Abstract:
The invention is a sternal retractor comprising a pair of arms each of which includes a downward extending blade, and one of which includes a proximal portion and a distal portion pivotally mounted on the proximal portion, a curved cross bar on which said arms are disposed so that in use the retractor can open the bottom of the sternum wider than the top of the sternum to minimize damage to the upper ribs and numbness, which sometimes occurs in the hands of open chest surgery patients. The retractor also has applications within 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 
     1. Field of the Invention 
     This invention relates to the field of medical surgical tools, and more particularly, to retractors for chest surgery. 
     2. Art Background 
     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. 
     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. 
     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. 
     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. 
     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. 
     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 
     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. 
     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. 
     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. 
     In accordance with one aspect of the invention, a surgical sternal retractor is provided, including a bar, and a pair of arms mounted on the bar. At least one of the arms is mounted to slide along the bar and to be locked in place on the bar. Each of the arms includes a blade extending downward along the arm from a proximal end of the blade to a distal end of the blade at a distal end of the arm. At least one of the arms includes a proximal portion mounted on the bar and a distal portion mounted by a hinge to pivot on the proximal portion between the proximal end of the blade and the bar. 
     Preferably, the bar is curved so that proximal and distal ends of the blades of the pair of arms are additionally separated by different distances as the arms are moved apart, with the arms being configured for mounting to extend from the bar in a first direction or opposite the first direction. Preferably, the bar includes gear teeth extending along a first side and a side opposite the first side, with at least one of the arms including a rotatably mounted pinion engaging the teeth extending along the first side of the bar with the arms mounted to extend from the bar opposite the first direction, and engaging the teeth extending along the side of the bar opposite the first side with the arms mounted to extend from the bar opposite the first direction. 
     In accordance with another aspect of the invention, a method for sternal retraction is provided, including: inserting blades extending downward from arms within a sternal retractor into a split within the sternum; spreading the arms within the sternal retractor through a short distance to begin sternal retraction; rotating a distal portion of one of the arms, including one of the blades; about a pivot point attaching the distal portion of the arm to a proximal portion of the arm; locking the distal portion in place on a proximal portion of the arm including the distal portion; and spreading the arms within the sternal retractor further to complete sternal retraction. For example, the distal portion is rotated toward the other arm with the bar located near the abdomen of the patient, and with the bar being curved so that, as the arms are spread apart, the distal ends of the blades are spread apart through a first distance, and the proximal ends of the blades are spread apart through a distance greater than the first distance. 
     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. 
     It is another object of the present invention to provide a retractor which minimizes injury to the brachial plexus during open chest surgery. 
     It is another object of the present invention to provide a retractor which minimizes the risk of broken ribs, particularly the shorter ribs. 
     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. 
     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. 
     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 
         FIG. 1  is a perspective view of a retractor built in accordance with a preferred embodiment of the present invention assembled in a first configuration. 
         FIG. 2  is a perspective view of the retractor of  FIG. 1  assembled in a second configuration. 
         FIG. 3  is a perspective exploded view of the retractor of  FIG. 1 . 
         FIG. 4  is a side view of a first arm within the retractor shown in  FIG. 2 . 
         FIG. 5  is a plan view of the retractor assembled as shown in  FIG. 2 . 
         FIG. 6  is a side view of the a second arm within the retractor shown in  FIG. 1 . 
         FIG. 7  is a plan view of the retractor assembled as shown in  FIG. 1 . 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     As shown in  FIGS. 1 ,  3 ,  4 ,  6 , and  7 , a retractor  23  of the present invention comprises generally a cross bar or rack  22 , a first arm  24 , comprising a proximal portion  24 A and a distal portion  24 B, and second arm  26 .  FIG. 1  is a perspective view of the retractor  23 , while  FIG. 3  is an exploded perspective view thereof.  FIGS. 4 and 6  are side views of the first arm  24  and the second arm  26 , respectively.  FIG. 7  is a plan view of the retractor  23  assembled as shown in  FIG. 1 . The distal portion  24 B of the first arm  24  is pivotally connected to the proximal portion  24 A thereof by a hinge  59  and is further held in position by a locking mechanism  60 . When the locking mechanism  60  is released, the distal portion  24 B may be rotated about the hinge  59  to be locked in a new position. For example, the distal portion  24 B can be rotated between a medial position, in which it is shown in  FIG. 1 , and an inward position, indicated by dashed lines  24 C. 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 cross bar  22  is curved so that the arms  24  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 . The distal portion  24 B of the first arm  24  includes a downwardly extending blade  32 , and the second arm  26  includes a downwardly extending blade  33 . 
     When the arms are closed to be adjacent to each other with the distal portion  24 B of the of the first arm  24  held in the inward position, in which it is shown with dashed lines in  FIG. 1 , by the locking mechanism  60 , the distal portion  24 B of the first arm  24  and the second arm  26  are substantially parallel to each other, facilitating the insertion of the blades  32 ,  33  into an open sternum. One, or possibly both, of the arms  24 ,  26  may be moved along the bar  22  preferably by a moving means comprising a pinion  28  driven by a handle  30 . This arrangement allows the present invention to be installed and to force the severed 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 adapted to secure the sternum after it is severed. The present invention includes the use of blades which are longer than those depicted 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. 
       FIGS. 1 and 7  are views of the retractor  23  assembled in a first configuration, for use with the bar  22  disposed closer to the head of a patient than to the abdomen.  FIG. 1  is a perspective view of the retractor  23  so assembled, while  FIG. 7  is a plan view thereof. with the distal end  39  of the blade  32  and the distal end  40  of blade  33  being further apart than their proximal ends  41 ,  42 . Accordingly, as used in the configuration of  FIG. 1 , the retractor  23  positively forces the sternum into a specific angled position dictated by the curvature of the bar  22  and the distance between the arms  24 .  26 . In this way the chest opening can be small at area adjacent the short ribs and larger at the area adjacent the longer ribs. 
       FIGS. 2 and 5  are views of the retractor  23  assembled in a second configuration, for use with the bar  22  near the abdomen.  FIG. 2  is a perspective view of the retractor  23  so assembled, while  FIG. 5  is a plan view thereof. 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  22  can be chosen to provide the best view for the surgeon in a manner which is well known in the art. When the retractor  23  is used in the second orientation of  FIG. 2 , the blades  32 ,  33  are first placed into the severed sternum with the locking mechanism  60  holding the distal portion  24 B of the first arm  24  in the inward position, as indicated by dashed lines  24 C in  FIG. 2  to have the blades together for initial positioning. After the arms  24 ,  26  are moved apart through a short distance, the distal portion  24 B of the first arm  24  is moved to the medial position, in which it is shown in  FIG. 2 , to be subsequently held in place by the locking mechanism  59 . 
     As is further shown in  FIGS. 1 ,  3 ,  6  and  7 , the bar  22  comprises teeth on sides  25  and  27 , and arms  24  and  26  have blades  32  and  33 , respectively. Arm  26  has a pinion  28 , rotatably mounted within a hole  29 , a crank  30 , attached to the pinion  28 , and a locking pin  31 , which screws into hole  51  to secure the arm in a desired position. The proximal portion  24 A has a 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  the arm with means for disconnecting said arm  24  from said bar  22  so that the arms can be reversed if desired to change the retractor  23  between the first configuration of  FIG. 1  and the second configuration of  FIG. 2 , reversing the direction of curvature of the bar  22  relative to the arms  24 ,  26  to locate the bar either above or below the surgical area. Similarly, arm  26  can be removed from bar  22  so that it can be reversed between the first configuration of  FIG. 1  and the second configuration of  FIG. 2  Bar  22  is provided with a flattened area  43  onto which arm  24  may be secured. Arms  24  and  26  have slots  49  and  46 , respectively, in which the bar  22  may be disposed in use. 
     As particularly shown in  FIG. 3 , the distal portion  24 B of the first arm  24  is pivotally attached to the proximal portion  24 A thereof by a hinge  59 , including a pin  55  extending through a hole  61  in the proximal portion  24 A and through a pivot hole  63  in the distal portion  24 B. A locking pin or screw  60  extends through one of a plurality of holes  58  within the distal portion  24 B of the first arm  24  and through holes  56  within the proximal portion  24 A of the first arm  24 . When the locking screw  60  extends through a central hole  53  within the plurality of holes  58 , the distal portion  24 B of the first arm  24  is held in the medial position, in which it is shown in  FIGS. 1 and 2 . When the locking screw  55  extends through a first lateral hole  64 , the distal portion  24 B is held in the inward position indicated by dashed lines  24 C in  FIGS. 2 ,  7 . When the locking screw  60  extends through a second lateral hole  57 , the distal portion  24 B is held in an outward position (not shown). 
     In the preferred embodiment, the bar  23  is approximately 8 inches long, for adult sternal retractors and has a curvature of 40 degrees. The curvature of the bar  23  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. 
     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.