Abstract:
A system for implanting an interspinous process spacer comprises a deformation instrument adapted to engage a pair of opposing arms of the interspinous process spacer and operable to move the opposing arms relative to one another to deform the interspinous process spacer from an uncollapsed state to a collapsed state. The system further comprises a cannula adapted to receive the collapsed interspinous process spacer from the deformation instrument and direct the interspinous process spacer to an area between a pair of spinous processes.

Description:
BACKGROUND  
       [0001]     Lumbar spinal stenosis (“LSS”, and sometimes called sciatica) is a condition of the spine characterized by a narrowing of the lumbar spinal canal. With spinal stenosis, the spinal canal narrows and pinches the spinal cord and nerves, causing pain in the back and legs. One surgical technique for relieving LSS involves distracting adjacent vertebrae and implanting an interspinous process spacer to maintain the desired separation between the segments. This technique is somewhat less invasive than alternative treatments such as decompressive laminectomy, but may actually provide significant benefits to patients experiencing LSS symptoms. As with other surgeries, one consideration when performing surgery to implant an interspinous spacer is the size of the incision that is required to allow introduction of the device. Interspinous spacers previously known to the art were not easily implanted with minimally invasive surgical techniques. A need exists for instrumentation and methods for implanting an interspinous process spacer using minimally invasive surgical techniques.  
       SUMMARY  
       [0002]     In one embodiment, a system for implanting an interspinous process spacer comprises a deformation instrument adapted to engage a pair of opposing arms of the interspinous process spacer and operable to move the opposing arms relative to one another to deform the interspinous process spacer from an uncollapsed state to a collapsed state. The system further comprises a cannula adapted to receive the collapsed interspinous process spacer from the deformation instrument and direct the interspinous process spacer to an area between a pair of spinous processes.  
         [0003]     In another embodiment, a system for minimally invasive implantation of an interspinous process spacer comprises a pair of actuators adapted for insertion between a pair of collapsible arms of the interspinous process spacer and a pivot joint connecting the pair of actuators and adapted to cause the actuators to move apart and to thereby move the collapsible arms from an uncollapsed state to a collapsed state.  
         [0004]     In another embodiment, a method comprises selecting an interspinous process spacer having a first pair of opposing arms interconnected by a blocking member. The method further comprises selecting a deformation instrument having a first movable portion and a second movable portion, engaging the first movable portion with one of the opposing arms, and engaging the second movable portion with the other opposing arm. The method further includes moving the first movable portion relative to the second movable portion to move the interspinous process spacer into a collapsed state. The method also includes inserting a first guide tube into a space between a pair of spinous processes and inserting the interspinous process spacer in the collapsed state into the first guide tube.  
         [0005]     Additional embodiments are included in the attached drawings and the description provided below. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0006]      FIG. 1  is a sagittal view of a section of a vertebral column.  
         [0007]      FIG. 2  is an interspinous process spacer engaged with a spacer deformation instrument according to one embodiment of the present disclosure.  
         [0008]      FIG. 3  is an implantation system including the instrument and spacer of  FIG. 2 .  
         [0009]      FIG. 4  is an interspinous process spacer engaged with a spacer deformation instrument according to another embodiment of the present disclosure.  
         [0010]      FIG. 5  is an implantation system including the instrument and spacer of  FIG. 4 .  
         [0011]      FIG. 6  is an interspinous process spacer engaged with a spacer deformation instrument according to another embodiment of the present disclosure.  
         [0012]      FIG. 7  is an implantation system including the instrument and spacer of  FIG. 6 .  
         [0013]      FIG. 8  is an implantation system according to another embodiment of the present disclosure.  
         [0014]      FIG. 9  is an implantation system and interspinous process spacer according to another embodiment of the present disclosure.  
         [0015]      FIG. 10  is an implantation system according to another embodiment of the present disclosure.  
         [0016]      FIG. 11  is an implantation system according to another embodiment of the present disclosure.  
         [0017]      FIG. 12  is an interspinous process spacer according to another embodiment of the present disclosure.  
         [0018]      FIG. 13  is a view of the spacer of  FIG. 12  after transformation to an uncollapsed state.  
         [0019]      FIGS. 14-15  show an interspinous spacer according to another embodiment of the present disclosure. 
     
    
     DETAILED DESCRIPTION  
       [0020]     The present disclosure relates generally to vertebral device implantation systems, and more particularly, to systems and procedures for minimally invasive interspinous process spacer implantation. For the purposes of promoting an understanding of the principles of the invention, reference will now be made to the embodiments, or examples, illustrated in the drawings and specific language will be used to describe the same. It will nevertheless be understood that no limitation of the scope of the invention is thereby intended. Any alterations and further modifications in the described embodiments, and any further applications of the principles of the invention as described herein are contemplated as would normally occur to one skilled in the art to which the invention relates.  
         [0021]     Referring first to  FIG. 1 , the reference numeral  10  refers to a vertebral joint section or a motion segment of a vertebral column. The joint section  10  includes adjacent vertebral bodies  12 ,  14 . The vertebral bodies  12 ,  14  include spinous processes  16 ,  18 , respectively. An interspinous process space  20  is located between the spinous processes  16 ,  18 .  
         [0022]     Referring now to  FIG. 2 , an interspinous process spacer  30  is adapted for implantation in the interspinous space  20 . The interspinous spacer  30  is designed to maintain a minimal distance between the spinous processes of adjacent vertebrae  12 ,  14 . As such, the spacer  30  has a blocking portion  32  that keeps the vertebrae from coming together. The spacer  30  may be designed to fit snugly around the spinous processes, and thus to avoid being dislodged by movement of the spine. In this embodiment, the spacer  30  achieves a snug fit by including “arms”  34 ,  36 , extending from the blocking portion  32  upward along both sides of the upper spinous process, and “arms”  38 ,  40  extending from the blocking portion  32  downward along both sides of the lower spinous process. The arms  34 ,  36 ,  38 ,  40  may keep the spacer  30  from moving laterally with respect to the spinous processes. In  FIG. 2 , spacer  30  is shown in an uncollapsed, generally “H” shaped configuration. The shape as well as the material properties of the spacer may allow it to assume a collapsed configuration which may further allow the spacer to be implanted using a minimally invasive surgical technique.  
         [0023]     An interspinous process spacer may be formed from a wide variety of biocompatible materials including those that can undergo reversible elastic deformation. Examples of such materials include elastic or rubbery polymers, hydrogels or other hydrophilic polymers, or composites thereof. Examples of suitable polymers may include silicone, polyurethane, silicone-polyurethane copolymers, polyesters, polyethylenes, polyethyleneterephthaltates, polyaryletherketone (PAEK) polyether block copolymer (PEBAX), ABS (acrylonitrile butadiene styrene), ANS (acrylonitrile styrene), delrin acetal; PVC (polyvinyl chloride), PEN (polyethylene napthalate), PBT (polybutylene terephthalate), polycarbonate, PEI (polyetherimide), PES (polyether sulfone), PET (polyethylene terephthalate), PETG (polyethylene terephthalate glycol), polyamide, aromatic polyamide, polyether, polyester, polymethylmethacrylate, polyurethane copolymer, ethylene vinyl acetate (EVA), ethylene vinyl alcohol, FEP (fluorinated ethylene polymer), .PTFE (polytetrafluoroethylen- e), PFA (perfluoro-alkoxyalkane), polypropylene, polyolefin, polysiloxane, liquid crystal polymer, ionomer, poly(ethylene-co-methacrylic) acid, SAN (styrene acrylonitrile), nylon, polyether block amide and thermoplastic elastomer.  
         [0024]     The spacer material may be a solid, sheet/film, fiber, mesh and/or braided configurations. The elastomeric material can be formed into a solid one-piece, monoblock unit having the configuration described above. In one alternative, the spacer may be fillable or have otherwise alterable material properties as described more fully below.  
         [0025]     Examples of suitable polyurethanes for use in forming a spacer may include thermoplastic polyurethanes, aliphatic polyurethanes, segmented polyurethanes, hydrophilic polyurethanes, polyether-urethane, polycarbonate-urethane and silicone polyetherurethane. Other suitable hydrophilic polymers include polyvinyl alcohol hydrogel, polyacrylamide hydrogel, polyacrylic hydrogel, poly(N-vinyl-2-pyrrolidone hydrogel, polyhydroxyethyl methacrylate hydrogel, and naturally occurring materials such as collagen and polysaccharides, such as hyaluronic acid and cross-linked carboxyl-containing polysaccharides, and combinations thereof.  
         [0026]     In other embodiments, the spacer is made of a metal that can undergo reversible elastic deformation, such as shape memory metals or nickel titanium. Further description of interspinous process spacers, of the type shown in  FIG. 2 , is provided in detail in pending U.S. patent application Ser. No. 10/851,889, entitled “Interspinous Spacer” which is incorporated herein by reference.  
         [0027]      FIG. 2  also depicts an interspinous process spacer deformation instrument  42 . The instrument  42  includes supports  44 ,  46  pivotally connected by pivot mechanism  48  and arranged in an “X” shaped configuration. The pivot mechanism  48  may allow the supports  44 ,  46  to pivotally move relative to each other in the directions shown in  FIG. 2 . The movement of the pivot mechanism  48  may be controlled or biased by a mechanical spring mechanism, a ratchet mechanism, a shape memory material, or other bias or control mechanisms known in the art. The supports  44 ,  46  include projections  50 ,  52 , respectively which, as shown in  FIG. 2 , may be configured to extend between arms  44 ,  46  of the spacer  30 . The projections  50 ,  52  may be fitted with rollers  54 ,  56 , respectively. The opposite side of the supports  44 ,  46  may also be fitted with corresponding projections and rollers to fit between arms  38 ,  40  of the spacer  30 .  
         [0028]     Referring now to  FIG. 3 , the deformation instrument  42  may be used to deform the spacer  30  into a collapsed state suitable for implanting the spacer  30  into a patient in a minimally invasive way. With the deformation instrument  42  positioned as shown in  FIG. 2  with the rollers  54 ,  56  engaged with the arms  34 ,  36 , respectively, the supports  44 ,  46  are pivoted about the pivot mechanism  48 . As the supports  44 ,  46  are moved, the rollers  54 ,  56  are separated, moving the spacer  30  into a collapsed state with arms  34  and  38  moved toward one another and arms  36 ,  40  moved toward each other. As the supports  44 ,  46  are moved, the rollers  54 ,  56  may roll along the arms  34 ,  36 , reducing friction while collapsing the spacer  30 .  
         [0029]     A cannula  58  may be inserted into the vicinity of a patient&#39;s vertebral column and positioned adjacent to or between the spinous processes  16 ,  18  of a spinal joint  10 . The spacer  30 , now in a collapsed state, may be positioned at the opening of the cannula  58 . An insertion instrument  60 , such as a probe, may then be used to push the spacer  30  along the rollers  54 ,  56 , into the cannula  58 , and into the interspinous process space  20 . As the spacer  30  is pushed from the cannula  58 , it returns from the collapsed state to the uncollapsed state and assumes its original “X” shape with the blocking portion  32  positioned between the adjacent spinous processes  16 ,  18  and the unfolded arms  34 ,  38  extending upward and downward along one side of two spinous processes, as shown in  FIG. 3 . The cannula  58  is then withdrawn as the spacer  30  is ejected, and the second pair of arms  36  and  40  unfolds to extend upward and downward along the second side of the spinous processes, as shown in  FIG. 3 .  
         [0030]     The surgery may be accomplished using, for example, a posterior oblique approach through a small incision in the patient&#39;s back. Prior to the implantation of the interspinous process spacer, the interspinous space may be prepared by removing soft tissue from around the spinous processes. The spinous processes may also be distracted to enlarge the space for receiving the spacer.  
         [0031]     Referring now to  FIG. 4 , the spacer  30  may be reduced to a collapsed state using an alternative embodiment of a deformation instrument. The deformation instrument may include a pulling device  70  that may include wires attached to each of the arms  34 ,  36 ,  38 ,  40 . In use, the wires may be used to collapse the spacer  30  by pulling arms  38 ,  38  together and arms  36 ,  40  together. As shown in  FIG. 5 , the collapsed spacer  30  may then be introduced to cannula  58 , with the wires  70  removed, and implanted between the spinous processes  16 ,  18  as described above.  
         [0032]     Referring now to  FIG. 6 , a deformation instrument  80  may, alternatively, be used to reduce the spacer  30  from an uncollapsed to a collapsed state. The instrument  80  may comprise a pair of actuators or supports  82 ,  84  connected by a pivot mechanism  86 . In use, the pivot mechanism  86  may be positioned between the arms  34 ,  36  of the spacer  30  with the supports  82 ,  84  engaged with the arms. The deformation instrument  80  may include a second pivot mechanism  88  and arms  90 ,  92  that are substantially similar to those described above for positioning between the arms  38 ,  40 . The movement of the pivot mechanism  86  may be controlled or biased by a mechanical spring mechanism, a ratchet mechanism, a shape memory material, or other bias or control mechanisms known in the art.  
         [0033]     With the deformation instrument  80  positioned within the spacer  30 , pivot mechanism  86  may be operated to move the supports  82 ,  84  from a “V” shaped configuration to a straight or elongated configuration (as shown in  FIG. 7 ). The pivot mechanism  88  and supports  90 ,  92  located between arms  38 ,  40  may operate in a similar manner to reduce the spacer  30  from an uncollapsed state to a collapsed state. The straightened supports  82 ,  84 ,  90 ,  92  may form a portion of a guide tube which may serve a similar function as the cannula  58  described above.  
         [0034]     As shown in  FIG. 7 , with the collapsed spacer  30  positioned within the guide tube formed by the straightened supports  82 ,  84 ,  90 ,  92 , the insertion instrument  60  may be used to push the spacer  30  through the guide tube and into the interspinous process space  20  where it is allowed to return to its uncollapsed state.  
         [0035]     Referring now to  FIG. 8 , in an alternative embodiment to cannula  58  or the guide tube created by supports  82 ,  84 ,  90 ,  92 , a multi-part cannula  100  may include two cannula halves  102 ,  104 . The cannula half  102  may be sized and configured to fit within a flare  106  of the cannula  104  to form a single, essentially continuous cannula. The collapsed spacer  30  may be deformed using any of the deformation instruments described above and inserted through the cannula  100  using any of the techniques described above. The multi-part cannula  100  may suitable for situations in which the arms  36 ,  40  are collapsed prior to collapsing the arms  34 ,  38 . The multi-part cannula  100  allows one half of the spacer  30  to be held in a collapsed position while the opposite half of the spacer is being collapsed.  
         [0036]     Referring now to  FIG. 9 , a spacer  120  includes a body  122  having arms  126 ,  128  and a body  124  having arms  130 ,  132 . The spacer  120  may further include a spring  134  to bias the arms into an uncollapsed position. Such an embodiment may work much like a pair of scissors, with the four arms  126 ,  128 ,  130 ,  132  extending from a central pivot. As with scissors, the device may be converted from a generally “X”-shaped device to a generally “I”-shaped device by pivoting one pair of arms relative to the other. Such a spacer is disclosed in detail in pending U.S. patent application Ser. No. 10/851,889, entitled “Interspinous Spacer” which is incorporated herein by reference.  
         [0037]     The spacer  120  may be collapsed using any of the deformation instruments disclosed above or any other deformation technique known in the art. In a collapsed configuration, as shown in  FIG. 9 , arms  132 ,  128  are drawn together, and arms  126 ,  130  are drawn together. The spacer may then be delivered to the interspinous process space  20  using any of the cannula configurations disclosed above. When the spacer  120  is ejected from the cannula, the spring  134  may bias the spacer  120  to return to its uncollapsed state.  
         [0038]     Referring now to  FIG. 10 , in this embodiment, precision alignment through a minimally invasive approach may be achieved with an installation instrument  110  used to install a spacer  111  between spinous processes  16 ,  18 . The installation instrument  110  includes a fixed member  112  which is connectable to either a fixed location on the patient&#39;s body or to an external location. A swing member  114  may have a distal end pivotally connected to the fixed member  112 . A proximal end of the swing member  114  may be connected to a curved member  116 . The curved member  116  may be a curved cannula capable of receiving an interspinous process spacer. Alternatively, the curved member may have a holder for attaching a spacer to a distal end of the curved member. The swing member  114  may be connected to the curved cannula  116  with a release knob  117  to allow for simplified release and locking of the curved cannula  116  to the swing member  114 .  
         [0039]     In use, the fixed member  112  may be held stable relative to the interspinous space  20 . An interspinous process spacer  111  may be collapsed using one of the methods described above or any other known in the art. With the swing member  114  detached or extended away from the interspinous process space  20 , the collapsed spacer may be inserted through the curved cannula  116 . The swing arm  114  may then be pivoted to move the curved cannula to the interspinous process space  20 . The spacer  111  may then be ejected from the curved cannula  116 . The use of the installation instrument  110  may reduce the invasiveness of the spacer implantation by delivering the spacer to the interspinous space with a controlled and precise technique. Such a technique may improve efforts to preserve the surrounding soft tissue. Several features of the minimally invasive installation instrument are disclosed in pending U.S. patent application Ser. No. 10/769,569 which is incorporated herein by reference.  
         [0040]     In this embodiment, the spacer  111  may be similar to either spacer  30  or spacer  120  but may include additional features which permit a more minimally invasive implantation using the installation instrument  110 . For example, the spacer  111  may be “banana” shaped or slightly curved in the direction of insertion. The curvature of the spacer  111  may match the curvature of the curved cannula  116 .  
         [0041]     Referring now to  FIG. 11 , in an alternative embodiment, a cannula  136  may have a distal end section with an opening  138  that may be enlarged to permit distraction of the adjacent spinous processes. In use, the cannula  136  may be inserted through a minimally invasive opening and positioned between the spinous processes  16 ,  18 . Once in position, the opening  138  may be enlarged to further separate the spinous processes and provide additional space to position a spacer. The enlargement of the opening may be mechanically or thermally actuated.  
         [0042]     The deformation instruments, installation instruments, and cannula systems described above may also be used to deliver other types of interspinous process devices. For example, as shown in  FIGS. 12 and 13 , a fillable spacer  140  may inserted between the spinous processes  16 ,  18  in a collapsed and unfilled state. Once in position, the fillable spacer  140  may be injected or otherwise filled with any of a variety of filling materials to transform the spacer  140  from the collapsed state to an uncollapsed state.  
         [0043]     Examples of injectable materials for injection into the inflatable interspinous process spacers include elastomers, hydrogels, or rigid polymers. Examples of elastomers include silicone elastomers, polyurethane elastomers, silicone-polyurethane copolymers, polyolefin rubbers, butyl rubbers, or combinations thereof. Example of hydrogels include polysaccharides, proteins, polyphosphazenes, poly(oxyethylene)-poly(oxypropylene) block polymers, poly(oxyethylene)-poly(oxypropylene) block polymers of ethylene diamine, poly(acrylic acids), poly(methacrylic acids), copolymers of acrylic acid and methacrylic acid, poly(vinyl acetate), sulfonated polymers, or combinations thereof. Examples of rigid polymers include polymethylmethacrylate, silicones, polyurethanes, polyvinyl alcohol, polyamide, aromatic polyamide, polyether, polyesterliquid crystal polymer, ionomer, poly(ethylene-co-methacrylic) acid, PBT (polybutylene terephthalate), polycarbonate, or combinations  
         [0044]     Suitable materials may be natural or synthetic. The filling materials may cure or polymerize in situ. The filling materials may be transformable such that when the spacer is filled and in an uncollapsed state, the material may harden to create a rigid spacer.  
         [0045]     In an alternative embodiment as shown in  FIG. 14 , a fillable spacer  150  may include one or more inflatable chambers  152 . In this example, the arms of the spacer  150  may be formed of solid elastomeric material and the blocking portion of the spacer may include the inflatable chamber  152  to allow the physician to create a customized distraction between the spinous processes. This spacer  150  may be inserted in a collapsed state, with the arm folded into a low profile package, using any of the instruments described above. When implanted the arms of the spacer  150  may unfold as shown in  FIG. 14  and the chamber  152  may be subsequently filled with a material, including those filling materials described above, to distract the spinous processes to a desired level as shown in  FIG. 15 . The in situ curable materials may cure to a compliant or rigid mass depending upon the materials selected. Biological or pharmaceutical agents may be added to the filling material.  
         [0046]     The arms of the spacer may be elastic or rigid and formed of any of the materials listed above. When used with rigid arms, an injectable material capable of setting or curing can lock the rigid arms into a desired position.  
         [0047]     The partially inflatable spacer  150  may be incrementally adjustable to allow for better fit and customized distraction. Because the chambers  152  may be filled to different levels, the need to maintain large inventories of implants in a wide variety of sizes may be reduced.  
         [0048]     The delivery of any of the spacers described above may facilitated by lubricating any of the instruments described above. Suitable lubricants may include oils, solvents, bodily fluids, fat, saline, or hydrogel coatings. For example, in  FIG. 3 , a lubricant may be applied to the rollers  54 ,  56 , and to the interior shaft of the cannula  58  to reduce friction and ease the passage of the spacer  30 .  
         [0049]     In still another alternative, spinous process systems may include artificial ligaments or tethers for connecting two or more spinous processes. These ligaments may be connect to or extend through a spacer and wrap around one or both of the adjacent spinous processes to hold the spacer securely in place. Such ligaments may be elastic or non-elastic and may be made of woven or braided textiles.  
         [0050]     Although only a few exemplary embodiments have been described in detail above, those skilled in the art will readily appreciate that many modifications are possible in the exemplary embodiments without materially departing from the novel teachings and advantages of this disclosure. Accordingly, all such modifications and alternative are intended to be included within the scope of the invention as defined in the following claims. Those skilled in the art should also realize that such modifications and equivalent constructions or methods do not depart from the spirit and scope of the present disclosure, and that they may make various changes, substitutions, and alterations herein without departing from the spirit and scope of the present disclosure. It is understood that all spatial references, such as “horizontal,” “vertical,” “top,” “upper,” “lower,” “bottom,” “left,” “right,” “anterior,” “posterior,” “superior,” “inferior,” “upper,” and “lower” are for illustrative purposes only and can be varied within the scope of the disclosure. In the claims, means-plus-function clauses are intended to cover the elements described herein as performing the recited function and not only structural equivalents, but also equivalent elements.