Abstract:
Devices, systems and methods for delivering a curable, stabilizing material into a central region of a bone structure. Precise placement of the curable substance into a central region of a bone structure through a unipedicular approach. One primary advantage is its ability to create a central cavity in a vertebral body (or to centrally deliver bone cement) through a unipedicular approach. A curved needle having increased rigidity in its flexible end when the end is disposed in its straight position. This increased rigidity is due to a novel tensioning mechanism and to a segmented tube design (as opposed to the conventional longitudinally-slotted tube design).

Description:
BACKGROUND OF THE INVENTION 
       [0001]    In vertebroplasty, the surgeon seeks to treat a compression fracture of a vertebral body by injecting bone cement such as PMMA into the fracture site. One clinical report describes mixing two PMMA precursor components (one powder and one liquid) in a dish to produce a viscous bone cement; filling 10 cc syringes with this cement, injecting it into smaller 1 cc syringes, and finally delivering the mixture into the desired area of the vertebral body through needles attached to the smaller syringes. 
         [0002]    This injection of the stabilizing material into damaged or compromised bone sites has proven highly beneficial for patients. However, these materials are typically delivered through a straight needle that accesses the vertebral body through a pedicle. Because the pedicle are present at the lateral edges of the vertebral body, pedicle-based delivery has difficulty in delivering material to the central (mid-line) region of the vertebral body. One proposed solution is to fill the central region from a lateral needle tip—however, this approach may lead to overfilling and leakage. Another proposed solution is bipedicular delivery—which is delivery through each of the pedicles. However, the proposed bipedicular access and delivery techniques necessitate multiple needle sticks and therefore a greater risk of tissue damage and infection. Also, neither proposed solution provides precision in the placement of the stabilizing material, which is desirable to prevent overfilling. 
         [0003]    Curved needle devices have been proposed as a solution to this issue, but these are prone to breaking due to a lack of strength, rigidity and/or fatigue strength. 
         [0004]    Therefore, a need exists in the field of vertebral body augmentation for an improved device for delivering stabilizing material to the damaged or compromised bone sites. 
         [0005]    U.S. Pat. No. 5,002,543 (Bradshaw) discloses a steerable tip fracture reduction device. In particular, Bradshaw discloses a steerable intramedullary fracture reduction device has an elongated shaft with a steerable tip pivotally mounted to the distal end of the shaft. A tip actuating apparatus near the proximal end of the shaft enable the operator to steer the tip and the shaft into successive segments of the fractured bone, even when the segments are transversely or rotationally displaced so that the segments can be aligned by the shaft. 
         [0006]    U.S. Pat. No. 7,476,226 (Weikel) discloses tools for use in the creation of cavities in bones. The tools include a probe, a cannula that provides percutaneous passageway to the interior of the treated bone, a bone tamp, and a system for delivering bone filler material into the cavity. The bone tamp has a shaft that is inserted into the bone through the cannula. The end of the shaft that is inserted into the bone may have a flapper tip that extends out of axial alignment with the shaft upon deployment by the physician. Once the tip is deployed, the bone tamp can be rotated to form the cavity. The cavity may then be treated with a medicament, filled with bone filler material, or both. Other tools and materials described herein may be used to lift or restore the treated bone closer to its natural anatomy. 
         [0007]    US Patent Publication 2002-0026197 (Foley) discloses instrumentation for treatment of the spine, including an elongate member having a deformable distal end portion at least partially formed of a flexible and preferably elastic material. The distal end portion has an initial configuration for placement adjacent a vertebral body and a deformed configuration defining at least one outwardly extending projection for displacement of at least a portion of the vertebral body. The elongate member preferably comprises a rod member, a sleeve member and an actuator mechanism for imparting relative linear displacement between the rod and sleeve members to effect outward deformation of the distal end portion of the sleeve member. In one embodiment, the instrumentation is used to compact cancellous bone to form a cavity within a vertebral body. In another embodiment, the instrumentation is used to reduce a compression fracture. In yet another embodiment, the instrumentation is used to distract a disc space between adjacent vertebral bodies. 
         [0008]    US Patent Publication 2010-0010298 (Bakos) discloses an apparatus, system, and method for use with an endoscope. A flexible overtube having a proximal end and a distal end defines a hollow lumen therebetween to receive a flexible shaft portion of an endoscope therein. The proximal end of the flexible overtube is configured to remain outside of a patient and the distal end is configured to enter the patient through a natural orifice. At least one fluid tight seal is located at the proximal end of the flexible overtube to prevent leakage of fluids around the flexible shaft of the endoscope when the flexible shaft of the endoscope is positioned within the flexible overtube. The system further includes a flexible endoscope. The method includes introducing the system into a patient though a natural orifice of the patient and performing an endoscopic translumenal procedure. 
       SUMMARY OF THE INVENTION 
       [0009]    The present invention relates to devices and methods for stabilizing bone structures. More particularly, it relates to devices, systems and methods for delivering a curable, stabilizing material into a central region of a bone structure. 
         [0010]    The present invention provides for vertebral fracture stabilization, as well as precise placement of the curable substance into a central region of a bone structure through a unipedicular approach. 
         [0011]    One primary advantage of the present invention is its ability to create a central cavity in a vertebral body (or to centrally deliver bone cement) through a unipedicular approach. 
         [0012]    The present invention is a curved needle having increased rigidity in its flexible end when the end is disposed in its straight position. This increased rigidity is due to a novel cable tensioning mechanism and to a segmented tube design (as opposed to the conventional longitudinally-slotted tube design). 
         [0013]    The curved needle of the present invention also displays decreased fatigue stress in the flexible end during bending (in comparison to slotted tube designs) because no component of the tube of the present invention is internally bent. This is due to use of a cable and separate, nested tube segments in the present invention. Therefore, the present invention displays an increased durability of the flexible tubular end. Lastly, the present invention provides for increased control. This increased control is due to its slow curve progression brought about by providing a high number of driving screw turns, that is, a low pitch. 
         [0014]    In preferred embodiments, the steerable needle has a unique driving mechanism that comprises a) a driving screw that includes both left-hand and right-hand threads, and b) cable couplings that slide in opposite directions, pulling and releasing the cable. The advantages provided by the two couplings that slide in opposite directions are the constant tension of the cables, and the rigidity and stability of the curved end. 
         [0015]    Therefore, in accordance with the present invention, there is provided a steerable needle comprising:
       i) a tube having a rigid proximal end portion and a flexible distal end portion,   ii) a cable having a proximal end portion and a distal end portion, the distal end portion of the cable being attached to the flexible distal end portion of the tube, and   iii) a drive mechanism comprising :
           a) a driving screw comprising a proximal thread and a distal thread, wherein the proximal thread has a first direction, the distal thread has a second direction, and the first direction is opposite the second direction, and   b) first and second cable couplings adapted to slide in opposite directions, pulling and releasing the cable.   
           iv) a proximal handle connected to the rigid proximal portion of the tube, the handle comprising an actuator connected to the proximal end portion of the cable for tensioning the cable.       
 
         [0022]    In other preferred embodiments, the steerable needle comprises a cable-tensioning means. 
         [0023]    In some embodiments, the steerable needle possesses a pre-tensioned cable. The advantage of the pre-tensioned cable is that, when used with a particular tube design, it forces the tube to a straight configuration, and so provides rigidity in the flexible distal portion of the straightened tube. 
         [0024]    Therefore, in accordance with the present invention, there is provided a steerable needle comprising:
       i) a tube having a rigid proximal end portion and a flexible distal end portion,   ii) a cable attached to the flexible distal end portion of the tube,   iii) a proximal handle connected to the rigid proximal portion of the tube, the handle comprising an actuator connected to the cable for tensioning the cable,
 
wherein the cable is under tension, and
 
wherein the flexible distal end portion of the tube is substantially straight.
       
 
         [0028]    Generally, the flexible end of the tube comprises a column of nested segments. The separate nature of these segments allows for the overall bending of the tube end without requiring any bending within any single segment. Thus, the separate nature of the nesting segments provides an increased flexural fatigue strength of the device. In some embodiments, each end of each nested cylindrical segment is flat. Accordingly, tensioning of the cable associated with these segments produces a compression of this column of segments, thereby providing rigidity to the flexible tube end in its straight configuration. 
         [0029]    Therefore, in accordance with the present invention, there is provided a steerable needle comprising:
       i) a tube having a rigid proximal end portion and a flexible distal end portion,   ii) a cable running along (and preferably within) the tube and having a proximal end portion and a distal end portion, the distal end portion of the cable being attached to the flexible distal end portion of the tube,   iii) a proximal handle connected to the rigid proximal portion of the tube, the handle comprising an actuator connected to the cable for tensioning the cable,
 
wherein the flexible distal end portion of the tube comprises a plurality of nested, separate tubular segments.
       
 
         [0033]    Some embodiments of the present invention are characterized by an ease of manual control. In these embodiments, motion of the flexible tube end is controlled by the controlled movement of the cable couplings, which is driven by a high number of the driving screw turns. Such control can also be attained by predetermining the pitch of the screw. Preferably, the screw thread has a pitch of between 1 mm and 2 mm. If the pitch is smaller than 1 mm, then an excessive number of turns is required to obtain appropriate curvature of the flexible distal end portion of the device. If the pitch is greater than 2 mm, the user has substantially less manual control over the device. 
         [0034]    Therefore, in accordance with the present invention, there is provided a steerable needle comprising:
       i) a tube having a rigid proximal end portion and a flexible distal end portion,   ii) a cable attached to the flexible distal end portion of the tube,   iii) a drive mechanism comprising :
           a) a driving screw comprising a proximal thread and a distal thread, wherein the proximal thread has a first direction, the distal thread has a second direction,   b) first and second cable couplings adapted to slide in opposite directions, pulling and releasing the cable,   
           iv) a proximal handle connected to the rigid proximal portion of the tube, the handle comprising an actuator connected to the cable for tensioning the cable,
 
wherein the proximal thread has a pitch of between 1 mm and 2 mm.
       
 
     
    
     
       DESCRIPTION OF THE FIGURES 
         [0041]      FIG. 1  discloses a curved needle assembly. 
           [0042]      FIG. 2  discloses a driving mechanism. 
           [0043]      FIG. 3  discloses a driving mechanism displayed without a cover. 
           [0044]      FIG. 4  illustrates the flexible distal end portion of the steerable needle. 
           [0045]      FIGS. 5   a  and  5   b  disclose distal tip segments. 
           [0046]      FIG. 6  discloses an outer shell component of  FIG. 5   a.    
           [0047]      FIG. 7  discloses an insert  19  component of  FIG. 5   a.    
           [0048]      FIG. 8  illustrates an intermediate nesting segment. 
           [0049]      FIG. 9  illustrates a proximal nesting segment of the flex. 
           [0050]      FIG. 10  discloses a hypodermic tube assembly. 
           [0051]      FIG. 11  illustrates an axial cross-section of a funnel component. 
           [0052]      FIG. 12  illustrates one half-shell of handle insert component. 
           [0053]      FIG. 13  illustrates a driving screw component. 
           [0054]      FIG. 14  illustrates a cable coupling component. 
           [0055]      FIGS. 15 ,  16  and  17  illustrate the various parts of the cable clamping and tensioning mechanism. 
           [0056]      FIGS. 18   a  and  18   b  illustrate views of the left cover component of the handle. 
           [0057]      FIGS. 19   a  and  19   b  illustrate the right cover of the handle. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0058]    Now referring to  FIG. 1 , there is provided a curved needle assembly  1 . The instrument comprising: tube assembly  2 , shrink tubing  3 , handle  4 , driving handle  5 , and luer fitting  6 . 
         [0059]    Now referring to  FIG. 2 , the driving mechanism  7  comprises a split wire funnel  8 , split handle inserts  9 , left and right cable couplings  10  and driving shaft  11 . 
         [0060]      FIG. 3  shows the driving mechanism without a cover. 
         [0061]      FIG. 4  illustrates the flexible distal end portion of the steerable needle  13 , which comprises a top segment  14 , intermediate segments  15  and bottom segment  16 . The flexible portion acts via unidirectional action, as adjacent segments define a gap  17  therebetween. During actuation of the flex, these gaps close to produce the concave side of the flex. 
         [0062]      FIG. 5   a  discloses a distal tip segment  14  comprising outer shell  18 , pressed or welded insert  19 , central hole  20  and a side hole for injecting cement  21 .  FIG. 5   b  discloses one preferred distal tip segment  101  having an integral construction. 
         [0063]      FIG. 6  shows the outer shell  18  component of  FIG. 5   a.    
         [0064]      FIG. 7  shows the insert  19  component of  FIG. 5   a . The insert includes a groove  22  in its generally cylindrical body for the cable fixation, two small holes  24  for the cable insertion, and two radiused protrusions  23  for nested connection, alignment and pivoting relative to its adjacent intermediate segment  15 . 
         [0065]      FIG. 8  illustrates intermediate nesting segment  15  comprising horizontal surfaces  25  and  26  and angled surfaces  28  and  29 , small holes for the cable insertion  30 , central hole  31  for cement injection, radiused protrusion  32  and cavity  27 . 
         [0066]    Generally, an intermediate nesting segment comprises a distal end having one of a radiused projection and a radiused recess, and a proximal end having the other of the radiused projection and the radiused recess. In some embodiments, at least one of the nested, separate segments has a generally cylindrical shape defining a longitudinal axis, and wherein the radiused projection and radiused recess are each provided on a line parallel to the longitudinal axis. These conditions allow for linear nesting along one surface of the flexible portion of the needle. 
         [0067]    In preferred embodiments, the distal end of the intermediate segment  15  further has a flat surface, its corresponding proximal end further has a flat surface, and the radiused projection and radiused recess are each provided on a line substantially parallel to the longitudinal axis. 
         [0068]    In some nesting arrangements, the flexible portion of the needle comprises a first nesting segment and a second nesting segment adjacent the first nesting segment, wherein the first nesting segment comprises a projection, the second nesting projection comprises a recess, wherein the projection is nested in the recess, and wherein the first and second nesting segments define a gap therebetween. 
         [0069]    In some embodiments, a first intermediate segment comprises a generally cylindrical shape having a first end having first and second projections extending therefrom, and a second end comprising first and second recesses therein. In some embodiments, the first and second projections define first and second end surfaces therebetween, the first and second recesses define third and fourth surfaces therebetween, wherein the first and third surfaces are parallel and the second and fourth surfaces are skewed. In embodiments producing the gap, the second and fourth surfaces are oriented towards each other. 
         [0070]    In some embodiments, the projections define a first radius, the recesses define a second radius, and the first radius is substantially equal to the second radius. This allows for a high degree of nesting. 
         [0071]      FIG. 9  illustrates the proximal segment  16  of the flex. It has a substantially cylindrical body, a pair of distal recesses, but no proximal projections. This segment  16  may be welded to the hypodermic tubing  34  (which is shown in  FIG. 10 ) that is proximal thereto within the device. 
         [0072]      FIG. 10  shows the hypodermic tube assembly  33  comprising the bottom segment  16 , the hypodermic tube  34 , and the coupling  35  welded to the tube  34 . 
         [0073]      FIG. 11  illustrates an axial cross-section of funnel  8 , which includes a hole  36  for cement delivery, a hole  40  for aligning the driving shaft  11 , channels  37  for receiving the cable, a flange  39  for assembly with handle inserts  9 , holes  38  for receiving the pins that hold the funnel together, and holes  41  for attaching the funnel to the handle insert cover  9 . 
         [0074]      FIG. 12  illustrates one half-shell of handle insert  9  comprising groove  43  for funnel assembly, holes  42  for attaching inserts to the funnel by pins, slots  44  and  46  for guiding the cable couplings  10 , the groove  45  for aligning with the flange of driving screw  11 , hole  47  for guiding the driving screw  11 , and holes  48  for assembly with the other half-shell of the handle insert using pins. 
         [0075]      FIG. 13  illustrates the driving screw  11  comprising left  49  and right  50  threads, and an intermediate flange  51  for aligning the screw with handle inserts  9 . 
         [0076]      FIG. 14  illustrates cable coupling  10  comprising indicator of the flex angle  52 , tensioning screw  53 , male clamp  54 , alignment guide  56 , female clamp  57 , pin  58 , and nut  59 . Cable  55  is fed into male clamp  54  to secure the cable. 
         [0077]    In general, the cable tensioning mechanism works as follows: The cable is threaded through segments  14 - 16 , tube assembly  33 , funnel  8  and screw  53 . The cable ends are held by the female clamp  57  and male clamp  54  of the two cable couplings  10 . By turning nut  59 , the screw  53  of the two cable couplings  10  is pulled back, thereby tensioning both ends of the cable. 
         [0078]      FIGS. 15 ,  16  and  17  illustrate the various parts of the cable clamping and tensioning mechanism.  FIG. 15  discloses one preferred tensioning screw component  53  of the cable coupling. This screw component  53  has a thread thereon.  FIG. 16  discloses one preferred female-threaded clamp component  57  of the cable coupling.  FIG. 17  discloses one preferred male-threaded clamp component  54  of the cable coupling. 
         [0079]      FIGS. 18   a  and  18   b  illustrate views of the left cover  60  of the handle  4 , while  FIGS. 19   a  and  19   b  illustrate the right cover  61  of handle  4 . 
         [0080]    To assemble the device, the cable  55  is threaded through the hole  24  of the insert  19 , looped through the groove  22  and threaded back into hole  24 . The cable is then locked by the outer shell  18  assembly with the insert  19 . The middle segments  15  are then threaded into the cable with their horizontal surfaces  25  facing the same direction. The flexible end  13  is then assembled with the tube assembly  33  and the cable ends are threaded through the tube. The left and right couplings  10  are assembled onto the driving shaft  11  and then the assembly is surrounded with the handle inserts  9 . The funnel  8  is assembled with handle inserts  9 . The cable ends are then guided into the funnel channels  37  and the hole of the tensioning screw  53 . The tube assembly  2  is then assembled with the funnel  8  and cables are pre-tensioned by hand. 
         [0081]    The cable ends are locked by the male clamp  54 . The final tensioning of the cable is achieved by turning the nuts. When this is done, the covers  60  and  61  are placed around the assembly and locked. The shrink tubing  3  is placed over the flexible end to prevent cement leakage. 
         [0082]    The flexing of the distal flexible end of the device is achieved by rotating the driving handle  5 . This rotation in turn turns the driving shaft  11 , and cable couplings  10  slide in opposite directions—pulling and releasing the cable. As the cable is fixed at the tip segment, it slides through the segments, either flexing or straightening the flexible end of the device. 
         [0083]    The present invention can be practiced through a unipedicular approach as well as a bipedicular approach. 
         [0084]    To inject cement into the vertebral body, an injection system having a cement reservoir containing flowable cement is attached to the luer  6  and cement is flowed through the central hole of the driving screw, funnel and the tube assembly into the flexible end of the device, and is finally ejected through the side hole  21  and into the vertebral body. 
         [0085]    In the embodiments shown, the device ejects cement through a hole in the sidewall of the tube. However, in other embodiments, the cement may be axially ejected via an endhole opening through a distal end portion of the tube. 
         [0086]    Preferred bone pastes include bone cements (such as acrylic-based bone cements, such as PMMA-based bone cements), pastes comprising bone particles (either mineralized or demineralized or both; and either autologous, allogenic or both), and ceramic-based bone cements (such as HA and TCP-based pastes). 
         [0087]    In some embodiments, the flexible needle of the present invention may also be used as a conduit for cement delivery. In some embodiments thereof, the proximal end portion of the tube is fluidly connected to a cement reservoir.