Abstract:
The present invention generally relates to a dilator with a curved tip. The curved tip is machined through a specific range of diameters so that a physician can establish the diameter of the opening with the dilator inserted. The angle of the dilator also allows the physician to access the interspinous ligament through a minimally invasive opening in the patients back, minimizing the trauma caused to surrounding body tissue.

Description:
RELATED CASES  
       [0001]    This application claims priority to United States Provisional Patent Application entitled CURVED DILATOR AND METHOD, filed Jul. 18, 2001, Serial No.  60 / 306 , 289  which is incorporated herein by reference. 
     
    
     
       FIELD OF THE INVENTION  
         [0002]    The present invention generally relates to an instrument for dilating body tissue. More specifically, the present invention relates to an instrument that dilates the interspinous ligament which allows for precise initial placement of a trial sizing instrument or of an actual implant.  
         BACKGROUND OF THE INVENTION  
         [0003]    Typically, a physician will use a dilating tool to create and dilate an opening in tissue. Such a tool, however, may not be configured to be conveniently positioned relative to the surgical site.  
         SUMMARY OF THE INVENTION  
         [0004]    An embodiment of the present invention is a device for creating and dilating a hole in, for example, the interspinous ligament. The curved tip of the device has a range of dimensions so that a physician can also establish the diameter of the hole with the same device. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0005]    [0005]FIG. 1 is a perspective view of an embodiment of the present invention;  
         [0006]    [0006]FIG. 2 is a perspective view of another embodiment of the present invention;  
         [0007]    [0007]FIG. 3 is a perspective view of yet another embodiment of the present invention;  
         [0008]    [0008]FIG. 4 is a perspective view of yet another embodiment of the present invention; 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0009]    The device or curved dilator  100  creates and step or gradually dilates an opening in body tissue. In the preferred embodiment, the device  100  creates and step dilates an opening in the interspinous ligament. Referring to FIG. 1, the device  100  has an elongated body  102 , a handle  104  and a tapered curved tip  106 . The elongated body  102 , including the tapered curved tip  106 , is manufactured out of material such as, but not limited to, titanium-6A1-4V EL1 alloy which conforms to ASTM Standard F136-96: Standard Specification Wrought Titanium 6 Aluminum 4 Vandium ELI (Extra Low Interstitial) Alloy (R56401) for surgical implant applications.  
         [0010]    Implants are inserted between adjacent spinous processes to distract the spine segments and maintain them in a slightly flexed position to relieve symptoms of lumbar spinal stenosis and other conditions that cause pain which is associated with the back. Such implants have a spacer which remains in place between the adjacent spinous processes. The diameter of the spacer can vary to accommodate each patient.  
         [0011]    An opening must be created in the interspinous ligament so that the implant can be inserted. The device  100  is used to step or gradually dilate the interspinous ligament and to confirm the correct implant size prior to its insertion. The curved tip  106  has a gradual taper with a first end  110  and a second end  108 . The diameter of the tapered curved tip  106  gradually increases from the first end  110  to the second end  108 . The diameter at the first end  110  and the second end  108  are preferably precisely machined to a known measurement. The device  100  can be marked so that the physician knows the range of diameters to which the device  100  was machined. For example, the handle  104  may be color coded, whereby a specific color correlates to a range of diameters or the largest diameter for a device  100 . The color coding on the handle  104  helps the physician quickly distinguish the difference between the various devices  100 .  
         [0012]    A physician may have several of the devices  100 ,  200 ,  300 ,  400  (see FIGS.  1 - 4 ) so that he or she may create and further dilate an opening. For example, a first device  100  may have a tapered curved tip  106  where the first end  110  has a diameter of one millimeter and the second end  108  has a diameter of three millimeters. The second device  200  may have a first end  210  with a diameter of three millimeters and a second end  208  having a diameter of six millimeters (see FIG. 2). The third device  300  may have a first end  310  with a diameter of six millimeters and a second end  308  having a diameter of nine millimeters (see FIG. 3). The fourth device  400  may have a first end  410  with a diameter of nine millimeters and the second end  408  having a diameter of twelve millimeters (see FIG. 4). One of obvious skill in the art will appreciate that these examples do not limit the possible ranges of diameters of the tapered curved tip  106 ,  206 ,  306 ,  406 . Even though several different dilators may be used, the rest of the application will refer to the device  100  as illustrated in FIG. 1.  
         [0013]    A physician can insert the first end  110  of first device  100  into the interspinous ligament to create an opening. By urging the curved tip  106  further into the interspinous ligament, up to the second end  108 , the opening is dilated to three millimeters. Generally an implant device has a spacer with a diameter larger than three millimeters, and thus the physician will remove the first device  100  from the opening and select a second device  200 . As the opening is at three millimeters, the physician should select a second device  200  where the first end  210  has a diameter of three millimeters and a second end  208  having a diameter of six millimeters. By inserting the second device  200  into the opening, the larger diameter curved tip  206  will further dilate the opening. This process should continue until the diameter of the opening is substantially the same as the diameter of the device to be implanted within the patent. The diameter of the opening is the diameter of the curved tip  206 .  
         [0014]    The device  100  can approach the interspinous ligament from one direction, through an incision. The tapered curved tip  106  is easily inserted into the spinous ligament. Typically, to insert an implant, a small incision is made while the patient is lying on his or her side. The curved tip  106  allows the physician to access the interspinous ligament through the small incision. By inserting the elongated body  102  into the incision, the physician can manipulate the curved tip  106  with the handle  104  and create an opening in the interspinous ligament with the curved tip  106 . Accessing the interspinous ligament through a single incision further minimizes damage to surrounding body tissue.  
         [0015]    Accordingly, the invention of the device can be used for an inventive method of dilation. The method includes making an incision in the patient and inserting the curved tip  106  of the tool preferably perpendicular to the back in a direction from a posterior position to an anterior position. The tip  106  is then preferably inserted perpendicularly until it comes into the region above the interspinous ligament that is to be dilated. At that point, the tip  106  is substantially parallel to the ligament that is to be dilated. The handle of the device  100  would then be rotated and/or pivoted as the tip  106  is then urged into the interspinous ligament up to the second end  108 . The device  100  can then be removed. Should further dilation be required, subsequent devices  100  with larger curved tips can be used.  
         [0016]    The foregoing description of preferred embodiments of the present invention has been provided for the purposes of illustration and description. It is not intended to be exhaustive or to limit the invention to the precise forms disclosed. Many modifications and variations will be apparent to practitioners skilled in the art. The embodiments were chosen and described in order to best explain the principles of the invention and its practical application, thereby enabling others skilled in the art to understand the invention with various embodiments and with various modifications as are suited to the particular use contemplated. It is intended that the scope of the invention be defined by the following claims and their equivalents. The aspects, features, and advantages of the invention are also demonstrated in the figures and the claims.