ; the outer guiding member is advanced into position within the joint, and then joint-spacing balloon catheter  5  is advanced down the central lumen  58  of outer guiding member  57  so that the distal end of joint-spacing balloon catheter  5  is properly disposed within the interior of the joint. 
         [0110]    More particularly,  FIG. 23A  is a schematic view showing an outer guiding member  57  which may be used to deploy joint-spacing balloon catheter  5  within the joint. In many instances, the portal location does not directly align with the entrance of the joint space (i.e., with the acetabular rim region). Outer guiding member  57  has a curve at its distal end which can be aligned with the entrance of the joint space, thus facilitating the delivery of joint-spacing balloon catheter  5  into the interior of the joint space. The joint-spacing balloon catheter  5  is advanced through the central lumen  58  of outer guiding member  57  and exits in a direction which better facilitates navigating the distal end of the joint-spacing balloon catheter around the femoral head. The joint-spacing balloon catheter  5  could have a pre-shaped distal end that further enables guidance into the joint space. Alternatively, joint-spacing balloon catheter  5  could be steerable as discussed above. In practice, outer guiding member  57  is placed such that the distal tip of the outer guiding member is at or near the joint entrance ( FIGS. 23C and 23D ). Alternatively, the distal end of outer guiding member  57  can be placed within the joint space. The distal tip of outer guiding member  57  is oriented in the desired direction for proper placement of the balloon. Joint-spacing balloon catheter  5  is advanced through the central lumen  58  of outer guiding member  57  and into the joint space until balloon  15  is in the desired location (the arrows in  FIGS. 23C and 23D  indicate direction of balloon catheter delivery). The outer guiding member can be used to help adjust the final balloon position. The outer guiding member  57  can be left in place during the procedure to help tether the joint-spacing balloon catheter in position within the joint. Additionally, outer guiding member  57  can provide a conduit to remove the joint-spacing balloon catheter from the body. 
         [0111]    In one preferred form of the invention, balloon  15  is preferably approximately 28 mm in diameter, although it can also range from about 10 mm (or less) in diameter to about 50 mm (or more) in diameter if desired. Furthermore, the length of balloon  15  is preferably approximately 50 mm, although it can also range from about 10 mm (or less) in length to about 75 mm (or more) in length if desired. In this respect, it will be appreciated that balloons of various sizes may be used to address patients of different sizes, variations in anatomy, and/or different pathologies. 
         [0112]    Balloon  15  may be inflated with a pressure of up to about 1000 psi, and is preferably inflated with a pressure of up to about 200 psi, and is most preferably inflated with a pressure of up to about 100 psi. In this respect it will be appreciated that it is generally accepted that a force of about 50-80 lbs. is sufficient to distract the hip joint. In order for joint-spacing balloon catheter  5  to support this force, it must provide sufficient pressure over a sufficient surface area (force=pressure X area). Although there are a number of different balloon sizes and operating pressures which can be envisioned, there are limitations on the balloon size and pressure to consider. On the one hand, the balloon must be large enough to cover a sufficient amount of cartilage such that the pressure on the cartilage is lower than that which would damage the cartilage. On the other hand, the balloon must be small enough so as to permit access to and visualization of the operative areas. Hence, there is an optimal range of balloon size and operating pressure, and this optimal range is dependent on tissue dynamics. 
         [0113]    In one preferred form of the invention, balloon  15  is fabricated so as to be semi-compliant, although it can also be fabricated so as to be compliant or non-compliant if desired. Examples of semi-compliant balloon materials are polyurethane, nylon and polyether block amide (PEBA). An example of a compliant balloon material is silicone rubber. An example of a non-compliant balloon material is polyethylene terapthalate (PET). A compliant or semi-compliant balloon is generally preferred since it will deform under load to the shape of the surface which the balloon is contacting in order to help distribute load onto that surface. A semi-compliant balloon is generally most preferred since it will retain some aspects of its pre-load shape even when under load, which can be helpful in directing or maintaining bone positioning, particularly when the leg is being manipulated while in a distracted state. The thickness of the balloon material is preferably in the range of about 0.001″ to about 0.020″, and is most preferably between about 0.002″ and about 0.012″. The durometer of the balloon material is preferably in the range of about 30 Shore A to about 85 Shore D, and is most preferably between about 40 Shore D and about 85 Shore D. 
         [0114]    If desired, the surfaces of balloon  15  can be textured (e.g., with dimples, ridges, etc.) or covered with another material (e.g., a coating or covering) so as to prevent slippage of the balloon along cartilage when the balloon is being used to support a joint. At the same time, this surface texture or non-slip covering is configured so as to engage the cartilage without causing cartilage damage. In one preferred form of the invention, only a portion of the outer surface of the balloon is textured or covered with a non-slip material. For example, the portion of the balloon which faces the acetabulum could be textured or covered with a non-slip material, but the portion of the balloon which faces the femoral head could be non-textured or non-covered, so as to keep the surface facing the acetabulum from slipping while allowing the surface facing the femoral head to slide relative to the femoral head. In another preferred form of the invention, a majority of the balloon surface is textured or covered with a non-slip material. In yet another preferred form of the invention, two or more different textures or non-slip coverings are provided on the outer surface of the balloon, e.g., depending on the particular cartilage surface which they may engage. 
         [0115]    In yet another embodiment of the invention, the balloon is covered with a low friction material which enables slippage of the joint surface on the balloon. The low friction material may cover some or all of the balloon surface. 
         [0116]    The balloon may comprise both low slippage and low friction coverings if desired. 
         [0117]    Furthermore, if desired, fluoroscopic markings can be incorporated into or disposed on elongated shaft  10 , or incorporated into or disposed on balloon  15 , or incorporated into or disposed on another part of joint-spacing balloon catheter  5 , so as to render the apparatus visible under X-ray. Such fluoroscopic markings may comprise radiopaque ink applied to the apparatus, radiopaque bands applied to the apparatus, radiopaque material incorporated in the construction of the apparatus, and/or a radiopaque fluid used to inflate the balloon (such as a contrast agent). By way of example but not limitation, a radiopaque band material could comprise platinum. By way of further example but not limitation, a radiopaque fluid could comprise a contrast agent such as Dodecafluoropentane. 
         [0118]    In one preferred form of the invention, balloon  15  is preferably inflated with a liquid medium, e.g., saline; however, it could also be inflated with a gaseous medium, e.g., air. Among other things, the balloon can be inflated with a high viscosity fluid. This latter construction may be beneficial in the event of a balloon puncture as it would slow the pace of balloon deflation. If desired, a fluid could be used which changes viscosity when subject to changes in temperature, electrical charge, magnetic field, or other means. Alternatively, the balloon can be filled with a compound which increases in viscosity when exposed to saline. This latter construction can be advantageous in certain circumstances, e.g., during a balloon puncture, the escaping fluid would react to the saline present in the joint and could at least partially seal the puncture hole in the balloon. 
         [0119]    Where balloon  15  is inflated with a gaseous medium, and that gaseous medium is air, inflation/deflation control mechanism  50  may comprise a pump, and supply port  55  may be open to the atmosphere. 
         [0120]    In one aspect of the invention, and looking now at  FIGS. 24-28 , joint-spacing balloon catheter  5  further comprises one or more expandable elements  60  in addition to balloon  15 . These expandable elements  60  can be another balloon, a collapsible braid, and/or some other structure which can expand when desired to a larger dimension. Expandable element  60  can be used to releasably secure joint-spacing balloon catheter  5  to the joint capsule. In one embodiment, and as shown in  FIG. 24 , an expandable element  60  is located at the distal end of the joint-spacing balloon catheter. This expandable element  60  is expanded once the distal end of the balloon catheter (and the expandable element  60 ) has passed through the capsule  62  at the far side of the joint, so that the expandable element is deployed on the far side of the capsule, whereby to stabilize balloon  15  within the joint. See  FIG. 25 . In another embodiment, a second expandable element  60  is expanded adjacent to the internal surface of the far capsule, as shown in  FIG. 26 , so that the far side of the capsule is sandwiched between the two expandable elements  60 , whereby to further stabilize balloon  15  within the joint. In this respect it should be appreciated that the two expandable elements  60  may or may not be expanded simultaneously. In yet another embodiment, and looking now at  FIG. 27 , one or more expandable elements  60  are disposed proximal to the balloon, to tether the joint-spacing balloon catheter to capsule  62  at the proximal portion of the joint, such as is shown in  FIG. 28 . 
         [0121]    In another embodiment ( FIG. 28A ), a second cannula  63  is used to secure the distal end of joint-spacing balloon catheter  5  relative to the anatomy. More particularly, the distal tip of the joint-spacing balloon catheter, or a flexible element  64  which extends from the distal end of the joint-spacing balloon catheter (e.g., a guidewire), is passed into the tip of the second cannula  63 . The flexible element could be a wire, a suture, a ribbon, a catheter, a braid, or some other construction which is flexible or semi-flexible. The flexible element  64  can be received within the second cannula or, if desired, gripped within the second cannula. A gripping feature (not shown) could be provided in the second cannula to achieve this. Alternatively, the flexible element  64  could pass entirely through the second cannula. In any case, this construction results in the tip of joint-spacing balloon catheter  5  being stabilized in position by the second cannula  63 . 
         [0122]    Additionally, and looking now at  FIG. 29 , another lumen  65  can be provided for a guidewire, obturator, light fiber, electrical wire, or the like, or as an additional inflation lumen, etc. And, as shown in  FIG. 30 , further lumens  70  can be provided for working instruments, etc. If desired, a pre-shaped guidewire or obturator can be placed through one of the lumens of elongated shaft  10  in order to bias the tip direction of the joint-spacing balloon catheter  5  as the joint-spacing balloon catheter is advanced over the pre-shaped guidewire or obturator. Alternatively, a second steerable wire can be placed through one of the lumens, so as to enable steering of the balloon catheter in a second direction. 
         [0123]    To improve resistance to kinking, or to provide the shaft with the desired stiffness and torsional characteristics, a braid or coil  71  ( FIG. 30 ) could be incorporated into the catheter. The braid or coil could comprise a stainless steel wire, a Nitinol wire, etc. Braid or coil  71  could be incorporated at any section of joint-spacing balloon catheter  5 , but is preferably located in at least the flexible section of the catheter. 
         [0124]    In  FIGS. 17-19 , balloon  15  is shown with a generally cylindrical configuration. However, if desired, balloon  15  can have different configurations. Thus, for example, and looking now at  FIGS. 31 and 32 , balloon  15  can comprise a pair of opposing flat surfaces  72 ; or, and looking now at  FIGS. 33 and 34 , balloon  15  can have an hourglass shape which includes an intermediate section  73  of reduced diameter; or, and looking now at  FIG. 35 , balloon  15  can have a generally hourglass shape with a pair of opposing flat surfaces  72 . The aforementioned hourglass shapes, although depicted symmetrical, can also be asymmetric. For example, one end of the hourglass-shaped balloon may be of a larger dimension (length, diameter, etc.) than the other end of the hourglass-shaped balloon. 
         [0125]    Balloon  15  may also be in the form of an arc or other curvature (i.e., a geometry where one side has a greater curvature than the other side), or some other shape (e.g., U-shaped), so as to fit around the ligamentum teres. See  FIG. 36 . Additionally, balloon  15  could have the shape of a torus, so as to provide a seat for the ball of the femur. See  FIGS. 37 and 38 . 
         [0126]    It is also possible to provide joint-spacing balloon catheter  5  with more than one balloon  15 . Where more than one balloon is provided, the balloons can be disposed in series (i.e., end-to-end, such as is shown in  FIG. 39 ), or in parallel (such as shown in  FIGS. 40 and 41 ), with or without complementary geometries (such as shown in  FIGS. 42 and 43 ), or combinations of such geometries (such as shown in  FIG. 44 ), or toroidal (such as is shown in  FIG. 45 ), etc. The shafts of the multiple balloons may be separated at their distal end (such as is shown in  FIG. 40 ) or may be joined at their distal ends (such as is shown in  FIG. 41 ). Multiple balloons may be of the same construction, or they may be of different constructions. For example, multiple balloons may be of different sizes, shapes, materials, compliances, coatings, surface textures, coverings, colors, and/or other aspects of construction. Additionally, the multiple balloons may be inflated to different pressures and/or volumes. 
         [0127]    These multiple balloons  15  can also be disposed in a mutually-supporting configuration, as shown in  FIGS. 46-52 . By arranging the multiple balloons  15  in a mutually-supporting configuration, the multiple balloons  15  may better conform to the acetabulum and femoral surfaces, which would be beneficial in order to reduce pressure on the cartilage and/or to help maintain the balloons in position within the joint space (i.e., to prevent slipping). In this form of the invention, a balloon catheter  5  could have an assembly of balloons  15  that would collectively act as a compliant or semi-compliant device even though the individual balloons are non-compliant, or vice versa. An additional benefit of arranging the multiple balloons  15  in a mutually-supporting configuration is that if one of the balloons deflates, the other balloons can still maintain a substantial portion of the joint space. In one preferred construction, the balloons  15  can slide against each other to spread out, e.g., to spread out in a lateral direction. Where joint-spacing balloon catheter  5  comprises multiple balloons  15 , preferably, a separate inflation/deflation lumen is provided for each balloon, so that each balloon can be separately inflated or deflated, although a single inflation/deflation lumen could be used to simultaneously inflate/deflate more than one balloon. By permitting each balloon of a group of balloons to be selectively inflated, the surgeon can influence the manner in which the ball of the femur is supported relative to the acetabular cup. In one preferred manner of use, each of the balloons may be inflated to a different volume (and/or pressure) than others of the balloons. This approach can be used to impart a specific shape to the overall balloon structure. Also, some of the balloons  15  can be made compliant, and others non-compliant, so as to achieve a desired pressure distribution and/or shape for the overall balloon structure. 
         [0128]    It is also possible to provide each of the balloons  15  with a plurality of separate internal chambers  75  ( FIGS. 53-55 ). Preferably each of these separate chambers  75  can be selectively inflated so as to influence the manner in which the ball of the femur is supported relative to the acetabular cup. Thus, in this sort of construction, selective inflation of the various chambers can be used to adjust the position of the ball of the femur within the acetabular cup when the pulling force on the distal end of the leg is relaxed. The use of multiple chambers may also provide a safer design. More particularly, in the event that one of the chambers  75  is punctured during a procedure, the use of multiple chambers  75  may permit some joint distraction to be maintained, thus reducing the chances that, for example, an instrument will be wedged between the femoral head and acetabulum. 
         [0129]    If desired, balloons  15  can be formed so as to be puncture resistant in order to minimize the possibility of inadvertently deflating the balloon, e.g., with an errant surgical instrument. To this end, and looking now at  FIG. 56-59 , a balloon  15  can embed, or sandwich, a puncture-resistant structure  80  (e.g., a coil or mesh or strand or braid formed out of Nitinol, or stainless steel, or a polymer, etc.) between two layers of material (preferably a non-abrasive elastomer). Alternatively, the puncture-resistant structure  80  could be placed on one side of, or embedded within, a single sheet of material, such as is shown in  FIG. 60 . This puncture-resistant structure  80  may be a separate element added to the wall of the balloon or a coating applied to the wall of the balloon. The puncture-resistant structure  80  may also be a layer of material within the side wall of the balloon; for example, the outer layer may be a puncture-resilient material (such as polyurethane) to enhance puncture resistance, while the inner layer material maintains the balloon pressure (such as PET). In one preferred construction, puncture-resistant structure  80  covers a substantial portion of the balloon surface. In another preferred construction, the puncture-resistant structure  80  covers a smaller portion of the balloon surface; in this instance, the surface incorporating the puncture-resistant structure  80  is disposed on the side of the balloon where instruments are used (which could puncture the balloon). 
         [0130]    Furthermore, if desired, and looking now at  FIGS. 60A-60D , the distal end of joint-spacing balloon catheter  5  could include a shroud  82  disposed over balloon  15 . Shroud  82  may be formed out of a puncture-resistant material so as to protect balloon  15  from inadvertent puncture. Additionally, and/or alternatively, shroud  82  could be formed so as to define the volume created within the joint when balloon  15  is inflated. This construction can be advantageous where balloon  15  is formed out of a compliant material and it is desired to control the manner in which space is created within the joint, i.e., by using a non-compliant or semi-compliant shroud  82 . Additionally, and/or alternatively, shroud  82  could be formed out of a material which provides slippage (e.g., it can be formed out of ePTFE). This can be beneficial in a number of ways. First, it can facilitate easier delivery of the balloon into the joint, including passage through the entry cannula. In a similar way, shroud  82  can also facilitate easier removal of the joint-spacing balloon catheter from the joint, including through the entry cannula. By having enhanced slippage properties, shroud  82  can also facilitate joint manipulation on the balloon. The shroud&#39;s geometry (e.g., tapered ends) can also facilitate ease of delivering and removing the joint-spacing balloon catheter to and from the joint space; this may be particularly beneficial if the balloon catheter goes through an entry cannula. Alternatively, the shroud  82  could be formed out of a material which prevents slippage on the joint surface (e.g. a low durometer elastomer). This can be beneficial to enable the balloon to remain stationary on the joint surfaces once it has been placed in the joint space. Additionally, and/or alternatively, shroud  82  can be constructed so as to provide better endoscopic visualization of the balloon; for example, shroud  82  can be an opaque color. 
         [0131]    Alternatively, and looking now at  FIGS. 61-63 , a shield  85  could be placed alongside balloon  15  to protect the balloon from being punctured from that direction. Shield  85  is preferably introduced into the joint after the balloon has been inserted and inflated, but shield  85  could also be inserted into the joint prior to that if desired. Shield  85  could be made out of a material similar to the puncture-resistant structure  80  described above. 
         [0132]    Alternatively, and looking now at  FIGS. 64-68 , a balloon-within-a-balloon configuration can be used to provide one or more secondary “fail-safe” (or “safety”) balloons  90  within the primary balloon  15 —such a construction can minimize the risk that joint distraction will be lost in the event that the primary balloon  15  is inadvertently deflated, e.g., by an accidental puncture. If desired, the inner balloon  90  can be made of a different material than the outer balloon  15 . In one preferred construction, inner balloon  90  is non-compliant and outer balloon  15  is semi-compliant. The inner and outer balloons could also have different wall thicknesses, geometries, or other aspects of construction as discussed above. 
         [0133]    Alternatively, a different type of secondary structure can be deployed in balloon  15  in order to prevent balloon  15  from completely collapsing in the event that it is punctured. In one embodiment, and looking now at  FIG. 69 , a wire  95  is delivered into the interior of the balloon and fills up a portion of the internal balloon volume; in the event that the balloon is punctured, wire  95  provides support to prevent the joint space from collapsing. Wire  95  is preferably made of Nitinol, but could also be formed out of another metal or polymer if desired. In another embodiment, and looking now at  FIG. 70 , a wire  100  is delivered across the length of the balloon and set in a bowed configuration. The bowed wire  100  provides mechanical support in the event the balloon is punctured. In  FIG. 71 , an exemplary mechanical scaffold  105  is shown deployed in the interior of the balloon so as to provide a safety mechanical support. In  FIG. 72 , an expandable foam  110  is deployed within the interior of the balloon; foam  110  expands to fill some or most of the internal balloon space. In one embodiment, expandable foam  110  absorbs fluid and will therefore absorb saline within the balloon. This construction can reduce the speed at which a punctured balloon will deflate. 
         [0134]    In yet another embodiment ( FIGS. 73 and 74 ), the balloon is filled with beads  115 . Beads  115  could be absorbent polymer or foam, or non-absorbent. As shown in  FIGS. 75-77 , if beads  115  are non-absorbent, the balloon&#39;s inflation fluid can be evacuated from the balloon after beads  115  have been introduced into the inflated balloon, leaving a compact “bean bag” structure to maintain the joint space. As shown in  FIG. 78 , beads  115  are preferably delivered into the interior of the balloon in a strand configuration, i.e., mounted on a filament  116 . This approach has the additional advantage that, in the event that the balloon should lose its integrity, beads  115  can be safely removed without leaving any beads in the hip joint, i.e., by pulling proximally on filament  116 . If desired, beads  115  can be disposed between a primary outer balloon  15  and secondary inner balloon  90 . 
         [0135]    If desired, joint-spacing balloon catheter  5  can include pressure regulation, e.g., a release valve (not shown) to ensure that a balloon is not inflated beyond a maximum level, or an alarm or other alert (not shown) to advise the user that a balloon has been inflated beyond a pre-determined level. This can be important to avoid damage to the patient&#39;s tissue or to reduce the risk of inadvertent balloon rupture. 
         [0136]    Furthermore, a check valve (not shown) may be installed on the inflation port(s)  55  to enable joint-spacing balloon catheter  15  to be disconnected from the fluid reservoir while maintaining pressure in balloon  15 . 
         [0137]    It is also possible to place markings (e.g., longitudinal lines) along the body of balloon  15 , or to color the balloon material, so as to improve endoscopic visualization of the balloon, including to show the degree of balloon inflation. Alternatively, the fluid used to inflate the balloon could be colored, or the balloon surface could have texture, in order to aid visualization of the balloon. Alternatively, a transparent, thick-walled balloon  15  can be used to increase visualization of the balloon by increasing the refraction of light, which will make the balloon foggy in appearance. Alternatively, a coating could be applied to the balloon material which improves the endoscopic visualization of the balloon. Alternatively, a second balloon or an expandable extrusion could be placed over the primary balloon so as to improve endoscopic visualization. The second balloon and/or expandable extrusion may be colored for improving endoscopic visualization. This configuration can also add to the puncture resistance of the primary balloon and assist in the delivery and retrieval of the primary balloon. 
         [0138]    The joint-spacing balloon catheter  5  may also comprise a sensor (not shown). The sensor can measure the temperature of the surrounding tissue or fluid in the joint (e.g., the sensor may be a temperature sensor). The sensor may also detect characteristics of the adjacent cartilage, such as thickness, density, and/or quality (e.g., the sensor may be an ultrasound device, etc.). The sensor could be located on shaft  10  or on balloon  15 , or on another portion of joint-spacing balloon catheter  5 . 
       External Distraction of the Limb 
       [0139]    In the foregoing description, the external distraction of the limb is generally discussed in the context of applying a distally-directed distraction force to the distal end of the leg. However, it should be appreciated that the distally-directed distraction force may be applied to another portion of the leg, e.g., to an intermediate portion of the leg, such as at or about the knee. Thus, as used herein, the term “distal end of the leg” is meant to include substantially any portion of the leg which is distal to the ball of the femur, such that by applying the external distraction force to the leg, a tension load is imposed on the intervening tissue. Furthermore, as used herein, the term “intervening tissue” is intended to mean the tissue which is interposed between the location where the external distraction force is applied to the leg and the ball of the femur. 
       Inflatable Perineal Post 
       [0140]    The present invention also preferably comprises the provision and use of a novel inflatable perineal post for facilitating joint distraction. 
         [0141]    More particularly, and looking now at  FIGS. 79 and 80 , there is shown an inflatable perineal post  120  which generally comprises a relatively narrow, substantially rigid inner core  125  surrounded by a relatively wide, substantially soft inflatable balloon  130 . In an alternative embodiment as is shown in  FIGS. 81 and 82 , inflatable perineal post  120  comprises a soft inflatable balloon  130  is supported on one or more sides by a substantially rigid support structure  135 . Such a non-cylindrical construction, with inflation being directed along selected directions, can be highly beneficial, since it can reduce engagement of the non-working portions of the perineal post with patient anatomy (e.g., the genitalia). Still other post shapes and configurations can be envisioned by one skilled in the art in view of the present disclosure. 
         [0142]    The inflatable balloon  130  of the inflatable perineal post  120  is preferably constructed out of a semi-compliant material, but it could also be compliant or non-compliant. The inflatable balloon  130  of the inflatable perineal post  120  may involve a covering (not shown) for contact with the patient; this covering may be a non-slip material. The inflatable balloon  130  is preferably inflated with a manual or electric pump. The inflatable perineal post  120  could include a read-out panel displaying the balloon pressure. 
         [0143]    The inflatable perineal post  120  may also comprise physiologic sensors (not shown) for monitoring parameters such as patient skin temperature and blood flow. Such parameters may be reflective of patient conditions of interest to the surgeon, e.g., a falling patient skin temperature is frequently indicative of reduced blood flow. These physiologic sensors could be incorporated into the surface of the balloon, or they could be separate sensors which are included as part of a kit provided with the inflatable perineal post. The physiologic sensors are adapted to be connected to a monitor so as to provide read-outs on the monitor. 
         [0144]    In use, the deflated perineal post balloon is positioned between the patient&#39;s legs, the joint is distracted by pulling on the distal end of the leg so that the ball of the femur is spaced from the acetabular cup, the perineal post balloon is inflated, a joint-spacing balloon catheter  5  is inserted into the distracted joint, the balloon  15  is inflated, the force applied to the distal end of the leg is relaxed so that the ball of the femur settles back down onto the one or more inflated balloons  15 , and then the perineal post balloon  130  is at least partially deflated. At this point the arthroscopic surgery can be conducted without trauma to the patient&#39;s tissue, due to either the distal distraction of the leg or due to engagement of the perineal post with the tissue of the patient. At the conclusion of the surgery, the distal end of the leg is pulled distally again, the perineal post balloon  130  is inflated, the joint-spacing balloon  15  is deflated, the joint-spacing balloon catheter  5  is removed from the joint, and the joint is reduced. Alternatively, the perineal post balloon could be inflated prior to pulling on the distal end of the leg. Or, alternatively, the perineal post balloon  130  could be deflated prior to withdrawal of the force being applied to the distal end of the leg. In some cases, only one of either (i) pulling on the leg, or (ii) inflating of the perineal post is performed in order to remove or re-position the joint-spacing balloon. 
         [0145]    If desired the inflatable perineal post  120  may be used to replace a standard perineal post, and is used in conjunction with a standard traction table; in other words, in this form of the invention, the inflatable perineal post  120  is not used in conjunction with a joint-spacing balloon catheter  5 . 
       One Preferred Form of the Invention 
       [0146]    In one preferred form of the present invention, the aforementioned novel method for distracting the joint is implemented using the aforementioned novel joint-spacing balloon catheter  5  and the aforementioned inflatable perineal post  120 . 
         [0147]    More particularly, in this form of the invention, the hip joint is first distracted by pulling on the distal end of the leg just above the ankle, and then inflating the inflatable perineal post, where the perineal post is positioned between the patient&#39;s legs. The leg may be adducted so as to lever the femur laterally. Alternatively, the inflatable perineal post could be inflated prior to the distal end of the leg being pulled distally. 
         [0148]    Next, the surgeon identifies a portal location for joint-spacing balloon catheter delivery. Then a needle is placed into the joint, the stylet is removed, a guidewire is delivered through the needle, and then the needle is removed. The guidewire can be placed in the desired delivery path of the joint-spacing balloon catheter  5 . 
         [0149]    An arthroscopic cannula or outer guiding member may then be emplaced if desired; in this instance, the guidewire may be removed if desired. 
         [0150]    Next, a joint-spacing balloon catheter  5  of the appropriate size is selected from a kit providing a range of differently-sized joint-spacing balloon catheters. Then the joint-spacing balloon catheter  5  is delivered over the guidewire (either percutaneously or through a cannula) to the target site between the femoral head and the acetabulum. The joint-spacing balloon catheter  5  may be rotated as appropriate if there is asymmetry in the balloon&#39;s shape. Alternatively, the joint-spacing balloon catheter  5  may be delivered through a cannula without the use of a guidewire. 
         [0151]    Next, a syringe (or other inflation device) is secured to the joint-spacing balloon catheter  5 , and the balloon  15  is inflated to the desired pressure and/or size. If there is more than one balloon  15 , the additional balloon(s) can be inflated. If the additional balloon(s) are used to affect the direction of joint spacing, the pressure and/or size of each balloon is adjusted so as to achieve the desired joint spacing direction. 
         [0152]    Once the balloon has been inflated to the desired pressure and/or size, the distraction force applied to the leg is at least partially removed, allowing the head of the femur to rest on the inflated balloon (which is itself supported by the acetabulum). 
         [0153]    Additionally, the inflatable perineal post  120  is deflated as appropriate; this could occur before the leg distraction force is released. 
         [0154]    The balloon  15  can be re-positioned by re-applying distraction force to the leg and/or re-inflating the inflatable perineal post  120 , deflating balloon  15  and re-positioning the joint-spacing balloon catheter  5 , re-inflating the balloon of the joint-spacing balloon catheter, then releasing the leg distraction and/or deflating the inflatable perineal post. The balloon  15  may be placed in a location which directs the distraction in a preferred direction. Alternatively, where the joint-spacing balloon catheter comprises a plurality of balloons, the balloons may be inflated to different sizes and/or pressures in order to direct the joint distraction in a preferred direction. 
         [0155]    With the balloon maintaining the joint distraction, the leg may be manipulated (i.e. rotated, flexed, etc.) in order to visualize and access pathology through the established portals. 
         [0156]    Then the arthroscopic surgery is conducted. The leg may be manipulated a number of times through the procedure in order to visualize, access and treat pathology. 
         [0157]    At the conclusion of the arthroscopic surgery, the hip joint is distracted again, e.g., by pulling on the distal end of the leg just above the ankle, so as to lift the head of the femur off the balloon. The perineal post balloon may be inflated. The balloon  15  of the joint-spacing balloon catheter is deflated and the joint-spacing balloon catheter is removed. 
         [0158]    Thereafter, the distraction force applied to the leg may be removed, allowing the head of the femur to settle back on the acetabulum. 
         [0159]    In another form of the invention, while the distal end of the leg is held stationary, the perineal post  120  is inflated to break the suction seal of the hip joint and enable the joint-spacing balloon catheter  5  to be placed in the joint and inflated. In this case, no pulling on the leg is performed. This would have the benefit of eliminating a piece of equipment from the surgery and reducing the corresponding surgical time associated with using that equipment. 
         [0160]    In yet another form of the invention, the joint-spacing balloon catheter  5  can perform some or all of the joint distraction. In one embodiment, a first joint-spacing balloon catheter  5  is placed adjacent to the femoral head and the balloon is inflated. The leg is then manipulated in abduction or adduction (depending on balloon location), thus levering the femoral neck against the balloon. This levering creates a gap at the acetabular rim. A second joint-spacing balloon catheter  5  is then inserted into the gap and delivered into the joint space (the space between the femoral head and the acetabulum). The balloon of the second joint-spacing balloon catheter is then inflated and distracts the joint; that is, opens up the joint space. In one embodiment, the first balloon is placed on the lateral/superior aspect of the femoral neck. Once the second balloon is inflated, the first balloon can be deflated and withdrawn. The first balloon may be of a different size and shape as the second balloon. It also may be inflated to a different pressure. 
       Kits 
       [0161]    The joint-spacing balloon catheter  5  and the inflatable perineal post  120  may be offered as part of a single kit. A guidewire or obturator, outer guiding member and a balloon inflation device may additionally be provided. 
       Use of the Present Invention for Other Applications 
       [0162]    It should be appreciated that the present invention may be used for distracting the hip joint in an open, more invasive procedure. The present invention can also be used in hip joint pathologies where joint distraction is not needed but space creation is needed, e.g., to visualize and/or to address pathologies in the peripheral compartment or pathologies in the peritrochanteric space. Additionally, the present invention may be used for distracting joints other than the hip joint (e.g., it may be used to distract the shoulder joint). 
       Modifications of the Preferred Embodiments 
       [0163]    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.