Abstract:
Embodiments of the invention include expandable implants incorporated into a system for deploying the expandable implants to replace skeletal structures such as one or more vertebrae or portions of the spine or vertebrae. Some embodiments include related methods of implanting devices using deployment systems.

Description:
FIELD OF THE INVENTION 
     The present invention relates generally to the field of replacing portions of the human structural anatomy with medical implants, and more particularly relates to an expandable implant incorporated into a system for deploying the expandable implant to replace skeletal structures such as one or more vertebrae or portions of the spine or vertebrae. 
     BACKGROUND 
     Expandable medical implants are often useful at least because the implants may be introduced into a surgical site with a reduced profile that facilitates reduced disruption of surrounding tissues. Expandable medical implants may be useful in at least some spinal fusion procedures and in at least some vertebral body replacement procedures. Spinal fusion procedures are often effective to restore proper vertebral spacing and relieve pressure on nerves and consequent pain. Also, it is sometimes necessary to remove one or more vertebrae, or a portion of the vertebrae, from the human spine in response to various pathologies. For example, one or more of the vertebrae may become damaged as a result of tumor growth, or may become damaged by a traumatic or other event. Removal, or excision, of a vertebra may be referred to as a vertebrectomy. Excision of a generally anterior portion, or vertebral body, of the vertebra may be referred to as a corpectomy. An implant is usually placed between the remaining vertebrae to provide structural support for the spine as a part of a corpectomy or vertebrectomy. This may generally be referred to as vertebral body replacement. 
     Many prior art devices have deployed expandable medical implants with the aid of relatively large or complex insertion, expansion, distraction, and retraction instruments. Some devices require a significant incision and retraction of tissue to enable controlled expansion of the implant. A smaller incision may be particularly useful with a posterior approach to the spine. To effectively make a posterior approach, an implant may be placed through a window created between a nerve root, the spinal cord, and an extent of an excised vertebra. The nerve root may be mobilized to increase the size of the window slightly, but excess movement may risk damage to the nerve root. Therefore, for a posterior approach, an initially small expandable implant may have particular utility. A posterior approach may be preferred for patients with circumferential tumors or for patients more susceptible to the risks associated with a more extensive anterior approach. Similarly, initially small implants enabling minimal tissue disruption may be useful from any surgical approach to reduce trauma to surrounding tissues and to enhance patient recovery. Likewise, a deployment mechanism that does not require tissue disruption beyond the disruption required to introduce an implant is advantageous. 
     Connections between bones and implants may also be useful in replacing bones or portions of joints or appendages such as the legs and arms, or other bones. Examples include, but are not limited to, a femur, tibia, fibula, humerus, radius, ulna, phalanges, clavicle, and any of the ribs. Use of the mechanisms described and claimed herein are equally applicable to treatment or repair of such bones or appendages. 
     SUMMARY 
     One embodiment of the invention is a system for deploying an expandable medical implant. The expandable medical implant may include a base and an expandable end and an enclosed volume between the base and the expandable end. The expandable medical implant may also include an elongated member with a distal end and a proximal end. The distal end is coupled to the expandable end of the expandable medical implant, and the elongated member is in contact with the base of the expandable medical implant to provide a connection between the expandable end and the base. The proximal end extends from the expandable implant and the proximal end is configured to receive a force applied along its length. 
     An embodiment of the invention is a method of implanting an expandable medical implant. The method may include providing an expandable medical implant with a base and an expandable end and an enclosed volume between the base and the expandable end, and an elongated member with a distal end and a proximal end wherein the distal end is coupled to the expandable end of the expandable medical implant and the elongated member is in contact with the base of the expandable medical implant. The method may also include introducing the expandable medical implant through an incision in a patient, and applying a compressive force to the elongated member to push apart the base and the expandable end of the expandable medical implant. 
     Another embodiment of the invention is a method of implanting an expandable medical implant. The method may include providing an expandable medical implant with a base and an expandable end and an enclosed volume between the base and the expandable end, and an elongated member with a distal end and a proximal end. The distal end is coupled to the expandable end the expandable medical implant and the elongated member are in contact with the base of the expandable medical implant. The method may also include applying a tensile force to the elongated member to pull together the base and the expandable end of the expandable medical implant, introducing the expandable medical implant through an incision in a patient, and releasing the tensile force applied to the elongated member to allow the base and the expandable end of the expandable medical implant to separate. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a cross-sectional view of an embodiment of a system for deploying an expandable medical implant. 
         FIG. 2  is a perspective view of at least a portion of an expandable medical implant in an unexpanded state. 
         FIG. 3  is a perspective view of the expandable medical implant of  FIG. 2  with a portion of the implant removed to illustrate internal components. 
         FIG. 4  is a perspective view of at least a portion of an expandable medical implant in an expanded state. 
         FIG. 5  is a perspective view of the expandable medical implant of  FIG. 4  with a portion of the implant removed to illustrate internal components. 
         FIG. 6  is a cross-sectional view of an embodiment of a system for deploying an expandable medical implant in an unexpanded state. 
         FIG. 7  is a cross-sectional view of the system for deploying an expandable medical implant of  FIG. 6  in an expanded state. 
         FIG. 8  is a cross-sectional view of an embodiment of a system for deploying an expandable medical implant in an unexpanded state, including an elevation view of a biasing member. 
         FIG. 9  is a cross-sectional view of the system for deploying an expandable medical implant of  FIG. 8  in an expanded state, including an elevation view of a biasing member. 
         FIG. 10  is a cross-sectional view of an embodiment of a system for deploying an expandable medical implant in a partially expanded state. 
     
    
    
     DETAILED DESCRIPTION 
       FIG. 1  illustrates a system  100  for deploying an expandable medical implant  1 . The expandable medical implant  1  includes a base  2  and an expandable end  3 . The illustrated expandable medical implant  1  includes a membrane  5  and an expansion mechanism  6 . The expansion mechanism  6  shown in  FIG. 1  is a bellows. The expansion mechanism of other embodiments may be, without limitation, a combination of nested, telescoping cylinders, as illustrated in  FIGS. 6-9 , a ratchet mechanism, a threaded or partially threaded mechanism, or any other mechanism that may drive or hold expansion of an expandable medical implant. 
     The membrane  5  is illustrated in a partially expanded configuration in  FIG. 1 . The membrane  5  of some embodiments is configured to be placed between vertebrae and expanded such that an upper surface  52  contacts a first vertebra and an opposite lower surface  53  contacts a second vertebra to provide support between the vertebrae. The longitudinal axis, or linear expansion direction L, of the expandable medical implant  1  is illustrated in  FIG. 1 . Lateral expansion of the membrane  5  is also accomplished in some embodiments. As used herein, the term lateral means directions approximately normal to the linear expansion direction L. 
     The membrane  5  may be constructed, in whole or in part, of a non-permeable material. The membrane  5  may include compliant or non-compliant balloon materials such as those commonly used to manufacture coronary and Kyphoplasty medical devices. Such materials may include, but are not limited to, mylar, rubber, polyurethane, vinyl, latex, polyethylenes, ionomer, and polytetrapthalate (PET), as well as less flexible materials such as Kevlar®, PEBAX®, stainless steel, titanium, nickel-titanium alloys, and other metals and alloys and/or ceramics. A compliant membrane may include reinforcing to limit one or both of the size and shape of the membrane to a clinically advantageous extent. A non-compliant membrane may expand more elastically to more completely fill an irregular opening, depending on the amount of material introduced into the membrane. 
     Likewise the membrane  5  may be constructed, in whole or in part, of a permeable material, which allows a certain amount of a fill material to pass through the membrane  5 . All or a portion may be made permeable by fabricating a material, including but not limited to, the membrane materials listed above, into a fabric, weave, mesh, composite, bonded fiber assembly, or any other manufacture known to those skilled in the art. For example, all or part of the upper surface  52  and the opposite lower surface  53  may be constructed of a permeable material to allow fill material to move through the membrane  5  and to come into contact with vertebrae. 
     In the embodiment shown in  FIG. 1 , the expansion mechanism  6  defines an enclosed volume, and the membrane  5  defines an enclosed volume that incorporates the enclosed volume of the expansion mechanism  6 . The enclosed volumes of both the expansion mechanism  6  and the membrane  5  are therefore volumes between the base  2  and the expandable end  3 . 
     The system  100  for deploying an expandable medical implant  1  shown in  FIG. 1  includes an elongated member  101  with a distal end  103  and a proximal end  102 . The illustrated distal end  103  is coupled to the expandable end  3  of the expandable medical implant  1 . The elongated member  101  is in contact with the base  2  of the expandable medical implant  1  at a point  8  to provide a connection between the expandable end  3  and the base  2 . The proximal end  102  extends from the expandable implant  1  in  FIG. 1  through an opening or port  7 . The illustrated connection between the expandable end  3  and the base  2  with the elongated member  101  is a sliding connection because the elongated member  101  slides relative to the base  2  when the elongated member is removed from or pushed into the port  7 . 
     The proximal end  102  is configured to receive a force applied along its length. Arrow  105  shows the direction of a pushing or compressive force applied along the length of the elongated member  101  at its proximal end  102 . Arrow  107  shows the direction of a pulling or tensile force applied along the length of the elongated member  101  at its proximal end  102 . In other embodiments where the elongated member  101  is actuated by an alternative mechanism, the force applied to the elongated member  101  may be a twisting, winding, turning, or other effective force to push apart or pull together the base  2  and the expandable end  3 . For example, and without limitation, the elongated member  101  may include threaded portions, turnbuckle portions, fasteners, or multiple members that move relative to one another to lengthen or shorten the elongated member  101 . In some embodiments, the elongated member  101  is a wire, rod, or other relatively rigid device that is capable of transmitting both tensile and compressive forces to either or both pull together or push apart the base  2  and the expandable end  3 . In other embodiments where it is only necessary to pull together the base  2  and the expandable end  3 , the elongated member  101  may be a strand, string, rope, cable, or other member configured primarily to transmit tensile forces. 
     In some embodiments, elasticity in the material of the expansion mechanism  6  may serve as a biasing force to bias the expansion mechanism  6  toward an expanded or unexpanded state, as may be advantageous in various circumstances. For example, it may be advantageous to bias the expansion mechanism  6  toward an unexpanded state to provide a low profile device for insertion. Other devices, such as but not limit to the elongated member  101 , or a fluid injected through the port  7 , may be used to expand the expansion mechanism  6 . A fluid that drives linear expansion of the expandable medical implant  1  or maintains linear expansion of the expandable medical implant  1  may be introduced through the port  7 . The fluid may be merely for expansion and retention, or may be a component of a fill material intended to remain in the expansion mechanism  6 . As used in association with this function, a fluid may be a paste, gel, liquid, suspension, granular mixture, or similar substance. A substance as described herein will be considered a fluid even if it later cures or hardens to a non-fluidic state. Both the expansion mechanism  6  and the membrane  5  may be initially unexpanded linearly. The port  7  may also be used to handle the expandable medical implant  1  or to guide the implant into a position where it can be effectively deployed. 
     In other circumstances, it may be preferred to bias the expansion mechanism  6  toward an expanded state. With such an embodiment, another component, such as but not limit to the elongated member  101 , may be used to keep the expansion mechanism  6  in an unexpanded state while the expandable medical implant  1  is inserted. Following insertion, the expansion mechanism  6  may be released and allowed to increase toward its expanded state by releasing the elongated member  101  relative to the base  2 . 
       FIGS. 2-5  show components of a system for deploying an expandable medical implant  11 . The expandable medical implant  11  includes a base  12  and an expandable end  13 . The illustrated expandable medical implant  1  includes an expansion mechanism  16  ( FIGS. 2 and 4 ) and a stabilizing structure  9  ( FIGS. 3 and 5 ). The expansion mechanism  16  is removed from  FIGS. 3 and 5  to clearly show the stabilizing structure  9 . The expansion mechanism  16  shown is a bellows, but the expansion mechanism of other embodiments may be, without limitation, a telescoping mechanism, a ratchet mechanism, a threaded or partially threaded mechanism, or any other mechanism that may drive or hold expansion of an expandable medical implant. The embodiment of  FIGS. 2-5  does not show a membrane such as the membrane  5  illustrated in  FIG. 1 , but other embodiments may include a membrane of a similar type in cooperation with the expandable medical implant  11 . 
     The stabilizing structure  9  is illustrated in  FIG. 3  with the expandable medical implant  11  in an unexpanded state, and in  FIG. 5  with the expandable medical implant  11  in an expanded state. Superior fingers  91  are spaced apart to create superior channels  92  among the superior fingers  91 . Inferior fingers  93  are spaced apart to create inferior channels  94  among the inferior fingers  93 . In operation, the inferior fingers  93  slide in the superior channels  92 , and the superior fingers  91  slide in the inferior channels  94  to maintain a substantially linear expansion of the expandable medical implant  1  while the base  12  and the expandable end  13  are moved toward or away from each other. In the embodiment shown, the stabilizing structure  9  is within the enclosed volume between the base and the expandable end. However, in other embodiments, the stabilizing structure may be outside of the enclosed volume. 
     The system for deploying an expandable medical implant  11  shown in  FIGS. 2-5  includes an elongated member  101  with a distal end  103  and a proximal end  102  ( FIG. 5 ). The illustrated distal end  103  is coupled to the expandable end  13  of the expandable medical implant  11 . The elongated member  101  is in contact with the base  12  of the expandable medical implant  11  at least within the port  17  to provide a connection between the expandable end  13  and the base  12 . The proximal end  102  extends from the expandable medical implant  11  through a port  17 . The illustrated connection between the expandable end  13  and the base  12  with the elongated member  101  is a sliding connection because the elongated member  101  slides relative to the base  12  when the elongated member  101  is removed from or pushed into the port  17 . 
     The proximal end  102  is configured to receive a force applied along its length. Arrow  105  shows the direction of a pushing or compressive force applied along the length of the elongated member  101  at its proximal end  102 . Arrow  107  shows the direction of a pulling or tensile force applied along the length of the elongated member  101  at its proximal end  102 . In other embodiments where the elongated member  101  is actuated by an alternative mechanism, the force applied to the elongated member  101  may be a twisting, winding, turning, or other effective force to push apart or pull together the base  12  and the expandable end  13 . The character and function of the elongated member  101  is essentially similar to the character and function described in association with  FIG. 1 . 
     In some embodiments, elasticity in the material of the expansion mechanism  16  may serve as a biasing force to bias the expansion mechanism  16  toward an expanded or unexpanded state, as may be advantageous in various circumstances. The character and function of the expansion mechanism  16  and biasing of the expansion mechanism  16  are essentially similar to the character and function described in association with  FIG. 1 . 
       FIGS. 2-5  illustrate nozzles  14  extending from the expandable medical implant  11 . The illustrated nozzles  14  are open to the interior of the expandable medical implant  11 . In some embodiments, a balloon (not shown) may extend from an open, distal end of the nozzles  14 . The balloon may be in fluid communication with the interior of the expandable medical implant  11 . The nozzles  14  and balloons of some embodiments are configured to extend from expandable medical implant  11  and into an endplate of an adjacent vertebra. The balloons may be filled with a material, such as a flowable material, to assist in attachment of the expandable medical implant  11  to the adjacent vertebrae. One or both of the flowable material and the balloons may additionally have a therapeutic effect on the vertebrae. For example, and without limitation, the nozzles  14 , the flowable material, and the balloons, alone or in combination, may help to stabilize the vertebrae. The flowable material passed through the nozzles  14  or used to inflate the balloons may be a curable material or may be a material that is used to expand the balloons, but does not cure in place. Once expanded, the balloons may also receive additional materials that permanently fill the balloons, or that have an additional therapeutic effect on the vertebrae. Any of the materials for use through the nozzles  14  or in the balloons may also be a fill material as described in detail below. In addition to the nozzles  14  or balloons, one or both ends of an embodiment of the expandable medical implant  11  my include teeth, spikes, ridges, indentations, roughening, knurling, or any other device for enhancing fixation between a vertebra and the expandable medical implant  11 . 
       FIGS. 6 and 7  illustrate a system  200  for deploying an expandable medical implant  21 . The expandable medical implant  21  includes a base  22  and an expandable end  23 . The illustrated expandable medical implant  21  includes a membrane  25  and telescoping cylinders  26 . Rather than the telescoping cylinders  26  of the illustrated embodiment, other embodiments may be, without limitation, a bellows, a ratchet mechanism, a threaded or partially threaded mechanism, or any other mechanism that may drive or hold expansion of an expandable medical implant. 
     The telescoping cylinders  26  and membrane  25  are illustrated in an unexpanded state in  FIG. 6 , and in an expanded state in  FIG. 7 . The membrane  25  of some embodiments is configured to be placed between vertebrae and expanded such that an upper surface  252  contacts a first vertebra and an opposite lower surface  253  contacts a second vertebra to provide support between the vertebrae. The longitudinal axis, or linear expansion direction L, of the expandable medical implant  21  is illustrated in  FIG. 7 . Lateral expansion of the membrane  25  is also accomplished in some embodiments. As used herein, the term lateral means directions approximately normal to the linear expansion direction L. 
     The membrane  25  may be constructed, in whole or in part, of a non-permeable material or of a permeable material, which allows a certain amount of a fill material to pass through the membrane  25 . The membrane  25  may include compliant or non-compliant balloon materials such as those commonly used to manufacture coronary and Kyphoplasty medical devices. These and other operable materials are essentially similar to the materials described in association with  FIG. 1  above. 
     In the embodiment shown in  FIGS. 6 and 7 , telescoping cylinders  26  along with the base  22  and expandable end  23  define an enclosed volume. The membrane  25  defines an enclosed volume that incorporates the enclosed volume of the telescoping cylinders  26  along with the base  22  and expandable end  23 . The enclosed volumes of both the telescoping cylinders  26  along with the base  22  and expandable end  23 , and the membrane  25  are therefore volumes between the base  22  and the expandable end  23 . 
     The system  200  for deploying an expandable medical implant  21  shown in  FIGS. 6 and 7  includes an elongated member  101  with a distal end  103  and a proximal end  102 . The illustrated distal end  103  is coupled to the expandable end  23  of the expandable medical implant  21 . The elongated member  101  is in contact with the base  22  of the expandable medical implant  21  at a point  28  to provide a connection between the expandable end  23  and the base  22 . The proximal end  102  extends from the expandable implant  21  in  FIG. 7  through an opening or port  27 . The illustrated connection between the expandable end  23  and the base  22  with the elongated member  101  is a sliding connection because the elongated member  101  slides relative to the base  22  when the elongated member is removed from or pushed into the port  27 . 
     The proximal end  102  is configured to receive a force applied along its length. Arrow  105  shows the direction of a pushing or compressive force applied along the length of the elongated member  101  at its proximal end  102 . Arrow  107  shows the direction of a pulling or tensile force applied along the length of the elongated member  101  at its proximal end  102 . In other embodiments where the elongated member  101  is actuated by an alternative mechanism, the force applied to the elongated member  101  may be a twisting, winding, turning, or other effective force to push apart or pull together the base  22  and the expandable end  23 . For example, and without limitation, the elongated member  101  may include threaded portions, turnbuckle portions, fasteners, or multiple members that move relative to one another to lengthen or shorten the elongated member  101 . In some embodiments, the elongated member  101  is a wire, rod, or other relatively rigid device that is capable of transmitting both tensile and compressive forces to either or both pull together or push apart the base  22  and the expandable end  23 . In other embodiments where it is only necessary to pull together the base  22  and the expandable end  23 , the elongated member  101  may be a strand, string, rope, cable, or other member configured primarily to transmit tensile forces. 
     It may be advantageous to bias the telescoping cylinders  26  toward an unexpanded state to provide a low profile device for insertion. Other devices, such as but not limit to the elongated member  101 , or a fluid injected through the port  27 , may be used to expand the telescoping cylinders  26 . A fluid that drives linear expansion of the expandable medical implant  21  or maintains linear expansion of the expandable medical implant  21  may be introduced through the port  27 . The fluid may be merely for expansion and retention, or may be a component of a fill material intended to remain in the telescoping cylinders  26 . As used in association with this function, a fluid may be a paste, gel, liquid, suspension, granular mixture, or similar substance. A substance as described herein will be considered a fluid even if it later cures or hardens to a non-fluidic state. Both the telescoping cylinders  26  and the membrane  25  may be unexpanded linearly. The port  27  may also be used to handle the expandable medical implant  21  or to guide the implant into a position where it can be effectively deployed. 
     In other circumstances, it may be preferred to bias the telescoping cylinders  26  toward an expanded state. With such an embodiment, another component, such as but not limit to the elongated member  101 , may be used to keep the telescoping cylinders  26  in an unexpanded state while the expandable medical implant  21  is inserted. Following insertion, the telescoping cylinders  26  may be released and allowed to increase toward its expanded state by releasing the elongated member  101  relative to the base  22 . 
       FIGS. 8 and 9  show a specific embodiment that also includes a spring  39  that may server as a biasing member to bias a telescoping cylinder  36  toward either an unexpanded or expanded state. The spring  39  is shown in elevation view, although the expandable medical implant  31  is shown in cross-sectional view. The embodiment of  FIGS. 8 and 9  is similar to the embodiment of  FIGS. 6 and 7 , but includes the spring  39  to bias the telescoping cylinder  36 , particular adaptations to accommodate the spring  39 , and one telescoping cylinder  36  along with a base  32  and an expandable end  33 , rather than two telescoping cylinders  26  as are shown in the embodiment of  FIGS. 6 and 7 . 
     The adaptations to accommodate the spring  39  include a shoulder  34  against which the spring  39  may push or pull, depending on whether the spring is biased toward an expanded or unexpanded state. It may be advantageous to bias the telescoping cylinder  36  toward an unexpanded state to automatically provide a low profile device for insertion. Other devices, such as but not limit to the elongated member  101 , or a fluid injected through the port  37 , may be used to expand the telescoping cylinder  36 . A fluid that drives linear expansion of the expandable medical implant  31  or maintains linear expansion of the expandable medical implant  31  may be introduced through the port  37 . The fluid may be merely for expansion and retention, or may be a component of a fill material intended to remain in the telescoping cylinder  36 . As used in association with this function, a fluid may be a paste, gel, liquid, suspension, granular mixture, or similar substance. A substance as described herein will be considered a fluid even if it later cures or hardens to a non-fluidic state. Both the telescoping cylinder  36  and the membrane  35  may be initially unexpanded linearly. The port  37  may also be used to handle the expandable medical implant  31  or to guide the implant into a position where it can be effectively deployed. 
     In other circumstances, it may be preferred to bias the telescoping cylinder  36  toward an expanded state. With such an embodiment, another component, such as but not limit to the elongated member  101 , may be used to keep the telescoping cylinder  36  in an unexpanded state while the expandable medical implant  31  is inserted. Following insertion, the telescoping cylinder  36  may be released and allowed to increase toward its expanded state by releasing the elongated member  101  relative to the base  32 . 
       FIG. 10  illustrates a system  400  for deploying an expandable medical implant  41 . The expandable medical implant  41  includes a base  42 , an expandable end  43 , and an opposite expandable end  44  that extends from the base  42  in a direction opposite from the expandable end  43 . The illustrated expandable medical implant  41  includes a membrane  45  and an expansion mechanism  46 . The expansion mechanism  46  shown in  FIG. 10  is a pair of bellows that extend in two directions away from the base  42 . The expansion mechanism of other embodiments may be, without limitation, a combination of nested, telescoping cylinders, a ratchet mechanism, a threaded or partially threaded mechanism, or any other mechanism that may drive or hold expansion of an expandable medical implant. 
     The membrane  45  is illustrated in a partially expanded configuration in  FIG. 10 . The membrane  45  of some embodiments is configured to be placed between vertebrae and expanded such that an upper surface  454  contacts a first vertebra and an opposite lower surface  453  contacts a second vertebra to provide support between the vertebrae. The longitudinal axis, or linear expansion direction L, of the expandable medical implant  41  is illustrated in  FIG. 10 . Lateral expansion of the membrane  45  is also accomplished in some embodiments. As used herein, the term lateral means directions approximately normal to the linear expansion direction L. 
     The membrane  45  may be constructed, in whole or in part, of a non-permeable material or of a permeable material, which allows a certain amount of a fill material to pass through the membrane  45 . The membrane  45  may include compliant or non-compliant balloon materials such as those commonly used to manufacture coronary and Kyphoplasty medical devices. These and other operable materials are essentially similar to the materials described in association with  FIG. 1  above. 
     In the embodiment shown in  FIG. 10 , the expansion mechanism  46  defines an enclosed volume, and the membrane  45  defines an enclosed volume that incorporates the enclosed volume of the expansion mechanism  46 . The enclosed volumes of both the expansion mechanism  46  and the membrane  45  are therefore volumes between the base  42  and the expandable end  43 . 
     The system  400  for deploying an expandable medical implant  41  shown in  FIG. 10  includes an elongated member  101  with a distal end  103  and a proximal end  102 . The illustrated distal end  103  is coupled to the expandable end  43  of the expandable medical implant  41 . The elongated member  101  is in contact with the base  42  of the expandable medical implant  41  at a point  48  to provide a connection between the expandable end  43  and the base  42 . The proximal end  102  extends from the expandable implant  41  in  FIG. 10  through an opening or port  47 . The illustrated connection between the expandable end  43  and the base  42  with the elongated member  101  is a sliding connection because the elongated member  101  slides relative to the base  42  when the elongated member is removed from or pushed into the port  47 . The expandable medical implant  41  shown in  FIG. 10  additionally includes an opposite elongated member  111  with a distal end  113  and a proximal end  112 . The illustrated distal end  113  is coupled to the opposite expandable end  44  of the expandable medical implant  41 . The opposite elongated member  111  is in contact with the base  42  of the expandable medical implant  41  at a point  49  to provide a connection between the opposite expandable end  44  and the base  42 . The proximal end  112  extends from the expandable implant  41  in  FIG. 10  through the port  47 . The illustrated connection between the opposite expandable end  44  and the base  42  with the opposite elongated member  111  is a sliding connection because the opposite elongated member  111  slides relative to the base  42  when the elongated member is removed from or pushed into the port  47 . 
     The proximal end  112  of the illustrated embodiment is configured to receive a force applied along its length. Arrow  105  shows the direction of a pushing or compressive force applied along the length of the elongated member  111  at its proximal end  112 . Arrow  107  shows the direction of a pulling or tensile force applied along the length of the elongated member  111  at its proximal end  112 . In other embodiments where the opposite elongated member  111  is actuated by an alternative mechanism, the force applied to the opposite elongated member  111  may be a twisting, winding, turning, or other effective force to push apart or pull together the base  42  and the opposite expandable end  44 . For example, and without limitation, the opposite elongated member  111  may include threaded portions, turnbuckle portions, fasteners, or multiple members that move relative to one another to lengthen or shorten the opposite elongated member  111 . In some embodiments, the opposite elongated member  111  is a wire, rod, or other relatively rigid device that is capable of transmitting both tensile and compressive forces to either or both pull together or push apart the base  42  and the opposite expandable end  44 . In other embodiments where it is only necessary to pull together the base  42  and the opposite expandable end  44 , the elongated member  111  may be a strand, string, rope, cable, or other member configured primarily to transmit tensile forces. 
     In some embodiments, the elongated member  101  and the opposite elongate member  111  may be, in whole or in part, joined along their lengths. In some embodiments, the joining is near their respective proximal ends  102 ,  112 . In this configuration, operation of the elongated member  101  and opposite elongated member  111  may be accomplished by a common application of a pushing or pulling force to the joined elongated members  101 ,  111 . 
     In some embodiments, elasticity in the material of the expansion mechanism  46  may sever as a biasing force to bias the expansion mechanism  46  toward an expanded or unexpanded state, as may be advantageous in various circumstances. For example, it may be advantageous to bias the expansion mechanism  46  toward an unexpanded state to provide a low profile device for insertion. Other devices, such as but not limit to the elongated member  101 , the opposite elongated member  111 , or a fluid injected through the port  47 , may be used to expand the expansion mechanism  46 . A fluid that drives linear expansion of the expandable medical implant  41  or maintains linear expansion of the expandable medical implant  41  may be introduced through the port  47 . The fluid may be merely for expansion and retention, or may be a component of a fill material intended to remain in the expansion mechanism  46 . As used in association with this function, a fluid may be a paste, gel, liquid, suspension, granular mixture, or similar substance. A substance as described herein will be considered a fluid even if it later cures or hardens to a non-fluidic state. Both the expansion mechanism  46  and the membrane  45  may initially be unexpanded linearly. The port  47  may also be used to handle the expandable medical implant  41  or to guide the implant into a position where it can be effectively deployed. 
     In other circumstances, it may be preferred to bias the expansion mechanism  46  toward an expanded state. With such an embodiment, another component, such as but not limit to the elongated member  101  and the opposite elongated member  111 , may be used to keep the expansion mechanism  46  in an unexpanded state while the expandable medical implant  41  is inserted. Following insertion, the expansion mechanism  46  may be released and allowed to increase toward its expanded state by releasing one or both of the elongated member  101  and the opposite elongated member relative to the base  2 . 
     As shown in  FIGS. 2-5 , the cross-sectional shape of some embodiments of the expandable medical implant  11  is substantially circular. However, the cross-sectional shape of any of the expandable medical implants may be any functional shape, such as but not limited to, generally oval, rectangular, triangular, polygonal, concave-convex, or combinations of these shapes. 
     In any of the embodiments of  FIGS. 1-10 , the expansion mechanisms, bases, expandable ends, telescoping cylinders, or other components that interact with the membranes, may include one or more transfer openings from a component to an interior of the membranes. In some embodiments, the transfer opening is a hole through which a fluid or fill material, or both, may pass. Fluid, fill material, or both may enter the respective expandable medical implants through the ports  7 ,  17 ,  27 ,  37 ,  47  and pass through one or more transfer openings and into the membrane. In some embodiments, a valve is provided at the transfer opening to control flow to the membrane. The valve may be controlled by direct manipulation or through instrumentation connected through the port  7 ,  17 ,  27 ,  37 ,  47 . 
     Fill material may enter the expandable medical implant as a fluid, and then harden or cure in the implant. In some embodiments, a non-hardenable and non-curing fluid is used to expand, or to hold expansion in, the implant or one or some of the components of the implant. A fill material may then be introduced into at least the membrane  5 ,  25 ,  35 ,  45  to provide support between an upper surface and lower surface of the membrane. The fill material may be a paste, gel, liquid, suspension, granular mixture, or similar substance. Non-limiting examples of fill materials include bone cement, paste, morselized allograft, autograft, or xenograft bone, ceramics, or various polymers. An example bone cement is polymethylmethacrylate (PMMA), which may be made from methylmethacrylate, polymethylmethacrylate, esters of methacrylic acid, or copolymers containing polymethylmethacrylate and polystyrene. Additional non-limiting examples of the fill material include semi-rigid flowable or hardenable material such as silicone or various types of urethane materials. It should further be understood that other types of fill materials which are not necessarily hardenable or curable may be used in association with the present invention. For example, the fill material may comprise beads or small particles or grains of material, some of which may, in aggregate, achieve a harder consistency as a result of interlocking or compaction. In some embodiments, the fill material may also include a bone growth promoting substance. Osteogenic or bone growth promoting substances may include, without limitation, autograft, allograft, xenograft, demineralized bone, synthetic and natural bone graft substitutes, such as bioceramics and polymers, and osteoinductive factors. A separate carrier to hold materials within the device may also be used. These carriers may include collagen-based carriers, bioceramic materials, such as BIOGLASS®, hydroxyapatite and calcium phosphate compositions. The carrier material may be provided in the form of a sponge, a block, folded sheet, putty, paste, graft material or other suitable form. The osteogenic compositions may include an effective amount of a bone morphogenetic protein (BMP), transforming growth factor β 1 , insulin-like growth factor, platelet-derived growth factor, fibroblast growth factor, LIM mineralization protein (LMP), and combinations thereof or other therapeutic or infection resistant agents, separately or held within a suitable carrier material. Introduction of fluid or fill material into an expandable medical implant embodiment may be through a syringe or similar device, through direct placement, or by any other effective mechanism. 
     Each of the embodiments disclosed herein may be described as a system for deploying an expandable medical implant. The system includes an expandable medical implant with a base and an expandable end and an enclosed volume between the base and the expandable end. The system also includes a means for pushing apart or pulling together the base and the expandable end. 
     Embodiments of the implant in whole or in part may be constructed of biocompatible materials of various types. Examples of implant materials include, but are not limited to, non-reinforced polymers, carbon-reinforced polymer composites, PEEK and PEEK composites, low density polyethylene, shape-memory alloys, titanium, titanium alloys, cobalt chrome alloys, stainless steel, ceramics and combinations thereof. If a trial instrument or implant is made from radiolucent material, radiographic markers can be located on the trial instrument or implant to provide the ability to monitor and determine radiographically or fluoroscopically the location of the body in the spinal space. In some embodiments, the implant or individual components of the implant may be constructed of solid sections of bone or other tissues. Tissue materials include, but are not limited to, synthetic or natural autograft, allograft or xenograft, and may be resorbable or non-resorbable in nature. Examples of other tissue materials include, but are not limited to, hard tissues, connective tissues, demineralized bone matrix and combinations thereof. 
     Some embodiments may also include supplemental fixation devices in addition to or as part of the expandable medical implant for further stabilizing the anatomy. For example, and without limitation, rod and screw fixation systems, anterior, posterior, or lateral plating systems, facet stabilization systems, spinal process stabilization systems, and any devices that supplement stabilization may be used as a part of or in combination with the expandable medical implant. 
     An embodiment of the invention is a method of implanting an expandable medical implant. The method embodiment includes providing the expandable medical implant with a base and an expandable end and an enclosed volume between the base and the expandable end. The expandable medical implant may also include an elongated member with a distal end and a proximal end. The distal end is coupled to the expandable end of the expandable medical implant and the elongated member is in contact with the base of the expandable medical implant. The method may also include introducing the expandable medical implant through an incision in a patient. Introduction through an incision of some embodiments is conducted while the expandable medical implant is an unexpanded or less than fully expanded state. Consequently, a smaller, less invasive incision is possible. 
     Method embodiments of the invention may also include applying a compressive force to the elongated member to push apart the base and the expandable end of the expandable medical implant. The base and the expandable end may be pushed apart partially or temporarily to properly locate the expandable medical implant while imaging or alignment procedures are accomplished. For example, and without limitation, portions of the base and the expandable end may be pressed against vertebrae on one or both sides of the expandable medical implant. If proper alignment is confirmed, the expandable medical implant may be secured in place. If proper alignment is not achieved, tensile force may be applied to the elongated member, or compressive force released, to reduce the expansion of the expandable medical implant while the expandable medical implant is repositioned or removed. 
     Another method embodiment includes providing the expandable medical implant with a base and an expandable end and an enclosed volume between the base and the expandable end. The expandable medical implant may also include an elongated member with a distal end and a proximal end. The distal end is coupled to the expandable end of the expandable medical implant and the elongated member is in contact with the base of the expandable medical implant. Method embodiments of the invention may also include applying a tensile force to the elongated member to pull together the base and the expandable end of the expandable medical implant. The method may additionally include introducing the expandable medical implant through an incision in a patient. Introduction through an incision of some embodiments is conducted while the expandable medical implant is an unexpanded or less than fully expanded state. Consequently, a smaller, less invasive incision is possible. 
     The tensile force on the elongated member may be released to allow the base and the expandable end of the expandable medical implant to separate. In some embodiments, elasticity in components of the expandable medical implant, or a separate biasing member, may be included with the expandable medical implant to urge the base away from the expandable end. The base and the expandable end may be allowed to expand partially or temporarily to properly locate the expandable medical implant while imaging or alignment procedures are accomplished. For example, and without limitation, portions of the base and the expandable end may be pressed against vertebrae on both sides of the expandable medical implant. If proper alignment is confirmed, the expandable medical implant may be secured in place. If proper alignment is not achieved, tensile force may be applied to the elongated member to reduce the expansion of the expandable medical implant while the expandable medical implant is repositioned or removed. 
     A fill material may be introduced into the enclosed volume between the base and the expandable end of some embodiments. The fill material may serve as a supplement to mechanisms of the expandable medical implant that otherwise secure the implant in place, or the fill material may be a primary component to secure the expandable medical implant in place. The fill material may occupy only a portion of the volume between the base and the expandable end, or it may be used to further expand portions of the expandable medical implant such as the membrane  5 ,  25 ,  35 ,  45 , one or both linearly and laterally. 
     Some portion of the elongated member may extend from the expandable medical implant after the expandable medical implant is secured in place. Therefore, an additional act of some methods embodiments is to remove at least a portion of the elongated member from the expandable medical implant. The elongated member may be cut or twisted off with an instrument, released from its connection to the expandable end of the implant. The elongated member may, at any position along its length, include a release mechanism, portion of reduced strength, or other characteristic that facilitates removal of all or a portion of the elongated member. 
     The expandable medical implant shown in  FIGS. 1-10  presents a small profile in its unexpanded state so that it is well-suited for implantation from a generally posterior approach. However, embodiments of the invention may include implantation from any surgical approach, including but not limited to, posterior, lateral, anterior, transpedicular, lateral extracavitary, in conjunction with a laminectomy, in conjunction with a costotransversectomy, or by any combination of these and other approaches. 
     Various method embodiments of the invention are described herein with reference to particular expandable medical implants. However, in some circumstances, each disclosed method embodiment may be applicable to each of the expandable medical implants, or to some other implant operable as disclosed with regard to the various method embodiments. 
     Terms such as lower, upper, anterior, posterior, inferior, superior, lateral, medial, contralateral, and the like have been used herein to note relative positions. However, such terms are not limited to specific coordinate orientations, but are used to describe relative positions referencing particular embodiments. Such terms are not generally limiting to the scope of the claims made herein. 
     While embodiments of the invention have been illustrated and described in detail in the disclosure, the disclosure is to be considered as illustrative and not restrictive in character. All changes and modifications that come within the spirit of the invention are to be considered within the scope of the disclosure.