Abstract:
A method and apparatus for filling a cavity in a patient&#39;s body with a material are provided. The apparatus can include a flexible tube, a barrel and a plunger. The flexible tube has a first end, a second end, and a lumen extending from the first end to the second end and operable to hold a material for conveyance through the first end into a cavity. The barrel is in fluid communication with the second end of the flexible tube and includes a lumen configured to receive material for delivery into the flexible tube. The plunger is configured to advance material through the lumen in the barrel and into the flexible tube. In one implememtation, there is substantially a one to one ratio of advancement of the plunger to a volume of material advanced from the rigid first end of the flexible tube.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS  
       [0001]     This application is a continuation-in-part of, and claims priority to, pending U.S. application Ser. No. 10/617,976, filed on Jul. 11, 2003, which is a divisional application of U.S. application Ser. No. 09/804,107, filed Mar. 12, 2001, now U.S. Pat. No. 6,613,054 issued Sep. 2, 2003, to Scribner, et al, which is a divisional application of U.S. application Ser. No. 09/134,323, filed Aug. 14, 1998, now U.S. Pat. No. 6,241,734 issued Jun. 5, 2001, Scribner et al. Priority is claimed to the above referenced applications and the contents of the above referenced applications are hereby incorporated by reference herein in their entirety. 
     
    
     TECHNICAL FIELD  
       [0002]     This invention relates to medical methods and apparatus.  
       BACKGROUND  
       [0003]     A vertebral compression fracture (VCF) can occur when a vertebral body is too weak to support a load and the spine collapses. A VCF may cause the spine to shorten, leading to spinal deformities and altering spinal biomechanics. Collapse may result in thoracic and lumbar spinal deformity and is often seen in elderly people. The spinal deformity, commonly known as a Dowager&#39;s Hump, is also referred to as kyphosis. Several causes can lead to a VCF, including osteoporosis, cancer or a traumatic incident, such as a fall or car accident.  
         [0004]     A treatment for a VCF can involve injecting a material into vertebra, either at low or high pressure. Optionally, a surgical balloon can first be inserted into a vertebra and expanded to restore a collapsed vertebra to its original shape. A material can then be inserted into the restored vertebra, which, upon hardening, can maintain the original shape of the vertebra. The technique of inserting a material into a cavity, such as a collapsed vertebra, can also be used to treat other medical conditions, for example, in knee or hand joints.  
       SUMMARY  
       [0005]     This invention relates to a method and apparatus for filling a cavity in a patient&#39;s body with a material. In general, in one aspect, the invention features an apparatus including a flexible tube, a barrel and a plunger. The flexible tube has a rigid first end, a second end, and a lumen extending from the first end to the second end and operable to hold a material for conveyance through the rigid first end into a cavity. The barrel is in fluid communication with the second end of the flexible tube and includes a lumen configured to receive material for delivery into the flexible tube. The plunger is configured to advance material through the lumen in the barrel and into the flexible tube. There is substantially a one to one ratio of advancement of the plunger to a volume of material advanced from the rigid first end of the flexible tube.  
         [0006]     In general, in another aspect, the invention features an apparatus including a flexible tube, a barrel and a plunger. The flexible tube has a rigid first end, a second end, and a lumen extending from the first end to the second end and operable to hold a material for conveyance through the rigid first end and into a cavity. The barrel is in fluid communication with the second end of the flexible tube and includes a lumen configured to receive material for delivery into the flexible tube. The barrel&#39;s lumen has a diameter substantially the same as a diameter of the flexible tube&#39;s lumen. The plunger is configured to advance material through the lumen in the barrel and into the flexible tube.  
         [0007]     In general, in another aspect, the invention features an apparatus including a flexible tube, a barrel and a plunger. The flexible tube has a first end and a second end, and a lumen extending from the first end to the second end and operable to hold a material for conveyance through the first end. The barrel is in fluid communication with the second end of the flexible tube and includes a lumen configured to receive material for delivery into the flexible tube. The plunger is configured to advance material through the lumen in the barrel and into the flexible tube.  
         [0008]     In general, in another aspect, the invention features an apparatus including a flexible tube, a barrel, a cartridge and a plunger. The flexible tube has a rigid first end, a second end, and a lumen extending from the first end to the second end and operable to hold a material for conveyance through the rigid first end into a cavity. The barrel is in fluid communication with the second end of the flexible tube and includes a lumen configured to receive a cartridge pre-loaded with material for delivery into the flexible tube. The cartridge is configured for insertion into the barrel and includes a lumen configured to receive material for delivery into the flexible tube. The plunger is configured to advance material through the lumen in the cartridge and into the flexible tube, such that there is substantially a one to one ratio of advancement of the plunger to a volume of material advanced from the rigid first end of the flexible tube.  
         [0009]     Implementations can include one or more of the following features. The apparatus can further include a cannula having a first end configured to receive the first end of the flexible tube and having a second end configured to provide the first end of the flexible tube access to the cavity. The lumen of the flexible tube can be pre-loaded with the material, and the plunger can be operable to advance material through the lumen in the barrel into the flexible tube. The pre-loaded material in the flexible tube is thereby advanced through the lumen and into the cavity.  
         [0010]     The apparatus can further include a connector (e.g., a luer fitting) connecting the flexible tube to the barrel, where the flexible tube is connected to the barrel such that a longitudinal axis of the barrel is at an angle in the range of 0° to 90° to a longitudinal axis of the flexible tube. In one implementation, the angle is substantially 40° to 50°. The barrel can include threads on an end of the lumen and the connector can further include threads configured to mate with the threads on the barrel. An assembly of the flexible tube connected to the barrel can be pre-loaded with the material, where the plunger is operable to advance at least some of the pre-loaded material into the cavity.  
         [0011]     The barrel can further include a plurality of lumens disposed in the barrel and configured to receive material for delivery into the flexible tube. The barrel can be rotatable about a longitudinal axis of the barrel, and each lumen of the plurality of lumens can be preloaded with material. Once a lumen has been emptied into the flexible tube by action of the plunger, the plunger can be withdrawn, the barrel can be rotated and the plunger can engage a next lumen to fill the flexible tube.  
         [0012]     The apparatus can further include a cartridge configured to receive material for delivery into the flexible tube, where the barrel&#39;s lumen is configured to receive the cartridge and to receive the material via the cartridge, and the plunger is configured to advance material through the lumen in the barrel via advancement through the cartridge.  
         [0013]     The apparatus can include a plurality of cartridges configured for insertion into the barrel, each cartridge including a lumen configured to receive material for delivery into the flexible tube. The barrel can further include a plurality of lumens configured to receive a plurality of cartridges. The barrel is rotatable about a longitudinal axis of the barrel and each lumen can be loaded with a cartridge pre-loaded with material, such that once a cartridge has been emptied into the flexible tube, the barrel can be rotated and a next cartridge used to fill the flexible tube.  
         [0014]     Implementations of the invention can realize one or more of the following advantages. The cavity filling assembly can allow an operator of the assembly to perform a cavity filling operation, while keeping the operator&#39;s hands outside of an x-ray field created by an imaging device required to assist the operator in maneuvering the assembly during the operation. For example, in a kyphoplasty procedure to fill a vertebra with bone filling cement, a C-arm imaging device is typically used to provide the operator with instantaneous imaging information necessary for the operator to perform a cavity filling operation. Preferably, the operator is able to manipulate the necessary cavity filling apparatus throughout the kyphoplasty procedure while only minimally exposing, if at all, his or her own body to an x-ray field created by the C-arm imaging device. The cavity filling assembly described herein is configured to allow the operator to keep his or her hands a distance from the C-arm imaging device while performing a cavity filling operation.  
         [0015]     The cavity filling assembly can be configured so as to be positioned during a cavity filling operation such that a material can be advanced through the assembly without interfering with an imaging device also required to perform the operation. For example, in a kyphoplasty procedure, a C-arm imaging device is typically used as discussed above. There can be relatively little clearance between the C-arm imaging device and the patient&#39;s body. The cavity filling assembly includes a nozzle assembly that can be inserted into a cannula that has been inserted into the patient&#39;s body. A barrel attached to the nozzle assembly can be used to receive the cavity-filling material and operate as a handle for the operator. A connector between the nozzle assembly and the barrel can be configured to connect the nozzle assembly to the barrel at a range of different angles. For example, the angle can be selected to accommodate the clearance between an imaging device and a patient&#39;s body, while maintaining a suitable flow path for the material through the cavity filling assembly.  
         [0016]     The cavity filling assembly can be configured to allow all of the cavity filling material necessary for a cavity filling operation to be loaded into the assembly at one time, so that iterative loading procedures are not required during the cavity filling operation. For example, a barrel including multiple chambers is described, where each chamber can be loaded with a cavity filling material, either directly or by inserting a loaded cartridge into the chamber. By providing multiple chambers, the barrel can be loaded at the start of the operation with sufficient material to completely fill the cavity, thereby facilitating the procedure.  
         [0017]     The details of one or more embodiments of the invention are set forth in the accompanying drawings and the description below. Other features, objects, and advantages of the invention will be apparent from the description and drawings, and from the claims. 
     
    
     DESCRIPTION OF DRAWINGS  
       [0018]      FIG. 1A  shows a perspective view of a cavity filling assembly.  
         [0019]      FIG. 1B  shows a perspective view of a nozzle assembly of the cavity filling assembly of  FIG. 1A .  
         [0020]      FIG. 1C  shows a perspective view of a barrel of the cavity filling assembly of FIG  1 A.  
         [0021]      FIG. 2  shows the cavity filling assembly of  FIG. 1A  inserted into a cannula that has been positioned in a patient&#39;s body cavity.  
         [0022]      FIG. 3A  shows a plunging assembly within a cartridge.  
         [0023]      FIG. 3B  shows the plunging assembly and cartridge of  FIG. 3A  inserted within the cavity filling assembly of  FIG. 1A .  
         [0024]      FIG. 4A  shows a side view of a connector for a cavity filling assembly.  
         [0025]      FIG. 4B  shows a perspective view of the connector of  FIG. 4A .  
         [0026]      FIG. 5  shows a front view of a cement mixer.  
         [0027]      FIG. 6  is a flowchart showing a process for filling a cavity with a material using a cavity filling assembly.  
         [0028]      FIG. 7  shows a multi-chambered barrel assembly.  
         [0029]     FIGS.  8 A-C show an alternative implementation of a multi-chambered barrel assembly. 
     
    
       [0030]     Like reference symbols in the various drawings indicate like elements.  
       DETAILED DESCRIPTION  
       [0031]     An apparatus and method is described for injecting a material into a cavity in a patient&#39;s body. For illustrative purposes, the apparatus and method shall be described in the context of injecting a bone filling cement into a vertebra of a patient to treat kyphosis, although the apparatus and methods can be used to treat other conditions.  
         [0032]      FIGS. 1A-1C  show an apparatus that can be used to inject a material into a cavity, such as a vertebra. In the implementation shown, a cavity-filling assembly  100  includes a nozzle assembly  102  and a barrel  104 . Referring to  FIG. 1B , the nozzle assembly  102  is shown and includes a connector  106  attached to a flexible tube  108  terminating in a rigid distal end  110 . Referring to  FIG. 1C , the barrel  104  includes a hollow interior and a fitting  112  configured to mate with the connector  106  of the nozzle assembly  102 .  
         [0033]     Referring to  FIG. 2 , the cavity-filling assembly  100  is shown with the nozzle assembly  102  inserted into a cannula  114 . The cannula  114  has been inserted into the cavity  116  within the patient&#39;s body that is to receive a cavity filling material. For example, the cavity  116  shown is a vertebra, which may or may not have been previously restored to an original shape using a surgical balloon. A small incision in the patient&#39;s back can be used to insert the cannula  114  into the cavity  116 . The nozzle assembly  102  can then be inserted into the cannula  114  to provide the distal end  110  access to the cavity  116 . Examples of cavity filling material include: bone cement (e.g., polymethyl methacrylate (PMMA) cement, ceramics); human bone graft (e.g., autograft, allograft); and synthetic derived bone substitutes (e.g., calcium sulfate, calcium phosphate, hydroxyapatite). Cavity filling materials can be supplemented with other therapeutic substances, e.g., antibiotics, growth factors and chemotherapeutic agents.  
         [0034]     Referring to  FIGS. 3A and 3B , an implementation of a plunging assembly  120  that can be used to advance the material through the barrel  104  and nozzle assembly  102  and into the cavity  116  is shown. The plunging assembly  120  includes a cartridge  122  and a plunger  124 . The cartridge  122  has a hollow interior that can be loaded with the material. The plunger  124  includes a plunging rod  126  that has an outer diameter configured to fit within the hollow interior of the cartridge  122 .  
         [0035]     The loaded cartridge  122  is inserted into the barrel  104  as shown in  FIG. 3B . In one implementation, the cartridge  122  is at least long enough so that when inserted into the barrel  104 , the cartridge  122  extends the entire length of the interior of the barrel  104 . The plunger  124  is inserted into the cartridge  122  and the plunging rod  126  is pushed through the interior of the cartridge  122  to advance the material contained therein. The material advances out of the cartridge  122  and either into the barrel  104  and then into the nozzle assembly  102 , or directly into the nozzle assembly  102 .  
         [0036]     The nozzle assembly  102  can be primed, i.e., pre-loaded with the material, so that when the plunging rod is pushed through the cartridge  122  and the material advances from the cartridge  122  into the nozzle assembly  102 , the pre-loaded material in the nozzle assembly  102  is forced out of the distal end  110  and into the cavity  116  ( FIG. 2 ).  
         [0037]     Referring again to FIGS.  1 A-C and  2 , including the flexible tube  108  in the nozzle assembly  102  can make it easier for an operator of the cavity-filling assembly  100  to maneuver the device during a cavity filling operation. For example, a C-arm imaging device for fluoroscopy may be used to provide instantaneous imaging data to the operator to assist the operator in filling a cavity  116  with the material. Maneuvering a cavity-filling device while constrained by the clearance between the C-arm imaging device and the patient&#39;s body can be difficult. The flexible tube  108  allows flexibility in positioning the cavity filling assembly  100  to accommodate the clearance constraint. Including a rigid distal end  110  at the end of the flexible tube  108  can make it easier for the operator to control the distal end  110  within the cavity  116 , particularly while discharging the material into the cavity  116 . The distal end  110  may include different configurations to further control dispensing of the cavity filling material.  
         [0038]     Other implementations of the cavity-filling assembly  100  are possible, including a cavity-filling assembly  100  with a differently configured nozzle assembly  102 . In one implementation, the nozzle assembly  102  can be a flexible tube  108  without a rigid distal end  110 , i.e., an entirely flexible nozzle assembly  102 . In another implementation, the flexible tube  108  can be replaced with a rigid tube. That is, the nozzle assembly  102  can be entirely rigid.  
         [0039]     Referring to  FIGS. 4A and 4B , the connector  106  included in the cavity-filling assembly  100  shown in FIGS.  1 A-C is shown. In one implementation, the connector  106  includes threads  132  to mate with threads  134  formed in the interior of the barrel  104 . For example, referring again to  FIG. 1C , the fitting  112  of the barrel  104  is shown, which includes a threaded interior surface  134  that can mate with the threads  132  formed on the connector  106 . A luer fitting  130 , in addition to threads  132 , can be present on the connector  106  for ease of pre-loading or priming the nozzle assembly  102  with cavity filling material. In another implementation, a luer fitting  130  can be used to connect to the barrel  104 . The connector  106  includes a connector face  136  that receives or attaches to the flexible tube  108  of the nozzle assembly  102 . In one implementation, the tubing is chemically or thermally bonded to the connector  106 . In another implementation, the tubing can be threaded or snap-fit with the connector  106  to allow the operator to easily change the flexible tube  108  for different applications, for example, to use a specially configured distal end. In the implementation shown, the connector face  136  is angled, such that a central axis of the barrel  104  attached to the luer fitting  130  or the threads  132  is at an angle θ to a central axis of a flexible tube  108  attached to the connector face  136 , as shown by the intersection of lines  138  and  140  at the angle θ. The connector face  136  can be angled such that the angle θ can range from approximately 0° to 90°, depending on the desired orientation of the flexible tube  108  relative to the barrel  104 . In one implementation, an angle of 45° is used.  
         [0040]     Other embodiments of the connector  106  can be used. For example, a different fitting can be used in place of the luer fitting  130 , e.g., a snug-fit, snap-on fit, or tapered fitting. The threads  132  formed on the connector  106  are optional.  
         [0041]     Referring again to FIGS.  1 A-C, the barrel  104  provides an extension from the nozzle assembly  102  that an operator can use as a handle during a cavity filling operation. The barrel  104  also acts to distance the operator&#39;s hands from the patient&#39;s body, which can also act to keep the operator&#39;s hands outside of a potentially harmful imaging field. For example, as described above, in a kyphoplasty operation a C-arm imaging device is typically used during the cavity filling operation to provide instantaneous imaging information to the operator. The barrel  104  operates as an extender that keeps the operator&#39;s hands and arms out of the imaging field created by the imaging device. The length of the barrel  104  and the length of the flexible tubing  108  can be designed based on how far the operator&#39;s hands must be from the imaging field. Further, there may be a relatively small clearance between the C-arm imaging device and the patient&#39;s body. The connector  106  between the nozzle assembly  102  and the barrel  104  allows the barrel  104  to be angled relative to the nozzle assembly  102  to achieve preferred flow characteristics. The flexible tubing  108  allows for low clearance. In one implementation, the barrel and plunging assembly can be a syringe.  
         [0042]     The cavity-filling assembly  100  shown in  FIGS. 1A-1C  is a two-part assembly including the nozzle assembly  102  and the barrel  104 . In another implementation, the cavity-filling assembly  100  can be a unitary apparatus wherein the nozzle assembly  102  and the barrel  104  are permanently affixed to one another. In this implementation, the cavity-filling assembly  100  can be primed by pre-loading the unitary cavity-filling assembly  100  with a material for injection into a cavity  116  ( FIG. 2 ). The material can be advanced through the cavity-filling assembly  100  and out of the distal end  110  by plunging the interior of the pre-loaded barrel  104  directly. That is, rather than inserting a cartridge  122  loaded with the material into the barrel  104 , the barrel  104  is loaded with the material and plunged using a plunging assembly  120  directly.  
         [0043]     In either the two-part or unitary cavity-filling assembly  100  implementations, the barrel  104  can be configured to have substantially the same inner diameter as the nozzle assembly  102 , so as to maintain a constant pressure across the cavity-filling assembly  100  as the material is advanced therethrough. Alternatively, the barrel  104  can be configured to have a larger inner diameter than the nozzle assembly  102 , to increase the amount of material that can be preloaded into the cavity-filling assembly  100 , thereby minimizing the number of loading iterations necessary to fill a cavity  116  ( FIG. 2 ).  
         [0044]     A cavity filling operation may require that the nozzle assembly  102  and barrel  104  be reloaded (either directly or via a cartridge  122 ) with material more than once in order to completely fill the cavity. As shown in  FIG. 7 , in one implementation, a barrel  700  can include multiple chambers  712 , each of which can be preloaded with the material. The chambers  712  can be arranged similar to the chambers in a revolver, in that the barrel  700  can be rotated about an axis  716  within a sleeve  704  to engage a chamber  712  with a connector  708  of the nozzle assembly  706  by way of an exit port  710 . In the implementation depicted, each chamber  712  is configured to receive a pre-loaded cartridge  714 . The material in the chambers  712  can be discharged one by one into the nozzle assembly  706 , e.g., by rotating the barrel  702  and plunging the cartridges  714 . In another implementation, each of the multiple chambers  712  can be loaded with material directly (i.e., without using cartridges) and the material discharged from the chambers  712  using a plunging assembly as described above. The implementation shown includes 6 chambers  712 , however, any number of chambers can be included.  
         [0045]     FIGS.  8 A-C show an alternative implementation of a multi-chambered barrel assembly  800 . The barrel assembly  800  includes a barrel  802  rotatable about a longitudinal axis within a sleeve  802 .  FIG. 8B  shows a longitudinal cross-sectional view of the barrel assembly  800 . The barrel  802  includes a central bore  806  having an inlet port  804 . Multiple chambers  808  are arranged about the central bore  806 , as shown in the cross-sectional view in  FIG. 8C . The chambers  808  can be filled with material via the central bore  806 . That is, material is injected into the central bore  806  by the inlet port  804 . A reservoir  810  in the sleeve  802  redirects the material into the chambers  808 . The barrel  802  can be rotated within the sleeve  802  to engage a chamber  808  with a connector of a nozzle assembly by way of an exit port  812 . The material in the chambers  808  can be discharged one by one into the nozzle assembly, e.g., by rotating the barrel  802  and plunging the chambers  808 . The implementation shown includes  7  chambers  808 , however, any numbers of chambers can be included.  
         [0046]     In one implementation where the barrel  104  is loaded with the material directly rather than using a cartridge  122 , the distal end of the barrel  104  used to load the material into the barrel  104  is configured to mate with a mixer used to mix and contain the material. Referring to  FIG. 5 , an example of a mixer  200  is shown. In one implementation, the mixer  200  can be a Kyphon® Mixer available from Kyphon Inc. The cavity filling material can be mixed directly in the mixer  200 , for example, a bone filling cement can be mixed by the addition of a liquid to a cement powder. The mixer  200  can include a dispenser  202  near the base that is configured to mate with the distal end of the barrel  104 . For example, the dispenser  202  can include a male portion of a luer fitting, and the distal end of the barrel  104  can include a female portion of a luer fitting that is configured to mate with the dispenser  202 . A plunger  204  included within the mixer  200  can be depressed to urge the material from the mixer  200  and through the dispenser  202  to load the cartridge  122 . If the barrel  104  includes multiple chambers, then each chamber may include a female portion of a luer fitting to mate with the dispenser  202 , and each chamber loaded separately; or a main loading chamber can be connected to a manifold to simultaneously load all the chambers.  
         [0047]     In one implementation, the cartridge  122  can be a KyphX® Bone Filler Device available from Kyphon Inc. The cartridge  122  (or nozzle) can include a fitting configured to mate with a fitting on a dispenser of a mixer, such as the mixer  200  shown in  FIG. 5 . For example, the cartridge  122  can include a female portion of a luer fitting that is configured to mate with a male portion of a luer fitting formed on the dispenser  202  of the mixer  200 . The cartridge  122  is attached to the dispenser  202  to load the cartridge  122  with the material.  
         [0048]     Referring again to FIGS.  3 A-B, in one implementation, the plunging assembly  120  is included with the KyphX® Bone Filler Device available from Kyphon Inc. The plunging assembly  120  is configured to plunge the cartridge  120  (or nozzle) of the KyphX® Bone Filler Device available from Kyphon Inc. Alternatively, if the barrel  104  of the cavity-filling assembly  100  is to be loaded directly with the material (rather than via a loaded cartridge), then the plunging assembly  120  can be adapted to plunge the barrel  104 , for example, to accommodate the interior diameter and length of the barrel  104 .  
         [0049]      FIG. 6  shows a process  600  for using the cavity filling assembly  100  to fill a cavity in a patient&#39;s body. Referring now to FIGS.  1 A-C,  2 ,  3 A-B and  6 , the material that will be used to fill the cavity is prepared (step  602 ). The cavity filling material can differ depending on the cavity to be filled, for example, in a kyphoplasty procedure a bone filling cement, such as polymethylmethacrylate (PMMA) or a calcium phosphate bone substitute, can be used. Preparing the material may include mixing a powder with a liquid and stirring until the cement mixture reaches a desired consistency. The cavity filling assembly  100  is loaded with the cavity filling material (step  604 ). For example, in an implementation including a separate nozzle assembly  102  and barrel  104 , the nozzle assembly  102  can be primed by loading the nozzle assembly  102  with the cavity filling assembly. The barrel  104  can also be loaded with the material, in a configuration that loads the barrel  104  directly rather than via a cartridge  122 .  
         [0050]     The cavity filling assembly  100  is assembled (step  606 ), if necessary. For example, if the cavity filling assembly includes a separate nozzle assembly  102  and barrel  104 , then the barrel  104  and nozzle assembly  102  can be joined by the connector  106 . The cavity filling assembly  100  is inserted into a cannula  114  that has been positioned within the cavity  116  in the patient&#39;s body (step  608 ). In one implementation, one or more surgical balloons are first inflated within the cavity  116  to restore the cavity  116  to an original shape or to create or enlarge the cavity  116 . The surgical balloons are removed, and optionally material, such as bone, may be removed from the cavity  116 . Once the cavity is prepared, the cavity filling assembly  100  is inserted into the cannula  114 .  
         [0051]     The material is advanced from the cavity filling assembly  100  into the cavity  116  (step  610 ). This step can include, if necessary, inserting one or more cartridges  122  into the barrel  104  to load the barrel  104  with the material, i.e., in a configuration where the barrel  104  is not directly loaded with the material. A plunging assembly  120  is positioned to either plunge the barrel  104  or a cartridge  122  contained within the barrel  104 . The plunging rod  122  is advanced into the barrel  104  or cartridge  122  to advance the material through the cavity filling assembly  100  and out the distal end  110  that is positioned within the cavity  116 .  
         [0052]     The operator can control the advancement of the plunging rod  122 , thereby controlling the advancement of the material into the cavity  116 . In one implementation, the material is advanced into the cavity  116  at a low pressure. If the inner diameters of the components of the cavity filling assembly  100 , i.e., of the nozzle assembly  102  and barrel  104  or cartridge  122 , are substantially the same, then the advancement of the plunging rod  122  is directly proportional to the advancement of the material from the distal end  110  of the nozzle assembly  102  into the cavity  116  (i e., an approximate one-to-one ratio). In one implementation, the diameters of the components of the cavity filling assembly  100  are uniform and allow for no drop-off or build-up of pressure in the cavity filing material. Further, the operator can retract the nozzle assembly  102  from the cannula  114  while advancing the plunging rod  122 , thereby pulling the distal end  110  out of the cavity  116  as the cavity  116  is filled with the material. That is, the front portion of the cavity can be filled first with the viscous material to ensure a solid, compact fill with no air gaps. The one-to-one ratio of the advancement of the plunging road to the advancement of the material, and the ability to retract the nozzle assembly  102  from the cavity  116  during the filling operation provides improved control to the operator over the cavity filling procedure.  
         [0053]     The cavity filling assembly  100  can be formed from any suitable material or combination of materials. The materials selected must be compatible with the cavity filling material that will be advanced through the assembly  100 . The materials used for the flexible tubing  108  should also provide kink resistance, burst resistance and thermal resistance. The flexible tube  108  can be formed from polyamides, nylon, Teflon®, or nylon with a Teflon lining, Pebax®, PEEK, polypropylene, polyethylene, PTFE, FEP, PFA, Radel® R polyphenylsulphone and the distal end can be formed from stainless steel. In a preferred embodiment, the flexible tubing can be formed of Pebax® with an inner stainless steel coil reinforcement. Examples of material for the barrel  104  and connector  106  include nylon, polyethylene, polycarbonate, aluminum, Radel® R polyphenylsulphone or stainless steel.  
         [0054]     A number of embodiments of the invention have been described. Nevertheless, it will be understood that various modifications may be made without departing from the spirit and scope of the invention. The logic flow depicted in  FIG. 6  does not require the particular order shown, or sequential order, to achieve desirous results, and the steps of the invention can be performed in a different order. Accordingly, other embodiments are within the scope of the following claims.