Abstract:
A system and method for manipulating intervertebral tissue in one embodiment includes a conduit, a segmented expansion media configured to pass through the conduit, and an expandable node comprising a plurality of abrading strands and operably connected to the intervertebral tissue removal system conduit so as to receive the segmented expansion media therein, the expandable node expandable from a first condition whereat the plurality of abrading strands define at least one opening having a first maximum diameter, to an expanded condition whereat the at least one opening has a second maximum diameter larger than the first maximum diameter, wherein the second maximum diameter is less than a minimum diameter of the segmented expansion media, such that insertion of the segmented expansion media through the intervertebral tissue removal system conduit and into the expandable node causes the expandable node to expand from the first condition to the expanded condition.

Description:
This application is a continuation of application Ser. No. 13/411,706, filed on Mar. 5, 2012, which issued as U.S. Pat. No. 8,882,771 on Nov. 11, 2014, which is a divisional of application Ser. No. 11/581,668, filed on Oct. 16, 2006 (now U.S. Pat. No. 8,137,352), the disclosures of which are hereby totally incorporated by reference in their entirety. 
    
    
     FIELD OF THE INVENTION 
     This invention relates to surgical devices and, more particularly, to devices used to loosen tissue for removal in a surgical patient. 
     BACKGROUND 
     The spinal column acts as a major structural support. Various mechanisms, however, affect the ability of intervertebral disks to provide the requisite stability and support. For example, the normal aging process tends to weaken the bones and tissues associated with the spinal column increasing the risk of spinal injuries. Additionally, sudden movements may cause a disk to rupture or herniate. A herniation of the disk is primarily a problem when the nucleus pulposus protrudes or ruptures into the spinal canal placing pressure on nerves which in turn causes spasms, tingling, numbness, and/or pain in one or more parts of the body, depending on the nerves involved. Further deterioration of the disk can cause the damaged disk to lose height and to produce bone spurs. These mechanisms may result in a narrowing of the spinal canal and foramen, thereby causing undesired pressure on the nerves emanating from the spinal cord. 
     Treatments of spinal cord conditions include various procedures which involve the removal of all or a portion of a spinal component. Such procedures may include the injection of an enzyme into an affected disk to dissolve tissues. The enzymes typically used in this procedure are protein-digesting enzymes which must be carefully placed with respect to the spinal defect to avoid inadvertent dissolution of spinal tissue. 
     Alternatively, surgical access to a spinal area may be obtained and a tool such as a curette, osteotome, reamer, rasp, or drill may be used to mechanically reshape a component of the spinal column. The tissue removed may include disk tissue which is causing pressure on a nerve or the spinal canal. This technique is highly invasive and traumatic to the body, and therefore requires an extended recovery period. Moreover, there are increased risks of future problems due to the removal of a portion of the lamina which is no longer in place to support and protect the spinal canal at the area where the surgery took place. 
     Surgical access may also be used for spinal fusion surgery. In a fusion procedure, a damaged disk may be completely removed. Parts of a bone from another part of the patient&#39;s body, such as the pelvis, are harvested, and the bone parts or grafts are subsequently placed between the adjacent vertebrae so that the adjacent vertebrae grow together in a solid mass. The recovery time for a normal spinal fusion surgery is significant due not only to the fact that normal movement cannot be allowed until detectable bone growth has occurred between the bone grafts and the adjacent vertebrae, but also due to the fact that the associated ligaments and muscles, both at the spinal location and the location where the bone grafts were harvested, must also recover. 
     Recently, efforts have been directed to replacing defective spinal column components. When this type of procedure is performed in a minimally invasive manner, it is known for various devices implanted during the procedure to be subsequently expelled from the intervertebral disks. This expulsion is frequently attributed to inadequate clearance of the nucleus during the minimally invasive surgical procedure. The result is that the interdiskal device extrudes from the cavity formed in the spinal column, increasing the potential for expulsion. 
     A need exists for a device for loosening tissue that is minimally invasive, easy to use, and safe. A further need exists for a device that may be used to loosen tissue associated with an area of the spinal column. Additionally, a device which can create a relatively large cavity through a small entry point is needed. A further need exists for a device which provides for both the loosening of tissue and the removal of loosened tissue. 
     SUMMARY 
     A system and method for manipulating intervertebral tissue in one embodiment includes an intervertebral tissue removal system conduit, a segmented expansion media configured to pass through the intervertebral tissue removal system conduit, and an expandable node comprising a plurality of abrading strands and operably connected to the intervertebral tissue removal system conduit so as to receive the segmented expansion media therein, the expandable node expandable from a first condition whereat the plurality of abrading strands define at least one opening having a first maximum diameter, to an expanded condition whereat the at least one opening has a second maximum diameter larger than the first maximum diameter, wherein the second maximum diameter is less than a minimum diameter of the segmented expansion media, such that insertion of the segmented expansion media through the intervertebral tissue removal system conduit and into the expandable node causes the expandable node to expand from the first condition to the expanded condition. 
     In one or more embodiments, each of the plurality of abrading strands define a generally rectangular cross-section. 
     In one or more embodiments each of the plurality of abrading strands define a generally triangular cross-section. 
     In one or more embodiments the plurality of abrading strands are formed in a net-like pattern. 
     In one or more embodiments the plurality of abrading strands are woven into the net-like pattern. 
     In one or more embodiments the net-like pattern includes at least one junction of at least two of the plurality of abrading strands, and each of the at least two of the plurality of abrading strands is adhered to the other of the at least two of the plurality of abrading strands at the at least one junction. 
     In one or more embodiments a system includes a ribbing member positioned radially outwardly of the plurality of abrading strands when the plurality of abrading strands is in the first condition, the ribbing member defining a plurality of openings through which portions of the plurality of abrading strands extend when the plurality of abrading strands is in the expanded condition. 
     In one or more embodiments the plurality of abrading strands are fixedly attached to the ribbing member. 
     In one or more embodiments the expandable node includes a first end portion operably connected to the intervertebral tissue removal system conduit, and a second end portion operably connected to a proximal portion of a tip member. 
     In one or more embodiments the tip member includes a plurality of cutting edges extending axially from a distal portion of the tip member to the proximal portion of the tip member. 
     In one or more embodiments the tip member includes at least one aspiration supply orifice in fluid communication with an aspiration supply conduit extending within the intervertebral tissue removal system conduit. 
     In one or more embodiments a method of removing intervertebral tissue includes inserting at least one abrading member for abrading tissue into an area to be cleared, an intervertebral tissue removal system conduit, inserting a segmented expansion media through an intervertebral tissue removal system conduit into an expandable node including a plurality of abrading strands, forcing the segmented expansion media against the plurality of abrading strands, thereby expanding the expandable node from a first condition whereat the plurality of abrading strands define at least one opening having a first maximum diameter, to an expanded condition whereat the at least one opening has a second maximum diameter larger than the first maximum diameter, wherein the second maximum diameter is less than a minimum diameter of the segmented expansion media. The method further includes abrading tissue in the area to be cleared with the expanded expandable node, and removing the abraded tissue from the area to be cleared. 
     In one or more embodiments abrading tissue in the area to be cleared with the expanded expandable node includes abrading tissue in the area to be cleared with corner portions of the plurality of abrading strands. 
     In one or more embodiments forcing the segmented expansion media against the plurality of abrading strands includes forcing the segmented expansion media against a plurality of abrading strands formed in a net-like pattern. 
     In one or more embodiments forcing the segmented expansion media against the plurality of abrading strands includes forcing the segmented expansion media against a plurality of abrading strands formed in a net-like pattern including at least one junction of at least two of the plurality of abrading strands, wherein each of the at least two of the plurality of abrading strands is adhered to the other of the at least two of the plurality of abrading strands at the at least one junction. 
     In one or more embodiments forcing the segmented expansion media against the plurality of abrading strands includes forcing portions of the plurality of abrading strands radially outwardly through a plurality of openings in a ribbing member. 
     In one or more embodiments inserting at least one abrading member includes inserting a tip member having a proximal portion operably connected to an end portion of the expandable node into the area to be cleared. 
     In one or more embodiments a method includes abrading tissue in the area to be cleared with a plurality of cutting edges extending axially from a distal portion of the tip member to the proximal portion of the tip member. 
     In one or more embodiments a method includes aspirating the area to be cleared with aspiration fluid provided through at least one aspiration supply orifice in the tip member which is in fluid communication with an aspiration supply conduit extending within the intervertebral tissue removal system conduit. 
     The above-described features and advantages, as well as others, will become more readily apparent to those of ordinary skill in the art by reference to the following detailed description and accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  shows a schematic view of an intervertebral tissue removal system with a single abrading member on a node of an expandable member wherein aspiration fluid is fed into an expansion media conduit through an inlet on a cannula to provide expansion media incorporating principles of the present invention; 
         FIG. 2  shows a cross-sectional view of the flow path of aspiration fluid through the cannula, conduit and expandable member of  FIG. 1 ; 
         FIG. 3  shows a partial cross-sectional view of the cannula of  FIG. 1  after puncturing a disc with the cannula in preparation for forming a cavity within the disc; 
         FIG. 4  shows a partial cross-sectional view of the cannula of  FIG. 3  with the conduit and expandable member inserted within the cannula while the expandable member is in a deflated condition; 
         FIG. 5  shows a partial cross-sectional view of the expandable member of  FIG. 1  indicating the flow path of expansion media through the expandable member when the pressure required to force the same amount of expansion media introduced into the expandable member out of the expandable member through an orifice is less than the pressure required to expand the node and the abrading member is in a first position; 
         FIG. 6  shows a partial cross-sectional view of the expandable member of  FIG. 1  indicating the flow path of expansion media through the expandable member when the pressure required to force the same amount of expansion media introduced into the expandable member out of the expandable member through an orifice is greater than the pressure required to expand the node such that the node flexes forcing the abrading member into a second position; 
         FIG. 7  shows a partial cross-sectional view of the expandable member of  FIG. 1  indicating the flow path of expansion media through the expandable member when the pressure required to force the same amount of expansion media introduced into the expandable member out of the expandable member through an orifice is greater than the pressure required to expand the node to the condition shown in  FIG. 6  such that the node further flexes forcing the abrading member into a third position; 
         FIG. 8  shows a schematic view of an alternative intervertebral tissue removal system with a number of abrading members on a node of an expandable member wherein aspiration fluid is fed into an expansion media conduit through an inlet on a cannula to provide expansion media incorporating principles of the present invention; 
         FIG. 9  shows a cross-sectional view of the expandable member and abrading members of  FIG. 8  in a deflated condition; 
         FIG. 10  shows a cross-sectional view of the expandable member and abrading members of  FIG. 8  in an expanded condition wherein tissue may be loosened to form a cavity having a diameter greater than the diameter of the cannula of  FIG. 8 ; 
         FIG. 11  shows a partial cross-sectional view of an alternative intervertebral tissue removal system wherein an aspiration fluid conduit and drainage conduit are provided to a cavity through a cannula separate from the expansion media conduit incorporating principles of the present invention; 
         FIG. 12  shows a partial plan view of an alternative embodiment of an expandable member in an unexpanded condition which includes multiple nodes, each node operably connected to two abrading members incorporating principles of the present invention; 
         FIG. 13  shows a partial plan view of the expandable member of  FIG. 12  in an expanded condition such that the abrading members are positioned to loosen tissue on two sides of the expandable member; 
         FIG. 14  shows a partial side plan view of an alternative embodiment of an expandable member in an expanded condition which includes a single node configured to provide a conical cavity that is enlarged away from the point of entry of the expandable member into a tissue space when used with an abrading member incorporating principles of the present invention; 
         FIG. 15  shows a front plan view of the expandable member of  FIG. 14 ; 
         FIG. 16  shows a partial side plan view of an alternative embodiment of an expandable member in an expanded condition which includes a single node configured to provide a conical cavity that is enlarged near the point of entry of the expandable member into a tissue space when used with an abrading member incorporating principles of the present invention; 
         FIG. 17  shows a front plan view of the expandable member of  FIG. 16 ; 
         FIG. 18  shows a partial side plan view of an alternative embodiment of an expandable member in an expanded condition which includes a two nodes which are symmetrical to each other and symmetrical about the longitudinal axis of the expandable member incorporating principles of the present invention; 
         FIG. 19  shows a front plan view of the expandable member of  FIG. 18 ; 
         FIG. 20  shows a partial side plan view of an alternative embodiment of an expandable member in an expanded condition which includes a two nodes which are symmetrical to each other and symmetrical along the longitudinal axis of the expandable member incorporating principles of the present invention; 
         FIG. 21  shows a front plan view of the expandable member of  FIG. 20 ; 
         FIG. 22  shows a side plan view of the expandable member of  FIG. 20  with abrading members coupled to the nodes incorporating principles of the present invention; 
         FIG. 23  shows a schematic view of an intervertebral tissue removal system with multiple abrading members on multiple nodes of an expandable member wherein expansion media is provided to each of the nodes from a first and a second syringe, respectively, and two drainage orifices are located between the nodes to provide for drainage of separately provided aspiration fluid and loosened tissue incorporating principles of the present invention; 
         FIG. 24  shows a partial plan view of the expandable member of  FIG. 23  with the nodes expanded to loosen tissue between the two sets of abrading members; 
         FIG. 25  shows a partial plan view of an alternative expandable member with abrading members configured on two nodes to loosen tissue outwardly of the abrading members incorporating principles of the present invention; 
         FIG. 26  shows a schematic view of an intervertebral tissue removal system that is similar to the intervertebral tissue removal system of  FIG. 23 , but with a different configuration of abrading members to provide cavities of different shapes incorporating principles of the present invention; 
         FIG. 27  shows a partial plan view of the expandable member of  FIG. 26  with the node farthest away from the entry point of the expandable member into a tissue space expanded to loosen tissue to form a conical cavity that is enlarged away from the point of entry of the expandable member into a tissue space; 
         FIG. 28  shows a partial plan view of the expandable member of  FIG. 26  with both nodes expanded to loosen tissue to form a cylindrical cavity; 
         FIG. 29  shows a partial plan view of the expandable member of  FIG. 26  with the node nearest the entry point of the expandable member into a tissue space expanded to loosen tissue to form a conical cavity that is enlarged closer to the point of entry of the expandable member into a tissue space; 
         FIG. 30  shows an expansion media in the form of elongated segments that are inter connected incorporating principles of the present invention; 
         FIG. 31  shows a partial schematic view of an intervertebral tissue removal system which can be used with the segmented expansion media of  FIG. 30  incorporating principles of the present invention; 
         FIG. 32  shows a partial cross-sectional view of the system of  FIG. 31 ; 
         FIG. 33  is a partial cross-sectional view of the system of  FIG. 31  with segmented expansion media within the expandable member prior to deformation of the expandable member; 
         FIG. 34  a partial cross-sectional view of the system of  FIG. 31  with segmented expansion media expanding the node of the expandable member; 
         FIG. 35  shows a cross-sectional view of the system of  FIG. 31  after the non-resilient node has been deformed with segmented media and after the segmented media has been withdrawn; 
         FIG. 36  shows a cross-sectional view of the system of  FIG. 35  with the deformed node partially compressed as the expandable member is pulled into the cannula; 
         FIG. 37  shows a partial plan view of an alternative expandable member with a node that includes a number of strands wherein the strands provide the abrading members in accordance with principles of the present invention; 
         FIG. 38  shows a partial perspective view of the node of the expandable member of  FIG. 37  in a fully expanded condition with openings between the strands; 
         FIG. 39  shows a partial plan view of the node of the expandable member of  FIG. 37  in a fully expanded condition with openings between the strands; 
         FIG. 40  shows a partial plan view of the node of the expandable member of  FIG. 37  expanded by a generally spherical expansion media which is sized to not fit through the openings between the strands; 
         FIG. 41  shows a plan view of an alternative expandable member with a node that includes a number of strands and support ribbing to divide the node into a plurality of shaped nodes which can be used without a cannula in accordance with principles of the present invention; 
         FIG. 42  shows a plan view of the expandable member of  FIG. 41  in an expanded condition; 
         FIG. 43  shows a plan view of an alternative expandable member with a guide rod that extends within a flexible expansion conduit in accordance with principles of the present invention; and 
         FIG. 44  shows a plan view of the expandable member of  FIG. 43  with the guide rod bent and the node in an expanded condition. 
     
    
    
     DETAILED DESCRIPTION 
       FIG. 1  depicts an intervertebral tissue removal system  100  which includes a fluid reservoir  102 , a cannula  104  and an expandable member  106 . The fluid reservoir  102  is in fluid connection with the cannula  104  through a tube  108  which is connected to a fluid inlet  110 . In this embodiment, the fluid reservoir  102  is configured to provide a liquid in the form of saline solution under pressure to the fluid inlet  110 . The fluid may be pressurized in a number of acceptable ways such as using a gas to pressurize the fluid reservoir  102  or a pump that takes suction from the fluid reservoir  102 . In alternative embodiments, the fluid may be in the form of a gas. In the embodiment of  FIG. 1 , however, the fluid is preferably a liquid. 
     An outlet port  112  is located on the cannula  104 . The outlet port  112  is in fluid connection with a drain  114  through a tube  116 . In alternative embodiments, the drain  114  may be replaced with a vacuum collection system so as to provide a suction source for the cannula  104  through the outlet port  112 . 
     The expandable member  106  is connected to a conduit  118  which extends into an internal bore  120  of the cannula  104  as best seen in  FIG. 2 . The expandable member  106  may be formed integrally with the conduit  118 . Alternatively, the expandable member  106  may be removably coupled to the conduit  118  to allow for the use of different expandable members with the intervertebral tissue removal system  100 . 
     Continuing with  FIG. 2 , the conduit  118  is in fluid connection with the fluid inlet  110  through an inlet port  122 . A coupling section  124  couples the conduit  118  to a motor section  126 . The motor section  126  provides motive force which is passed to the expandable member  106  through the conduit  118  and the coupling section  124 . The motive force may be translational, rotational, reciprocating or oscillatory. Additionally, the motive force may be provided by motors of various types or even manually. 
     Regardless of the type of motion desired, the interface between the source of the motive force and the other components of the system  100 , such as the conduit  118  and the cannula  104 , may be designed to account for relative motion between the various components as is known to those of ordinary skill in the appropriate art. By way of example, the motor  124  in this embodiment causes the conduit  118  to reciprocate within the cannula  104 . Accordingly, in addition to components such as bearings (not shown) and seals (not shown), the inlet port  122  is elongated to provide for fluid connection with the fluid inlet  110  as the conduit  118  reciprocates. Alternatively, the fluid may be provided directly to the conduit  118  without passing through the wall of the cannula  104 . 
     The expandable member  106  includes a housing  128  with a node  130  and an orifice  132 . The node  130  is sealingly attached to the housing  128  about the periphery of the node  130 . The node  130  is further made of a material which is more compliant than the material used to form the housing  128 . An abrading member  134  is attached to the housing  128  and extends along a portion of the node  130 . A hinge  136  is provided in the abrading member  134 . 
     Operation of the intervertebral tissue removal system  100  is described with initial reference to  FIG. 3 . After the surgical site is prepared in an acceptable manner, the cannula  104  is used to puncture a disc  138 . The conduit  118  and expandable member  106  are then inserted into the cannula  104  with the expandable member in an unexpanded condition as shown in  FIG. 4 . The insertion of the conduit  118  into the cannula  104  may be guided. For example, a slot and key arrangement may be used to ensure that the conduit  118  is properly aligned within the cannula  104 . Once the conduit  118  has been inserted to the appropriate depth, the conduit  118  is rotated into the position shown in  FIG. 2  such that the inlet port  122  is in fluid connection with the fluid inlet  110 . 
     The desired fluid supply is then connected to the fluid inlet port  110  and the outlet port  112  is directed to a drain or a vacuum device, resulting in the configuration of  FIG. 1 . Specifically, the tube  108  is used to connect the fluid reservoir  102  to the fluid inlet  110  and the tube  116  is used to connect the outlet port  112  to the drain  114 . Of course, the foregoing steps may be accomplished in a number of alternative variations. For example, the fluid supply and drain tubes may be connected prior to insertion of the conduit  118  within the cannula  104 . Additionally, the conduit  118  may be inserted within the cannula  104  prior to puncturing the disc  138 . This may be particularly desirable when the expandable member is in a bore or drill configuration. Thus, the expandable member may be used in puncturing the disc. 
     Once the expandable member  106  is positioned in the desired manner within the disc  138 , pressurized fluid is introduced into the conduit  118 . This may be accomplished by pressurizing the fluid reservoir  102  such that pressurized fluid is directed through the tube  108  and the fluid inlet  110  into the conduit  118  by way of the inlet port  122 . This flow is indicated by the single arrows in  FIG. 2 . As the fluid flows into the expandable member  106 , the abrading member  134  is initially in the condition shown in  FIG. 5 . 
     Some of the fluid exits the expandable member  106  through the orifice  132 . The orifice  132  is sized, however, to restrict the flow of fluid out of the expandable member  106 . Accordingly, when pressure is initially applied to the fluid from the fluid reservoir  102 , more fluid flows into the expandable member  106  than is allowed to flow out of the orifice  132 . This results in increased pressure within the expandable member  106 . As the pressure within the expandable member  106  increases, more fluid is forced through the orifice  132 . Thus, by controlling the pressure of the fluid introduced into the conduit  118 , the pressure within the expandable member  106  and thus the amount of fluid exiting the expandable member  106  through the orifice  132  may be controlled. 
     Moreover, because the node  130  is made from a material that is more resilient than the housing  128 , the node  130  may be made to deform or flex by increasing the pressure within the expandable member  106 . Accordingly, as the pressure within the expandable member  106  increases, the node  130  flexes outwardly against the abrading member  134 . The hinge  136  of the abrading member  134  is constructed to bend as the pressure exerted by the node  130  on the abrading member  134  increases. Thus, the abrading member  134  is rotated from the position shown in  FIG. 5  to the position shown in  FIG. 6  as the volume of the expandable member increases. At this higher pressure, more water is forced through the orifice  132  as indicated by the double arrows in  FIG. 6 . 
     Once the abrading member  134  is in the position shown in  FIG. 6 , the abrading member  134  may be used to loosen tissue by moving the expandable member  106  to the right as viewed in  FIG. 6 . As the abrading member  134  scrapes tissue, the loosened tissue is flushed by the fluid exiting the orifice  132  toward the internal bore  120  of the cannula  104 . Accordingly, the loosened tissue is directed out of the disc  138 , down the internal bore  120  to the outlet port  112  as indicated by the double arrows in  FIG. 2 . The fluid and the excised tissue then pass through the tube  116  to the drain  114 . 
     Thus, the expandable member  106  is used to create a cavity within the disc  138  that is larger than the diameter of the cannula  104  which is used to access the disc  138 . The expandable member  106  may be used to create an even larger cavity. By way of example, further increases in the pressure of the fluid within the expandable member  106  results in additional flexing of the node  130  outwardly against the abrading member  134  as the volume of the expandable member further increases. Thus, the abrading member  134  is further rotated from the position shown in  FIG. 6  to the position shown in  FIG. 7 . At this higher pressure, more water is forced through the orifice  132  as indicated by the triple arrows in  FIG. 7 . 
     Once the abrading member  134  is in the position shown in  FIG. 7 , the abrading member  134  may be used to loosen additional tissue by moving the expandable member  106  to the right as viewed in  FIG. 7 . As the abrading member  134  loosens additional tissue, the additional tissue is flushed by the fluid exiting the orifice  132  toward the internal bore  120  of the cannula  104 . Accordingly, the additional tissue is directed out of the disc  138 , down the internal bore  120  to the outlet port  112  as indicated by the double arrows in  FIG. 2 . The fluid and the additional tissue then pass through the tube  116  to the drain  114 . 
     Accordingly, the expandable member  106  may be controlled to provide cavities having a number of different sizes merely by controlling the pressure within the expandable member  106 . In one embodiment, one or more of the expandable member  106 , the abrading member  134  and the conduit  118  may be constructed with a radiopaque material to enhance the detection of the position of the tissue removal system components. This allows for more precise determination of tissue clearance. 
     Once the desired tissue has been removed, the pressure applied to the fluid from the fluid reservoir  102  is reduced. Accordingly, less fluid flows into the expandable member  106  which results in decreased pressure within the expandable member  106 . As the pressure within the expandable member  106  decreases, less fluid is forced through the orifice  132 . Additionally, because the material used to construct the node  134  is resilient, as the pressure within the expandable member  106  decreases, the node  130  tends to return toward the condition depicted in  FIG. 5  thereby reducing the volume of the expandable member. Additionally, the hinge  136  may be constructed of a shape retaining material. Thus, as the node  130  moves in a direction away from the abrading member  134 , the hinge  136  provides rotational force to the abrading member  134  such that the abrading member is rotated, for example, from the position shown in  FIG. 6  to the position shown in  FIG. 7 . The expandable member  106  may then be removed from the disc  138  by withdrawing the conduit  118  from the cannula  104 . 
     In an alternative embodiment shown in  FIGS. 8-10 , an intervertebral tissue removal system  140  includes a conduit  142  fluidly connected to an expandable member  144 . A fluid reservoir  146  is connected to the conduit  142  through a tube  148  and abrasive particles  150  are adhered to the expandable member  144 . The conduit  142  and the expandable member  144  are sized such that when the expandable member  144  is in the condition shown in  FIGS. 8 and 9 , the conduit  142  and the expandable member  144  fit within the cannula  104 . In this embodiment, the conduit  142  and the expandable member  144  are not permeable to the fluid within the fluid reservoir  146 . Accordingly, the fluid reservoir  146  is not used to provide aspiration fluid. 
     In operation, as pressurized media is introduced into the expandable member  144 , the abrasive particles  150  are forced outwardly away from the longitudinal axis of the expandable member  144  to the position shown in  FIG. 10 . In this embodiment, the pressure inside of the expandable member  144  is maintained by the fluid reservoir  146  at a constant pressure that is greater than the pressure needed to expand the expandable member  144 . The increased pressure forces the abrasive particles  150  against the tissue surrounding the expandable member  144 . Accordingly, as the expandable member  144  is moved, the abrasive material  150  may be used to loosen tissue completely about the perimeter of the expandable member  144 . Moreover, the increased pressure within the expandable member  144  causes the abrasive particles  150  to be constantly forced against the tissue adjacent to the expandable member  144  even as tissue is loosened. Thus, tissue is constantly being loosened so long as the expandable member  144  is being moved. 
     As set forth above, the fluid within the fluid reservoir  146  is not used to aspirate the cavity formed by the expandable member  144 . Thus, in accordance with one method, the expandable member  144  is deflated and removed periodically to allow for an aspiration fluid to be introduced into the cavity to assist in removal of loosened tissue. This staged aspiration may be performed a number of times during a particular surgery. 
     Alternatively, as shown in  FIG. 11 , a dedicated aspiration tube  152  may be introduced into the cavity through the cannula  104  along with a drain tube  154  to provide for continuous aspiration of the cavity. Specifically, an aspiration fluid is provided through the aspiration tube  152  to the cavity and the aspiration fluid and any loosened tissue is removed through the drain tube  154 . 
     A number of different types of expandable members maybe used in accordance with the present invention. By way of example,  FIG. 12  shows an expandable member  156 . The expandable member  156  is formed and operated in a manner substantially similar to the expandable member  106 . The main differences are that the expandable member  156  includes a number of nodes  158  which are in fluid connection through an inter-nodal conduit (not shown), and each of the nodes  158  is operably connected to two abrading members  160 . Thus, when the nodes  158  are expanded as shown in  FIG. 13 , the abrading members  160  may be used to loosen tissue on opposite sides of the expandable member  156 . 
       FIGS. 14-21  depict some alternative embodiments of expandable members in an expanded condition. The expandable member  162  shown in  FIGS. 14 and 15  includes a node  164  which is symmetrical about the longitudinal axis  166  of the expandable member  162  but which is not symmetrical along the longitudinal axis  166 . With reference to  FIGS. 16 and 17 , the expandable member  168  includes a node  170  which is symmetrical about the longitudinal axis  172  of the expandable member  168  but which is not symmetrical along the longitudinal axis  172 . 
     The expandable member  174  shown in  FIGS. 18 and 19  includes a node  176  and a node  178  which are symmetrical both to each other and about the longitudinal axis  180  of the expandable member  174 . With reference to  FIGS. 20 and 21 , the expandable member  182  includes a node  184  and a node  186  which are symmetrical to each other but which are not symmetrical along the longitudinal axis  188  of the expandable member  182 . The nodes  184  and  186  thus define flutes extending along the expandable member  182 . 
     Various types of abrading members may be combined with the expandable members described above as well as other expandable members to provide a variety of abrading capabilities. By way of example,  FIG. 22  shows the expandable member  182  of  FIG. 17  with an abrading member  190  on the node  184  and an abrading member  192  on the node  186 . In the embodiment of  FIG. 22 , the abrading members  190  and  192  are blades having cutting edges  194  and  196  that extend along a substantial portion of the length of the abrading members  190  and  192 , respectively. Alternatively, the abrading members may comprise abrasive particles adhered to the nodes  184  and  186 . Additionally, the abrading members  190  and  192  may be serrated, providing a number of chisel like projections along the nodes  184  and  186 . 
     Moreover, abrading members may be coupled to expandable members in a variety of ways to provide different abrading characteristics. By way of example, the intervertebral tissue removal system  200  shown in  FIG. 23  includes two fluid reservoirs  202  and  204 , a cannula  206  and an expandable member  208 . The expandable member  208  includes nodes  210  and  212 . The fluid reservoirs  202  and  204 , which in this embodiment are syringes, are in fluid communication with the nodes  210  and  212 , respectively, through tubes  214  and  216 . Two valves  218  and  220  are provided along the tubes  214  and  216  which are conduits providing expansion media to the nodes  210  and  212 . Each of the nodes  210  and  212  is configured to control a set of abrading members  222  and  224 , respectively. 
     The intervertebral tissue removal system  200  further includes an aspiration fluid supply  226 . An aspiration orifice  228  and an aspiration orifice  230  are in fluid connection through an aspiration conduit  232  with a collection container  234 . 
     In operation, either of the nodes  210  and  212  may be expanded or both may be expanded, depending upon the cavity to be formed. For purposes of the present example, both nodes  210  and  212  are to be filled. Accordingly, after the expandable member  208  is positioned within a space to be abraded, the valves  218  and  220  are placed in the open position. The syringes  202  and  204  are then manipulated to force fluid from syringes  202  and  204  to the nodes  210  and  212 , respectively, through the tubes  214  and  216 , respectively. When the nodes  210  and  212  have been expanded such that the abrading members  222  and  224  are at the desired orientation, the valves  218  and  220  are placed in the shut position to maintain the abrading members  222  and  224  at the desired orientation. 
     Accordingly, when the nodes  210  and  212  are expanded, the abrading members  222  and  224  face each other. Thus, as the expandable member  208  moves to the right as viewed in  FIG. 24 , the set of abrading members  222  will loosen tissue contacting the abrading members  222  while the set of abrading members  224  will not loosen tissue contacting the abrading members  224 . As the expandable member  208  moves to the left as viewed in  FIG. 24 , however, the set of abrading members  224  will loosen tissue contacting the abrading members  224  while the set of abrading members  222  will not loosen tissue contacting the abrading members  222 . Thus, a cavity may be formed in the area between two abrading members using the intervertebral tissue removal system  200 . Advantageously, the aspiration orifices  228  and  230  are located between the abrading members  222  and  224 . Thus, the movement of the abrading members  222  and  224  direct loosened tissue toward the aspiration orifices  228  and  230 . 
     Alternatively, the intervertebral tissue removal system shown in  FIGS. 12 and 13  may be used to form a cavity which extends in a leftward direction from the abrading member  160 . In yet a further alternative embodiment, a cavity may be formed which extends in both the leftward and rightward directions. With reference to  FIG. 25 , the expandable member  236  includes nodes  238  and  240  which are configured to control a set of abrading members  242  and  244 , respectively. When the nodes  238  and  240  are expanded as shown in  FIG. 25 , a cavity may be formed which extends outwardly in both the leftward and rightward directions from the abrading members  242  and  244 . Therefore, the configuration of the abrading members can be selected to provide various abrading capabilities. 
     In a further embodiment shown in  FIG. 26 , a single intervertebral tissue removal system  250  provides the ability to form cavities of different shapes. The intervertebral tissue removal system  250  includes two fluid reservoirs  252  and  254 , a cannula  256  and an expandable member  258 . The expandable member  258  includes nodes  260  and  262 . The fluid reservoirs  252  and  254  are in fluid communication with the nodes  260  and  262 , respectively, through tubes  264  and  266 . Two valves  268  and  270  are provided along the tubes  264  and  266 . Abrading members  272  are attached to each of the nodes  260  and  262 . 
     Operation of the intervertebral tissue removal system  250  is substantially the same as operation of the intervertebral tissue removal system  200 . The main difference is the shape of a cavity formed by selective filling of the nodes  260  and  262 . Filling only node  260  provides the configuration shown in  FIG. 27  which may be used to form a conical cavity which is enlarged in the direction away from the entry point of the node  260  into the tissue. The additional inflation of the node  262  results in the configuration shown in  FIG. 28  which may be used to form a cylindrical cavity. Finally, filling only the node  262  provides the configuration shown in  FIG. 29  which may be used to form a conical cavity which is oriented opposite to the conical cavity of  FIG. 27 . 
     In an alternative embodiment, segmented expansion media  276  shown in  FIG. 30  is used to expand an expandable member. The segmented expansion media  276  includes a number of elongated segments  278  which are linked by connectors  280 . Alternatively, the segments may be interconnected by a single connector which extends through each of the segments with the segments allowed to slide along the connector. 
     Operation of a system incorporating the elongated segmented expansion media  276  is explained with reference to  FIGS. 31-36 . Expandable member  282  is sized to be inserted through a cannula  284  and includes a node  286 . An abrading member (not shown) may be adhered to the node  286 . Initially, the expandable member  282  is inserted through the cannula  284  in a deflated condition. A tool (not shown) is then used to insert the elongated segments  278  into the expandable member  282  until the node  286  is full as shown in  FIG. 33 . The node  286  is formed from a deformable material. Thus, continued insertion of the segmented expansion media  276  into the node  286  as shown in  FIG. 34  causes the node  286  to be expanded to an enlarged condition. 
     After the expandable member  282  has been manipulated to form a cavity, the segmented expansion media  276  is removed. The material used to form the node  286  in this embodiment is not resilient. Thus, as shown in  FIG. 35 , the node  286  remains in an expanded condition after the segmented expansion media  276  has been removed. Without the internal support provided by the segmented expansion media  276 , however, the node  286  may be collapsed by forcing the node  286  against the lip of the cannula  284  as shown in  FIG. 36 . 
       FIG. 37  shows an alternative expandable member  290  that includes a node  292  including a plurality of strands  294 . With reference to  FIGS. 38 and 39 , which show an expanded portion of the expandable member  290 , the node  292  is formed in a net-like pattern. Thus, the strands  294  define a number of openings  296 . The openings  296  may be formed in a number of ways. For example, portions of a metal plate may be removed, leaving a pattern of openings defined by the remaining metal. Alternatively, individual wires may be woven into a basket and some or all of the wire junctions may be soldered. Moreover, the openings may be configured to form shapes other than rectangular shapes. The salient characteristic in this embodiment is that the openings  296 , even when the node  292  is fully expanded, must be smaller than at least some of the media used to expand the expandable member  290 . 
     By way of example,  FIG. 40  depicts a portion of the node  292  which has been expanded using a segmented expansion media  298 . The segmented expansion media  298  is generally spherical. The diameter of the individual segments of the segmented expansion media  298  is selected such that the segmented expansion media  298  cannot pass through the openings  296 . Thus, as the segmented expansion media  298  is forced into the expandable member  290 , the node  292  is forced into an expanded condition. In this embodiment, the segmented expansion media  298  is not inter-connected. 
     The use of segmented expansion media further allows for the passage of fluid through the same conduit used to introduce the segmented media. As shown most clearly in  FIG. 40 , even when the segmented expansion media  298  is tightly packed, interstitial spaces  300  provide a pathway for fluid through the segmented expansion media  298 . When the interstitial spaces  300  are significantly larger than the loosened pieces of tissue formed by abrading a cavity, the interstitial spaces  300  may be used to drain aspiration fluid and loosened tissue. In one such embodiment, the curvature of the segmented media is selected such that the segmented media cannot extend outside of the cutting envelope defined by the outer surface of the strands  294 . 
     As the pieces of loosened tissue approach the size of the interstitial spaces  300 , however, the segmented expansion media  298  may function as a filter. Thus, as tissue is abraded, the interstitial spaces  300  may clog with the loosened tissue. When the interstitial spaces  300  clog with the loosened tissue, the expandable member  290  may be removed and the interstitial spaces  300  flushed to remove the loosened tissue. Alternatively, the interstitial spaces  300  may be used as conduits to provide aspirating fluid to the tissue cavity, with drainage of the aspiration fluid and loosened tissue provided through a separate conduit. 
     In the embodiment of  FIG. 38 , the strands  294  of the node  292  have a generally rectangular cross-section. Thus, the corners of the strands  94  function as abrading members that loosen tissue as the expandable member  290  is manipulated within, for example, a disc. In alternative embodiments, the strands may be other shapes such as circular or triangular (e.g. wedge wire). Additionally, the orientation of the strands may be modified to present different cutting angles to the tissue to be loosened as the expandable member is manipulated to clear a cavity. 
     Additionally, the node may be configured to provide different shapes. For example, the expandable tool  302  shown in  FIG. 41  includes a node  304  with strands  306 . Ribbing  308  is provided about the strands  306 . The strands  306  are coupled to a conduit  310  at one end and to a tip  312  at the other end. The ribbing  308  is constructed of a material that is more rigid than the strands  306 . Thus, when the node  304  is expanded, the ribbing  308  constrains the strands  306  resulting in the shape shown in  FIG. 42 . The ribbing  308  thus functions to divide the node  304  into a plurality of nodes of different shapes. In this embodiment, the strands  306  are not fixedly attached to the ribbing  308 . In alternative embodiments, the strands may be coupled to the ribbing. In further alternative embodiments, the ribbing is provided integrally with the conduit and the node is attached to the outer surface of the ribbing. 
     The tip  312  in this embodiment is further configured to provide access to an area in which tissue is to be loosened. The tip  312  includes a plurality of cutting edges  314  which define flutes  316 . The cutting edges  314  loosen tissue when the expandable tool  302  is rotated so as to allow the forward movement of the expandable tool  302  into the area in which tissue is to be removed. The tip  312  further includes aspiration supply orifices  318 . The aspiration supply orifices  318  provide aspiration fluid from an aspiration fluid supply conduit (not shown) within the conduit  310 . The aspiration fluid and loosened tissue may then removed through the openings between the strands  306  and the interstitial spaces between the expansion media in a manner similar to that discussed above with respect to  FIG. 40 . 
     In an alternative embodiment shown in  FIG. 43 , an intervertebral tissue removal system  320  includes a cannula  322 , a conduit  324  and an expandable member  326 . The expandable member  326  includes a node  328  which is operably coupled to an abrading member  330 . A guide rod  332  is located within the inner bore  334  of the conduit  324  and an orifice  336  extends from the inner bore  334  to the outer surface of the conduit  324 . The intervertebral tissue removal system  320  also includes a collection tube  336 . 
     The conduit  324  in this embodiment is made of a flexible material. Accordingly, the conduit  324  may be bent or twisted. The conduit  324  is not, however, radially flexible. Thus, as pressure in the inner bore  334  increased, the volume of the inner bore  334  does not increase appreciably. Accordingly, the guide rod  332  provides the structural rigidity for the conduit  324 . 
     The guide rod  332  in this embodiment is constructed of an inherent memory metal such as nitinol, commercially available from Memry Corporation of Bethel, Conn. Inherent memory metals are imbued with a “memory” such that the particular shape of a device made from the metal can be “programmed” into the metal so that when a particular external condition is present, the device alters its shape to the programmed shape. The external condition may be thermal or electrical, such as a magnetic field. In this embodiment, the guide rod  332  is configured to maintain a substantially straight configuration at room temperature. When exposed to a higher temperature, however, the guide rod  332  changes to the shape shown in  FIG. 44 . 
     The intervertebral tissue removal system  320  is operated much in the same manner as the intervertebral tissue removal system  100  of  FIG. 1 . The main difference is that in the embodiment of  FIGS. 43 and 44 , the saline solution which is used to expand the node  328  is provided at a temperature which also causes the guide rod  332  to curve into the shape shown in  FIG. 44 . Of course, by modifying the temperature of the saline solution, a greater or lesser amount of curvature may be achieved. 
     Alternatively, the guide rod  332  may be configured to change shape when exposed to body temperature. In further alternative embodiments, the shape of the guide rod may be controlled by a magnetic field or the guide rod may be formed as a bimetallic rod comprising metals with different thermal expansion characteristics. In yet another embodiment, a guide rod may be made from a flexible, shape retaining material which formed to present an angled shape in a relaxed condition. In this embodiment, the guide rod is deformed for insertion within a cannula. As the guide rod exits the cannula, the guide rod attempts to return to the angled shape, thereby providing pressure against tissue, allowing an abrasive member to then loosen the tissue. In any event, once the abrasive member  330  is in the desired position as a function of both the expansion of the node  328  as well as the shape of the guide rod  332 , tissue may be loosened to create the desired cavity. 
     Depending upon the particular configuration, intervertebral tissue removal system components may be made from a variety of materials in addition to the materials identified above. For example, the abrading member may be constructed from stainless steel, titanium, polymers, polyesters, or polyurethanes. The expansion device may be made from rigid or compliant materials including stainless steel, titanium, memory metals, silicones, polyesters, polyurethanes, poly ether ether ketone (PEEK) or polypropylenes. Additionally, the materials may be used to deliver chemicals to the area in which a cavity is to be formed. By way of example, but not of limitation, any of the various components may be imbedded or coated with a medication for relieving pain or with an enzyme for dissolving tissue. 
     While the present invention has been illustrated by the description of exemplary processes and system components, and while the various processes and components have been described in considerable detail, applicant does not intend to restrict or in any way limit the scope of the appended claims to such detail. Additional advantages and modifications will also readily appear to those ordinarily skilled in the art. The invention in its broadest aspects is therefore not limited to the specific details, implementations, or illustrative examples shown and described. Accordingly, departures may be made from such details without departing from the spirit or scope of applicant&#39;s general inventive concept.