Abstract:
An apparatus comprises a body portion having a sidewall with one or more threads and defining a lumen. The apparatus includes a brace portion having a sidewall that defines a lumen that is fluidically coupled to the lumen of the body portion. The sidewall of the brace portion has one or more threads that are configured to matingly couple to the threads of the body portion. The brace portion has a contact surface configured to contact a bodily tissue of a patient when a cannula is disposed within the lumen of the body portion and the lumen of the brace portion. The brace portion and the body portion are collectively configured to maintain a position of the cannula within a body of the patient relative to the bodily tissue when the cannula is disposed within the lumen of the brace portion and the lumen of the body portion.

Description:
REFERENCE TO RELATED APPLICATION 
       [0001]    This application claims priority to and the benefit of U.S. Patent Provisional Application No. 61/515,139, filed Aug. 4, 2011, entitled “Apparatus and Method for Restricting Movement of a Cannula during a Surgical Procedure,” which is incorporated herein by reference in its entirety. 
     
    
     BACKGROUND 
       [0002]    The invention relates generally to medical devices, and more particularly to methods and apparatus for restricting the movement of a cannula during a surgical procedure. 
         [0003]    Minimally invasive or percutaneous surgical procedures often involve the use of catheters and/or cannulas for providing access to internal tissue (e.g., bone, soft tissue, etc.). In such procedures, an opening is formed in the skin, either by making an incision or using a device such as a trocar. Once the opening is formed in the skin, the catheter or cannula can be advanced to a desired location. In connection with certain procedures, the cannula can be advanced into soft tissue and/or a bony structure. 
         [0004]    In some surgical procedures, temporary or permanent implants are delivered through a cannula and positioned in a desired location. In some procedures, medical devices, or portions thereof, are removed through the cannula after a procedure is performed. In certain instances, when the force required to remove the medical device through the cannula is greater than the frictional force maintaining the position of the cannula, the cannula can be advanced further into the body, causing tissue damage or inhibiting the removal of the medical device from the body through the cannula. For example, in connection with a spinal procedure, a pod is delivered into a vertebra, filled with a bone cement and then extracted. When the pod is extracted through the cannula, the cannula may have enough frictional force from contact with the bone to prevent movement of the cannula. If the force retaining the pod in the vertebral body is greater than the cannula-bone interface frictional force, however, the extraction of the pod will force the cannula further into the body (i.e., in a distal direction) instead of pulling the pod out of the body (i.e., in a proximal direction). 
         [0005]    Thus, a need exists for methods and apparatus for restricting movement of a cannula during a surgical procedure. 
       SUMMARY OF THE INVENTION 
       [0006]    In some embodiments, an apparatus includes a first portion and a second portion. The first portion includes a guide member and a coupling portion that collectively define a lumen configured to receive a cannula therethrough. The guide member is configured to move relative to the coupling portion between a first position and a second position when the cannula is disposed within the lumen. The first portion has a first configuration when the guide member is in the first position relative to the coupling portion. The first portion has a second configuration when the guide member is in the second position relative to the coupling portion. The second portion is coupled to a distal end of the first portion. The second portion defining a lumen configured to receive at least a portion of the cannula. The lumen of the second portion is in fluid communication with the lumen of the first portion. The second portion includes a contact surface that is configured to contact a bodily tissue of a patient when at least a portion of the cannula is disposed through the lumen of the second portion and within the body of the patient. The second portion and the first portion are collectively configured to maintain a position of the cannula relative to the bodily tissue when at least a portion of the cannula is disposed through the lumen of the first portion, the lumen of the second portion and within the body of the patient. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0007]      FIG. 1  is a schematic illustration of a cannula holder according to an embodiment of the invention. 
           [0008]      FIGS. 2-8  are perspective views of apparatus according to embodiments of the invention. 
       
    
    
     DETAILED DESCRIPTION 
       [0009]    Medical devices are described herein. In some embodiments, a medical device includes a retainer having a brace and a body portion. The brace and body portion collectively define an opening configured to receive a cannula therethrough. The brace is configured to be disposed adjacent bodily tissue and the body portion is configured to be disposed between a hub of a cannula and the brace. The body portion is adjustable between multiple configurations such that it is configured to maintain the cannula in position relative to bodily tissue. As described in greater detail herein, in some embodiments, the brace is positioned against a patient&#39;s skin. In some embodiments, the brace is positioned against a bony structure. Accordingly, instead of relying completely on the friction between the cannula and the bone to prevent anterior (i.e., distal) advancement of the cannula, the load applied during removal of a medical device through the cannula is distributed onto other tissues. By increasing the area to which the withdrawal forces are applied, the cannula retainer reduces the probability of cannula advancement and associated negative clinical outcomes (e.g., tissue damage, incorrect device placement, etc.). 
         [0010]    In some embodiments, the retainer is a modification of the cannula shaft, a modification to the cannula hub or a separate device that is attached to the cannula. The retainer can be permanently attached to the cannula, configured to slidably engage the cannula before placement into the patient, or configured to fit onto the cannula shaft in such a way as to allow installation after the cannula has been positioned in the patient. 
         [0011]    In some embodiments, the cannula tip can be modified to include flutes, knurls, threads, etc to increase or supplement frictional forces between the cannula shaft and the bone. Such a modification can be instead of or in addition to use of the retainer as described herein. In other embodiments, the cannula can include a retractable retention mechanism configured to engage the bone to limit movement of the cannula shaft with respect to the bone. 
         [0012]    In some embodiments, a method includes forming an opening in a bodily tissue, inserting a cannula into the opening, coupling a retainer to the cannula, and adjusting the retainer to maintain the position of the cannula relative to the bodily tissue. In some embodiments, the cannula is coupled to the retainer before the cannula is inserted in the bodily tissue. 
         [0013]    As used in this specification, the words “proximal” and “distal” refer to direction closer to and away from, respectively, an operator (e.g., surgeon, physician, nurse, technician, etc.) who would insert the medical device into the patient, with the tip-end (i.e., distal end) of the device inserted inside a patient&#39;s body first. Thus, for example, the end of a medical device first inserted or closest to the inside of the patient&#39;s body would be the distal end, while the end of the medical device to last enter the patient&#39;s body or furthest from the body would be the proximal end of the medical device. 
         [0014]      FIG. 1  is a schematic illustration of a retainer  100  according to an embodiment of the invention. As described herein, in some embodiments, the retainer  100  can be used to maintain a cannula or catheter in a location within bodily tissue. For example, the retainer  100  can be used to maintain the position of a cannula relative to a bone (e.g., a long bone, a vertebral body or the like), an organ, or soft tissue. Although described herein as being configured for use with surgical procedures involving vertebra, in other embodiments, the retainer  100  can be used with any percutaneous or minimally invasive procedure in which it is desirable to maintain the position of the access cannula or catheter. 
         [0015]    The retainer  100  includes a brace  110  and a body portion  120 . In some embodiments, the brace  110  is configured to be positioned against the skin of a patient. In other embodiments, the brace  110  is configured to be positioned against internal bodily tissue (e.g., a bone) into which the cannula is inserted. In embodiments in which the brace  110  is to be positioned against the bone, the diameter of the brace need only be slightly greater than the diameter of the opening in the bone through which the cannula is inserted. 
         [0016]    The body portion  120  can be reconfigured or adjusted to facilitate maintaining the position of the cannula. In some embodiments, a length of the body portion  120  can be changed to prevent advancement of the cannula further into the body. For example, in a first configuration, the body portion has a length L. The body portion  120  is maintained in the first configuration until the cannula is positioned appropriately within the bodily tissue. Once the cannula is inserted to a desired depth/position, the body portion  120  is moved to a second configuration having a length L′, which is at least substantially equal to the distance between the hub H of the cannula C and brace  110 . 
         [0017]    As discussed in greater detail herein, in some embodiments, the body portion has multiple portions movable relative to one another such that the length of the body portion can change. For example, the body portion  120  can include a first portion and a second portion that are telescopically arranged, threadedly engaged, etc. such that the length L of the body portion can move to length L′. 
         [0018]    In some embodiments, prior to insertion of the cannula, the brace  110  is positioned adjacent the body portion  120 . After the cannula is inserted into the body and is appropriately positioned, the brace  120  is moved into position (i.e., against the skin or bone). 
         [0019]      FIG. 2  illustrates a retainer  200  including a brace  210  and a body portion  220 . The brace  210  and the body portion  220  are configured to receive a cannula C. The brace  210  includes a tissue-contacting portion  212  and a ball and socket joint  214 . After the cannula is placed at the desired depth, the tissue-contacting portion  212  is extended to press against the patient&#39;s skin. The angle of the brace  210  is adjustable to account for different anatomies by using the ball and socket joint  214 . In some embodiments, the brace is adjustable by a pin joint, swivel joint, or some other method. 
         [0020]    The body portion  220  is adjustable by moving threaded adjustment portion  222  relative to barrel  224 . As the barrel moves along the length of the threaded adjustment portion  222 , the overall length of body portion  220  changes. In some embodiments, instead of using the threaded adjustment portion  222  and barrel  224 , the body portion can include telescoping portions that are locked in place using friction fit, screws, pins, etc. 
         [0021]      FIG. 3  illustrates a retainer  300  including a brace  310  and body portion  320 . The brace  310  includes a skin contacting portion  312  and ball and socket joint  314 . Body portion  320  includes a threaded post  322  disposed in socket  318  about which a barrel  324  is threadedly engaged. The distance between cannula hub H and brace  310  can be modified to maintain the cannula C in position relative to the tissue into which the cannula C is inserted. 
         [0022]      FIG. 4  illustrates a retainer  400  including a brace  410  and a body portion  420 . Brace  410  includes a skin-contacting portion  412  and a ball and socket joint  414 . The body portion  420  includes a collet locking assembly (not shown) configured to maintain the cannula C in place such that it cannot move relative to the brace  410 . Body portion  420  is configured to be rotated from a first configuration in which the cannula C is free to slide through the retainer  400  and a second configuration in which the body portion  420  is locked around the cannula C, thereby preventing movement of the cannula C. 
         [0023]      FIG. 5  illustrates a retainer  500  including a brace  510  and a body portion  520 . Brace  510  includes a skin-contacting portion  512  and a ball and socket joint  514 . The ball and socket joint  514  is configured to adjustably lock in place such that when a desired angle/position of insertion of the cannula C is achieved, the ball and socket joint  514  is prevented from further movement. The body portion  520  includes a collet locking assembly (not shown) configured to maintain the cannula C in place such that it cannot move relative to the brace  510 . 
         [0024]    Although the retainer  100  shown and described above includes a brace  110  configured to be positioned against the skin of a patient, in other embodiments, a retainer can include a brace that can be at least partially disposed within the body and/or that can be positioned against the internal bodily tissue (e.g., a bone) into which the cannula is inserted. For example,  FIG. 6  shows a retainer  600  that can be used to limit the movement of a cannula C relative to the internal bodily tissue into which the distal portion of the cannula C is inserted. More particularly, as described herein, the retainer  600  is configured to limit movement of the cannula C relative to the internal bodily tissue in the distal direction. In other embodiments, the retainer  600  can be configured to limit the movement of the cannula C in both the distal and proximal direction. In yet other embodiments, the retainer  600  can be configured to limit the rotational movement of the cannula C relative to the internal bodily tissue. 
         [0025]    The internal bodily tissue can be any suitable bodily tissue within which a portion of the cannula C is disposed. For example, as shown in  FIG. 6 , the internal bodily tissue can be a vertebra  30 . The vertebra  30  includes a spinous process  38 , a spinal cord canal  80 , a pedicle  82  and a vertebral body  36 . The vertebral body  36  includes an outer portion  32  formed from a cortical bone surrounding an inner portion  34  formed from cancellous bone. As described herein, the distal portion of the cannula C can be disposed within a cavity defined within the inner portion  34  of the vertebral body  36 . A pod and/or expandable member can be delivered into the vertebra  30 , filled with a bone cement and then extracted. 
         [0026]    The retainer  600  includes a brace  610  and a body  620 . The brace  610  includes a contact surface  612  and a threaded portion  614 . The body  620  includes a threaded portion that corresponds to the threaded portion  614  of the brace  610 . In use, the brace  610  and the body  620  are each disposed about the shaft of the cannula C such that the proximal end portion of the body  620  is in contact with the hub H of the cannula, and the brace  610  is threadably coupled to the distal end portion of the body  620 . As described above, the brace  610  can be rotated relative to the body  620  and/or the cannula C to adjust the length L between the contact surface  612  of the brace  610  and the hub H of the cannula C. Similarly stated, the brace  610  can be rotated relative to the body  620  and/or the cannula C to adjust the length L of the retainer  600 . 
         [0027]    In use, the retainer  600  is disposed about the cannula C, and the cannula C is inserted into the body such that a distal end portion of the cannula is within the vertebra and the contact surface  612  is disposed against the outer portion  32  of the vertebra  30 . The distance within which the distal end portion of the cannula C is disposed within the vertebra  30  can be adjusted by adjusting the length L of the retainer  600 , as described above. In some embodiments, the retainer  600  can be disposed into the body until the contact surface  612  is in position against the bodily tissue, and then the cannula C can be inserted into the body through the retainer  600  until the hub H contacts the proximal portion of the body  620  of the retainer  600 . 
         [0028]    Although shown in  FIG. 6  as being disposed against the pedicle  42 , in other embodiments, the contact surface  612  of the retainer  600  can be disposed against any suitable surface of the vertebra  30 . In some embodiments, the contact surface  612  can have a shape and/or contour that corresponds to a contour of a portion of the bodily tissue against which the contact surface  612  is placed. In this manner, the contact surface  612  can be configured to evenly distribute any forces transmitted to the surface of the bodily tissue during the extraction process. In other embodiments, the contact surface and/or any other portion of any of the retainers disclosed herein can include any suitable mechanism and/or structure to increase the friction between the retainer and the bodily tissue against which the retainer is disposed. For example, in some embodiments the brace of any of the retainers described herein can include a surface feature, such as, for example, flutes, knurls, and/or threads, that is configured to engage a portion of the bodily tissue to limit movement of the retainer (and thus, the cannula) relative to the bodily tissue. In other embodiments, the retainer can include a movable and/or expandable portion configured to expand and/or move to engage a portion of the bodily tissue after the retainer is disposed with the body. 
         [0029]    The size of the distal end portion of the brace  610  (i.e., the portion adjacent the contact surface  612 ) need only be slightly greater than the size of the opening through the outer portion of the vertebra  30 . In this manner, the brace  610  is configured to be disposed into the body via the same incision and/or path through which the cannula C is disposed. 
         [0030]    Although the retainer  600  is shown and described as circumscribing the cannula C, in other embodiments, a retainer need only surround a portion of the cannula C. In such embodiments, the retainer can be disposed about the cannula after the cannula has been inserted into the body. For example,  FIG. 7  shows a retainer  700  according to an embodiment. The retainer  700  includes a brace  710  and a body  720 . The brace  710  includes a contact surface  712  and a threaded portion  714 . The brace  710  defines an opening  715  such that the brace  710  only partially circumscribes the cannula C. 
         [0031]    The body  720  includes a threaded portion that corresponds to the threaded portion  714  of the brace  710 . The body  720  defines an opening  717  such that the body  720  only partially circumscribes the cannula C. In use, the brace  710  and the body  720  are each disposed about the shaft of the cannula C such that the proximal end portion of the body  720  is in contact with the hub H of the cannula, and the brace  710  is threadably coupled to the distal end portion of the body  720 . As described above, the brace  710  can be rotated relative to the body  720  and/or the cannula C to adjust the length L between the contact surface  712  of the brace  710  and the hub H of the cannula C. Similarly stated, the brace  710  can be rotated relative to the body  720  and/or the cannula C to adjust the length L of the retainer  700 . Moreover, the openings  715  and  717  allow the retainer  700  to be disposed about the cannula C after the cannula C is disposed into the body. 
         [0032]      FIG. 8  illustrates a retainer  800  including a brace  810  and a body portion  820 . Brace  810  includes a contact portion  812  configured to contact an internal bodily tissue, as described herein. The body portion  820  includes a clamp assembly  822  configured to maintain the cannula C in place such that it cannot move relative to the brace  810  and/or the body portion  820 . 
         [0033]    While various embodiments of the invention have been described above, it should be understood that they have been presented by way of example only, and not limitation. Where methods described above indicate certain events occurring in certain order, the ordering of certain events may be modified. Additionally, certain of the events may be performed concurrently in a parallel process when possible, as well as performed sequentially as described above.