Patent Publication Number: US-2023149058-A1

Title: Method and apparatus for augmenting bone

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation of U.S. patent application Ser. No. 16/566,949, filed Sep. 11, 2019, which is a continuation of U.S. patent application Ser. No. No. 15/977,454, filed May 11, 2018, now U.S. Pat. No. 10,413,340, issued Sep. 17, 2019, which is continuation of U.S. patent application Ser. No. 14/700,255, filed on Apr. 30, 2015, now U.S. Pat. No. 9,987,055, issued Jun. 5, 2018, which is a divisional of U.S. patent application Ser. No. 12/859,732, filed on Aug. 19, 2010, now U.S. Pat. No. 9,247,970, issued Feb. 2, 2016, which claims the benefit of U.S. Provisional Patent Application Ser. No. 61/235,196, filed on Aug. 19, 2009. The entire disclosures of each application listed in this paragraph are hereby incorporated by reference into the present application as if set forth in their entirety herein. 
    
    
     TECHNICAL FIELD 
     The present disclosure relates generally to implant for augmenting or supporting bone, and in particular relates to expandable implants. 
     BACKGROUND 
     Vertebral compression fractures (“VCF”) represent a common spinal injury and may result in prolonged disability. Generally speaking, VCF involves collapsing of one or more vertebral bodies in the spine. VCF usually occurs in the lower vertebrae of the thoracic spine or the upper vertebrae of the lumbar spine. VCF generally involves fracture of the anterior portion of the affected vertebral body. VCF may result in deformation of the normal alignment or curvature, e.g., lordosis, of the vertebral bodies in the affected area of the spine. VCF and/or related spinal deformities may result, for example, from metastatic diseases of the spine, from trauma or may be associated with osteoporosis. Until recently, doctors were limited in how they could treat VCF and related deformities. 
     Recently, minimally invasive surgical procedures for treating VCF have been developed. These procedures generally involve the use of a cannula or other access tool inserted into the posterior of the targeted vertebral body, usually through the pedicles. 
     In one such procedure, a cannula or bone needle is passed through the soft tissue of the patient&#39;s back. Once properly positioned, a small amount of polymethylmethacrylate (PMMA) or other orthopedic bone cement is pushed through the needle into the targeted vertebral body. This technique may be effective in the reduction or elimination of fracture pain, prevention of further collapse, and a return to mobility in patients. However, this technique typically does not reposition the fractured bone into its original size and/or shape and, therefore, may not address the problem of spinal deformity due to the fracture. 
     Other treatments for VCF generally involve two phases: (1) reposition or restoration of the original height of the vertebral body and consequent lordotic correction of the spinal curvature; and (2) augmentation or addition of material to support or strengthen the fractured or collapsed vertebral body. 
     One such treatment involves inserting, through a cannula, a catheter having an expandable member into an interior volume of a fractured vertebral body, wherein the interior volume has a relatively soft cancellous bone surrounded by fractured cortical bone therein. The expandable member is expanded within the interior volume in an attempt to restore the vertebral body towards its original height. The expandable member is removed from the interior volume, leaving a void within the vertebral body. PMMA or other bone filler material is injected through the cannula into the void to stabilize the vertebral body. The cannula is then removed and the cement cures to augment, fill or fix the vertebral body. 
     Another approach for treating VCF involves inserting an expandable mesh graft bladder or containment device into the targeted vertebral body. The graft bladder remains inside the vertebral body after it is inflated with PMMA or an allograft product. 
     It is desirable in the art to provide a safe and effective apparatus and method for aiding and/or augmenting fractured or otherwise damaged vertebral bodies and other bones. 
     SUMMARY 
     In accordance with one embodiment, an expandable implant system is configured to increase the height of a fractured target bone. The expandable implant system includes a primary implant and an auxiliary implant. The primary implant includes a primary implant body configured to move from a collapsed configuration to an expanded configuration. The primary implant body defines an internal void. The auxiliary implant is configured to be disposed in the internal void of the primary implant body and expanded from a collapsed configuration to an expanded configuration. The auxiliary implant defines a central body portion and at least a pair of nodes that extend out from the central body portion. The nodes at least partially define at least one pocket when the auxiliary implant is in its expanded configuration while disposed in the primary implant. 
    
    
     
       DESCRIPTION OF THE DRAWINGS 
       The foregoing summary, as well as the following detailed description of an example embodiment of the application, will be better understood when read in conjunction with the appended drawings, in which there is shown in the drawings an example embodiment for the purposes of illustration. It should be understood, however, that the application is not limited to the precise arrangements and instrumentalities shown. In the drawings: 
         FIG.  1 A  is a schematic side elevation view of a series of vertebrae including a target vertebra whose vertebral body has been compressed; 
         FIG.  1 B  is a schematic side elevation view of the series of vertebrae illustrated in  FIG.  1 A , showing a primary expandable implant disposed in the vertebral body of the target vertebra in a compressed insertion configuration; 
         FIG.  1 C  is a schematic side elevation view of the series of vertebrae illustrated in  FIG.  1 B , showing the primary implant in an expanded configuration so as to restore height to the vertebral body of the target vertebra; 
         FIG.  1 D  is a perspective view of an implant system, including a primary implant illustrated in  FIG.  1 C  and an auxiliary implant disposed in the primary implant, showing the primary implant assembly in an expanded configuration; 
         FIG.  2 A  is a perspective view of the primary implant illustrated in  FIG.  1 D , shown in a collapsed configuration; 
         FIG.  2 B  is a perspective view of the primary implant illustrated in  FIG.  2 A , shown in an expanded configuration; 
         FIG.  2 C  is a side elevation view of the primary implant illustrated in  FIG.  2 B ; 
         FIG.  2 D  is an end elevation vie of the primary implant illustrated in  FIG.  2 B ; 
         FIG.  3 A  is a perspective view of a first linkage of the primary implant constructed in accordance with an alternative embodiment; 
         FIG.  3 B  is a perspective view of a second linkage of the primary implant of  FIG.  3 A ; 
         FIG.  3 C  is a top plan view of the primary implant inserted into a target bone in accordance with one embodiment; 
         FIG.  3 D  is a top plan view of an implant system inserted into a target bone in accordance with an alternative embodiment; 
         FIG.  3 E  is a top plan view of an implant system inserted into a target bone in accordance with an alternative embodiment; 
         FIG.  4 A  is a perspective view of an implant system inserted in a target bone, the implant system including a pair of implant assemblies, each including a primary implant an auxiliary implant disposed in the primary implant, wherein the implant system is shown in an expanded configuration; 
         FIG.  4 B  is a top plan view of the implant system illustrated in  FIG.  4 A ; 
         FIG.  4 C  is a perspective view of one of the implant assemblies illustrated in  FIG.  4 A ; 
         FIG.  4 D  is a top plan view of the implant assembly illustrated in  FIG.  4 C ; 
         FIG.  4 E  is an end elevation view of the implant assembly illustrated in  FIG.  4 D , showing bone stimulating material injected into pockets disposed between the primary and auxiliary implants; 
         FIG.  4 F  is an end elevation view of the auxiliary implant illustrated in  FIG.  4 A , shown in a folded or collapsed insertion configuration; 
         FIG.  4 G  is a perspective view of the auxiliary implant illustrated in  FIG.  4 A , including channels in accordance with an alternative embodiment; 
         FIG.  4 H  is a sectional end elevation view of the auxiliary implant illustrated in  FIG.  4 G ; 
         FIG.  5 A  is a perspective view of an implant system constructed in accordance with an alternative embodiment inserted in a target bone, the implant system including a pair of implant assemblies, each including a primary implant an auxiliary implant disposed in the primary implant, wherein the implant system is shown in an expanded configuration; 
         FIG.  5 B  is a top plan view of the implant system illustrated in  FIG.  5 A ; 
         FIG.  5 C  is a side elevation view of one of the implant assemblies of the implant system illustrated in  FIG.  5 A ; 
         FIG.  5 D  is a perspective view of one of the implant assembly illustrated in  FIG.  5 C ; 
         FIG.  5 E  is a top plan view of the implant assembly illustrated in  FIG.  5 C ; 
         FIG.  5 F  is an end elevation view of the implant assembly illustrated in  FIG.  5 E , showing bone stimulating material injected into pockets disposed between the primary and auxiliary implants; 
         FIG.  5 G  is an end elevation view of the auxiliary implant illustrated in  FIG.  5 A , shown in a folded or collapsed insertion configuration; 
         FIG.  6 A  is a perspective view of an implant system constructed in accordance with an alternative embodiment inserted in a target bone, the implant system including a pair of implant assemblies, each including a primary implant an auxiliary implant disposed in the primary implant, wherein the implant system is shown in an expanded configuration; 
         FIG.  6 B  is a top plan view of the implant system illustrated in  FIG.  6 A ; 
         FIG.  6 C  is a side elevation view of one of the implant assemblies of the implant system illustrated in  FIG.  6 A ; 
         FIG.  6 D  is a perspective view of one of the implant assembly illustrated in  FIG.  6 C ; 
         FIG.  6 E  is a top plan view of the implant assembly illustrated in  FIG.  6 C ; 
         FIG.  6 F  is an end elevation view of the implant assembly illustrated in  FIG.  6 E , showing bone stimulating material injected into pockets disposed between the primary and auxiliary implants; 
         FIG.  6 G  is an end elevation view of the auxiliary implant illustrated in  FIG.  6 A , shown in a folded or collapsed insertion configuration; 
         FIG.  6 H  is an end elevation view of an implant assembly similar to the implant assembly illustrated in  FIG.  6 F , but constructed in accordance with an alternative embodiment; 
         FIG.  7 A  is an implant assembly including a primary implant, and an auxiliary implant constructed in accordance with an alternative embodiment, showing the implant assembly in an expanded configuration; 
         FIG.  7 B  is a perspective view of the auxiliary implant illustrated in  FIG.  7 A ; 
         FIG.  7 C  is a perspective view of the auxiliary implant illustrated in  FIG.  7 B , showing a bladder being inserted into a support sleeve in a collapsed configuration; 
         FIG.  7 D  is a sectional end elevation view of the implant assembly illustrated in  FIG.  7 A , taken along line  7 D- 7 D; 
         FIG.  7 E  is a sectional end elevation view of an auxiliary implant similar to  FIG.  7 D , but constructed in accordance with an alternative embodiment; 
         FIG.  7 F  is a sectional end elevation view of an auxiliary implant assembly similar to the auxiliary implant assembly illustrated in  FIG.  7 E , but constructed in accordance with another alternative embodiment. 
         FIG.  8 A  is a perspective view of a support sleeve constructed in accordance with an alternative embodiment; 
         FIG.  8 B  is a perspective view of a support sleeve constructed in accordance with another alternative embodiment; 
         FIG.  8 C  is a top plan view of an enlarged an implant sleeve constructed in accordance with an alternative embodiment; 
         FIG.  8 D  is a top plan view of an enlarged an implant sleeve constructed in accordance with another alternative embodiment; and 
         FIG.  9    is a sectional end elevation view of an auxiliary implant assembly similar to the auxiliary implant assembly illustrated in  FIG.  7 E , but wherein the sleeve is compliant and expandable in accordance with an alternative embodiment. 
         FIG.  10 A  is a perspective view of an opening assembly of an implant insertion assembly, including a cannulated body and an opening device received in the cannulated body; 
         FIG.  10 B  is a perspective view of the opening device illustrated in  FIG.  10 A ; 
         FIG.  10 C  is a perspective view of the cannulated body illustrated in  FIG.  10 A ; 
         FIG.  10 D  is a top plan view of the insertion assembly installed in a target vertebral body through the pedicle; 
         FIG.  10 E  is a top plan view of the primary implant and an expansion body inserted into the target vertebral body by the insertion assembly illustrated in  FIG.  10 D ; 
         FIG.  10 F  is a top plan view similar to  FIG.  10 E , but showing the expansion body in an expanded configuration biasing the primary implant to an expanded configuration; 
         FIG.  10 G  is a top plan view similar to  FIG.  10 F , but showing the expansion body deflated and removed from the primary implant, which remains in its expanded configuration; 
         FIG.  10 H  is a top plan view similar to  FIG.  10 G , but showing the auxiliary implant inserted into the expanded primary implant in a collapsed configuration via the insertion assembly; 
         FIG.  10 I  is a top plan view similar to  FIG.  10 H , but showing the auxiliary implant expanded to its expanded configuration inside the primary implant; 
         FIG.  10 J  is a to plan view similar to  FIG.  10 I , but showing the insertion assembly removed from the target vertebra; 
         FIG.  11 A  is a perspective view of the opening assembly as illustrated in  FIG.  10 A , but wherein the opening device has a curved distal end; 
         FIG.  11 B  is a perspective view of the opening device illustrated in  FIG.  11 A ; 
         FIG.  11 C  is a perspective view of the cannulated body illustrated in  FIG.  10 A ; 
         FIG.  11 D  is a top plan view of the insertion assembly installed in a target vertebral body through the pedicle; 
         FIG.  11 E  is a top plan view of the primary implant and an expansion body inserted into the target vertebral body by the insertion assembly illustrated in  FIG.  11 D ; 
         FIG.  11 F  is a top plan view similar to  FIG.  11 E , but showing the expansion body in an expanded configuration biasing the primary implant to an expanded configuration; 
         FIG.  11 G  is a sectional end elevation view of the expansion body illustrated in  FIG.  11 F , taken along line  11 G- 11 G; 
         FIG.  11 H  is a top plan view similar to  FIG.  11 G , but showing the auxiliary implant inserted into the expanded primary implant in a collapsed configuration via the insertion assembly 
         FIG.  11 I  is a schematic sectional end elevation view of the auxiliary implant illustrated in  FIG.  11 H , taken along line  111 - 111 ; 
         FIG.  11 J  is a top plan view similar to  FIG.  11 H , but showing the auxiliary implant expanded to its expanded configuration inside the primary implant, and showing the insertion assembly removed from the target vertebra; 
         FIG.  12 A  is a top plan view of the insertion assembly installed in a target vertebral body via a lateral or trans-psoas approach; 
         FIG.  12 B  is a top plan view similar to  FIG.  12 A , but showing the expansion body expanded inside the primary implant in the vertebral body; and 
         FIG.  12 C  is a top plan view similar to  FIG.  12 B , but showing the expansion body removed from the primary implant, and the auxiliary implant inserted into the primary implant via the insertion assembly. 
     
    
    
     DETAILED DESCRIPTION 
     Referring initially to  FIGS.  1 A-D , an expandable implant system  18  includes at least one implant assembly  19 , such as a pair of implant assemblies  19 , that are configured to be inserted into a target bone, which can be a vertebra  17  as illustrated. In particular, each implant assembly  19  can be implanted in the vertebral body portion  21  of the vertebra  17  that has been subjected to trauma, such as a vertebral compression fracture (“VCF”), and has a reduced anterior height H 1  and an increased kyphotic angle ( FIGS.  1 A-B ) with respect to an anatomically normal height prior to the trauma. The implant assembly  19  includes a primary expandable implant  20 , which can be a stent, that can be implanted into the vertebral body portion  21  via a minimally invasive surgical technique, such as, for example, through one or more cannulas, preformed holes or percutaneously. Once implanted, the expandable implant  20  is configured to reposition and stabilize the target bone to re-establish structural integrity and reduce or eliminate painful micro-movements. 
     As generally understood by one of ordinary skill in the art, it should be understood that while the expandable implant assembly  19  is illustrated as usable in an interior volume of the targeted vertebral body portion  21  in the spine (for example, in the lumbar, thoracic or cervical regions), it is appreciated that the expandable implant system  18  can be used in other parts of the body such as, for example, in an intervertebral disc space for cage, nucleus replacement, etc., between tissue and bone, in long bones such as proximal humerus and proximal tibia or bones in the hand, face, feet, extremities, cranium, or in nearly any bone in the human body, or as intervertebral spacers to restore intervertebral space height, and thus implanted in a degenerated intervertebral disc, or after removal of the intervertebral disc in an intervertebral space. 
     Thus, the primary implant  20  has a first insertion configuration having a corresponding first insertion size that is configured to allow the primary implant  20  to be inserted into an interior volume of the target bone. Once inserted into the target bone, the expandable implant can be expanded in situ from the insertion configuration to a second expanded configuration having a corresponding second expanded size that is greater than the insertion size. When in the expanded configuration, the primary implant  20  can generally create a cavity within the interior volume of the vertebral body portion  21 , stabilize the vertebral body portion  21 , and occupy a portion of, or augment, the interior volume of the vertebral body portion  21 . Thus, the primary implant  20  is expandable to an expanded configuration that restores the height of the vertebral body portion to a second anterior height H 2  that is greater than the first anterior height H 1 , and a reduced or eliminated kyphotic angle with respect to that illustrated in  FIGS.  1 A-B . The second height H 2 , for instance, can be an anatomically desirable height. The implant assembly  19  further includes an auxiliary implant  110  is configured to be inserted into the primary implant  20 , for instance through the cannula, in a retracted configuration, and subsequently expanded inside the primary implant to support the primary implant in its expanded configuration such that the expandable implant system  18  can absorb post-operative anatomical forces subjected to the vertebra  17  during normal anatomical function, and maintain its structural integrity. The implants  20  and  110  can be made from any suitable reinforced biocompatible material, and can include titanium, a titanium alloy, polyetherether ketone (PEEK), polyetherketoneketon (PEKK) or the like. 
     Referring now to  FIGS.  2 A-D , the primary implant  20  is illustrated as including a substantially annular implant body  22  disposed about a central axis  24  that extends in an axial direction A. The implant  20  can be made from a polymeric material with directed fibres, and can be coated if desired with one or more antibiotic agents in order to inhibit infections. In accordance with one embodiment, the implant  20  is made from a Phynox (e.g., L605 alloy, or CoCrWNi alloy) material, though the implant  20  can alternatively be made from any suitable alternative material, such as stainless steel, Elgiloy (CoCrMo), Titanium, Ti-6A1-7Nb (TAN), Ti-6A1-4V (TAV), polyetheretherketone (PEEK), or any biocompatible plastic such as PEEK, PET, PUR, PCU, Silicones, or the like. The implant  20  can further be coated with an osteoconductive layer such as sprayed Hydroxyapatite or other Ca and P compositions. The implant  20  can be manufactured by selective laser cutting process in order to change the geometry as desired. 
     The implant body  22  includes an inner surface  22   a  that defines an internal void  23 , and an opposed outer surface  22   b.  The implant body  22  includes a plurality of connected linkages  26 . Each linkage  26  includes a first and second opposed flexible and plastically deformable side portions  28  and  30 , respectively, and first and second opposed flexible end portions  32  and  34 , respectively, that provide flexible and plastically deformable hinges connected between the side portions  28  and  30 . The end portions  32  and  34  can be curved or otherwise shaped as desired, and define a radius of curvature in accordance with the illustrated embodiment. Likewise, the side portions  28  and  30  are substantially straight and parallel along the axial direction when the implant  20  is in the insertion configuration, though it should be appreciated that the side portions  28  and  30  can define any suitable shape and spatial relationship as desired. 
     In accordance with the illustrated embodiment, the linkages  26  are arranged in at least one, such as a plurality of, columns  27 , and at least one, such as a plurality of, rows  29 . The columns  27  extend along a column direction that is coincident with the axial direction A in the illustrated embodiment. The rows  29  extend along a row direction that is circumferential so as to define an annulus in the illustrated embodiment. The ends of the linkages  26  are integrally or directly connected to each other along the column direction as illustrated, though it should be appreciated that the linkages  26  could alternatively be connected to each other indirectly via a connection member. The sides of the linkages  26  are indirectly connected to each other via corresponding circumferential arms  36 , though it should be appreciated that the sides of the linkages  26  could alternatively be directly connected to each other. It can thus be said that the linkages  26  are connected to each other, either indirectly or indirectly, along the column and row directions so as to define respective columns  27  and rows  29 . 
     In accordance with one embodiment, the side portions  28  and  30  extend axially, that is they extend along a direction having an axial component. Otherwise stated, the side portions  28  and  30  extend along a direction that is angularly offset with respect to a radial direction R that extends along a direction perpendicular with respect to the central axis  24 . Accordingly, as will be appreciated from the description below, the side portions  32  and  34  are configured to expand and plastically deform when a radially outward force is applied to the implant body  22 , thereby expanding the size of the internal void  23 . The implant  20  can be expanded from its insertion configuration to its expanded configuration by inserting a sufficient volume of thermosetting bone filler material into the internal void  23  of the implant  20 , such that the material fills the void  23  and applies a radially outward expansion force F against the linkages  26 . For instance, as will be described in more detail below, the implant assembly  19  can include an expansion device  58 , such as an expandable bladder  69  (see  FIGS.  10 E-F ), that is temporarily placed inside the implant body  22  and expanded so as to expand the implant body  22 , such that the implant body  22  is plastically deformed in an expanded configuration. The bladder can then be deflated and removed from the implant body  22 , and the auxiliary implant  110  can be implanted in the primary implant and subsequently expanded so as to augment, support, and stabilize the primary implant  20 . 
     In accordance with the embodiment illustrated in  FIG.  2 A , when the primary implant  20  is in the compressed or collapsed insertion configuration, each given linkage defines a length L 1  that extends between the opposed end portions  32  and  34 . Furthermore, when the implant  20  is in the insertion configuration, the side portions  28  and  30  extend substantially parallel to each other and are separated from each other by a first or insertion distance D 1 , which extends circumferentially in accordance with the illustrated embodiment. Otherwise stated, the side portions  28  and  30  are separated by the first distance D 1  at a select location along the length of the side portions  28  and  30 . Thus, the circumference of the implant body  22  is at least partially defined by the first distance D 1 . When the implant  20  is in the insertion configuration, the implant body  22  defines a first cross-sectional distance CS 1 , which can be a diameter, for instance when the implant defines a cylindrical surface as illustrated. The first cross-sectional distance CS 1 , and thus the first distance D 1 , provides the implant  20  with the first insertion size that is configured to allow the implant  20  to be inserted into an interior volume of the target bone. 
     The expandable implant  20  is configured to expand from the insertion configuration illustrated in  FIG.  2 A  to the expanded configuration illustrated in  FIGS.  2 B-D . Each linkage  26  can be substantially identically constructed, and thus defines substantially the same initial length L 1  and distance D 1  as the other linkages  26 . When the radially outward expansion force F is applied to the inner surface of the linkage body  22 , and in particular to the linkages  26 , the linkages  26  expand circumferentially. For instance, the initial distance extending between the side portion  28  and  30  of at least one up to all of the linkages  26  increases from the first insertion distance D 1  to a second expanded distance D 2  that is greater than the first insertion distance D 1 . Simultaneously, the length of at least one up to all of the linkages  26  is reduced from the first length L 1  to a second expanded length L 2  that is less than the first insertion length L 2 . Assuming that the expansion force F is distributed uniformly about the implant body  22 , the identically constructed linkages  26  will expand substantially uniformly, and the implant body  22  will expand to a second expanded cross-sectional distance or diameter CS 2  that is greater than the first insertion cross-sectional distance or diameter CS 1 . 
     While the linkages  26  can all be substantially identically constructed as described above with respect to  FIGS.  2 A-D , it is appreciated that at least one, such as a first plurality, of the linkages  26  can be constructed differently than at least one, such as a second plurality, of the linkages  26 . For instance, referring to  FIGS.  3 A-B , the implant  20  can include a first plurality of elements or linkages  26   a  and a second plurality of elements or linkages  26   b.  The linkages  26   a  can be circumferentially spaced from the linkages  26   b,  such that they are on circumferentially opposed sides of the implant body  22  relative to each other. Otherwise stated, a first select number of columns  27 , and in particular adjacent columns  27  can include linkages  26   a,  while a second select number of columns  27 , and in particular adjacent columns  27 , can include linkages  26   b.  Alternatively or additionally, the linkages  26   a  can be axially spaced from the linkages  26   b,  such that a first select number of rows  29 , and in particular adjacent rows  29 , can include linkages  26   a,  while a second select number of rows  29 , and in particular adjacent rows  29 , can include linkages  26   b.    
     In accordance with the illustrated embodiment, the axial insertion length L 1  of the first plurality of linkages  26   a  is greater than the axial insertion length L 1  of the second plurality of linkages  26   b  when the implant  20  is in the insertion configuration, such that the circumferential distance of the first plurality of linkages  26   a  is substantially equal to the circumferential distance of the second plurality of linkages  26   b  (though the circumferential distances could be different between the linkages  26   a  and the linkages  26   b  as desired). Furthermore, the linkages  26   a  can have a wall thickness T 1  that is greater than the wall thickness Ti of the linkages  26   b.  It should thus be appreciated that the circumferential distance of the first plurality of linkages  26   a  is configured to expand greater than the circumferential distance of the second plurality of linkages  26   b.  In accordance with one embodiment, the first plurality of linkages  26   a  expands at a greater rate than the second plurality of linkages  26   b  when subjected to substantially the same expansion force as the second plurality of linkages  26   b.    
     Each implant assembly  19  can thus include the primary implant  20  and the auxiliary expandable implant  110  that are configured to be inserted into a target bone, such as a vertebral body portion  21  of a vertebra  17 . While the expandable implant system  18  can include a pair of implant assemblies  19  implanted into the vertebral body portion  21  as illustrated, it should be appreciated that includes at least one implant assembly  19 . For instance, in embodiments where one implant assembly  19  is implanted into the vertebral body portion  21 , the implant assembly can be centrally disposed in the vertebral body portion  21  so as to prevent the intrusion of disc material from the pressurized adjacent intervertebral disc into or through the broken endplates into the vertebral body portion  21 . 
     When implanted into the target bone, the implant  20  can be configured to produce a symmetric cylindrical shape under a uniform expansion force as illustrated in  FIG.  3 C , or the implant  20  can be configured to produce an asymmetrically curved shape that resembles the shape of a banana under a uniform expansion force, as illustrated in  FIG.  3 D . Alternatively still, the implant  20  can assume any shape when expanded. For instance, as illustrated in  FIG.  3 E , the symmetrical shape of the implant  20  can be cigar-shaped, whereby the implant  20  defines opposed outer surfaces  35  that are curved, such as convex, along its axial direction of extension and elongation. It is also appreciated that the expandable implant system  18  can include a pair of implant assemblies  19 , or a single implant assembly that is centrally implanted into the vertebral body  21  so as to prevent intrusion of the adjacent intervertebral disc into the fractured vertebral body  21  as described in more detail below. 
     In accordance with one embodiment, the implant  20  is inserted into the target bone in its insertion configuration, whereby the linkages  26  can be referred to as in a compressed or collapsed configuration, which can be folded as illustrated, such that the implant  20  can be passed through a cannula, through the openings formed in the pedicles or in lateral openings extending into the vertebral body portion  21 , and into an interior cavity of the vertebral body portion  21 , as described in more detail below. The implant  20  can follow a guide path of a guide wire in accordance with one embodiment. The guide path can be straight or curved, and thus the implant  20  can be flexible so as to follow the curved guide path. When the target bone is the vertebral body portion  21 , the plastic deformation of the primary implant  20  allows the implant  20  to provide augmentation in the anterior aspect of the vertebral body portion  21 . 
     When the primary implant  20  includes the first plurality of linkages  26   a  and the second plurality of linkages  26   b,  Hooke&#39;s Law demonstrates that the implant body  22  can assume an asymmetrical or bent shape when the implant body  22  is expanded elastically. It should be appreciated, however, that expansion of the linkages  26   a  and  26   b  occurs beyond the elastic deformation limit, such that the implant body  22  undergoes plastic deformation. Due to the inflation and expansion of the auxiliary implant  110 , the primary implant  20  can be substantially in its expanded configuration. 
     Example Embodiment—Application of the Hooke&#39;s Law 
     Definitions:
         ε Strain   σ Tensile Strength   A Cross-sectional area of bar   A i 0.4 mm2;   A o 0.2 mm2   l Length of bar   l i 8 mm   l o    10  mm   E Modulus of Elasticity Phynox: 203-400 Mpa       

     Elongation: Δl=ε·l 
     Whereas strain is: ε=σ/E 
     And: Δl=σ·l/E 
     Assumption, where “i” indicates the region of the implant body  22  having the second plurality of linkages  26   b  (which can be located at a circumferentially inner end of the implant body  22 ), while “o” indicates the region of the implant body  22  having the first plurality of linkages  26   a  (which can be located at a circumferentially outer end of the implant body  22 ), and the expansion is under a substantially uniform expansion force (or tensile force). The resulting tensile strength of the second plurality of linkages  26   b  and the first plurality of linkages  26   a,  respectively, is as follows: 
       σ i   =F/A   i =120 N/ 0.2 mm2=600[ N /mm2]
 
       σ o   =F/A   o =120 N/ 0.4 mm2=300[ N /mm2]
 
     The resulting elongation of the second plurality of linkages  26   b  and the first plurality of linkages  26   a,  respectively, is as follows: 
       Δ l   i   =σ   i   ·l   i   /E =300 MPa·   8   mm/203′400 MPa=0.011 mm
 
       Δ l   o   =σ   o   ·l   o   /E =600 MPa·   10   mm/203′400 MPa=0.030 mm
 
     Based on this analysis, the implant  20  expands at the region of linkages  26   a  significantly more than at the region of linkages  26   b  (approximately 3 fold in above-identified example). Consequently, the implant  20  becomes bent during expansion since the second plurality of linkages  26   b  has a smaller elongation compared to the first plurality of linkages  26   a . It should be appreciated that the numbers of the above example are merely assumptions used to demonstrate the bending effect based on different linkage sizes of the expansion implant  20 , and do not represent actual test data. 
     Referring now to  FIGS.  1 D and  4 A -F, the auxiliary expandable implant  110  is configured to be inserted into the internal void  23  of the primary implant  30  when the primary implant  30  is in the expanded configuration. In particular, the auxiliary implant  110  is insertable into the internal void  23  in a compressed or collapsed insertion configuration (see  FIG.  4 F ), and subsequently expanded in situ inside the internal void  23  to an expanded configuration. The auxiliary implant  110  defines an implant body  112  that includes at least one contact surface  114 , such as a plurality of contact surfaces  114  that contact and support the inner surface of the implant body  22 , so as to support the primary implant  20  in its expanded configuration. When the auxiliary implant  110  is in the insertion configuration, the contact surfaces  114  are recessed and spaced from the primary implant body  22 . When the auxiliary implant body  112  is expanded to the expanded configuration, the contact surfaces  114  contact the inner surface of the primary implant body  22 . The contact surfaces  114  can provide a radially outward directed support force onto the implant body  22 . As illustrated in  FIG.  4 F , the auxiliary implant  110  can be inserted into the internal void  23  of the primary implant  20  in its compressed or collapsed insertion configuration inside a sleeve  116 , the sleeve  116  can be subsequently removed, and the auxiliary implant  110  can be subsequently expanded. 
     The auxiliary implant  110  can be expanded from the insertion configuration to the expanded configuration via in-situ injection of a hardening, bone filler material  123 , such as for example a biocompatible bone cement, into the interior  115  of the implant body  112  (see, e.g.,  FIG.  4 H ) via a port  125  that extends through the implant body  112 . In accordance with one embodiment, the bone cement is load-bearing polymethylmethacrylate (PMMA), which is self hardening (e.g., self-curing), though it should be appreciated that the bone filler material can be selected from any suitable bone filling material as desired. The bone cement can also contain radiopacifiers, such as barium sulfate and/or zirconium oxide (ZrO2) to visualize the cement build-up and manage any potential cement leakage in case of leakage in the auxiliary implant  110 . However, the bone cement can be devoid of biological constituents since it&#39;s shielded from the vertebra  21  under normal operating conditions. 
     When in the expanded configuration, the auxiliary implant  110  can define any suitable shape as desired. For instance the implant body  112  be substantially equilaterally triangular, so as to define the shape of the Greek letter “delta.” It should be appreciated that the triangular shape of the implant body  112  can assume any geometric configuration as desired. In accordance with the illustrated embodiment, the implant body  112  defines a substantially triangular central body portion  118  having side surfaces  119  that can be shaped as desired, such as curved (e.g., concave) or substantially straight, and a plurality of nodes  120  that extend radially out from the vertices of the implant body  112 . In accordance with the illustrated embodiment, three nodes  120  are spaced circumferentially equidistantly, though they can be spaced at consistent or variable spacing about the implant body  112 . Furthermore, the auxiliary implant  110  can include any number of nodes  120  as desired. Each node  120  can include a neck  122  and a stabilizing support foot  124  that defines a greater circumferential dimension than the neck  122 . The support feet  124  define respective radially outer contact surfaces  114  configured to contact the primary implant body  22  in the manner described above. The contact surfaces  114  can be shaped as desired. For instance, the contact surfaces  114  can be curved (e.g., convex) or substantially straight. 
     It should be appreciated that the expanded configuration can include unfolding the auxiliary implant body  112 , and that the auxiliary implant body  112  can be non-compliant when injected with the bone filler material  123 , such that the bone filler material  123  unfolds the implant body  112  from the folded insertion configuration illustrated in  FIG.  4 F , but does not substantially stretch the implant body  112  from the unfolded configuration. Accordingly, the implant body  112  maintains a substantially constant surface are in both the folded or collapsed, and unfolded or expanded, configurations. Alternatively, the implant body  112  can be compliant and semi-stretchable or stretchable in situ after the implant body  112  has been unfolded with respect to the insertion configuration, thereby increasing the outer surface area of the auxiliary implant  110  in the expanded configuration with respect to the collapsed or folded configuration. Accordingly, a sufficient quantity of bone filler material  123  can be injected into the implant body  112  that causes the implant body to unfold from the insertion configuration and subsequently stretch, either elastically or plastically, with respect to the unfolded configuration. Thus, the expanded configuration of the auxiliary implant  110  can include both an unfolded configuration and a stretched configuration. 
     Referring now to  FIG.  4 E , the implant assembly  19  can define a plurality of pockets  126  disposed in the internal void  23  between the implant body  112  and the primary implant  20 . In particular, each pocket  126  is disposed circumferentially between adjacent nodes  120 , and radially between the central body portion  118  and the primary implant  20 . Thus, the implant assembly  19  can define three pockets  126  as illustrated, or can define any alternative number of pockets  126  as desired, such as at least one pocket  126 . Accordingly, a bone stimulating material or bone-growth material  128  can be inserted into the pockets  126  so as to facilitate bone growth into the implant assembly  19 . The bone stimulating material  128  can be, for example, calcium phosphate, bone chips harvested from the patient, allograft (harvested from a cadaver), ceramic granules such as hydroxyapatite (HA) based granules, calcium phosphate (CaP) based cements, and the like. In use, the bone stimulating material  128  can promote biological activity, such as bone in-growth and exchange of nutrients between cranial and caudal vertebral endplates. 
     While the pockets  126  described above can be discrete and separate from each other with respect to fluid communication, it should be appreciated that the implant assembly  19  can be constructed such that the pockets  126  are in fluid communication with each other. For instance, referring also to  FIGS.  4 G-H , the auxiliary expandable implant body  112  can further define at least one channel  130 , such as a plurality of channels  130  that extend between and through the side walls  119 , so as to place two or more of the pockets  126  in fluid communication. Furthermore, the channels  130  can be in fluid communication with each other such that the associated pockets  126  are in fluid communication. The channels  130  can be isolated from the interior  115  of the implant body  112  such that the bone filler material  123  is isolated with respect to the pockets  126 . The channels  130  facilitate the transfer of bone stimulating material  128  between the pockets  126 . For instance, bone stimulating material can be inserted into one pocket  126 , and can travel under pressure through the channels  130  into the other pockets  126 . Furthermore, the channels  130  facilitate biological activity such as, for example, bone in-growth through the channels  130  to provide for better rotational stability. The channels  130  can be elongate in the horizontal direction, the vertical direction, and at oblique angles relative to the horizontal and vertical directions. It should be further appreciated that the channels  130  can be in fluid communication with the interior  115  of the implant body  112  such that bone stimulating material injected into the interior  115  both expands the implant  110  and further introduces the bone stimulating material into the pockets  126 . Alternatively, the contact surfaces  114  can define an uneven contact with the primary implant  20  so as to define channels that place the pockets  126  in fluid communication with each other. 
     While the auxiliary implant  110  has been described as having a triangular shape, it should be appreciated that the implant  110  can define any alternative shape as desired that is suitable to support the primary implant  20  during a patient&#39;s normal anatomical function. For instance, referring now to  FIGS.  5 A-G , the auxiliary expandable implant body  112  can be substantially X-shaped. In accordance with the illustrated embodiment, the implant body  112  defines a substantially square or rectangular central body portion  118  having side surfaces  119  that can be shaped as desired, such as curved (e.g., concave) or substantially straight, and a plurality of nodes  120  that extend radially out from the corners of the implant body  112 . In accordance with the illustrated embodiment, four nodes  120  are spaced circumferentially equidistantly, though they can be spaced at consistent or variable spacing about the implant body  112 . Furthermore, the auxiliary implant  110  can include any number of nodes  120  as desired. The implant  110  is expandable from a compressed or collapsed configuration illustrated in  FIG.  5 G  to the expanded position, for instance as illustrated in  FIG.  5 A . 
     Accordingly, referring to  FIG.  5 F , the implant assembly  19  can define four pockets  126  disposed in the internal void  23  between the implant body  112  and the primary implant  20 . In particular, each pocket  126  is disposed circumferentially between adjacent nodes  120 , and radially between the central body portion  118  and the primary implant  20 . The pockets  126  can be separated and isolated from each other via the implant body  112 , or can be placed in fluid communication with each other in the manner described above. Accordingly, a bone stimulating material  128  can be inserted into the pockets  126  so as to facilitate bone growth into the implant assembly  19 . The bone stimulating material  128  can be, for example, calcium phosphate, hydroxyapatite, allograft, and the like. In use, the bone stimulating material  128  promotes biological activity, such as bone in-growth and exchange of nutrients between cranial and caudal vertebral endplates. 
     Referring now to  FIGS.  6 A-G , the auxiliary expandable implant body  112  can be substantially I-shaped. In accordance with the illustrated embodiment, the implant body  112  defines a substantially rectangular elongate central body portion  118  having side surfaces  119  that can be shaped as desired, such as curved (e.g., concave) or substantially straight, and a pair of nodes  120  that extend radially and circumferentially out from the outer ends the implant body  112 . In accordance with the illustrated embodiment, two nodes  120  are spaced circumferentially equidistantly 180° apart, though they can be spaced at consistent or variable spacing about the implant body  112 . Furthermore, the auxiliary implant  110  can include any number of nodes  120  as desired. The implant  110  is expandable from a compressed or collapsed configuration illustrated in  FIG.  6 G  to the expanded position, for instance as illustrated in  FIG.  6 A . 
     Accordingly, referring to  FIG.  6 F , the implant assembly  19  can define a pair of pockets  126  disposed in the internal void  23  between the implant body  112  and the primary implant  20 . In particular, each pocket  126  is disposed circumferentially between adjacent nodes  120 , and radially between the central body portion  118  and the primary implant  20 . The pockets  126  can be separated and isolated from each other via the implant body  112 , or can be placed in fluid communication with each other in the manner described above. Accordingly, a bone stimulating material  128  can be inserted into the pockets  126  so as to facilitate bone growth into the implant assembly  19 . The bone stimulating material  128  can be, for example, calcium phosphate, hydroxyapatite, allograft, and the like. In use, the bone stimulating material  128  promotes biological activity, such as bone in-growth and exchange of nutrients between cranial and caudal vertebral endplates. 
     Referring now to  FIG.  6 H , the auxiliary expandable implant body  112  can be substantially double I-beam shaped. In accordance with the illustrated embodiment, the central body portion  118  of the implant body  112  defines a pair of parallel spaced elongate legs  118   a  and  118   b,  each having side surfaces  119  that can be shaped as desired, such as curved (e.g., concave) or substantially straight, and a pair of nodes  120  that extend radially and circumferentially out from the outer ends the legs  118   a  and  118 . In accordance with the illustrated embodiment, two nodes  120  are spaced circumferentially equidistantly 180° apart, though they can be spaced at consistent or variable spacing about the implant body  112 . Furthermore, the auxiliary implant  110  can include any number of nodes  120  as desired. 
     The expandable auxiliary implant  110  can be fabricated using any desirable manufacturing technique as desired. For instance, a plurality of biocompatible and inflatable thin-walled sheets (of polymeric material, for example) can be welded together, either ultrasonically or via light beam so as to form the implant body  112  that, expand into the above-illustrated configurations when filled with the bone filler material  123 . For example, the expandable implant  110  can be manufactured by bonding two or more sheets of PEEK (or other biocompatible materials that are either inflatable or unfoldable). 
     Referring now to  FIGS.  7 A-D , the implant assembly  19  can include the expandable primary implant  20  and the expandable auxiliary implant  110  constructed in accordance with an alternative embodiment. For instance, the auxiliary implant  110  can include an implant body  112 , which includes a central body portion  118  and an expandable balloon or bladder  140  that can be inserted into the central body portion  118  in a collapsed configuration, and injected with the bone filler material  123  under pressure, which causes the bladder  140  to expand to an expanded configuration. The bladder  140  can be made from any suitable expandable material, such as a polyurethane family polymer, for instance PCU (polycarbonate-urethane), such as Bionate. The central body portion  118  can likewise be made from any suitable material (which can be expandable or rigid), such as metal or a rigid polymer, such as PEEK, to locally restrain the bladder  140  and allow the bladder to define nodes  120  that contact the primary implant  20 . 
     In accordance with the illustrated embodiment, the central body portion  118  is illustrated as an annular sleeve, and elongate along a central axis  142  that can be coextensive with the central axis  24  of the primary implant  20 . The central body portion  118  defines an interior  115  that can be cylindrical or alternatively shaped as desired. The auxiliary implant  110  further defines at least one opening illustrated as a slot  144 , such as a plurality of slots  144  that extend through the central body portion  118 . Alternatively, the auxiliary implant  110  can be include a plurality of linkages  26  as described above with respect to the primary implant  20  (see  FIGS.  2 A-D ). The central body portion  118  can include any number of slots or openings  144  spaced circumferentially and/or axially as desired. As will be appreciated from the description below, the slots  144  can define node locations for the auxiliary implant body  112 . Thus, the slots  144  can be spaced circumferentially equidistantly as illustrated, or can define variable circumferential distances therebetween as desired. 
     During operation, the expandable bladder  140  can be placed inside the interior  115  of the central body portion  118  in its collapsed configuration (see  FIG.  7 C ). The auxiliary implant  110 , in its collapsed configuration, can then be placed inside the primary implant  20  which can be expanded prior to insertion of the auxiliary implant  110 . Alternatively, the central body portion  118  can first be inserted inside the primary implant  20 , and the expandable bladder  140 , in its collapsed configuration, can subsequently be inserted into the interior of the central body portion  118 . The bladder  140  can include a port  146  at its proximal end that can be coupled to a docking/dedocking mechanism that is configured to deliver bone filler material  123  into the internal void  145  of the bladder  140 . The bladder  140  is compliant and thus stretchable as the bone filler material  123  is inserted through the port  146  so as to create a positive pressure in the internal void  145 . For instance, a liquid such as liquid bone cement can be injected into the port  146  that causes the bladder  140  to expand, in turn causing portions of the bladder  140  to extend through the openings  144  so as to define nodes  120  that extend out from the central body portion  118 . Because the bladder  140  stretches in situ, the bladder  140  increases in outer surface area as it expands in situ. The bone cement then hardens once the cement fully polymerizes, typically no later than 30 minutes. 
     As the bladder  140  expands inside the central body portion  118 , a portion of the bladder  140  extends through the slots  144  so as to create a mushroom shaped nodes  120 , each defining a neck  122  that extends through the slot  144  and a stabilizing support foot  124  that extends out from the slot  144  defines a greater circumferential dimension than the neck  122 . support feet  124  define respective radially outer contact surfaces  114  configured to contact the primary implant body  22  in the manner described above. Thus, the bone filler material  123  can be inserted into the bladder  140  until the bladder  140  has expanded to the point that the contact surfaces  114  abut the inner surfaces of the primary implant body  22 . As illustrated in  FIG.  7 D , the auxiliary implant  110  can include a pair of slots  144  spaced 180° apart from each other, thereby defining a pair of nodes  120 . Thus, the auxiliary implant  110  can be substantially I-shaped as illustrated in  FIG.  7 D . As illustrated in  FIG.  7 E , the auxiliary implant  110  can include three slots  144  spaced 120° apart from each other, defining three nodes  120 . Thus, the auxiliary implant  110  can be substantially triangular as illustrated in  FIG.  7 E . As illustrated in  FIG.  7 F , the auxiliary implant  110  can include four slots  144  spaced 90° apart from each other, defining four nodes  120 . Thus, the auxiliary implant  110  can be substantially X-shaped. It should thus be appreciated that the auxiliary implant  112  (for instance the bladder  140 ) can be compliant and stretchable in response to the introduction of bone filler material  123 , whereas the auxiliary implant  112  of the type illustrated in  FIGS.  4 - 6    can be constructed non-compliant and rigid The nodes  120  of the auxiliary implant  112  and the primary implant  20  can define pockets that can be filled with a bone stimulating material in the manner described above with respect to  FIG.  4 E . 
     Referring now to  FIGS.  8 A , the auxiliary implant body  112  can define bifurcated slots  144  that are axially aligned. Furthermore, the slots  144  can be arranged in columns that overlap each other circumferentially as illustrated in  FIG.  8 B . Thus, the slots  144  can be arranged in the central body portion  118  in any orientation and configuration as desired. Furthermore, the slots  144  can be shaped as desired. For instance, the slots  144  can be rectangular and elongate in a direction substantially parallel to the central axis  142  as illustrated in  FIG.  7 C . Alternatively, as illustrated in  FIG.  8 C , the slots  144  can be keyhole-shaped, having outer portions  144   a  and a middle portion  144   b  that is disposed between the outer portions  144   a  and wider than the outer portions  144   a.  Alternatively, one or both of the outer portions  144   a  can be wider than the middle portion  144   b.  Alternatively still, as illustrated in  FIG.  8 D , the slots  144  can be diamond-shaped. It is appreciated that the size and shape of the slots  144  can at least partially determine the size and shape of the node  120  that extends through the slots  144 . 
     While the central body portion  118  can remain substantially rigid as the bladder  140  expands from the collapsed configuration to the expanded configuration as illustrated in  FIGS.  7 A- 7 F , it is appreciated that the central body portion  118  can alternatively be compliant, and part or all of the central body portion  118  expand in response to outward expansion forces imparted from the expanding bladder  140  onto the central body portion  118 . For instance, as illustrated in  FIG.  9   , the central body portion  118  can expand radially outward at locations adjacent the slots  144  as the bladder  140  expands through the slots  144 . 
     While the auxiliary implant  112  is placed inside the primary implant  20  and expanded in accordance with the embodiment illustrated in  FIG.  7 A , it should be appreciated that the auxiliary implant  112  can define a stand-alone implant that is inserted into the target bone, such as the vertebral body portion of a vertebra in its collapsed configuration, and subsequently expanded to restore height to the vertebral body portion. 
     Referring now also to  FIGS.  10 A-D , the implant system  18  can include at least one expandable implant assembly  19  as described above, along with an implant insertion assembly  50  that facilitates the insertion and expansion of the primary and auxiliary implants  20  and  110  within the target bone. The expandable implant assembly  19  may be implanted into the vertebral body portion  21  via any approach now or hereafter known in the art including, for example, via an anterior approach, a mono-axial or bilateral approach, a trans-pedicular approach, para-pedicular approach, extra-pedicular approach, trans-psoas, and the like. 
     In accordance with the embodiment illustrated in  FIGS.  10 A-J , implant assembly  19  is inserted via a bilateral, transpedicular approach. The insertion assembly  50  can include an opening assembly  52  configured to create an opening through the target bone that provides a guide path through which the implant assembly  19  is implanted. The opening assembly  52  includes a cannulated body  62   a,  an opening device  62   b  that is received inside the cannulated body  62   a,  and an aiming device  54  that supports the opening assembly  52 . 
     The elongate cannulated body  62   a  that defines a proximal end  64   a  and an opposed distal end  66   a,  and a cannula  68   a  that extends through the cannulated body  62   a  from the proximal end  64   a  to the distal end  66   a  along the direction of elongation. The cannulated body  62   a  is substantially straight and is connected to a handle  67   a  at the proximal end  64   a.  The cannula  68   a  can extend through the respective handles  67   a.  The opening device  62   b  is sized to be received in the cannula  68   a,  and defines a proximal end  64   b  and an opposed distal end  66   b . The opening device  62   b  includes a handle  67   b  coupled to the proximal end  64   b.  The distal end  66   b  can provide a cutting blade  65  illustrated as a cutting edge or alternatively configured opening member that is configured to cut through the target bone. The opening device  62   b  can further define a cannula  68   b  that extends from the proximal end  64   b  to the distal end  66   b  and through the handle  67   b.  Alternatively, the opening device  62   b  can be a solid body. The insertion assembly  50  can include a pair of symmetrically shaped opening assemblies  52  that can be inserted into the target vertebral body portion  21  when, for instance, implanting a pair of expandable implant assemblies  19 . 
     During operation, the opening devices  62   b  can be inserted into the proximal end  64   a  of the cannulated body  62   a,  such that the cutting blade  65  extends out from the distal end  66   a  of the cannulated body  62   a.  In accordance with one embodiment, the opening devices  62   b  can be inserted into the vertebra  70  along a transpedicular approach. A stab incision can be used to access the pedicles  72  of the target vertebra  17 , under intra-operative radiological observation. Both pedicles  72  of the targeted vertebra  17  can be opened by driving the distal cutting blades  65  into the respective pedicles  72 , such that the opening devices  62   b  penetrate the cortical bone of the corresponding pedicles  72 . The opening devices  62   b  can then be translated along the pedicle axes, so as to perforate the arched channel through the cancellous bone within the vertebral body portion  21 . 
     The aiming device  54  includes a body  78  and a pair of spaced apertures  80  extending through the body  78  sized to receive the corresponding pair of cannulated bodies  62   a . The apertures  80  are oriented so as to aim the cannulated body  62   a,  and thus the opening device  62   b,  with the pedicle  72  along a desired insertion path into the vertebral body portion  21  of the vertebra  17  so as to create an insertion channel  73  in the vertebral body portion  21 . 
     Once the opening devices  52  have been inserted into the vertebra  70 , the components of the expandable implant assembly  19  can be inserted into the channel  73  that has been formed in the vertebral body portion  21 . In particular, the implant assembly components can be inserted through the cannula  68   b  of the opening device  62   b,  or the opening device  62   b  can be removed from the cannulated body  62   a,  and the implant assembly components can be inserted through the cannula  68   a  of the cannulated body  62   a.  For instance, the opening device  62   b  can be constructed as a solid body. However, even if the opening device  62   b  is cannulated, the implant assembly components are inserted through the cannula  68   b  of the opening device  62   b,  it can still be said that the implant assembly components are implanted into the target bone through a guide path that is defined the cannula  68   a.  The guide path can further be defined by the cannula  68   b  in accordance with certain embodiments. For the purposes of illustration, the opening device  62   b  is shown removed from the cannulated body  62   a  after the channel  73  has been formed. 
     Referring now also to  FIG.  10 E , the insertion assembly  50  further includes an expansion body  69  that can be made from rubber, plastic, or other suitable material that provides an expandable bladder or other flexible member configured to occupy the internal void  23  of the implant body  22 . The expansion body  69  is inserted through the cannulated body  62   a  and into the primary implant  20  that has been implanted in the vertebral body portion  21  of the vertebra  17 . For instance, the primary implant  20  can travel inside the cannulated body  62   a  along a guide wire that is aligned with the channel  73 . Alternatively, the expandable body  69  can be pre-inserted into the implant  20 , and the expansion body  69  and the implant  20  can be inserted into the channel  73  together in unison. 
     The expansion body  69  is closed at a distal end  105 , and define a port at an opposed proximal end, such that, as illustrated in  FIG.  10 F , an expansion media can be inserted through the cannulated body  62   a  and the proximal port and into the expansion body  69 , which can be a balloon that expands inside the primary implant  20 . The expansion media can be any fluid as desired, such as air, saline solution, water, or the like. As the expansion body  69  expands, it imparts a radially outward force on the body of the primary implant  20 , which urges the primary implant  20  to expand to its expanded configuration as described above. Once the primary implant  20  has expanded, the expansion media can be removed from the expansion body  69 , which causes the expansion body  69  to contract. For instance, a docking and dedocking mechanism can be coupled to the port of the expansion body  69  so as to introduce and remove the expansion media into and from the expansion body  69 . The expansion body  69  can then be removed from the cannulated body  62   a  as illustrated in  FIG.  10 G . Thus, it can be said that the expansion body  69  is temporarily implanted in the target vertebral body  21 . 
     As described above, the primary implant plastically expands to its expanded configuration illustrated in  FIG.  10 G . Accordingly, after the expansion body  69  is removed, the plastically deformed primary implant  20  remains within the interior volume of the vertebral body portion  21 , and is configured to withstand the intra-operative, temporary forces (which can be between approximately 100N and approximately 200N) experienced by the spine of a patient lying in a prone or supine position on the operating table. 
     Referring now also to  FIG.  10 H , once the expansion body has been removed, the auxiliary implant  110  can be inserted through the cannulated body  62   a  and into the internal void  23  of the primary implant  20 . The auxiliary implant  110  is illustrated as the triangular-shaped implant described above with reference to  FIGS.  1 D and  4 A -F, though it should be appreciated that the auxiliary implant  110  having any suitable shape can be inserted inside the primary implant  20  in its collapsed or insertion configuration. The auxiliary implant  110  can be inserted into the cannulated body  62   a  surrounded by the sleeve  116  ( FIG.  4 F ) that maintains the implant  110  in its collapsed configuration. The sleeve  116  can be removed once the implant  110  has been inserted into the cannulated body  62   a,  or can be removed once the implant  110  has been inserted into the primary implant  20 . 
     Referring to  FIGS.  4 H and  10 I , once the auxiliary implant  110  is disposed in the internal void of the primary implant  20 , the proximal end of the auxiliary implant  110  can be coupled to a source of bone filler material  123 , such as for example a biocompatible bone cement. For instance, a secondary cannula can be inserted into the cannulated body  62   a,  and coupled to an inlet on the implant body  112  to the interior  115  at one end, and a pressurized source of bone filler material  123  at its other end. Thus, the bone filler material  123  can be injected into the interior  115  of the implant body  112 , thereby causing the implant body  112  to expand inside the primary implant  20  to a size that causes the contact surfaces  114  abut the implant  20 . The contact surfaces  114  can be oriented as desired, and extend cranially and caudally in accordance with one embodiment so as to absorb compression forces imparted onto the vertebral body  21 . Once the bone filler material hardens, the secondary cannula and the cannulated body  62   a  can be twisted, pried, or otherwise actuated to break away from the expanded auxiliary implant  110  and removed from the target vertebra  17 , as illustrated in  FIG.  10 J . The implant assembly  19  is configured to withstand the post-operative, “permanent” forces (which can be between approximately 500N and approximately 5,000N) that are experienced by the spine during normal post-operative anatomical function of the patient (e.g., standing, walking, sitting, jumping, etc). For instance, the PMMA-based bone cement can typically withstand loads greater than 10,000N under static or fatigue load modes. Accordingly, the auxiliary implant  110  can withstand higher forces than the primary implant  20 . 
     It should be appreciated that while the primary implant  20  is expanded prior to insertion of the auxiliary implant  110  in accordance with the illustrated embodiment, the auxiliary implant  110  can be pre-installed inside the primary implant  20  in its compressed or collapsed configuration prior to implantation of the primary implant  20  in the vertebral body portion  21 . Accordingly, the primary and auxiliary implants  20  and  110  can inserted into the vertebral body  21  in unison, such that expansion of the auxiliary implant  110  expands the primary implant  20 . Alternatively still, the auxiliary implant  110  can be implanted into the vertebral body  21  in its compressed or collapsed configuration without the primary implant  20 , and subsequently expanded to restore height to the vertebral body  21 . 
     Referring also again to  FIG.  4 E , once the implant assembly  19  has been expanded inside the target vertebral body  21  in accordance with the illustrated embodiment, the bone stimulating material  128  can subsequently be inserted into at least one of the pockets  126 , up to all of the pockets  126 . For example, the bone stimulating material  128  can be introduced into the channel  73  (created as described with respect to  FIG.  10 D ) under pressure, which causes the bone stimulating material  128  to flow into the pockets  126 . Alternatively, the bone stimulating material  128  can be directed into the pockets  126  in any manner as desired. While the insertion assembly  50  has been illustrated as implanting a pair of implant assemblies  19  on opposed sides of the vertebral body portion  21 , it should be appreciated that only a single implant assembly  19  can alternatively be implanted as desired. 
     Referring now to  FIGS.  11 A-C , the opening device  62   b  can be curved at a location proximate to the distal end  66   b,  and is further flexible, such that the distal end  66   b  extends in a substantially straight configuration when disposed in the cannula  68   a,  but is bent when disposed outside of the cannula  68   a.  The opening device  62   b  can be formed from any suitable elastic bent material, such as Nitinol (or a nickel-titanium alloy). Accordingly, as illustrated in  FIG.  11 D , when the opening assembly  52  is inserted into the pedicle of the target vertebra  17 , and the opening device  62   b  is translated forward such that the distal end  66   b  travels out from the cannulated body  62   a,  the distal end  66   b  curves as it is driven through the cancellous bone so as to create a curved or arched channel  73 . The distal end  66   b  can have a length sufficient such that the curved channel  73  passes through the lateral midline  77  of the vertebral body portion  21 , such that the lateral midline  77  intersects the channel  73 . 
     Next, as illustrated in  FIG.  11 E , the expansion body  69  is inserted through the cannulated body  62   a  and into the primary implant  20 , and the expansion body  69  and primary implant  20  are inserted into the channel  73 . The expansion body  69  and the implant  20  can be implanted together in unison, or the implant  20  can be inserted first, and subsequently the expansion body can be inserted into the implant  20 . The primary implant  20  can be asymmetrical, or banana-shaped, as described above with reference to  FIG.  3 D  such that the implant  20  defines a curvature that is substantially equal to the curvature of the curved channel  73 . The implant  20  and the guide wire, for instance, or alternative structure that defines an insertion path for the implant  20  into the channel  73  can be keyed such that the implant  20  is inserted into the channel in a predetermined orientation whereby the curvature of the implant  20  will be oriented with the curvature of the channel  73 . 
     Referring to  FIG.  11 F , an expansion media can be inserted through the cannulated body  62   a  and into the expansion body  69  that causes the expansion body  69  to expand inside the primary implant  20 . The expansion media can be any fluid as desired, including liquids such as contrast media, saline solution, water, mixes thereof, or the like. As the expansion body  69  expands, it imparts a radially outward force on the body of the primary implant  20 , which urges the primary implant  20  to expand to its expanded configuration as described above. As illustrated in  FIG.  11 G , the expandable body  69  can be thicker on one side than the other, such that the body  69  becomes curved, or banana-shaped, upon expansion. Expansion of the expandable body  69  causes the primary implant  20  to expand at a location substantially central with respect to the lateral midline  77  of the vertebral body portion  21 . 
     Referring now also to  FIG.  11 H , once the expansion body  69  has been deflated and removed, the auxiliary implant  110  can be inserted through the cannulated body  62   a  and into the internal void  23  of the primary implant  20 . As schematically illustrated in  FIG.  11 I , the auxiliary implant  110  can be thicker at one side than another, such that the implant  110  can become curved, or banana shaped, upon expansion inside the primary implant  20 . Alternatively, a plurality of “straight” auxiliary implants  110  can be implanted inside the primary implant at locations spaced from each other. 
     As illustrated in  FIG.  11 J , once the auxiliary implant(s)  110  is disposed in the internal void of the primary implant  20 , the proximal end of the auxiliary implant(s)  110  can be coupled to a source of bone filler material  123 , such as for example a biocompatible bone cement. For instance, a secondary cannula can be inserted into the cannulated body  62   a,  and coupled to an inlet to the implant  110  at one end, and a pressurized source of bone filler material at its other end. Thus, the bone filler material can be injected into the implant  110 , thereby causing the implant  110  to expand inside the primary implant  20  in the manner described above. Once the bone filler material hardens, the secondary cannula and the cannulated body  62   a  can be twisted, pried, or otherwise actuated to break away from the expanded auxiliary implant  110  and removed from the target vertebra  17 , as illustrated in  FIG.  11 J . The resulting implant assembly  19  is positioned such that the lateral midline  77  intersects the implant assembly  19 , which can be curved about a caudal-cranial axis. Thus, it can be said that the implant assembly  19  is laterally centered or at least partially laterally centered in the vertebral body  21 . It can also be said that the implant assembly  19  is aligned or at least partially aligned with the lateral midline  77 . In accordance with the illustrated embodiment, the implant assembly  19  is substantially centered with respect to the intervertebral discs that are adjacent and cranial and caudal with respect to the target vertebra  21 . Accordingly, the implant assembly  19  can be located in the vertebral body  21  at the region of maximum load bearing, and resist the forces applied to the vertebral body  21  by the adjacent pressurized intervertebral discs, and can thus limit or prevent the intrusion of the adjacent intervertebral discs into or through the broken end plates of the fractured vertebral body  21 . 
     Alternatively, a pair of the banana-shaped implant assemblies  19  can be inserted into the vertebral body on opposed sides of the lateral midline (see  FIG.  3 D ) via a corresponding pair of insertion assemblies as described above with respect to  FIGS.  10 D-J . Alternatively still, the implant assemblies  19  can be positioned so as to abut each other (or be placed in close proximity) at the lateral midline  77  so as to provide the structural stability that limits or prevents the intervertebral discs from protruding into the vertebral body portion  21 . 
     Referring now to  FIGS.  12 A-C , the implant assembly  19  can be inserted into the vertebral body portion via a lateral or trans-psoas approach. For instance, the opening assembly  52  can be inserted laterally into the vertebral body portion  21 , and the distal end  66   b  of the opening device  62   a  can be translated out from the cannulated body  62   a  in along a lateral direction through the cancellous bone portion of the vertebral body  21 , so as to create a channel  73  in the vertebral body  21  that crosses or intersects the lateral midline  77 . The primary implant  20  and the expansion body  69  can be implanted into the channel  73  and expanded, and the expansion body  69  can be deflated and removed from the vertebra  17  in the manner described above. The primary implant  20  can be substantially centered with respect to the lateral midline  77  of the vertebral body  21 . The auxiliary implant  110  can then be inserted into the implant  20  and expanded, and the insertion assembly  50  can be removed in the manner described above. The auxiliary implant  110  can be symmetrical, for instance cylindrical as illustrated in  FIG.  3 C  or cigar-shaped as illustrated in  FIG.  3 E . Thus, the symmetrical implant assembly  19  can be implanted laterally into the vertebral body  21 , and extend substantially laterally within the vertebral body  21  at a location substantially aligned with the lateral midline  77  so as to prevent or limit intrusion of adjacent intervertebral discs into the fractured vertebral body. 
     Certain example embodiments have been described with respect to an expandable implant assembly that can augment an interior volume of a target bone, thereby increasing or restoring the height of the bone, filling a cavity formed in the bone and/or stabilizing, aiding and/or augmenting the bone. It should be appreciated that while the expandable implant assembly  19  has been described as used in a target bone that has been illustrated as the spine (for example, in the lumbar, thoracic or cervical regions), those skilled in the art will appreciate that the implant assembly  19  may be implanted and subsequently expanded in the manner described above in other parts of the body, for instance to augment an alternative target bone, including for example long bones such as proximal humerus and proximal tibia or bones in the hand, face, feet, extremities, cranium, or nearly any bone in the human body. Moreover, the implant assembly  19  can be used as an intervertebral spacer in a degenerated disc or in an intervertebral space after a discectomy has partially or fully removed the intervertebral disc. Furthermore, it should be appreciated that a kit can be provided that includes one or more components of the implant system  18 , up to all of the components of an implant system usable to insert and expand at least one expandable implant assembly  19  in the manner described herein, including components of different sizes, shapes, and configurations. 
     It should be appreciated that the illustrations and discussions of the embodiments shown in the figures are for exemplary purposes only, and should not be construed limiting the disclosure. One skilled in the art will appreciate that the present disclosure contemplates various embodiments. It should be further appreciated that the features and structures described and illustrated in accordance one embodiment can apply to all embodiments as described herein, unless otherwise precluded. It should be understood that the concepts described above with the above-described embodiments may be employed alone or in combination with any of the other embodiments described above. Those skilled in the relevant art, having the benefit of the teachings of this specification, may effect numerous modifications to the invention as described herein, and changes may be made without departing from the scope and spirit of the invention, for instance as set forth by the appended claims.