as shown in fig1 , 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 fig1 . 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 . in the configuration shown in fig1 , 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 fig2 , discussed below , is disposed with the bar near the abdomen , the retractor in the configuration of fig1 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 fig2 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 . in fig3 hinch of the arm and spring pin mechanism 52 , 53 , 54 , 55 , 56 , 57 , 58 , 59 and 60 are shown . referring to fig2 , 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 fig1 or inward toward each other as shown in fig2 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 . as is further shown in fig1 , 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 fig1 , 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 fig1 . 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 . 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 . 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 .
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 .