Abstract:
An interspinous process spacer is disclosed. The interspinous process spacer may be configured to be minimally invasive and adjustable.

Description:
PRIORITY 
       [0001]    This application claims the benefit of U.S. Provisional Application Ser. No. 61/522,663, filed on Aug. 11, 2011, which is hereby incorporated by reference in its entirety herein. 
     
    
     FIELD 
       [0002]    The present invention generally relates to an interspinous process spacer. More particularly, the present invention relates to a minimally invasive, adjustable interspinous process spacer. 
       BACKGROUND 
       [0003]    Lumbar spinal stenosis (“LSS”, and sometimes called sciatica) is a condition of the spine characterized by a narrowing of the lumbar spinal canal. With lumbar spinal stenosis, the spinal canal narrows and pinches the spinal cord and nerves, causing pain in the back and legs. The most common symptoms of spinal stenosis are pain and difficulty when walking, although numbness, tingling, hot or cold feelings in the legs, and weakness or tiredness may also be experienced. In extreme cases, spinal stenosis can cause cauda equina syndrome, a syndrome characterized by neuromuscular dysfunction that may result in permanent nerve damage. 
         [0004]    A surgical technique has been developed in which the vertebrae are distracted and an interspinous process spacer is implanted to maintain the desired separation between the segments. This technique is somewhat less invasive than decompressive laminectomy, which may provide significant benefits to patients experiencing LSS symptoms. 
         [0005]    As with other surgeries, when performing surgery to implant an interspinous process spacer, one consideration is the size of the incision that is required to allow introduction of the device. Medical treatments that can be performed in a less invasive manner are greatly sought after by the medical community and patients alike. In some procedures, less invasive techniques are advantageous because they have shorter recovery periods, result in little to no blood loss, and greatly decrease the chances of significant complications. Moreover, less invasive techniques are generally less expensive for the patient. 
         [0006]    In view of the many advantages of less invasive procedures, it would be highly advantageous to have an interspinous process spacer and an associated procedure amenable to less invasive techniques. 
       SUMMARY 
       [0007]    An interspinous process spacer addressing the above-noted issues is disclosed. The interspinous process spacer may be configured to be minimally invasive and adjustable. 
         [0008]    In an embodiment of the present invention, the interspinous process spacer may include a spacer body and bone contacting extensions. According to one aspect of the present invention, the bone contacting extensions may include bone engaging protrusions. In one embodiment, the bone engaging protrusions may be angled down toward the bone in the range of about 2-8 degrees to pull the implant down tightly to the bone. 
         [0009]    In one embodiment of the present invention, the spacer may be implanted in as a one piece construct. In another embodiment, the spacer of the present invention may be assembled in situ. 
         [0010]    In one embodiment of the present invention, the bone contacting extensions may be removably connected to a distraction tool. According to one aspect of the present invention, the spacer may be opened after implantation using a distraction tool. In an embodiment, the spacer of the present invention may be incrementally opened. In yet another embodiment, the movable bone contacting extensions may move independently to accommodate variations in patient&#39;s anatomy. In an embodiment, a screw or other mechanism may be used to tighten the bone contacting extensions into a desired position after distraction. 
         [0011]    In yet another embodiment of the present invention, a spring clip or other mechanism may be connected to the distraction tool such that the distraction tool remains in an upright and tense position relative to the patient. In an embodiment of the present invention, the distraction tool is configured to keep the bone contacting extensions parallel to one another and aligned to the spacer body. 
         [0012]    According to one embodiment of the present invention, the distraction tool may include markings to indicate the size of spacer needed for the particular patient anatomy. In yet another embodiment, a sizing tool may be used to determine what size spacer will fit in the patient&#39;s anatomy. 
         [0013]    According to one embodiment of the present invention, the interior aspect of the bone contacting extensions may be contoured to allow for a tighter and closer fit down to the lamina. In an embodiment of the present invention, the exterior aspect of the bone contacting extensions may be configured to allow one spacer of the present to be placed directly abutting another spacer of the present invention to treat multiple spinal levels. 
         [0014]    In an embodiment of the present invention, a male-female dovetail may be used to fit an implantation tool to the spacer. 
         [0015]    In yet another embodiment of the present invention, a spacer sized smaller than the interspinous process space may be used with an anterior plate to compress the interspinous process space. In one embodiment of the present invention, the spacer may include dimples or other features to interact with a compression tool. According to one aspect of the present invention, a screw or other mechanism may be used to tighten the bone contacting extensions into a desired position after compression. 
         [0016]    The detailed technology and preferred embodiments implemented for the subject invention are described in the following paragraphs accompanying the appended drawings for people skilled in this field to well appreciate the features of the claimed invention. It is understood that the features mentioned hereinbefore and those to be commented on hereinafter may be used not only in the specified combinations, but also in other combinations or in isolation, without departing from the scope of the present invention. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0017]      FIG. 1  depicts a disassembled view of a spacer according to an embodiment of the present invention. 
           [0018]      FIG. 2  is a perspective view of an embodiment of the present invention. 
           [0019]      FIG. 3  is a perspective view of an embodiment of the present invention. 
           [0020]      FIG. 4  is a perspective view of an embodiment of the present invention. 
           [0021]      FIG. 5  depicts an embodiment of the present invention placed on a spine. 
           [0022]      FIG. 6  depicts an embodiment of the present invention placed on a spine. 
           [0023]      FIG. 7  depicts an embodiment of the present invention placed on a spine. 
           [0024]      FIG. 8  is a perspective view of a bone contacting extension according to an embodiment of the present invention. 
       
    
    
       [0025]    While the invention is amenable to various modifications and alternative forms, specifics thereof have been shown by way of example in the drawings and will be described in detail. It should be understood, however, that the intention is not to limit the invention to the particular example embodiments described. On the contrary, the invention is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the invention as defined by the appended claims. For illustrative purposes, cross-hatching, dashing or shading in the figures is provided to demonstrate sealed portions and/or integrated regions or devices for the package. 
       DETAILED DESCRIPTION 
       [0026]    In the following descriptions, the present invention will be explained with reference to example embodiments thereof. However, these embodiments are not intended to limit the present invention to any specific example, embodiment, environment, applications or particular implementations described in these embodiments. Therefore, description of these embodiments is only for purpose of illustration rather than to limit the present invention. It should be appreciated that, in the following embodiments and the attached drawings, elements unrelated to the present invention are omitted from depiction; and dimensional relationships among individual elements in the attached drawings are illustrated only for ease of understanding, but not to limit the actual scale. 
         [0027]      FIG. 1  depicts an embodiment of spacer  10  according to certain aspects of the present invention. Spacer  10  may include spacer body  12 . Spacer body  12  may have a width in the range of about 8-20 millimeters. Bone contacting extensions  14   a - 14   d  may be movably connected to spacer body  12 . 
         [0028]    Extensions  14   a - 14   d  may move independently of each other to accommodate variations in patient anatomy. Bone engaging projections  16  may be seen in  FIGS. 1-4 . Projections  16  may be angled down toward the bone to assist in pulling the implant tightly against the bone. 
         [0029]    Spacer  10  may be inserted between a patient&#39;s spinous process as a one piece construct. As a one piece construct, as shown in  FIG. 2 , spacer  10  may be placed down over the spinous process and rotated into the desired position. Once inserted, a compression tool may connect to dimples  18  and the tool may compress spacer  10 , pushing projections  16  into the bone. Spacer  10  may then be tightened into position. 
         [0030]    In another embodiment, spacer  10  may be assembled in situ. In such an embodiment, extensions  14  may be mounted on a distraction tool and placed on the interspinous process. The distraction tool may then be used to distract the interspinous process space. The distraction tool may incrementally move bone contacting extensions  14   a - d , thus opening spacer  10  to produce incremental distraction. Once the desired distraction is accomplished, the physician may perform a decompression. Spacer body  12  may then be placed onto the extensions, completing the construct. A compression tool may connect to dimples  18  and the tool may compress spacer  10 , pushing projections  16  into the bone. Spacer  10  may then be tightened into position. 
         [0031]    As can be seen in  FIG. 2 , extensions  14   a - d  may be incrementally moved to create a distance, D 1 , between  14   a  and  14   c  and/or D 2  between extensions  14   b  and  14   d.  Distances, D 1  and D 2  may be in the range of about 3-18 millimeters. Distances D 1  and D 2  are independent of each other, thus spacer  10  may be custom fit to the patient&#39;s anatomy.  FIG. 3  depicts a smaller D 1  and a relatively wider D 2 . 
         [0032]    As can be seen in  FIGS. 1-4 , the interior aspect of extensions  14   a - d  is contoured to fit down very close to the patient&#39;s lamina. As is also shown in  FIGS. 1-4 , the exterior aspect of extensions  14   a - d  is shaped to such that one or more spacers may be placed very close together, allowing treatment of multiple spinal levels. The contouring of extensions  14   a - d  further permits use of the spacer at L5-S1. 
         [0033]      FIGS. 5 and 6  depict how the exterior shape of extensions  14   a - 14   d  allows two spacers according to the present invention to be placed tightly next to each other on a spine.  FIG. 7  depicts a top view of a single spacer of the present invention placed on a spine. In an alternate embodiment, spacer  10  may be implanted in a desired open position and affixed to the patient. 
         [0034]    In yet another embodiment, spacer  10  may be used to compress the interspinous process. In this embodiment, an anterior plate may be used with spacer  10 . In this embodiment, the physician may choose a spacer narrow than the interspinous process space. A compression tool may connect to spacer  10  at dimples  18  and be used to compress the spacer and the interspinous process space. 
         [0035]    As can be seen in  FIG. 8 , bone contacting extensions may have arms  20   a  and  20   b  of different lengths. The example embodiment depicted in  FIG. 8  includes arm  20   b  having a longer length that arm  20   a.  The extra length on arm  20   b  may provide a surface contact point for guidance as the implant is being assembled in situ. 
         [0036]    The present invention may be embodied in other specific forms without departing from the spirit or essential attributes thereof, and it is, therefore, desired that the present embodiment be considered in all respects as illustrative and not restrictive. Those skilled in the art may recognize other equivalents to the specific embodiment described herein which equivalents are intended to be encompassed by the claims attached hereto.