Abstract:
A retractor has an oximeter sensor at its tip, which allows measuring of oxygen saturation of a tissue being retracted by the retractor. The tip includes one or more openings for at least one source and detector. A specific implementation is a spinal nerve root retractor with an oximeter sensor.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This patent application claims the benefit of U.S. provisional patent application 61/055,972, filed May 24, 2008, which is incorporated by reference. 
    
    
     BACKGROUND OF THE INVENTION 
     This invention relates to the field of medical devices and more specifically to a retractor device with an oximeter sensor. 
     Retractors play an important role in medicine. Retractors typically retract or hold aside tissues so that a physician (e.g., surgeon) can gain access to an area for operation or observation. It is critical that the retracted tissue is not damaged. 
     One area of medicine that retractors are commonly used is during spinal surgery. Tens of thousands of spinal surgeries are performed each year. The number of spinal surgeries is continuing to increase due, in part, to an aging population, active lifestyles, and a better understanding of what causes back pain. Back pain may be due to disc herniation, degenerative disc disease, spinal trauma, and osteoarthritis just to name a few examples. 
     The spinal cord is the main pathway through which the brain sends and receives signals. The nerve fibers in the spinal cord branch off to form pairs of nerve roots that travel through small openings between the vertebrae. These nerves control the body&#39;s function including the vital organs, sensation, and movement. 
     During spinal surgery, it is often necessary to retract, or hold, the nerve root aside so that the surgeon can access the surgical site. With current medical devices, however, it is difficult if not impossible, to tell whether the nerve root is being damaged during the retraction. Damage to the nerve root can be catastrophic. 
     There is, then, a continuing demand for medical devices that provide patient feedback, provide more features, are easier to use, and generally address the needs of patients, doctors, and others in the medical community. 
     Therefore, there is a need to provide improved systems and techniques for nerve retractors. 
     BRIEF SUMMARY OF THE INVENTION 
     A retractor has an oximeter sensor at its tip, which allows measuring of oxygen saturation of a tissue being retracted by the retractor. The tip includes one or more openings for at least one source and detector. A specific implementation is a spinal nerve root retractor with an oximeter sensor. 
     The invention is a surgical nerve root retractor with tissue oxygen saturation sensing capability to potentially prevent nerve root hypoxia during spinal surgical retraction. This device will potentially be less expensive and easier to use than laser Doppler blood flow measurements and potentially more accurate in determining the effect of surgical manipulation on the health of nerve roots. This device will be easier to apply than conventional electrophysiological monitoring and is very precise in location. 
     In an implementation, the retractor has a steel shaft, a handle connected to a proximal end of the shaft, and a tip connected to a distal end of the shaft. The tip has a retractor portion or blade and an oximeter sensor. The blade is angled sufficiently with respect to a bottom surface of the tip to retract tissue, such as an angle of about 90 degrees. However, the angle may vary from about 90 degrees to about 179 degrees. 
     In an implementation, the retractor has an oximeter sensor including a first sensor opening and a second sensor opening on a bottom side of the tip. There is a first optical fiber and a second optical fiber. The first optical fiber passes through a channel in the shaft and a distal end of the first optical fiber is connected to a first sensor opening of the tip. The second optical fiber passes through the channel in the shaft and a distal end of the second optical fiber is connected to a second sensor opening of the tip. There is a display, connected to the oximeter sensor via optical fibers, to show an oxygen saturation measurement made by the oximeter sensor. 
     Other objects, features, and advantages of the present invention will become apparent upon consideration of the following detailed description and the accompanying drawings, in which like reference designations represent like features throughout the figures. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  shows an oximeter system for measuring oxygen saturation of tissue. 
         FIG. 2  shows a perspective view of a first implementation of a tip. 
         FIG. 3  shows a bottom view of the first implementation of a tip. 
         FIG. 4  shows a perspective view of a second implementation of a tip. 
         FIG. 5  shows a bottom view of the second implementation of a tip. 
         FIG. 6  shows a perspective view of a third implementation of a tip. 
         FIG. 7  shows a bottom view of the third implementation of a tip. 
         FIG. 8  shows a side view of the third implementation of a tip. 
         FIG. 9A  shows a perspective view of the third implementation of the tip attached to a nerve retractor. 
         FIG. 9B  shows an internal channel of a retractor. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       FIG. 1  shows an oximeter system  101  for measuring oxygen saturation of tissue, such as a nerve root. The system includes a monitoring console  105 , a nerve root retractor  110 , and a cable  115  connecting the nerve root retractor to the monitoring console. The cable includes optical fiber. 
     The nerve retractor has a handle  113 , a shaft  116  connected at its proximal end  119  to the handle, and a tip  122  connected to a distal end  125  of the shaft. The tip includes a retractor portion or retractor blade  128  and an oximeter sensor  131 . 
     The shaft includes an internal channel or passageway. Optical fibers pass from sensor openings on the tip, through the channel, through the handle, and into the cable jacket or cable insulation. See  FIG. 9B , which shows a path of an internal channel ( 930 ) within a retractor. The shaft is made of steel. 
     The system is used by placing the oximeter sensor in contact with the nerve. Light is transmitted from the monitoring console, through optical fiber in the cable, out a sensor opening on the tip and into the nerve. The reflected light from the nerve is then received by another sensor opening on the tip, transmitted back to the monitoring console via optical fiber, and then processed. A screen  135  on the console displays the oxygen saturation measurement. 
       FIG. 2  shows a perspective view of a first implementation of a tip  205 . The tip includes a retractor blade and an oximeter sensor  210  attached to a top surface  215  of the tip. The tip attaches to a shaft  220 . The tip also includes a retractor portion  223 . Optical fibers are encased in a cable jacket  225 , travel along the shaft, into the oximeter sensor, and are exposed through an opening on a bottom surface  230  of the tip. Cable jacket  225  and shaft are wrapped with a tubing  235 . Such tubing may be heat-shrink tubing. 
     In a specific implementation of  FIG. 2 , the tip of the retractor has a length of about 17.5 millimeters, width of about 8 millimeters, and a thickness (not including the retractor blade) of about 5 millimeters. 
       FIG. 3  shows a bottom view of the first implementation of a tip  305 . The tip has a retractor blade and slot  310 , within which there are sensor openings. There are four sensor openings for ends of fiber optic cables. The openings  315   a ,  315   b ,  320   a , and  320   b  are for source and detector fibers. 
       FIG. 4  shows a perspective view of a second implementation of a tip  405  with an encasement  410  which contains optical fiber attached to the tip. 
     In a specific implementation of  FIG. 3 , the tip of the retractor has a length of about 17.5 millimeters, width of about 8 millimeters, and a thickness (not including the retractor blade) of about 3 millimeters. 
       FIG. 5  shows a bottom view of the second implementation of a tip  505 . The tip includes a retractor blade and four sensor openings on a bottom surface  510  of the tip. The sensor openings include openings  515   a ,  515   b ,  515   c , and  515   d . Optical fiber is connected to each of the sensor openings. The sensor openings can include sources and detectors. 
       FIG. 6  shows a perspective view of a third implementation of a tip  605 .  FIG. 7  shows a bottom view of the third implementation of a tip  705 . The tip includes two sensor openings on a bottom surface  710  of the tip. The two sensor openings include an opening  715  and an opening  720 . The openings include a source and detector. 
       FIG. 8  shows a side view of the third implementation of a tip  805 . A retractor portion or retractor blade  810  is at an angle  815  to a shaft  820  onto which the tip is attached. In an implementation, the angle is about 90 degrees. Angle  815  ranges from about 90 degrees to about 179 degrees. 
     In a specific implementation of  FIG. 8 , the tip of the retractor has a length of about 5 millimeters, width of about 3 millimeters, and a thickness (not including the retractor blade) of about 2 millimeters. 
       FIG. 9A  shows a side view of the third implementation of the tip  805  connected to a nerve retractor  910 . This figure shows the handle of the retractor, having a first end  915  and a second end  920 , as shown. The handle connects to the shaft and the tip via the first end. 
       FIG. 9B  shows a path of an internal channel  930  within a refractor. 
     This description of the invention has been presented for the purposes of illustration and description. It is not intended to be exhaustive or to limit the invention to the precise form described, and many modifications and variations are possible in light of the teaching above. The embodiments were chosen and described in order to best explain the principles of the invention and its practical applications. This description will enable others skilled in the art to best utilize and practice the invention in various embodiments and with various modifications as are suited to a particular use. The scope of the invention is defined by the following claims.