Abstract:
A sternal closure device for securing and retaining longitudinally divided halves of a sternum, the device having two sets of anterior and posterior longitudinally extended brace members with brace joining mechanisms extending through the sternal halves to join the anterior brace members to the posterior brace members, such that the sternal halves are compressed between the anterior and posterior brace members, and transverse bridging members that laterally connect the two sets of brace members, with securing mechanisms to retain the two sets of brace members in a contracted configuration with the sternal halves in abutting relation.

Description:
This application claims the benefit of U.S. Provisional Patent Application Ser. No. 60/708,085, filed Aug. 12, 2005. 
    
    
     BACKGROUND OF THE INVENTION 
     This invention generally relates to devices used to rejoin a human sternum that has been longitudinally severed, and more particularly relates to such devices that function in a clamping manner to retain the two severed sternum portions in a closed and abutting relationship post-operatively for an extended period of time such that healing of the sternum may occur. 
     It is often necessary in surgical operations to longitudinally sever the patient&#39;s sternum so that the ribs may be spread to provide access to internal organs such as the heart. It is then necessary to secure the bisected sternum halves together for post-operative recovery. Various closure techniques are used to accomplish this task. For example, holes may be drilled into the sternum halves and suture material passed through and tightened to cinch the sternum halves together. Apertured plates may be added to further rigidify the sternum post-operatively, with the suture material being passed through the apertures in the plate and the sternum. Encircling members may be wrapped around the sternum and tightened. Toothed bridging members extending across the cut line may be pressed into the sternum surfaces and/or secured with threaded rods extending between the sternal halves. 
     Another sternal closure technique involves the use of clamps having hook-like projections or engagement members on both ends, the clamp being positioned laterally relative to the sternal incision with the projections being disposed between adjoining rib pairs. The clamp is then contracted or compressed to shorten the device and force the sternal halves together, the clamp typically comprising two members joined in a telescoping manner. Locking or securing means, either permanent or releasable, maintain the clamp in the contracted configuration. 
     Examples of such techniques and devices are described in U.S. Pat. No. 3,473,528 to Mishkin et al., U.S. Pat. No. 4,201,215 to Crossett et al., U.S. Pat. No. 4,279,248 to Gabbay, U.S. Pat. No. 4,583,541 to Barry, U.S. Pat. No. 5,139,498 to Astudillo Ley, U.S. Pat. No. 6,051,007 to Hogendijk et al., U.S. Pat. No. 6,217,580 to Levin, U.S. Pat. No. 6,302,899 to Johnson et al., U.S. Pat. No. 6,540,769 to Miller, III, and U.S. Pat. No. 6,712,821 to Gabbay. 
     Problems occur with these techniques and devices when the sternum is relatively weak due to age, illness, etc., such that the bone material cannot bear the localized stresses imparted by the sutures, bone anchors or clamping devices of the known systems. Closure techniques that require suturing are excessively time consuming. Bracing devices that are not adjustable either in depth or width cannot be properly adapted to correspond to conditions of a particular patient. 
     It is an object of this invention to provide a sternal closure device having the functionality of a contractible sternal clamp, such that the sternal halves may be quickly and easily forced together and retained in position, but providing greater reinforcement and rigidity to the severed sternum, and which is also effective in circumstances where the sternum is in a weakened condition. It is an object to provide such a sternal closure device wherein longitudinal brace or scaffold members are secured to the sternal halves with the sternal halves retained in a force-spreading, compressive manner, the longitudinal brace members being joined by transversely extending bridging members, the bridging members having locking or securing means, preferably releasable, such that when the longitudinal bridging members and sternal halves are compressed together, the locking or securing means maintain the device in the contracted or tightened configuration with the sternal halves abutting. 
     SUMMARY OF THE INVENTION 
     The invention is in general a sternal closure device for post-operatively closing, securing and supporting a patient&#39;s sternum that has been longitudinally severed, i.e., bisected from top to bottom. The device comprises two laterally positioned assemblies of longitudinally extending brace or scaffold members, each assembly comprising a posterior brace member and an anterior brace member. The posterior and anterior brace members of each assembly are joined together by brace joining means extending through apertures or bores cut into the bone material of the left or right sternal half such that the sternal half is compressed, i.e., sandwiched, between the anterior and posterior brace member. The separation distance between the posterior and anterior brace members is adjustable such that the device is adaptable for use with sternums of differing thicknesses. 
     The left and right brace assemblies are joined together by transverse bridging members that connect the anterior brace members and span the sternal separation line or kerf. The transverse bridging members enable the separation distance between the left and right brace member sets to be adjusted, such that the two sets can be forced together to abut the sternal halves. The transverse bridging members are provided with locking or securing means, preferably releasable, such that the sternal halves are retained in abutment. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view of one embodiment of the sternal closure device. 
         FIG. 2  is a partial view of the device of  FIG. 1 , better illustrating the chosen embodiment for the securing means. 
         FIG. 3  is an end view of the device taken along line III-III of  FIG. 1 , the longitudinal brace members being shown in cross-section to better expose the brace joining means. 
         FIG. 4  is a partial view of the interlocking means for the transverse bridging members. 
         FIG. 5  is a partial view showing a bridging member receiving slot. 
         FIG. 6  is a partial view showing the hook end of a bridging member. 
         FIG. 7  is a perspective view of another embodiment of the sternal closure device, showing an alternative embodiment for the bridging members. 
         FIG. 8  is a partial view of the device of  FIG. 7 , better illustrating the chosen embodiment for the securing means, and showing the longitudinal brace members prior to being compressed together. 
         FIG. 9  is a partial view similar to  FIG. 8 , showing the longitudinal brace members in the compressed configuration. 
         FIG. 10  is an end view of the device taken along line X-X of  FIG. 7 , the longitudinal brace members being shown in cross-section to better expose the brace joining means. 
         FIG. 11  is a view of an embodiment of the sternal closure device in position on a severed sternum. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     With reference to the drawings, the invention will now be described in detail with regard for the best mode and the preferred embodiment. The invention is in the most general sense a sternal closure device used to close, secure and support a sternum post-operatively, the sternum having been longitudinally severed or bisected into left and right lateral halves to provide access to the interior of the chest. For ease of reference, the terms left and right as used herein shall mean the directions as seen by an observer facing the sternum of the patient, such that the right brace assembly and the right sternal half are disposed to the patient&#39;s sinistral side, while the left brace assembly and the left sternal half are disposed to the patient&#39;s dextral side. 
     A first embodiment of the invention is illustrated in  FIGS. 1 through 6 . The sternal closure device  10  comprises two sets of laterally disposed brace assemblies  20  and  30 , with left brace assembly  20  comprising a longitudinally extended top or anterior brace member  21  and a longitudinally extended bottom or posterior brace member  22  joined by brace joining means  40 , and with right brace assembly  30  comprising a longitudinally extended top or anterior brace member  31  and a longitudinally extended bottom or posterior brace member  32  joined by brace joining means  40 . Brace joining means  40  comprise members adapted to be positioned within apertures or bores provided in the sternal halves  91 / 92 , such that the brace joining means  40  pass through the sternal halves  91 / 92 . Preferably, the brace joining means  40  are such that the separation distance between the anterior brace members  21 / 31  and the posterior brace members  22 / 32  is adjustable to account for differences in the thickness of various sternums  90 , such that the sternal half  91  is compressed between the anterior and posterior brace members  21 / 22 , and such that the sternal half  92  is compressed between the anterior and posterior brace members  31 / 32 . Preferably, the brace joining members  40  comprise internally threaded sleeve or post members  41  extending anteriorly from the posterior brace members  22 / 32 , with the sleeve members  41  receiving threaded fasteners  42  that are disposed through fastener receiving apertures  11  correspondingly positioned in the anterior brace members  21 / 31 . In this manner the securing forces are not concentrated in localized points or areas, such as would occur with bone anchor screws or the like, but instead are dispersed along the lengths of the brace assemblies  20 / 30 . Likewise, no stresses are imparted to the ribs  93 . 
     The anterior brace members  21 / 31  and the posterior brace members  22 / 32  are composed of a relatively rigid, bio-compatible metal or similar material such that support and rigidity are imparted to the sternal halves  91 / 92 . The laterally disposed left and right brace assemblies  20 / 30  are connected to each other by transverse bridging means  50 , whereby the longitudinal juxtapositioning of the two brace assemblies  20 / 30  is held in fixed relation, while the lateral distance between the two brace assemblies  20 / 30  is variable. As shown in the embodiment of  FIGS. 1 through 6 , the transverse bridging means  50  may comprise overlapping arm members  51   a  and  51   b , each arm member  51   a / 51   b  comprising a hook end  52  that interlocks with bridging member receiving apertures or slots  12  disposed in the anterior brace members  21 / 31 . The bridging member receiving slots  12  are preferably provided with projections, teeth, ridges or similar mechanical interlocking members  13  that correspond to and mate with cooperating projections, teeth, ridges or similar mechanical interlocking members  53  disposed on the inner side of the hook ends  52 , as illustrated in  FIGS. 4 through 6 , in order to preclude relative movement between the bridging means  50  to the anterior brace members  21 / 31 . 
     The sternal closure device  10  is further provided with locking or securing means  60 , preferably releasable in the event the sternum  90  needs to be separated in the future, whereby the left and right brace assemblies  20 / 30  can be brought together and locked or secured in a desired position laterally, typically such that the edges of the sternal halves  91 / 92  are in abutting relation with the longitudinal sternal incision or kerf  99  closed. In the embodiment of  FIGS. 1 through 6 , the securing means  60  comprises a threaded bolt  61  mounted in a threaded aperture  63  disposed in the lowermost arm member  51   b , with the shaft of the bolt  61  positioned in a slot  62  disposed in the uppermost arm member  51   a . A washer flange member  64  is positioned atop the uppermost arm member  51   a . Tightening of the bolt  61  forces the two arm members  51   a / 51   b  together to preclude lateral movement. Preferably the mutually facing surfaces of the arm members  51   a / 51   b  are provided with projections, teeth, ridges or other mechanically interlocking members  54  to further preclude relative lateral movement. Most preferably, the interlocking members  54  are configured in a ratchet-like manner, whereby movement of the arm members  51   a / 51   b  to shorten the separation distance between the brace assemblies  20 / 30  is more readily accomplished than movement to separate the brace assemblies  20 / 30 . Alternatively, the ratcheting members  54  may be structured such that separation of the brace assemblies  20 / 30  is completely precluded, in which instance additional bolts  61 , threaded apertures  63  and the like are not necessary. 
     To utilize the device, bores are cut into the sternal bone material in each sternal half  91 / 92 . A guide template or the anterior brace members  21 / 31  themselves may be used to properly position the bores. The posterior brace plates  22 / 32  are then positioned beneath the sternal halves respectively with the sleeve members  41  inserted up into the bores. The anterior brace plates  21 / 31  are then positioned on top of the sternal halves  91 / 92  and the threaded fasteners  42  are threaded into the sleeve members  41 , thus defining the two brace assemblies  20 / 30  such that they are rigidly affixed to the respective sternal halves  91 / 92 . The transverse bridging means  50  are then positioned between the anterior brace members  21 / 31 . The sternal halves  91 / 92  and the brace assemblies  20 / 30  are then brought together such that the sternal halves  91 / 92  abut each other. The securing means  60  is then locked to prevent separation of the brace assemblies  20 / 30  and the sternal halves  91 / 92 . Should it be necessary to reopen the sternum, the securing means  60  can be released and the transverse bridging means  50  removed. A view of an embodiment showing the sternal closure device  10  in position on the sternum  90  is shown in  FIG. 11 . 
     An alternative embodiment for the sternal closure device  10  is illustrated in  FIGS. 7 through 10 . In this embodiment, at least one of the anterior brace members  21 / 31  has a different configuration, in that the transverse bridging means  50  comprises lateral arm members  55  affixed rigidly to or formed as an integral component of the anterior brace member  21  or  31 . The securing means  60  comprises arm brackets  65  that are secured to the anterior brace member  21  or  31  to receive the lateral arm members  55 . The arm brackets  65  are provided with bracket bolts or similar fasteners  66  that are mated with threaded apertures in the anterior brace member  21  or  31 , whereby tightening of the bracket bolt  66  forces the arm bracket  65  against the lateral arm member  55  to fix the relative lateral positions of the two brace assemblies  20 / 30 . Preferably, the lateral arm members  55  and either the arm brackets  65  or the upper surface of the anterior brace member  21  or  31  are provided with lateral arm interlocking members  56 , such as projections, teeth, ridges or the like. While the illustrations show all lateral arm members  55  extending from only one of the anterior brace members  21 / 31 , i the lateral arm members  55  could extend in opposing directions from both anterior brace members  21 / 31 , with the securing means  60  correspondingly disposed on both anterior brace members  21 / 31 . 
     The brace assemblies  20 / 30  of the sternal closure device  10  of this embodiment are affixed to the sternal halves as previously described. When the brace assemblies  20 / 30  and sternal halves have been brought together, the securing means  60  are locked by tightening the bracket bolts  66 , thereby affixing the relative positions of the sternal halves  91 / 92  and the brace assemblies  20 / 30 . 
     It is contemplated that equivalents and substitutions to certain elements set forth above may be obvious to those skilled in the art, and therefore the true scope and definition of the invention is to be as set forth in the following claims.