Abstract:
The invention is a sternal retractor comprising a pair of arms which one of them has hinch at the proximal part of it with sternum engaging blades thereon and a curved cross bar on which said arms are disposed such that in use the retractor can open the bottom of the sternum more than the top of the sternum to minimize damage and injury to the upper ribs and numbness which sometimes results in the hands of open chest surgery patients. The retractor also has application for other surgical procedures, as well, for the same general purpose of providing an opening of varying size along the length of an incision.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    1. Field of the Invention 
         [0002]    This invention relates to the field of medical surgical tools, and more particularly, to retractors for chest surgery. 
         [0003]    2. Art Background 
         [0004]    In open chest surgery, and particularly for cardiac surgery, the sternum is split with chest saw and is held open by a retractor. The sternum is a short bone in the middle of the chest to which all of the ribs are attached either directly, or indirectly. The ribs attached to the top of the sternum are shorter than the ribs attached to the bottom of the sternum. Accordingly, when the chest is opened using the retractor, more stress is placed on the shorter upper ribs than the longer lower ribs, as explained in more detail below. Such stress causes various problems including broken ribs. 
         [0005]    Typical prior art retractors, also termed sternal spreading or chest spreading retractors, comprise two elongated metal members, termed arms, with blades disposed thereon to capture the sternum, the arms being parallel to each other, and a rack or bar with teeth on which the arms are disposed. One of the arms is fixed in position for moving the other arm along the rack. The prior art retractors opened so that the arms remain parallel with respect to each other throughout their range of motion. Accordingly, in use, the sternum was displaced an equal amount along the entire length of the retractor. Prior art retractors include those devices which have long blades, short blades, multiple short blades or bent arms. Also, for pediatric and small patients, a small sized retractor of the same general configuration as described above may be used. 
         [0006]    One recent prior art device comprises a pair of blades which are pivotable through the plane defined by the blades and the bar connecting them. This device is intended to provide pressure evenly along the entire sternum and it opens in a generally triangular configuration as opposed to the generally rectangular configuration. However, the device does not provide positive control of the movement of the sternum as it is opened and does not necessarily open the sternum to a desired position. The device is described in U.S. Pat. No. 4,627,421 issued to Symbas et al. 
         [0007]    Another prior art device described in Chaux et al., U.S. Pat. No. 4,852,552 comprises a sternal retractor with blades which rotate in two different axes to permit one portion of the split sternum to be raised above the other portion in order to provide access to particular portions of the chest cavity. 
         [0008]    It has been observed that as a result of the use of such prior art devices, that following the surgery, a substantial percentage of patients develop a neuropathy in which numbness occurs in their left or right hand, and specifically, in the fourth and/or fifth digits (the ring finger and little finger). This numbness usually disappears after a while, but it has been known to occur for a substantial period of time, and in any event, such numbness is at best annoying to the surgical patients. The apparent cause of this numbness is that in opening the chest, the opening of the ribs puts substantial pressure on the lower branch of the brachial plexus. The lower ribs are longer and also have more cartilage which permits them to be spread more easily and with less risk than the upper ribs. Also, the lower ribs are not connected to any neurologically important portion of the plexus. 
         [0009]    One method of overcoming this problem of applying excessive pressure to the upper ribs and the adjacent portion of the plexus has been for the surgeon to attempt to position the retractor as low as possible so that there is minimal pressure on the upper, shorter ribs. However, this approach is not particularly desirable because the surgeon is not able to position the retractor in the most advantageous position for retraction of the chest. The present invention overcomes the foregoing deficiencies of the prior art devices and methods. 
       SUMMARY OF THE INVENTION 
       [0010]    The present invention is a retractor of the general type found in the prior art with certain improvements therein which eliminate the problem which occurs during cardiac or other open chest surgery wherein numbness of the fourth and fifth digits of the right and/or left hand is caused when the chest is opened and held open with the prior art retractors and methods. The present invention also minimizes the risk of breaking ribs, particularly the shorter ribs, during such surgery. 
         [0011]    The present invention comprises a retractor, a specifically a sternal spreader, having two arms with blades disposed on each arm, said arms being disposed on a cross bar, sometimes referred to as a rack. The invention specifically comprises the cross bar being curved rather than straight, as is provided in the prior art. The arms remain generally perpendicular to the cross bar as they moved along the cross bar closer to and away from each other, but in view of the curvature of the cross bar, one end of the arms is always closer to each other than the other end of the arms. 
         [0012]    Preferably, for an adult sternal spreader, when the end of the arms adjacent with the short ribs is approximately  4  inches apart, the end of the arms adjacent the long ribs is approximately 8 inches apart. Also preferably, the curvature of the cross bar is approximately 40 degrees. Of course the curvature of the cross bar can be varied considerably, the important feature being that the arms spread apart to form a generally triangularly-shaped opening in the chest as the sternum is spread apart. Any form of attachment means for attaching the arms to the cross bar and moving the arms along the cross bar may be employed, the preferred system comprising a rack and pinion. 
         [0013]    It is an object of the present invention to provide a retractor which is structurally simple and which does not obstruct the surgeon&#39;s view of the chest cavity, and particularly which does creates the largest possible viewing area with a minimal amount of trauma to the ribs. 
         [0014]    It is another object of the present invention to provide a retractor which minimizes injury to the brachial plexus during open chest surgery. 
         [0015]    It is another object of the present invention to provide a retractor which minimizes the risk of broken ribs, particularly the shorter ribs. 
         [0016]    It is another object of the present invention to provide a retractor which can be used in a plurality of configurations with the cross bar being disposed either above or below the surgical area. 
         [0017]    It is yet another object of the present invention to provide a retractor which can be provided a variety of sizes and curvatures and with a variety in the number of blades, as required. 
         [0018]    These and other objects of the present invention are achieved by providing a retractor which is shown in several presently preferred embodiments in the drawings which are described briefly below. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0019]      FIG. 1  is a perspective view of the preferred embodiment of the present invention. 
           [0020]      FIG. 2  is another perspective view of the preferred embodiment of the present invention. 
           [0021]      FIG. 3  is a perspective exploded view of the present invention in the configuration shown in  FIG. 1 . 
           [0022]      FIG. 4  is a side view of the present invention shown in  FIG. 2 . 
           [0023]      FIG. 5  is a top view of the present invention shown in  FIG. 2 . 
           [0024]      FIG. 6  is a side view of the present invention shown in  FIG. 1 . 
           [0025]      FIG. 7  is a top view of the present invention shown in  FIG. 1 . 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0026]    As shown in  FIG. 1 ,  3 ,  6 , and  7 , the retractor  23  of the present invention comprises generally a cross bar or rack  22  and a first arm  24  ( 24 A,  24  B) and second arm  26 . The cross bar  22  has in the preferred embodiment teeth on two opposing surfaces  25  and  27  for reasons that will be explained below. The critical element of the present invention is that the cross bar  22  is curved so that the arms  24  ( 24 A,  24  B) and  26  are not parallel to each other when the arms are opened or spread apart, but are angled outward away from each other as shown in  FIG. 1 . When the arms are closed and adjacent to each other by medial position over the hinch  59  at the proximal part of the arm  24  which is stabilized by spring pin  60  at medial position, they are substantially parallel to each other thereby facilitating the insertion of the blades in an open sternum. One and possibly, both arms may be moved along bar  22 . Preferably, the moving means comprises a pinion  28  driven by handle  30 . This arrangement allows the present invention to be installed and to force the cut portions of the sternum apart. The arms have disposed thereon blades  32  and  33  which are common to prior art chest separators and which are adopted to secure the sternum after it is cut. The present invention includes the use of blades which are longer than those depict as well as multiple blades on a single arm, and angled arm blades, all of which is well known in the art, and after a short distance opening the fixed arm will be moved to straight (neutral) position and held in place by pin spring  60  and continued to the desired opening. 
         [0027]    In the configuration shown in  FIG. 1 , the bar  22  would be disposed closer to the head of a patient than the abdomen, so that  39  of the blade  32  and end  40  of blade  33  are further apart than ends  41  and  42 . Accordingly, in use, the invented retractor positively forces the sternum into a specific angled position dictated by the curvature of the bar  22  and the distance between the arms. In this way the chest opening can be small at area adjacent the short ribs and larger at the area adjacent the longer ribs. Thus, while the retractor of  FIG. 2 , discussed below, is disposed with the bar near the abdomen, the retractor in the configuration of  FIG. 1  would be used so that the bar is disposed near the head of the patient. It will be appreciated in this connection that the reversible nature of the preferred embodiment of the present invention is not a requirement of the invention but is the preferred embodiment for purpose of obtaining multiple uses for a single device. The positioning of the bar can be chosen to provide the best view for the surgeon in a manner which is well known in the art. In the  FIG. 2  use of the retractor at the start the fixed arm will be at the lateral position to have the blades together for initial positioning and after the short distance of opening it will be moved to straight (neutral) position and held by pin and spring for the rest of opening to the desired opening position. 
         [0028]    In  FIG. 3  hinch of the arm and spring pin mechanism  52 ,  53 ,  54 ,  55 ,  56 ,  57 ,  58 ,  59  and  60  are shown. 
         [0029]    Referring to  FIGS. 2 ,  4 , and  5 , the retractor  10  of the present invention comprises generally a cross bar or rack  12 , and a first arm  14  ( 14 A,  14  B) and pin spring  60  and second arm  16 . The cross bar  12  has in the preferred embodiment teeth on two opposing surfaces  15  and  17  for reasons that will be explained below. The critical element of the present invention is that the cross bar  12  is curved so that the arms  14  ( 14 A,  14 B) and  16  are not parallel to each other when the arms opened or spread apart, but are angled either outward away from each other as shown in  FIG. 1  or inward toward each other as shown in  FIG. 2  as described above. When the arms are closed and adjacent to each other, by lateral position of the arm over the hinch  59  or medial position of the arm over the hinch  59  so that they are substantially parallel to each other thereby facilitating the insertion of the blades in an open sternum and after a short distance opening the arm will be moved to straight (neutral) position along the arm and held in place with spring pin  60  and opened for the desired position. One and possibly both arms may be moved along bar  12 . Preferably, the moving means comprises a pinion  18  driven by handle  20 . This arrangement allows the present invention to be installed and to force the cut portions of the sternum apart. The arms have disposed thereon blades  19  and  21 , which are common to prior art chest separators and which are adapted to secure the sternum after it is cut. The present invention includes the use of blades which are longer than those depict as well as multiple blades on a single arm, all of which is well known in the art. 
         [0030]    As is further shown in  FIGS. 1 ,  3 ,  6  and  7 , the bar  22  comprises teeth on sides  25  and  27  and arms  24  ( 24  A,  24  B) and  26  have blades  32  and  33  respectively. Arms  26  has pinion  28  and crank  30 , and as shown, has locking pin  31  which screws into hole  51  to secure the arm in the desire position. Arm  24  ( 24  A,  24  B) has locking pin  29  which secures it in place as well by screwing into hole  50  and impinging on the bar  22 . Pinion  28  comprises individual teeth  44  adapted to mate with the teeth on bar  22  so that the arm  26  can be cranked open to spread open the chest. The locking pin  29  provides the arm  24  ( 24  A,  24  B) with a means for disconnecting said arm  24  ( 24  A,  24  B) from said bar  22  so that the arms can be reversed if desired to the configuration of  FIG. 1 , to extend in the direction of the curve of the bar if it is desired to locate the bar above the surgical area rather than below it. Similarly, arm  26  can be removed from bar  22  so that it can be reversed in the configuration of  FIG. 1 . Bar  22  is provided with a flattened area  43  onto which arm  24  ( 24  A,  24  B) may be secured. Arms  24  ( 24  A,  24  B) and  26  have slots  49  and  46 , respectively, in which the bar  22  may be disposed in use. 
         [0031]    In the preferred embodiment, the bar is approximately 8 inches long, for adult sternal retractors and has a curvature of 40 degrees. The curvature of the bar may be regular, that is, with a single radius of curvature or it may have multiple radii of curvature along its length to provide variation in the angle of the blades with respect to each other. The curvature of the bar can be of any desired radius, the preferred curvature providing an opening of 8 inches at the bottom of the sternum and an opening of 4 inches at the top of the sternum. The blades can be short, long, multiple or slightly angled to provide the desired secure opening of the sternum. 
         [0032]    It will be obvious to a person of ordinary skill in the art that a number of modifications and changes can be made to the subject invention without departing from the spirit and scope of the present invention, which is defined by the claims appended hereto and all equivalents thereof.