Abstract:
An expandable medical implant is provided with an implantable cage body. The proximal and distal ends of the cage body may each be provided with a tapered or cam portion. The implant may further include a proximal flexure, a distal flexure, a proximal plug member having a tapered portion configured to mate with the tapered portion of the proximal end of the cage body, and a distal plug member having a tapered portion configured to mate with the tapered portion of the distal end of the cage body. The proximal plug member may be configured to move longitudinally such that the distal flexure moves and the circumference of the proximal end of the cage body resiliently expands. The distal plug member may be configured to move longitudinally such that the proximal flexure moves and the circumference of the distal end of the cage body resiliently expands. Methods are also disclosed.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application is a continuation of U.S. patent application Ser. No. 14/939,905 filed Nov. 12, 2015 which claims the benefit of U.S. Provisional Application No. 62/078,850 filed Nov. 12, 2014. 
     
    
     INCORPORATION BY REFERENCE 
       [0002]    All publications and patent applications mentioned in this specification are herein incorporated by reference in their entirety to the same extent as if each individual publication or patent application was specifically and individually indicated to be incorporated by reference. 
       FIELD 
       [0003]    The present disclosure generally relates to medical devices for stabilizing the vertebral motion segment or other bone segments. More particularly, the field of the disclosure relates to a universally expanding cage (UEC) and method of use for providing controlled spinal correction or other bond segment spacing and/or alignment. 
       BACKGROUND 
       [0004]    Conventional spine cages or implants are typically characterized by a kidney bean-shaped body comprising a hydroxyapatite-coated surface provided on the exterior surface for contact with adjacent vertebral segments or endplates which are shown in  FIG. 1 . A conventional spine cage with flat endplates is typically inserted posterolaterally proximate to the neuroforamen of the distracted spine after a trial implant creates a pathway. Optionally two parallel externally threaded conduits are inserted anteriorly to achieve lumbar arthrodesis. The implants are often of constant diameter whereas the L5-S1 disc space is trapezoidal, thus a ‘flat back’ syndrome may be iatrogenically created. Generally spine intradiscal implants are for lumbar fusion or cervical motion preservation, while a separate system of rods and screws corrects alignment. 
         [0005]    With the novel UECs disclosed herein, additional options include fusion throughout the spinal column, and deformity angular correction. 
         [0006]    Existing devices for interbody stabilization have important and significant limitations. Among the limitations are an inability to expand and distract the endplates. Consequently, if a cage that is “to small” is inserted it can ‘rattle around and never heal’. If the static cage is too big, it can injure adjacent nerves or destabilize the spine via end plate resection or subsidence. 
         [0007]    Current devices for interbody stabilization include static spacers composed of titanium, PEEK, and high performance thermoplastic polymer produced by VICTREX, (Victrex USA Inc, 3A Caledon Court, Greenville, S.C. 29615), carbon fiber, or resorbable polymers. Current interbody spacers may not maintain interbody lordosis and can contribute to the formation of a straight or even kyphotic segments and the clinical problem of “flatback syndrome.” Separation of the endplates increases space available for the neural elements, specifically the neural foramen. Existing static cages do not reliably improve space for the neural elements. Therefore, what is needed is an expanding cage that will increase space for the neural elements posteriorly between the vertebral bodies, or at least maintain the natural bone contours to avoid neuropraxia (nerve stretch) or encroachment. 
         [0008]    U.S. Pat. No. 7,985,256, filed Sep. 26, 2006 and titled “Selectively Expanding Spine Cage, Hydraulically Controllable in Three Dimensions for Enhanced Spinal Fusion”, and U.S. Pat. No. 7,819,921, filed Oct. 31, 2007 and titled “Linearly expanding spine cage for enhanced spinal fusion”, both provide detailed background on expanding spine cages. 
         [0009]    The cages disclosed in U.S. Pat. No. 7,985,256 above are restricted to use with hydraulics, and lumbar fusion. The cage disclosed in U.S. Pat. No. 7,819,921 allows for trapezoidal linear expanding, not uniform expansion, thus a trapezoidal L5 cage as disclosed therein will preserve natural lumbar lordosis. The disclosed cage was never developed. It is intended for use as two (2) parallel linearly expanding split conduits inserted anteriorly for lumbar fusion. 
         [0010]    In contrast, the UEC cages disclosed herein expands either uniformly, or at either end proximally or distally. Given the adjustment option the surgeon can correct angulation deformity with the novel UEC. 
         [0011]    Another problem with conventional devices of interbody stabilization includes poor interface between bone and biomaterial. Conventional static interbody spacers form a weak interface between bone and biomaterial. Although the surface of such implants is typically provided with a series of ridges or coated with hydroxyapetite, the ridges may be in parallel with applied horizontal vectors or side-to-side motion. That is, the ridges or coatings offer little resistance to movement applied to either side of the endplates. Thus, nonunion is common in allograft, titanium and polymer spacers, due to motion between the implant and host bone. Conventional devices typically do not expand between adjacent vertebrae. Since the UEC expands under surgeon control, the visible, palpable ‘goodness of fit’ setting can ideal lock opposing vertebral endplates at the time of surgery. As healing accrues, the implants become inert. Since no motion equates with no pain, clinical results are improved with UECs. 
         [0012]    Therefore, what is needed is a way to expand an implant to develop immediate fixation forces that can exceed the ultimate strength at healing, with improved abilities to enable disc space fixation solidarity while correcting spine angular deformity. Such an expandable implant ideally will maximize stability of the interface and enhance stable fixation. The immediate fixation of such an expandable interbody implant advantageously will provide stability that is similar to that achieved at the time of healing. Such an implant will have valuable implications enhancing early post-operative rehabilitation for the patient. 
         [0013]    Another problem of conventional interbody spacers is their large diameter requiring wide exposure. Existing devices used for interbody spacers include structural allograft, threaded cages, cylindrical cages, and boomerang-shaped cages. Conventional devices have significant limitation with regard to safety and efficacy. Regarding safety of the interbody spacers, injury to neural and aortic elements may occur with placement from an anterior or posterior approach. A conventional spine cage lacks the ability to expand, diminishing its fixation capabilities. Prior attempts to preserve lumbar motion have failed by extrusion of the implant after implantation. The risks to neural elements are primarily due to the disparity between the large size of the cage required to adequately support the interbody space, and the small space available for insertion of the device, especially when placed from a posterior or transforaminal approach. Existing boomerang cages are shaped like a partially flattened kidney bean. Their implantation requires a wide exposure and potential compromise of vascular and neural structures, both because of their inability to enter small and become larger, and due to the fact that their insertion requires mechanical manipulation during insertion and expanding of the implant. Once current boomerang implants are prepared for insertion via a trial spacer to make a pathway toward the anterior spinal column, the existing static cage is shoved toward the end point with the hope that it will reach a desired anatomic destination. Given the proximity of nerve roots and vascular structures to the insertion site, and the solid, relatively large size of conventional devices, such constraints predispose a patient to foraminal (nerve passage site) encroachment, and possible neural and vascular injury. 
         [0014]    Therefore, what is needed is a minimally invasive expanding spine cage that is capable of insertion with minimal invasion into a smaller aperture. Such a minimally invasive spine cage advantageously could be expanded with completely positional control or adjustment in three dimensions. What is also needed is a smaller expanding spine cage that is easier to operatively insert into a patient with minimal surgical trauma in contrast to conventional, relatively large devices that create the needless trauma to nerve roots in the confined space of the vertebral region. Existing interbody implants have limited space available for bone graft. Adequate bone graft or bone graft substitute is critical for a solid interbody arthrodesis. It would be desirable to provide an expandable interbody cage that will permit a large volume of bone graft material to be placed within the cage and around it, to fill the intervertebral space. Additionally, conventional interbody implants lack the ability to stabilize endplates completely and prevent them from moving. Therefore, what is also needed is an expanding spine cage wherein the vertebral end plates are subject to forces that both distract them apart, and hold them from moving. Such an interbody cage would be capable of stabilization of the motion segment, thereby reducing micromotion, and discouraging pseudoarthrosis (incomplete fusion) and pain. 
         [0015]    Ideally, what is needed is a spine cage or implant that is capable of increasing its expansion in height and angle, spreading to a calculated degree. Furthermore, what is needed is a spine cage that can adjust the amount of not only overall anterior posterior expansion, but also medial and lateral variable expansion so that both the normal lordotic curve is maintained, and adjustments can be made for scoliosis or bone defects. Such a spine cage or implant would permit restoration of normal spinal alignment after surgery and hold the spine segments together rigidly, mechanically, until healing occurs. 
         [0016]    What is also needed is an expanding cage or implant that is capable of holding the vertebral or joint sections with increased pullout strength to minimize the chance of implant fixation loss during the period when the implant is becoming incorporated into the arthrodesis bone block. 
       SUMMARY OF THE DISCLOSURE 
       [0017]    According to some aspects of the disclosure, an expandable medical implant is provided with an implantable cage body having a proximal end and a distal end. In some embodiments, the proximal and distal ends of the cage body are each provided with a tapered or cam portion. The cage body further has a longitudinal axis extending between the proximal end and the distal end of the cage body. The implant may further comprise at least one proximal flexure at least partially located adjacent to the proximal end of the cage body and configured to allow a circumference of the distal end of the cage body to resiliently expand. The implant may further comprise at least one distal flexure at least partially located adjacent to the distal end of the cage body and configured to allow a circumference of the proximal end of the cage body to resiliently expand. The implant may further comprise a proximal plug member having a tapered portion configured to mate with the tapered portion of the proximal end of the cage body. The proximal plug member may be configured to move longitudinally relative to the cage body from a first position to a second position such that the at least one distal flexure moves and the circumference of the proximal end of the cage body resiliently expands. The proximal plug member may also be configured to move from the second position to the first position such that the circumference of the proximal end resiliently contracts. The implant may further comprise a distal plug member having a tapered portion configured to mate with the tapered portion of the distal end of the cage body. The distal plug member may be configured to move longitudinally relative to the cage body from a third position to a fourth position such that the at least one proximal flexure moves and the circumference of the distal end of the cage body resiliently expands. The distal plug member may also be configured to move from the fourth position to the third position such that the circumference of the distal end resiliently contracts. 
         [0018]    In some embodiments, the cage body further comprises a first tapered bore at the proximal end configured to slidably receive the proximal plug member, and a second tapered bore at the distal end configured to slidably receive the distal plug member. The first tapered bore may threadably engage the proximal plug member such that when the proximal plug member is rotated relative to the cage body, the proximal plug member advances in a longitudinal direction relative to the cage body. The second tapered bore may threadably engage the distal plug member such that when the distal plug member is rotated relative to the cage body, the distal plug member advances in a longitudinal direction relative to the cage body. 
         [0019]    In some embodiments, the at least one proximal flexure comprises a generally circular and open ended aperture and a pair of generally flexible beam portions extending longitudinally from the aperture. The at least one proximal flexure may include a pair of longitudinally extending beam portions separated by a longitudinally extending gap, wherein the at least one proximal flexure further comprises a connector portion interconnecting proximal ends of the beam portions. The at least one proximal flexure may include a plurality of circumferentially spaced proximal flexures, and the at least one distal flexure may include a plurality of circumferentially spaced distal flexures. The plurality of proximal flexures may be rotationally staggered from the plurality of distal flexures. 
         [0020]    In some embodiments, each of the proximal flexures includes a pair of longitudinally extending beam portions separated by a longitudinally extending gap and bridged together by a connector portion interconnecting only proximal ends of the beam portions. Each of the distal flexures may include a pair of longitudinally extending beam portions separated by a longitudinally extending gap and bridged together by a connector portion interconnecting only distal ends of the beam portions. Each of the proximal flexures can share a beam portion with two of the distal flexures that are adjacent to each proximal flexure, thereby forming a continuous serpentine pattern along the cage body. 
         [0021]    In some embodiments, the implant includes a first adjustment member coupled to at least the proximal plug member such that when the first adjustment member is rotated, the proximal plug member is caused to move longitudinally. The implant may further include a second adjustment member coupled to the distal plug member such that when the second adjustment member is rotated, the distal plug member is caused to move longitudinally, thereby allowing the proximal and the distal ends of the cage body to be expanded and contracted independent from one another. The first and the second adjustment members may be coaxially nested one within the other and independently rotatable. In some embodiments, the first and the second adjustment members each have knobs axially spaced but adjacent to one another such that the knobs may alternately be rotated in unison or individually. At least one of the first and the second adjustment members may have a keyed end configured to slidably mate and rotationally couple with its associated plug member such that the at least one adjustment member can be removed from the expandable medical implant. 
         [0022]    In some embodiments, the cage body has a square or circular cross-section transverse to the longitudinal axis. 
         [0023]    In some embodiments, an expandable medical implant includes an implantable cage, a plurality of proximal flexures, a plurality of distal flexures, a proximal plug member, a distal plug member, and first and second adjustment members. In these embodiments, the implantable cage body has a proximal end and a distal end each provided with a threaded and tapered bore. The cage body has a longitudinal axis extending between the proximal end and the distal end of the cage body. The plurality of proximal flexures are circumferentially spaced and each is at least partially located adjacent to the proximal end of the cage body and configured to allow a circumference of the distal end of the cage body to resiliently expand. Each of the proximal flexures comprises a pair of longitudinally extending beam portions separated by a longitudinally extending gap and bridged together by a connector portion interconnecting only proximal ends of the beam portions. The plurality of distal flexures are circumferentially spaced and each is at least partially located adjacent to the distal end of the cage body and configured to allow a circumference of the proximal end of the cage body to resiliently expand. Each of the distal flexures comprises a pair of longitudinally extending beam portions separated by a longitudinally extending gap and bridged together by a connector portion interconnecting only distal ends of the beam portions. Each of the proximal flexures shares a beam portion with two of the distal flexures that are adjacent to each proximal flexure, thereby forming a continuous serpentine pattern along the cage body. The proximal plug member has a threaded and tapered circumference configured to mate with the threaded and tapered bore of the proximal end of the cage body. The proximal plug member is configured to move along the longitudinal axis relative to the cage body from a first position to a second position such that the plurality of distal flexures move and the circumference of the proximal end of the cage body resiliently expands. The proximal plug member is also configured to move from the second position to the first position such that the circumference of the proximal end resiliently contracts. The distal plug member has a threaded and tapered circumference configured to mate with the threaded and tapered bore of the distal end of the cage body. The distal plug member is configured to move along the longitudinal axis relative to the cage body from a third position to a fourth position such that the plurality of proximal flexures move and the circumference of the distal end of the cage body resiliently expands. The distal plug member is also configured to move from the fourth position to the third position such that the circumference of the distal end resiliently contracts. The first adjustment member is rotationally coupled to the proximal plug member such that when the first adjustment member is rotated, the proximal plug member is caused to move along the longitudinal axis. The second adjustment member rotationally coupled to the distal plug member such that when the second adjustment member is rotated, the distal plug member is caused to move longitudinally, thereby allowing the proximal and the distal ends of the cage body to be expanded and contracted independent from one another. The first and the second adjustment members are coaxially nested one within the other and independently rotatable. The first and the second adjustment members each have knobs axially spaced but adjacent to one another such that the knobs may alternately be rotated in unison or individually. At least one of the first and the second adjustment members may have a keyed end configured to slidably mate and rotationally couple with its associated plug member such that the at least one adjustment member can be removed from the expandable medical implant. 
         [0024]    According to some aspects of the disclosure, a method of distracting adjacent bone segments having opposing surfaces is provided. The method comprises the steps of inserting an expandable medical implant as described above between the opposing surfaces of the bone segments, and moving the proximal and the distal plug members longitudinally and independently from one another such that the proximal and the distal ends of the cage body expand independently to alter the distance and the angle between the opposing surfaces of the bone segments. In some embodiments, the method further includes the step of removing at least one adjustment member from the medical implant after the adjustment member has been used to move at least one of the proximal and distal plug members. In some embodiments, the bone segments are adjacent vertebrae, and the opposing surfaces are end plates of the adjacent vertebrae. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0025]    For the purpose of illustrating concepts of the disclosure, the drawings show aspects of one or more embodiments. However, it should be understood that the present disclosure is not limited to the precise arrangements and instrumentalities shown in the drawings, wherein: 
           [0026]      FIGS. 1-3  are a series of lateral representations of two vertebral bodies, wherein  FIG. 1  depicts the insertion of an exemplary Universally Expanding Cage (UEC) in its unexpanded state,  FIG. 2  depicts the UEC in place between the vertebral bodies and still in its unexpanded state, and  FIG. 3  depicts the inserted UEC in its expanded state. 
           [0027]      FIG. 4  is a perspective view of a first embodiment of a UEC in an unexpanded state according to aspects of the disclosure. 
           [0028]      FIG. 5  is an exploded perspective view showing the UEC of  FIG. 4 . 
           [0029]      FIG. 6  is a perspective view showing the cage body of the UEC of  FIG. 4 . 
           [0030]      FIG. 7  is a proximal end view of the UEC of  FIG. 4 . 
           [0031]      FIG. 8  is a side view of the UEC of  FIG. 4 . 
           [0032]      FIG. 9  is a side cross-sectional view of the UEC of  FIG. 4 . 
           [0033]      FIG. 10  is a perspective view of a second embodiment of a UEC in an unexpanded state according to aspects of the disclosure. 
           [0034]      FIG. 11  is an exploded perspective view showing the UEC of  FIG. 10 . 
           [0035]      FIG. 12  is a side view showing the UEC of  FIG. 10 . 
           [0036]      FIG. 13  is a proximal end view showing the UEC of  FIG. 10 . 
           [0037]      FIG. 14  is a distal end view showing the UEC of  FIG. 10 . 
           [0038]      FIG. 15  is a side cross-sectional view showing the UEC of  FIG. 10 . 
           [0039]      FIG. 16  is a perspective view of a third embodiment of a UEC in an unexpanded state according to aspects of the disclosure. 
           [0040]      FIG. 17  is an exploded perspective view showing the UEC of  FIG. 16 . 
           [0041]      FIG. 18  is a side view showing the UEC of  FIG. 16 . 
           [0042]      FIG. 19A  is a side cross-sectional view showing the UEC of  FIG. 16 . 
           [0043]      FIG. 19B  is an end cross-sectional view showing the UEC of  FIG. 16 . 
           [0044]      FIGS. 20A-20C  are a series of side views showing the progressive expansion of the UEC of  FIG. 16 , wherein  FIG. 20A  shows both ends of the UEC in the unexpanded state,  FIG. 20B  shows only one end expanded, and  FIG. 20C  shows both ends expanded. 
           [0045]      FIG. 21  is a perspective view of a fourth embodiment of a UEC in an unexpanded state according to aspects of the disclosure. 
           [0046]      FIG. 22  is a perspective view of a fifth embodiment of a UEC in an unexpanded state according to aspects of the disclosure. 
           [0047]      FIG. 23  is a distal end view showing the UEC of  FIG. 22 . 
           [0048]      FIG. 24  is a side view showing the UEC of  FIG. 22 . 
           [0049]      FIG. 25  is a side cross-sectional view showing the UEC of  FIG. 22 . 
           [0050]      FIG. 26  is a cranial to caudal view showing the insertion sites of dual UECs on a vertebral body in one example implementation. 
           [0051]      FIG. 27  is an oblique posterolateral view showing one of the insertion sites of the implementation of  FIG. 26 . 
           [0052]      FIG. 28  is an oblique posterolateral view showing the axes of adjustment provided by the implementation of  FIG. 26 . 
           [0053]      FIG. 29  is an oblique anterior view showing an anterior column implant. 
           [0054]      FIG. 30  is a posterior view showing a human spine exhibiting scoliosis. 
           [0055]      FIG. 31  is a posterior view showing the spine of  FIG. 29  after being corrected according to aspects of the disclosure. 
           [0056]      FIGS. 32A-32C  are anterior, lateral and oblique views, respectively, showing adjacent vertebral bodies having misalignments/uneven spacing. 
           [0057]      FIGS. 33A-33C  are anterior, lateral and oblique views, respectively, showing the vertebral bodies of  FIGS. 32A-32C  with the misalignments/uneven spacing corrected according to aspects of the disclosure. 
       
    
    
     DETAILED DESCRIPTION 
       [0058]    Referring to  FIG. 1-3 , a series of lateral views of vertebral segments  50  and  52  are shown, depicting the insertion and expansion of one embodiment of UEC (Universally Expanding Cage). The depicted vertebral bodies  50  and  52  have an average 8 mm gap between vertebral end plates, representing an average intervertebral space  54 . In a typical implementation, a complete discectomy is performed prior to the insertion of the UEC  56 . The intervertebral disc occupying space  54  is removed using standard techniques including rongeur, curettage, and endplate preparation to bleeding subcondral bone. The posterior longitudinal ligament is divided to permit expansion of the intervertebral space. 
         [0059]    The intervertebral space  54  may be distracted to about 10 mm using a rotating spatula (not shown). This is a well-known device that looks like a wide screw driver that can be placed into the disc space horizontally and turned 90 degrees to separate the endplates. A novel feature of the UEC is that after intervertebral disc space expansion and preparation (by curetting or ideally arthroscopically facilitated disc material removal), the UEC implant per se can be inserted through any orifice or angle that does not cause injury to nerves or other structures, positioned at the immediate implant location and consequent expansion platform to yield both the best fusion and angular correction results. 
         [0060]    In the example implementation depicted in  FIGS. 1-3 , UEC  56  is inserted posteriorly (in the direction of arrow  58 ) between vertebral bodies  50  and  52 , as shown in  FIG. 1 . The vertebral space  54  depicted is meant to represent any vertebral space in which it is desired to insert the UEC (sacral, lumbar, thoracic and/or cervical), and from any direction permitted by the surrounding anatomy. In accordance with an aspect of the disclosure, the UEC is reduced to a small size in its unexpanded state to enable it to be inserted through into the intervertebral space  54  as shown in  FIG. 1 .  FIG. 2  shows UEC  56  inserted between vertebral bodies  50  and  52 , with UEC  56  still in its unexpanded state. In one exemplary embodiment, dimensions of an unexpanded UEC are: 10-12 mm wide, 10 mm high and 28 mm long to facilitate insertion and thereby minimize trauma to the patient and risk of injury to nerve roots. These dimensions may accommodate the flat external surfaces. Once in place, the exemplary UEC  56  may be expanded to 140 percent of its unexpanded size (as shown in  FIG. 3 ), enabling 20 degrees or more of spinal correction depending on the 3D clinical pre-operation anatomic analysis. 
         [0061]    It should be noted that while the exemplary UEC  56  depicted in  FIGS. 1-3  is an implant intended to ideally fill the warranted space, other shapes of implants such as those shown in later figures and/or described herein may be used. In various embodiments, the implants may have a transverse cross-section that is circular, oval, elliptical, square, rectangular, trapezoidal, or other shape suited to fill the implant site and transmit the required loads. The implants may straight, curved, bean-shaped, and/or include other shapes and aspect ratios. Additionally, the external surfaces may be smooth, spiked, threaded, coated and/or further adapted as subsequently described in more detail. The UEC can be used at any spinal level the surgeon deems in need of fusion, and may be placed at any position and angle relative to the vertebral endplates as may be needed. One, two, or more UECs may be placed at any particular level to achieve the desired height and angles between vertebral bodies. As will be later described, multiple UECs may be used to adjust the overall cranio-caudal height, the anterior-posterior angle, and the medio-lateral angle between adjacent vertebral bodies. UECs may be implanted at multiple levels to obtain or restore the desired three dimensional curvature and positioning of the spine. 
         [0062]    Referring to  FIGS. 4-9 , a first embodiment of an exemplary UEC  100  according to aspects of the disclosure is shown.  FIG. 4  is an enlarged perspective view which shows details of UEC  100 . For ease of understanding, a proximal end  104  and a distal end  106  of UEC  100  can be defined as shown in  FIG. 4 . It should be noted that while the distal end  106  of UEC  100  is typically inserted first into a patient and proximal end  104  is typically closest to the surgeon, other orientations of this exemplary device and other devices described herein may be adopted in certain procedures despite the distal and proximal nomenclature being used. 
         [0063]    Referring to  FIG. 5 , an exploded perspective view shows the individual components of UEC  100 . In this first embodiment, UEC  100  includes a cylindrically-shaped cage body  108 , a proximal plug  110 , a distal plug  112 , a threaded actuator  114 , and a washer  116 . The terms “plug” and “plug member” are used interchangeably herein. Actuator  114  has a shank sized to slidably pass through a central bore within proximal plug  110  when UEC  100  is assembled. Actuator  114  also has threads on its distal end for engaging with a threaded central bore within distal plug  112 . Proximal plug  110  and distal plug  112  each have outer surfaces that are inwardly tapered to match inwardly tapered surfaces within cage body  108  (as best seen in  FIG. 9 ) With this arrangement, actuator  114  may be rotated in a first direction to draw distal plug  112  toward proximal plug  110  to outwardly expand cage body  108 , as will be subsequently described in more detail. 
         [0064]    Referring to  FIG. 6 , this perspective view shows details of cage body  108  of the first exemplary embodiment of UEC  100 . In this embodiment, cage body  108  includes eight longitudinally extending beam portions  118 , each separated from an adjacent beam portion  118  by a longitudinally extending gap  120 . In other embodiments (not shown), the cage body may include fewer or more than eight beam portions, and/or beam portions having a different or varying cross-section or shape. Cage body  108  of the current embodiment also includes eight circumferentially extending connector portions  122 . The connector portions  122  interconnect the ends of the beam portions  118 . Four of the connector portions  122  are located at the proximal end  104  of cage body  108 , and the other four connector portions  122  are located at the distal end  106 . The connector portions  122  located at the proximal end  104  are staggered in relation to the connector portions  122  located at the distal end  106  such that each pair of adjacent beam portions  118  are connected at only one end by a connector portion  122 . With this arrangement the beam portions  118  and connector portions  122  form a continuous serpentine or repeating S-shaped pattern. The beam portions  118  and or the connector portions  122  are configured to resiliently flex to allow the cage body  108  to increase in diameter when urged radially outward by plugs  110  and  112  (shown in  FIG. 4 ). When plugs  110  and  112  are not urging cage body  108  radially outward, the resiliency of beam portions  118  and or connector portions  122  allows cage body  108  to return to its original reduced diameter. It can be appreciated that as beam portions  118  and or connector portions  122  flex outwardly, gaps  120  become wider at their open ends opposite connector portions  122 . The outwardly facing surfaces of beam portions  118  may each be provided with one or more points or spikes  123  as shown, to permit cage body  108  to grip the end plates of the vertebral bodies. 
         [0065]    Referring to  FIG. 7 , an end view of the proximal end  104  of UEC  100  is shown. The enlarged head at the proximal end of actuator  114  may be provided with a recessed socket  124  as shown for removably receiving a tool for turning actuator  114 . Proximal plug  110  (and distal plug  112 , not shown) may be provided with radially outwardly extending protuberances  126  that reside in one or more gaps  120  and abut against the side of beam portions  118 . This arrangement prevents plugs  110  and  112  from rotating when actuator  114  is turned, thereby constraining plugs  110  and  112  to only move axially toward or away from each other. Proximal plug  110  (and distal plug  112 ) may be provided with through holes and or recesses  128  to allow for bony ingrowth from the vertebral bodies for more solidly healing/fusing UEC  100  in place. Longitudinally extending slots  130  (shown in  FIG. 4 ) may also be provided for this purpose, and or for packing plugs  110  and  112  with autograft, allograft, and/or other materials for promoting healing/fusion. 
         [0066]    Referring to  FIGS. 8 and 9 , a side view and side cross-sectional view, respectively, are shown. In operation, UEC  100  is expanded by inserting a tool such as a hex key wrench or driver (not shown) into the recessed socket  124  at the proximal end of actuator  114  and turning it clockwise. As best seen in  FIG. 9 , the distal end of actuator  114  is threaded into the central bore of distal plug  112 . Turning actuator  114  clockwise causes the distal end of actuator  114  to pull distal plug  112  towards the center of cage body  108  while the enlarged head at the proximal and of actuator  114  pushes proximal plug  110  towards the center. This movement in turn causes the ramped surfaces  132  of plugs  110  and  112  to slide inwardly along the ramped surfaces  134  located along the inside of beam portions  118  and connector portions  122  to cause these elements to flex and expand radially outward as previously described. This process may be reversed by turning actuator  114  counterclockwise. The resilient inward forces from the beam portions  118  and or connector portions  122  (and or the compressive forces from adjacent vertebral bodies) against plugs  110  and  112  causes the two plugs to separate axially, thereby allowing UEC  100  to return to its non-expanded state. 
         [0067]    Referring to  FIGS. 10-15 , a second embodiment of an exemplary UEC  200  according to aspects of the disclosure is shown.  FIG. 10  is a perspective view which shows details of UEC  200 . UEC  200  includes a proximal end  204  and a distal end  206 , and shares many of the same features of previously described UEC  100 , which are identified with similar reference numerals. 
         [0068]    Referring to  FIG. 11 , an exploded perspective view shows the individual components of UEC  200 . In this second embodiment, UEC  200  includes an elongated cylindrical cage body  208 , a proximal plug  210 , and a distal plug  212 . Distal plug  212  includes an integrally formed actuator rod  214  that extends along the internal central axis of cage body  208  towards proximal plug  210  when UEC  200  is assembled. Proximal plug  210  and distal plug  212  each have outer surfaces that are threaded and inwardly tapered to match threaded and inwardly tapered surfaces within cage body  208  (as best seen in  FIG. 15 ). With this arrangement, each plug  210  and  212  may be independently rotated to move the particular plug axially toward the middle of cage body  208  to outwardly expand that particular end  204  or  206  of cage body  208 , as will be subsequently described in more detail. 
         [0069]    As shown in  FIGS. 11 and 12 , cage body  208  includes eight longitudinally extending beam portions  218 , each separated from an adjacent beam portion  218  by a longitudinally extending gap  220 . In other embodiments (not shown), the cage body may include fewer or more than eight beam portions, and/or beam portions having a different or varying cross-section or shape. Cage body  208  of the current embodiment also includes eight circumferentially extending connector portions  222 . The connector portions  222  interconnect the ends of the beam portions  218 . Four of the connector portions  222  are located at the proximal end  204  of cage body  208 , and the other four connector portions  222  are located at the distal end  206 . The connector portions  222  located at the proximal end  204  are staggered in relation to the connector portions  222  located at the distal end  206  such that each pair of adjacent beam portions  218  are connected at only one end by a connector portion  222 . With this arrangement the beam portions  218  and connector portions  222  form a continuous serpentine or repeating S-shaped pattern. The beam portions  218  and or the connector portions  222  are configured to resiliently flex to allow the cage body  208  to increase in diameter when urged radially outward by plugs  210  and  212 . When plugs  210  and  212  are not urging cage body  208  radially outward, the resiliency of beam portions  218  and or connector portions  222  allows cage body  208  to return to its original reduced diameter. It can be appreciated that as beam portions  218  and or connector portions  222  flex outwardly, gaps  220  become wider at their open ends opposite connector portions  222 . The outwardly facing surfaces of beam portions  218  may each be provided with one or more points or spikes  223  as shown, to permit cage body  208  to grip the end plates of the vertebral bodies. 
         [0070]    Referring to  FIG. 13 , an end view of the proximal end  204  of UEC  200  is shown. The proximal plug  210  may be provided with a recessed socket  224  as shown for removably receiving a tool for turning proximal plug  210  in either direction, such as a five-lobed driver (not shown). Alternatively, other suitable types of recessed sockets, slots, protruding and/or keyed features may be utilized with a mating driver. The proximal end of actuator shaft  214  (which extends proximally from distal plug  212  inside cage body  208 ) may be accessed through a central bore  225  in proximal plug  210 . The proximal end of actuator shaft  214  may be shaped as shown to be received within a mating driver socket (such as a five-lobed socket, not shown), which can be removably extended into the center of cage body  208  through central bore  225 . With this arrangement, both the proximal plug  210  and the distal plug  212  can be independently accessed and rotated from the proximal end of UEC  200  so that the proximal end  204  and the distal end  206  of UEC  200  can be expanded or contracted independently. 
         [0071]    Referring to  FIG. 14 , an end view of the distal end  206  of UEC  200  is shown. By comparing  FIGS. 13 and 14 , it can be appreciated that connector portions  222  at the proximal end  204  of UEC  200  are staggered (i.e. rotated 45°) in relation to the connector portions  222  at the distal end  206  of UEC  200 . 
         [0072]    Referring to  FIG. 15 , a side cross-sectional view of UEC  200  is shown. In operation, the proximal end  204  of UEC  200  may be independently expanded by inserting a tool such as a five-lobed driver (not shown) into the recessed socket  224  of proximal plug  210  and turning it clockwise. Turning proximal plug  210  clockwise causes the threaded ramped surfaces  232  of plug  210  to translate inwardly (to the right in  FIG. 15 ) along the threaded ramped surfaces  234  located along the inside of beam portions  218  and connector portions  222  to cause these elements to flex and expand radially outward as previously described. This process may be reversed by turning proximal plug  210  counterclockwise, thereby allowing the proximal end  204  of UEC  200  to return to its non-expanded state. Similarly, the distal end  206  of UEC  200  may be independently expanded by inserting a tool such as a five-lobed socket (not shown) through the central bore  225  in proximal plug  210  until it engages with the proximal end of actuator  214 , which is attached to distal plug  212 . Turning distal plug  212  counterclockwise (from the perspective of the proximal end) causes the threaded ramped surfaces  232  of plug  212  to translate inwardly (to the left in  FIG. 15 ) along the threaded ramped surfaces  234  located along the inside of beam portions  218  and connector portions  222  to cause these elements to flex and expand radially outward as previously described. This process may be reversed by turning distal plug  212  clockwise, thereby allowing the distal end  206  of UEC  200  to return to its non-expanded state. 
         [0073]    The adjustment tools described above (not shown) for turning proximal plug  210  and distal plug  212  may be inserted one at a time into UEC  200 . Alternatively, the two tools may be nested together, with the tool for turning the distal plug  212  passing through a central bore in the tool for turning the proximal plug, as will be subsequently shown and described in relation to other embodiments. With this arrangement, both tools may be turned simultaneously or individually. In some embodiments, both proximal plug  210  and distal plug  212  are provided with right-handed threads, so that when both tools are simultaneously turned in the same direction, one end of UEC  200  expands while the other end contracts, thereby changing the outer surface angle of UEC  200  without substantially changing its overall diameter (i.e. without substantially changing the diameter or height of the midpoint of UEC  200 .) For example, by turning the two tools in the same direction, the lordotic angle between two vertebral bodies can be changed by UEC  200  without substantially changing the height between the two vertebral bodies. 
         [0074]    In other embodiments, one of the plugs  210  or  212  may be provides with a right-handed thread and the other plug provided with a left-handed thread. In these embodiments, when both adjustment tools are simultaneously turned in the same direction, both ends  204  and  206  of UEC  200  expand or contact together without substantially changing the outer surface angle of UEC  200 . For example, by turning the two tools in the same direction, the height between the two vertebral bodies can be changed by UEC  200  without substantially changing the lordotic angle between two vertebral bodies. 
         [0075]    In some embodiments, plugs  210  and  212  may each be provided with threads having a different pitch from the other. Such an arrangement allows both the height and the angle between adjacent vertebral bodies to be adjusted simultaneously in a predetermined relationship when both adjustment tools are turned together in unison. For example, proximal plug  210  may be provided with right-handed threads of a particular pitch while distal plug  212  may be provided with finer, left-handed threads having half the pitch of the proximal plug threads. In this embodiment, when both adjustment tools are turned together in a clockwise direction, both ends of UEC  200  expand at the same time but the proximal end  204  expands at twice the rate of the distal end  206 . This allows the surgeon to increase the height between adjacent vertebral bodies and at the same time angle the bodies away from him or her. One or both of the tools may then be turned individually to more finely adjust the height and angle between the vertebral bodies. 
         [0076]    In some embodiments the above-described adjustment tools may be removed from UEC  200  before the surgical procedure is completed. In some embodiments the above adjustment tools may remain in place after the procedure is completed. 
         [0077]    In some embodiments, UEC  200  is 50 mm long, has an unexpanded diameter of 10 mm, and an expanded diameter of 14 mm. In other embodiments, the UEC may be configured to expand to about 11, 12, or 13 mm, or more than 14 mm. In still other embodiments, the UEC may be configured with dimensions larger or smaller than these to conform to a particular anatomy or procedure. 
         [0078]    Referring to  FIGS. 16-20 , a third embodiment of an exemplary UEC  300  according to aspects of the disclosure is shown.  FIG. 16  is a perspective view which shows details of UEC  300 . UEC  300  includes a proximal end  304  and a distal end  306 , and shares many of the same features of previously described UECs  100  and  200 , which are identified with similar reference numerals. 
         [0079]    Referring to  FIG. 17 , an exploded perspective view shows the individual components of UEC  300 . In this third embodiment, UEC  300  includes a rectangular cage body  308 , a proximal plug  310 , a distal plug  312 , a proximal plug adjustment tool  313 , and a distal plug adjustment tool  314 . As in the previously described UEC  200 , both plugs  310  and  312  are threaded and tapered, and each end of cage body  308  is provided with an inwardly tapered and threaded bore configured to receive one of the plugs  310  or  312 . Adjustment tools  313  and  314  are similar in construction and operation to the adjustment tools previously described (but not shown) in reference to UEC  200 . Proximal plug  310  includes a mating recess on its proximal end (not shown) configured to removably receive the splined distal end of proximal plug adjustment tool  313  for rotating proximal plug  310 . Distal plug  312  includes a smaller mating recess on its proximal end (not shown) configured to removably receive the smaller splined distal end of distal plug adjustment tool  314  for rotating distal plug  312 . Both proximal plug adjustment tool  313  and proximal plug  312  are provided with central bores that permit the distal end of distal plug adjustment tool  314  to pass therethrough, through the center of cage body  308 , and partially into distal plug  312 . In this exemplary embodiment, the proximal ends of adjustment tools  313  and  314  each have a hexagonally-shaped head that permits them to be turned together in unison or individually (as previously described in relation to UEC  200 ), using wrench(es), socket(s) (not shown) and/or by hand. 
         [0080]    As shown in  FIGS. 16 and 17 , cage body  308  includes eight longitudinally extending beam portions  318 , each separated from an adjacent beam portion  318  by a longitudinally extending gap  320 . In other embodiments (not shown), the cage body may include fewer or more than eight beam portions, and/or beam portions having a different or varying cross-section or shape. It can be seen that in this embodiment, four of the gaps  320  are formed through the middle of the four faces of cage body  308 , and the other four gaps  320  are formed along the corner edges of cage body  308 . Cage body  308  also includes eight circumferentially extending connector portions  322 . The connector portions  322  interconnect the ends of the beam portions  318 . Circular apertures  321  may be provided as shown between the ends of gaps  320  and the connector portions  322  to relieve stress concentrations at those locations as connector portions  322  flex. Four of the connector portions/flexures  322  are located at the proximal end  304  of cage body  308  (across the corner edges of cage body  308 ), and the other four connector portions/flexures  322  are located at the distal end  306  (across the distal end of the faces of cage body  308 .) The connector portions  322  located at the proximal end  304  are staggered in relation to the connector portions  322  located at the distal end  306  such that each pair of adjacent beam portions  318  are connected at only one end by a connector portion  322 . As with previously described embodiments, the beam portions  318  and connector portions  322  form a continuous serpentine or repeating S-shaped pattern. The beam portions  318  and or the connector portions  322  are configured to resiliently flex to allow the cage body  308  to increase in circumference when urged radially outward by plugs  310  and  312 . When plugs  310  and  312  are not urging cage body  308  radially outward, the resiliency of beam portions  318  and or connector portions  322  allows cage body  308  to return to its original reduced circumference. It can be appreciated that as beam portions  318  and or connector portions  322  flex outwardly, gaps  320  become wider at their open ends opposite connector portions  322 . The outwardly facing surfaces of beam portions  318  may each be provided with one or more points or spikes  323  as shown, to permit cage body  308  to grip the end plates of the vertebral bodies. In this exemplary embodiment, spiked or knurled surfaces are provided along the top and bottom of UEC  300  while the side surfaces are left smooth. 
         [0081]    Referring to  FIGS. 18 and 19 , a side view and a side cross-sectional view, respectively, of UEC  300  are shown. In operation, the proximal end  304  of UEC  300  may be independently expanded by inserting proximal plug adjustment tool  313  into the mating recessed socket of proximal plug  310  (as shown in  FIG. 19 ) and turning it clockwise. Turning proximal plug  310  clockwise causes the threaded ramped surfaces  332  of plug  310  to translate inwardly (to the left in  FIGS. 18 and 19 ) along the threaded ramped surfaces  334  located along the inside of beam portions  318  and connector portions  322  to cause these elements to flex and expand radially outward as previously described. This process may be reversed by turning proximal plug  310  counterclockwise, thereby allowing the proximal end  304  of UEC  300  to return to its non-expanded state. Similarly, the distal end  306  of UEC  300  may be independently expanded by inserting a tool such as a five-lobed socket (not shown) through the central bore  325  in proximal plug  310  until it engages with the proximal end of actuator  314 , which is attached to distal plug  312 . Turning distal plug  312  counterclockwise (from the perspective of the proximal end) causes the threaded ramped surfaces  332  of plug  312  to translate inwardly (to the right in  FIGS. 18 and 19 ) along the threaded ramped surfaces  334  located along the inside of beam portions  318  and connector portions  322  to cause these elements to flex and expand radially outward as previously described. This process may be reversed by turning distal plug  312  clockwise, thereby allowing the distal end  306  of UEC  300  to return to its non-expanded state. 
         [0082]    Referring to  FIGS. 20A-20C , a series of sides views depicts the progression from a fully retracted and a fully expanded UEC  300 . In  FIG. 20A , cage body  308  is shown in a fully retracted position. In this figure, the height of each end of cage body  308  is labeled as 100% of retracted cage height. In  FIG. 20B , the proximal end  304  of cage body  308  has been fully expanded while the distal end  306  remains fully retracted. In this exemplary embodiment, each end is capable of being expanded to a height (and therefore also a width) that is 140% of the fully retracted height, as shown. In  FIG. 20C , the distal end  306  has also been expanded by 40%. 
         [0083]    In some embodiments, UEC  300  has a cage length of 50 mm, an unexpanded cage height of 10 mm, and an expanded cage height of 14 mm. The overall length of UEC  300  with adjustment tools  313  and  314  in place and in the unexpanded state may be 75 mm. In other embodiments, the UEC may be configured to expand to about 11, 12, or 13 mm, or more than 14 mm. In still other embodiments, the UEC may be configured with dimensions larger or smaller than these to conform to a particular anatomy or procedure. In some embodiments, the UEC can form an included angle between its top and bottom surfaces of at least 20 degrees. 
         [0084]    Referring to  FIG. 21 , a fourth embodiment of an exemplary UEC  400  according to aspects of the disclosure is shown.  FIG. 21  is a perspective view which shows details of UEC  400 . UEC  400  includes a proximal end  404 , a distal end  406 , cage body  408 , proximal plug  410 , distal plug  412 , proximal plug adjusting tool  413 , and distal plug adjusting tool  414 . Other than cage body  408  having a circular cross-section rather than a square cross-section, UEC  400  is essentially identical in construction and operation to previously described UEC  300 . In other embodiments (not shown), the UEC may have a cross-section transverse to the central longitudinal axis that is rectangular, trapezoidal, oval, elliptical or other shape. 
         [0085]    Referring to  FIGS. 22-25 , a fifth embodiment of an exemplary UEC  500  according to aspects of the disclosure is shown.  FIG. 16  is a perspective view which shows details of UEC  500 . UEC  500  includes a proximal end  504  and a distal end  506 , and shares many of the same features of previously described UECs  100 - 400 , which are identified with similar reference numerals. 
         [0086]    UEC  500  includes three components: a generally cylindrical, unitary cage body  508 ; a proximal actuator screw  510 ; and a distal actuator screw  512 . The heads of actuator screws  510  and  512  may be referred to as plug members. Cage body  508  includes two longitudinal, off-center slots  550  which each extend about three-quarters of the length of cage body  508 , and emanate from opposite ends and opposite sides of cage body  508 . Cage body  508  is also provided with two transverse slots  552 , each located adjacent to the closed end of one of the longitudinal slots  550 . Each transverse slot  552  extends from the outer circumference of cage body  508  and approaches the base of a longitudinal slot  550 . Each of the two pairings of a longitudinal slot  550  with a transverse slot  552  defines a cantilevered arm  554  that is connected with the remainder of the cage body  508  by a living hinge  556  near the closed ends of the two slots  550  and  552 . Each living hinge  556  allows its associated arm  554  to flex outwardly against a vertebral body. 
         [0087]    The open ends of longitudinal slots  550  are outwardly tapered to receive the enlarged, tapered heads of an actuator screw  510  or  512 , as best seen in  FIG. 24 . The opposite ends of actuator screws  510  and  512  extend through longitudinal slots  550  and thread into the opposite ends of cage body  508 . With this arrangement, each actuator screw  510  and  512  may be turned independently of the other, causing the screw to move axially relative to bone cage  508 . This axial movement causes the head of the screw to urge the tapered tip of the associated arm  554  outward, or allowing it to flex back inward when the screw is turned in the opposite direction. If both actuator screws  510  and  512  are turned in the same direction the same amount, UEC  500  expands uniformly and increases the height between adjacent vertebral bodies. If one of the two actuator screws  510  or  512  is turned more than the other, the surgeon is able to change the angle between the vertebral bodies. 
         [0088]    As best seen in  FIG. 23 , a slot  558  or other suitable feature may be provided in the end of each actuator screw  510  and  512  at the opposite end from the screw head. A hole  560  may also be provided through each end of cage body  508  to allow access to each of the two slots  558 . This arrangement allows both of the actuator screws  510  and  512  to be turned from either end  504  and/or  506  of cage body  508 . 
         [0089]    Referring to  FIGS. 26-28 , an example implementation utilizing two UECs  56  in tandem is shown. Each UEC  56  may be inserted as previously described in relation to  FIGS. 1-3 . In this implementation, UECs  56  are placed non-parallel to one another. As best seen in  FIG. 28 , this arrangement allows the surgeon to adjust the angle between the vertebrae about two different axes, and also translate the vertebrae with respect to one another about another axis. 
         [0090]      FIG. 29  is an oblique anterior view showing placement of an anterior column implant  56  on a vertebral body  52 . In this implementation, implant  56  is placed laterally across the vertebral body  52 , forward of the lateral midline. After adjustment of implant  56 , its plugs are flush with or recessed within the outer perimeter of the endplate of vertebral body  52  so as not to impinge upon adjacent tissue. 
         [0091]    Referring to  FIG. 30 , a human spine  76  is shown that exhibits scoliosis. According to aspects of the disclosure, dual UECs may be placed at various levels of the spine to treat the condition. For example, a single UEC or pairs of UECs may be implanted at the levels depicted by reference numerals  78 ,  80 ,  82  and  84  shown in  FIG. 30 . By using the adjustments described above relative to  FIG. 28 , the curvature of the spine may be adjusted in three dimensions at these four levels to a correct alignment, as shown in  FIG. 31 . 
         [0092]      FIGS. 32A-32C  are anterior, lateral and oblique views, respectively, showing adjacent vertebral bodies  50  and  52  having misalignments/uneven spacing. 
         [0093]      FIGS. 33A-33C  are anterior, lateral and oblique views, respectively, showing the vertebral bodies  50  and  52  of  FIGS. 32A-32C  with the misalignments/uneven spacing corrected according to aspects of the disclosure. 
         [0094]    The implants can be made of, for example, such materials as titanium,  64  titanium, or an alloy thereof,  316  or  321  stainless steel, biodegradeable and biologically active materials, e.g. stem cells, and polymers, such as semi-crystalline, high purity polymers comprised of repeating monomers of two ether groups and a ketone group, e.g. polyaryetheretherketone (PEEK)™, or Teflon™. 
         [0095]    To prevent movement of proximal and distal plugs or actuators after implantation, in some implementations a biocompatible adhesive or thread locking compound may be applied to one or more of the moving parts. In some embodiments (not shown) a pin may be inserted radially or axially between the plug/actuator and the cage body to lock the parts in place post operatively. In some embodiments, a ratchet, spring loaded detent, or other locking mechanism may be provided for this purpose. 
         [0096]    In general, as disclosed in the above embodiments, the cage body is cut with openings at every other end of each slot, like a sine wave, allowing expansion when the center of the cage becomes occupied with a cone or mandrill shaped unit. The cage body&#39;s series of alternating slots allows the expansion to take place while keeping the outside of the UEC one single piece. The slots plus the teeth on the surface allow for a solid grip on the bone surfaces and plenty of opportunities for good bone ingrowth. Also, by allowing the surgeon to make one end of the UEC thicker than the other, the effects of the cone (mandrill) introduction vary from uniform to selective conduit expansion. The UEC expansion mechanism is adaptable to both fixed fusion and mobile ‘motion preservation’ implants, with exteriors of the expanding implant per surgeon&#39;s choice (round, flat, custom, etc.) As such, in some implementations, relative motion may be preserved between the vertebral bodies adjacent the implanted UEC(s). In other implementations, it may be desirable to fuse the adjacent vertebral bodies around the implanted UEC(s). 
         [0097]    To provide motion preservation between adjacent vertebrae, robust compressible materials may be used between the UEC and one or both of the vertebral endplates, and/or one or more components of the UEC may comprise such materials. These materials may replicate the load distributing and shock absorbing functions of the annulus and nucleus of a natural disk. For example, in some embodiments the UEC may be provided with tapered plugs made of a resilient polymer to allow the UEC to compress and expand to accommodate relative motion of the adjacent vertebrae. Examples of biocompatible materials suitable for some UEC embodiments include Bionate®, a thermoplastic polycarbonate-urethane (PCU) provided by DSM Biomedical in Exton, Pa., and ChronoFlex®, a PCU provided by AdvanSource Biomaterials in Wilmington, Mass. 
         [0098]    The UEC provides advantages over currently existing technology that include correction of coronal plane deformity; introduction of interbody lordosis and early stabilization of the interbody space with rigidity that is greater than present spacer devices. This early stability may improve post-operative pain, preclude the need for posterior implants including pedicle screws, and improve the rate of successful arthrodesis. Importantly, the UEC provides improvement of space available for the neural elements while improving lordosis. Traditional implants are limited to spacer effects, as passive fillers of the intervertebral disc locations awaiting eventual fusion if and when bone graft in and around the implant fuses. By expanding and morphing into the calculated shape which physiologically corrects spine angulation, the UEC immediately fixes the spine in its proper, painless, functional position. As infused osteoinductive/osteoconductive bone graft materials heal, the patient becomes well and the implant becomes inert and quiescent, embedded in bone, and no longer needed. 
         [0099]    In some embodiments, the external surface of the UEC may be 3D printed to not only fit into the intervertebral space per se, but to match the surface topography at each insertion location. In other words, a 3D printed endplate may be utilized, computer calculated to fit and expand the disc space of the individual patient, resulting in both best ‘goodness of fit’ for fusion, and improved axial skeletal alignment. 
         [0100]    By creating to ‘maps’ that fit e.g. as a precisely congruent superior and inferior surface to fit into a particular patients disc space, and placing these UEC end plates on either side the novel UEC expansion mechanism, a patient&#39;s disc space AND overall spine alignment will be ideally treated toward best fusion (or motion preservation) and alignment. 
         [0101]    “Method of Surgery” instructions may recommend the surgeon and//or robotic unit deploy expansion as programmed to insert the UEC into a particular disc level of pathology, to achieve best results. For example, preoperative patient scans/films can predict ideal UEC surgeon use, such as “turn Knob A a certain number of rotations clockwise,” to maximize visible, palpable, and roentgenographic ‘Goodness of Fit’. With this approach, post activation, the UEC implant fits the location, entering at the predetermined best angle (in 3 axes) using the proprietary Method of Surgery and UEC insertion tools provided. 
         [0102]    In some embodiments, the UEC may be coated with hydroxyapatite. In some embodiments, toothed or 400 μm beaded surfaces may be utilized to promote bony ingrowth. Inflatable chambers may be provided within the endplate that can expand after being implanted. This approach addresses the 3-D congruence to proximate disc pathology. It can also allow for intervertebral arthrodesis or arthroplasty treatment and overall improved spinal alignment, integrating the internal proprietary expansion with the variable external endplate shapes and their contents. UEC inflatable endplates of polymer may be employed, such as tiny vacuoles, “bubblewrap”, and multiple or singular bladder constructs. If a portion of the disk space were collapsed, that region could be aptly elevated or expanded by the UEC endplate variation in material and/or inflation. The inflatable chambers may contain compressible gas (such as air,) granules as pharmacologics, and/or stem cells that are delivered via liquids. In cases where the UEC is compressible or force absorbing, the material and/or chamber could be used as a cushion or to ‘selectively direct and protect chondrocytes’ toward improvement of existing pathophysiology via best drug use or regeneration. 
         [0103]    The ‘preparation’ of the UEC insertion site will vary per surgeon. In some implementations, an arthroscopic burr may be advisable for removing 0.5 mm of cortical bone along with all aberrant disc contents under digital arthroscopic camera control. In other implementations, the surgeon may just carefully curette the intervertebral space to ‘clean it out’ in preparation for the UEC implant insertion. 
         [0104]    The UEC may be inserted directly into the insertion site, or may be inserted through proprietary or commercially available insertion tube. The insertion tube typically will have a blunt distal tip so that it can be inserted through an incision without causing tissue damage. The tube can be used with or without additional tissue retractors. The UEC may be preloaded into the insertion tube, or placed into the tube after the tube has been introduced into the insertion site. A pusher rod or other device may be utilized to deploy the UEC from the insertion tube into the insertion site. In some procedures, the placement of the UEC may be arthroscopically assisted. 
         [0105]    Note that regardless of the endplate preparation, in the deformed, aging, pathologic spine there will be pathology to correct. According to various aspects of the present disclosure, the UECs provided herein may accomplish this in several ways as pertains to the external implant composition. For example, the UEC can expand as an externally threaded conduit, either uniformly end to end resulting in same diameters at each end post-operatively (such as 40% overall expansion), or precisely at either end, thus creating an overall conical albeit expanded UEC. Also, the UEC can be flat superiorly and inferiorly as shown in the above drawings, thus more likely matching the rather flat vertebral body end plates. However, according to further aspects of the present disclosure, special care should be taken to consider both the peripheral end plate boney rim as thicker more prominent cortical bone at the vertebral end plates with a sunken or concave thinner interior (thus subject to potential subsidence). The UEC MOS (Method of Surgery) contemplated herein considers the preoperative findings (e.g. MRI, 3D CT scan, X-rays) to integrate information on bone density, specific disc space and longitudinal spine anatomy, topography and alignment. 
         [0106]    The various expanding cages disclosed herein and variations thereof are not limited to use in the spinal column but may be used between other bone segments throughout the human or animal body. For example, a UEC can be used during arthrodesis of a metatarsal joint. The UEC can aid in setting the orientation of the toe to a desired angle before fusion of the apposing bone segments occurs. Similarly, a UEC may be utilized in the knee, elbow or other body joints, or between two or more bone segments that have been fractured by trauma. 
         [0107]    According to various aspects of the disclosure: 
         [0108]    1) the UEC corrects spine surgical pathology both locally via horizontal (disc) and longitudinal vertical axial (scoliotic/kyphotic) spine deformity improvements. 
         [0109]    2) the UEC is applicable cervical through lumbar for
       A) arthrodesis (fusion) or   B) arthroplasty (motion preservation)   C) drug/cell therapy delivery       
 
         [0113]    3) the UEC can expand uniformly throughout implant length, and/or expand only proximally (toward the surgical incision) or distally, thus enabling clinical adjustments favorable to spine diseased or injured patients for local and overall spondylopathies. 
         [0114]    4) the UEC can be surgically inserted via outpatient MIS (Minimally Invasive—outpatient Surgery) as safe, efficacious implants “doing no harm” applying advantages from
       A) materials thicknesses for height differentials or   B) expansion adjustments surgically controlled (before/during or after implantation) or via prefabricated portals or injections—programing implant ‘mapped’ corrections using   C) polymers durometrically calculated with variable compressions, permanent or biodegradable activations at will.   D) inflation of the implant as via UEC surface chambers or bladder(s).   E) adding endplate biologics, foam, or other adaptables for best results.   F) UEC expansion can adapt to expand variable external surface parameters including flat, round, or customized external maximally congruent surfaces to interface as with proximate endplates.       
 
         [0121]    5) Delivery either via UEC materials per se (eluding substances—cells or pharmacologics) or through extrusion from a UEC container or delivery vesicle/depot/chamber/portal will enable not only immediate surgically correction but long term enhanced bone in growth and local/general therapeutic and/or regenerative clinical benefits. 
         [0122]    While the disclosure has been described in connection with example embodiments, it is to be understood that the disclosure is not limited to the disclosed embodiments and alternatives as set forth above, but on the contrary is intended to cover various modifications and equivalent arrangements included within the claim scope.