Abstract:
A device for treating vertebral bone including a releasably closed, removable filling member which can be placed within a plane separating superior and inferior portions of a vertebral body and oriented to promote its stabilization and realignment upon expansion of the filling member along the plane via injection of filler material, while minimally compacting bone or creating unsupported voids within the interior of the vertebral body.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims the benefit of U.S. Provisional Patent Application Ser. No. 60/739,209, filed Nov. 23, 2005, and is a continuation-in-part of U.S. patent application Ser. No. 10/949,217, filed Sep. 27, 2004, now U.S. Pat. No. 7,175,629, entitled “Extractable Filler for Inserting Medicine into Vertebral Body,” and is a continuation-in-part of U.S. patent application Ser. No. 10/652,470, filed Sep. 2, 2003, now U.S. Pat. No. 7,175,628, entitled “Extractable Filler for Inserting Medicine into Animal Tissue,” and is a continuation-in-part of U.S. patent application Ser. No. 10/651,988, filed Sep. 2, 2003, now U.S. Pat. No. 7,175,627, entitled “Extractable Filler for Inserting Medicine Into Animal Tissue,” all of which are incorporated herein by reference in their entirety. 
    
    
     FIELD OF THE INVENTION 
     This invention relates to medical devices and methods for use relating to the treatment of bone fracture. 
     BACKGROUND OF THE INVENTION 
     Previous treatment regimens for damaged and/or weakened spinal bones and cushioning/connective tissues are invasive procedures that cause significant trauma to the patient. Two surgical techniques have been developed in an attempt to treat fractured spinal bones in a minimally-invasive procedure. 
     One of these techniques, vertebroplasty, involves the injection of a flowable reinforcing material, usually polymethylmethacrylate (PMMA—commonly known as bone cement), through an 11-gage spinal needle or cannula device into an injured vertebral body. Shortly after cement injection, the liquid filling material polymerizes and increases in hardness, desirably supporting the vertebral body internally, alleviating pain and preventing further collapse of the injected vertebral body. 
     Another technique for treating vertebral fractures, kyphoplasty, is a more recently developed modification to the vertebroplasty technique. In a kyphoplasty procedure (also known as balloon-assisted vertebroplasty), an expandable device is inserted inside the damaged vertebral body, and is then expanded within the bone. Desirably, on removal of the expandable device this procedure creates a void within the bone that can be filled with bone cement or other load bearing material as a distinct segment of the treatment procedure, rendering the fractured bone load-bearing. In effect, the procedure creates an internal “cast,” protecting the bone from further fracture and/or collapse. 
     SUMMARY OF THE INVENTION 
     Embodiments of the present invention provide a devices and methods for the treatment of vertebral bone deformity resulting from collapse. According to one embodiment of the invention, the device includes a filling member capable of expanding to a final, pre-selected size and shape when filled with a filler material. The filling member is placed in an initially collapsed configuration along a separation plane within the vertebral body created by cutting across the vertebral body using osteotomy tools. Expansion of the filling member causes superior and inferior portions of the vertebral body defined by the separation plane to become realigned and at least partially restored to an original state. The filling member may be removed from the interior of the bone, leaving behind a support structure consisting of hardened filler material having the pre-selected geometry of the expanded filling member. According to an aspect of the present invention, expansion and removal of the filling member occurs absent compaction of cancellous bone or creation of unsupported voids or cavities in the interior of the vertebral bone. 
     In an embodiment of another aspect of the present invention, a device for treating a vertebral body having a superior portion, an inferior portion, and a separation plane defining the superior and inferior portions comprises a releasably closed filling member having an interior holding portion and a flexible wall provided with an opening at a distal end, a shaft portion connected to the filling member, and an injection port in communication with said holding portion. The filling member has a collapsed state for insertion into the separation plane and an expanded state with a preselected geometry. A filler material injected into the filling member causes expansion of the filling member and realignment of the superior and inferior portions of the vertebral body absent destructive compaction of cancellous bone. The superior and inferior portions are supported by the filler material capable of hardening into substantially the same preselected shape as the filling member and remaining in the vertebral body following withdrawal of the filling member. 
     In an embodiment of another of its aspects, the invention provides a method for treatment of a vertebral body comprising first accessing the interior of the vertebral body and creating a separation plane defining a superior and inferior portion of the vertebral body. According to this embodiment, an expandable device having a preselected geometry is introduced into the separation plane, and filler material is injected into the device, thereby repositioning the superior portion relative to the inferior portion of the vertebral body. Repositioning of the superior and inferior portions of the vertebral body occurs without creating voids or compacting bone within the interior of the vertebral body. 
     The invention, in yet another embodiment, provides a surgical kit for treating vertebral bone comprising an osteotomy tool for accessing the interior of a vertebral body and creating a plane separating a superior and inferior portion of the vertebral body, an expandable device having a preselected terminal shape, consisting of an interior holding portion and a flexible wall with an opening at a distal end, and injectable filler material capable of hardening to form a support structure with a preselected shape. 
     In still another embodiment of the present invention, a device for providing support in the interior of a vertebral body comprises a support structure having a preselected geometry when occupying a separation plane defining a superior and inferior portion of a vertebral body. According to this embodiment, the support structure may be injected in a non-solid form into an optionally extractable, expandable device, causing the superior and inferior portions to realign without compaction of cancellous bone. 
     In a further embodiment of the present invention, a support structure for vertebral bone is obtained by the process of first accessing the interior of a vertebral body and using osteotomy to create a separation plane defining a superior portion and inferior portion of the vertebral body. Filler material is injected into an expandable device positioned within the separation plane and having a preselected geometry. The expandable device is removed from the vertebral body after the superior and/or inferior portions have realigned absent compaction of cancellous bone, leaving behind the support structure. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The invention can be more readily understood with reference to the following embodiments and the examples depicted in the figures, which are schematic and are not to scale. 
         FIG. 1  shows a releasably closed apparatus and an aspect of a method for treating a fractured, cancellous or otherwise diseased vertebral body according to an embodiment of the present invention. As shown the apparatus is in a deployed but unfilled state. 
         FIG. 2  shows the releasably closed apparatus of  FIG. 1  in a deployed and partially filled state and a further aspect of the method for its use in treatment of the vertebral body. 
         FIG. 3  shows the support structure that remains in the repaired vertebral body. 
     
    
    
     DETAILED DESCRIPTION 
     In its various embodiments and aspects, the present invention provides a releasably closed, optionally extractable device and method of use for formation and/or placement of a stabilizing object or other support structure  60  (referred to collectively below, without limitation, as “support structure”) of predetermined form, volume or spatial orientation into a vertebral body  3  or other bone. The support structure  60 , when formed, can be useful in treating cancellous, fractured or otherwise diseased bone, such as the partial or complete restoration of the relative positioning of superior  2  and inferior  4  vertebral endplates and, with it, the treatment of kyphosis or other spinal conditions that can result from such diseased vertebrae. According to aspects of the present invention, a practitioner can select or provide for a predictable form or geometry of support structure  60  through the creation or selection of the extractable device. In other embodiments, the device for formation of the support structure  60  may be left intact, where it may be reabsorbed. 
       FIGS. 1-3  depict a cancellous or otherwise diseased vertebral body  3 , which, in a fractured condition, has collapsed in an upper portion (e.g., the superior portion  2 ) of the vertebral body  3 . Such collapse may result from compression fracture affecting those suffering from osteoporosis. In order to treat such fracture, in an embodiment of an aspect of the present invention, a releasably closed filling member  10  is inserted into the vertebral body  3 . The filling member  10  and the manner of its use may, without limitation, be of a type described in copending U.S. patent applications: Ser. No. 10/652,470 entitled “Extractable Filler for Inserting Medicine into Animal Tissue” filed Sep. 2, 2003; Ser. No. 10/651,988 entitled “Extractable Filler for Inserting Medicine into Animal Tissue” filed Sep. 2, 2003; Ser. No. 10/949,217 entitled “Extractable Filler for Inserting Medicine into Vertebral Body” filed Sep. 27, 2004; and provisional patent applications: 60/697,260 entitled “Devices and Methods for the Treatment of Bone Fracture” filed Jul. 5, 2005; 60/697,146 entitled “Device for Delivery of Bone Void Filling Materials” filed Jul. 7, 2005, all of which applications are subject to a common obligation of assignment with the present application and are incorporated herein by reference in their entirety. The deployment of filling member  10  may, though need not, occur following the creation of a separation plane  35  between superior  2  and inferior  4  portions of the vertebral body  3 . The presence of a separation plane  35  within the vertebral body  3  will allow for the alignment of the vertebral endplates in response to the filling member  10  in the condition of trauma induced fracture of non-osteoporotic bone. The presence of a separation plane  35  within the vertebral body  3  will allow for the alignment of the vertebral endplates  2  and  4  absent of destructive compaction of the cancellous bone  40 . 
     The filling member  10 , in one embodiment, comprises a holding portion  20  and a flexible wall  30 . The holding portion  20  and flexible wall  30  may constitute a vessel structure. The flexible wall  30  can be permeable or hermetic. In some embodiments it may be of a bioabsorbable material, if all or part of the filling member  10  is to be left behind. The filling member  10  may be connected to a shaft portion at one end. It can be inserted into a passage in the vertebral body  3  or can be inserted into a separation plane  35  according to the present invention. One feature of embodiments of certain aspects of this invention is that the filling member  10  can be placed at an orientation relative to the vertebral body  3 . In this case, a shape of the resulting support structure  60  can be provided with a preselected orientation with respect to the repaired vertebral body  70 . Once the filling member  10  is inserted into the passage or separation plane  35 , filler material  50  is injected into the filling member  10 . Filler material  50  is confined to the preselected shape and orientation of the filling member  10  absent of void creation within the vertebral body  3 . The formation of a separation plane  35  may divide the vertebral body  3  into superior  2  and inferior  4  portions. Filler material  50  may be of any suitable biocompatible material for use in bone. 
     The filling member  10  expands, according to an aspect of the present invention, to a predictable shape as the filler material  50  is injected. Expansion may, according to an aspect of the present invention, involve a transition from a collapsed state to an expanded state without elastic deformation of material from which the filling member  10  is constructed. In other embodiments, the material may stretch in one or more regions. Regardless, in an aspect of the present invention, the filling member  10  may have a preselected “terminal” form that it assumes when filled to a desired degree. Furthermore, in an aspect of the present invention, one or more aspects of the filling member  10  may be preselected. For one example, but without limitation, the leading edge of the filling member  10  may have a height and/or other dimension preselected in order to achieve a desired degree of height restoration in the vertebral body  3 . As the filling member  10  expands to a predictable shape, the superior portion  2  can be gradually repositioned in order to preferentially, restore height to the vertebral body  3 . In the course of so doing, or even if height is not fully restored, end plates associated respectively with the superior  2  and inferior  4  portions of the vertebral body  3  can be at least partially and in some cases fully restored to a substantially parallel orientation with respect to one another. The treatment leading to at least partial restoration of vertebral height and/or end plate parallelism may be accomplished, according to an aspect of the present invention, with minimal or no compaction of cancellous  40  or other interior vertebral bone. If, in other embodiments, compaction were to occur, a particular direction of compaction of the cancellous bone  40  could be dictated by the practitioner-selected predictable shape of the filling member  10 . 
     Use of the filling member  10  when inserted into the vertebral body  3 , according to an aspect of the present invention as described in one or more of the copending and commonly owned applications, provides continual support during the restoration of the vertebral body  3 . Similarly, according to an aspect of the present invention, the formation of voids, cavities or other hollow or otherwise unsupported spaces, or the need for increased volume of an existing passage within the vertebral body  3  can be partially or altogether avoided. Hydrostatic pressure in the filling material  50  prior to its setting, or its increasing rigidity during and after setting, provides such continual structural support. In other embodiments, such continual support may be provided via other mechanisms that need not necessarily be solid or have the properties of the deposited support structures  60  described and shown herein. Once the filling member  10  expands to its predictable shape, the filler material  50  is then allowed to increase in viscosity while curing to provide support. Once the filler material  50  viscosity has increased, the filler member  10  may be removed, according to an aspect of the present invention, from the vertebral body  3  without formation of an unsupported void in the bone. The support structure  60  which results from the higher viscosity or solidified filler material  50  remains in the repaired vertebral body  70 . 
     In an embodiment of another aspect of the present invention, the filler member  10  may expand to a preselected volume (which may or may not be accompanied by the assumption of a preselected or predictable shape). According to this embodiment of the present invention, a preselected volume of filler material  50  is injected or otherwise deposited into the filler member  10 . The filler member  10  expands to the predetermined volume, thereby providing a controlled relocation of at least a subset of superior portion  2  of vertebral body  3 . Once the filling member  10  expands to its predetermined volume, the filler material  50  is then allowed to increase in viscosity or solidify. When the filler material  50  has increased in viscosity or solidified, the filler member  10  is removed from the vertebral body  3  without formation of an unsupported void in the bone, in an embodiment of an aspect of the present invention. The support structure  60  which results from the filler material  50 , in an embodiment of an aspect of the present invention, and has one or more of a preselected form, volume and spatial orientation, remains in the repaired vertebral body  70 . 
     In an embodiment of an aspect of the present invention, the device comprises a releasably closed filling member  10  that is inserted into a vertebral body  3 . The filling member  10  may comprise the flexible wall  30  and the interior holding portion  20 . At a distal end of the holding portion  20 , an opening may be provided which is temporarily closed by sutures. Removal of the sutures after injection of filler material  50  into the holding portion  20  causes the opening to be exposed and allows the filling member  10  to be withdrawn from the vertebral body  3 . 
     In an embodiment of an aspect of the present invention, the filling member  10  has a predictable or other preselected form, volume and/or orientation and is inserted into a hole in the vertebral body  3 . A filler material  50 , such as but not limited to bone cement, then is injected through an injection port into the holding portion  20  of the filling member  10 . As the filler material  50  is injected through the injection port, the filling member  10  expands, thereby relocating some or all of the superior  2  and inferior  4  portions of the vertebral body  3  in a controlled and continuously supported manner. Expansion continues until the preselected or otherwise predictable form of the filling member  10  results. At this point, the filler material  50  is allowed to solidify, according to an aspect of the invention, into a shape that has substantially the same predictable form as the predictable form of the filling member  10 . Once the filler material  50  has solidified, the filling member  10  may be removed from the vertebral body  3 . A solid support structure  60  resulting from the solidified filler material  50 , according to an aspect of the present invention, remains in the vertebral body  3  to provide support for the repaired vertebral body  70 . In other aspects of the present invention, the support structure  60  can have one or more of a preselected shape, volume, spatial orientation, or other physical characteristic. 
     The filling member  10 , according to an embodiment of an aspect of the present invention, has a predetermined volume upon expansion. In this embodiment, the filler material  50  is injected into the filling member  10  until the amount of the filler material  50  injected reaches the predetermined volume of the filling member  10  upon expansion. The filler material  50  then solidifies and the filling member  10  is removed from the vertebral body  3 . A solid support structure  60  resulting from the solidified filler material  50  is left in the vertebral body  3  to provide support for the repaired vertebral body  70 . 
     In another embodiment of the present invention, the filling member  10  is inserted into the separation plane  35  in a particular orientation allowing for maximized repair and stability for the vertebral body  3 . In this embodiment, the predictable form of the filling member  10  and the location of the filling member  10  within the vertebral body  3  are chosen to place the resulting support structure  60  in a particular orientation within the vertebral body  3 . This specific orientation with respect to vertebral body  3  not only aids in height restoration at a particular position, but places the support structure  60  in a position which provides maximum support for the repaired vertebral body  70 . 
     Another feature of the embodiments of certain aspects of the present invention is that the filling member  10  and resulting support structure  60  have a predictable form. The predictable form can be a sac, bag, ball, cylinder, cone, rectangular column or any other geometric form. Furthermore, the predictable forms can be specifically designed for the individual patient to best address the degree of height restoration needed. One example of a predictable form is a cylinder that has, at one end, a cross section of greater area at a position closer to the collapsed portion of the vertebral body as compared to the opposite end of the cylinder, which has a cross section of smaller area. Alternatively, the predictable form could be substantially tubular. In this form, the cross sections perpendicular to a longitudinal axis of the holding portion of the filler member are substantially elliptical and have increasing areas thereof along a direction from the injection port to the opposite end of the holding portion. Alternatively, the predictable form could be a combination of two separate geometric forms. For example, predictable form could be a rectangular column at one end and a tubular shape at the other end. The rectangular column would provide more robust support vertically at the point of maximum height loss, while the tubular shaped portion could supply a more even support across the remaining portion of the vertebral body  3 . 
     Other objects, advantages and embodiments of the various aspects of the present invention will be apparent to those who are skilled in the field of the invention and are within the scope of the appended claims. For example, but without limitation, structural or functional elements might be rearranged, or method steps reordered, consistent with the present invention. In addition, although embodiments of the invention are described with respect to the treatment of osteoporotic vertebral compression fractures or other spine fractures, similar principles according to the present invention, and systems and methods that embody them, could be applied to other examples, which, even if not specifically described here in detail, would nevertheless be within the scope of the appended claims.