Abstract:
A distraction device enabling management of the evolving deformation of the trunk of a child during growth. The device is easy to implant on account of its compact shape and includes two rods which can be bent and deformed on the ends thereof and which are mounted on a central adjusting member which is provided with a small hole for engaging a small tool that is designed to adjust the distance separating the elements for attachment to the bone. The inventive device can be locked in a position which is determined by the tightening of two screws which are disposed on the adjusting device.

Description:
FIELD OF THE INVENTION 
     The invention relates to a tensioning device that is placed between the ribs of a child whose growth is incomplete and who has deformations or malformations particularly of the trunk. In such a case, surgeons who specialize in this type of intervention call it: distraction device. It permits correcting also congenital malformations such as those that appear in the course of growth, without hindering or blocking the latter; it is in particular thanks to the means used that this invention can solve the problem, until now unsolved. 
     PRIOR ART 
     The first treatments of scoliosis were based on movements of the vertebral column. Y Cotrel perfected this technique by employing in 1892 a traction and elongation device for the spinal column. This traction of the spinal column was very painful. For the most serious cases, it was followed by a plaster cast on the chest to seek to preserve as much as possible the correction that had been carried out. Most often, the doctor would prescribe the wearing of a corset which more or less maintained the spinal column. For the most serious deformations, the results were far from being satisfactory. The spinal column did not straighten sufficiently and the wearing of the corset was annoying. Despite all these drawbacks, this method is still used for treatment of scoliosis of young children. 
     About 30 years ago, Harrington was the first to implant in the back of a patient a rod with two hooks fixed at their ends to the bones to try to straighten the spinal column. The spinal column was straightened, but 6 months later, once the graft had set, the vertebrae formed a bony mass limiting the mobility of the untreated vertebrae. 
     The often great distance between the two hooks made it necessary that the rod connecting them be subjected to strong forces, giving rise to breaking of the rods and thus requiring the surgeon to intervene. An immobilization of 6 months in a plastic cast was often necessary. Moreover, the correction was effected only in a single plane. The sagittal balance (lumbar lordosis and anatomical thoraxic cyphosis) were not maintained, and postoperative problems followed for the patient. 
     Yves Cotrel in 1988 produced a device for supporting the vertebrae of the spinal column. He multiplied the contacts with the vertebrae so that instead of two hooks for one framework, there was a system which could have up to two hooks or two screws per vertebra, which permits reducing the forces on the rod connecting the implants. Moreover, he used a technique of three-dimensional straightening of the spinal column. The spinal column is not only straightened in the frontal plane but the lumbar lordosis and the thoraxic cyphosis are also restored. The rods and hooks are solidly fixed to each other ensuring the holding of the spinal column during the time the bony graft sets up. The patient can return to normal activity sometime after the procedure. At the end of six months, the spinal column is in principle fused, the material remains in place. It is also this type of intervention that is carried out most often nowadays. The column is corrected, it is true, but the affected vertebrae are blocked. The patient, to recover mobility in the trunk, is obliged to compensate with the intervertebral disks free from any material. 
     The great drawback of this procedure is thus that it definitively fixes the spinal column; the growth of the fused vertebrae is blocked. If the surgeon operates on a child whose growth is not complete, he will block the growth of the vertebrae behind, by leaving the frontal growth free, which gives rise to the development of a deformation in the form of a twist. This is the “crankshaft” phenomenon noted by Professor Dubousset. 
     This is why the fixing of the vertebrae is not to be performed in young children. In this case, there is used only the treatments by corsets or plastic casts to limit and slow the development of the deformation. As soon as the child will have grown sufficiently, the surgeon can secure the spine by the technique described above, which cannot in any way be adapted to the problems of growth. For certain children having congenital malformations, the fact of achieving adulthood is not possible and the surgeons are obliged to fuse several vertebrae to permit a minimum respiratory capacity. 
     The present invention which will now be described in three illustrative and non-limiting embodiments, will permit solving these problems that confront all children whose growth is not complete. 
    
    
     
       DESCRIPTION 
       The present distraction device is comprised of devices for hooking onto the suitable bones, for example to the ribs, and devices for adjusting the interval between the two hooking devices. 
       The hooking devices are independent of the original distance of the ribs to be covered: for example, one end of the hooking device can be hooked to one given rib and to another rib which is not necessarily the nearest one. 
       The adjustment means permit both adjusting and correcting the deformation which will develop with growth by checking this movement on the assembly of the distraction device, whose adjustment can easily be periodically modified. 
       This invention will be described in connection with three preferred embodiments which permit adapting on a case by case basis to the problem arising, by illustrating with the drawings examples of embodiment, 
         FIG. 1  shows an assembly view of a first type of distraction device for the bones 
         FIG. 2  is a top plan view of the assembly of the distraction device (first embodiment) 
         FIGS. 3 ,  4  and  5  show three examples of means for hooking to the bones, 
         FIG. 6  shows an assembly view of a modified embodiment of the device with its mini-tool (the second embodiment) 
         FIG. 7  shows a cross-sectional view (of the second embodiment) 
         FIG. 8  shows the adjustment means of the assembly of the distraction device (second embodiment) 
         FIG. 9  shows a top plan view of the distraction device in its third embodiment, 
         FIGS. 10 ,  11  and  12  show details of the adjustment device of the distraction device seen from above, an example of mini-tool for adjustment, and a perspective view, 
         FIG. 13  shows one of the distraction devices in place on the skeleton, 
         FIG. 14  shows a vertical cross-sectional view of a new distraction device of the 3rd embodiment comprising at the ends of the bendable or deformable rods supporting stirrups at their ends, 
         FIGS. 15A and 15B  show a perspective view of a hooking comprising at one end a tightening screw disposed in an enlargement and the detail of the jaws of a gripping member. 
     
    
    
     A first embodiment is a distraction device  1  which comprises: an adjustment device  100  and a device for hooking to the bones. 
     The adjustment device  100  comprises: at least one screw-threaded rod  11  with at its center an adjustment means  12  which can be of one piece with the rods or engaged on these rods, permitting the adjustment of the distraction device  1 . It has at its center a small central hole  120  for receiving a mini-tool  121 , the shape of the hole being suitable to the tool such that it will permit displacement of the hooking device located on the bones and thereby adjust their spacing. 
     The screw-threaded rod  11  has in its two symmetrical portions reversed screw threads (left and right) on which are screwed two hooking devices for the bones  13  and  14 . 
     These hooking devices  13  and  14  can be in a first embodiment two plates  131  and  132  for hooking to the bones by matching perfectly its form, they are provided with securement screws  133  and  134  offset with respect to the axis of the adjustment device. 
     When the child grows, a small incision is made exactly over the place of the hole  120  corresponding to the passage of the mini-tool, and the hooking devices  13  and  14  are adjusted, thereby avoiding any inconvenience as described in the case of inventions of the prior art which are not capable of following growth. 
     In a second embodiment, which is a modification of the first embodiment, the adjusting device  200  comprises:
         a central sleeve  27  permitting the desired spacing between two bones. This central adjustment sleeve  27  and at least one mini-hole  220  or several mini-holes  220  offset to permit easier access for example of a mini-rod which can be inserted to adjust at the desired location the distance between the two bones. Each screw-threaded rod with reversed pitch enters the central means which comprises on each end a suitable screw thread and on its external shape flats or cutoffs permitting turning it by external pressure of a mini-key adapted to its shape. This permits the surgeon to intervene for adjusting the device.       

     This adjustment device  200  is integrated very easily into the body by protecting the active portions  233  or  234  (screw-threaded rods  21   a  or  21   b ) from the tissues and from the surrounding skeleton. 
     The hooking device is in this case constituted for example by hooking means  23  and  24  which can be:
         either: stirrups  231  which screw onto screw-threaded rods  21   a  or  21   b  with blocking by a nut  25     or: hooks  235  and  236  formed of two male and female portions mating to the shape of the bone   or again a sliding hook  237  on the rod  21  which can be smooth, screw-threaded or milled and on which the hook will be fixed by a screw  2370  embedded in an enlargement forming part of the hook  237  ( FIG. 5 ).       

     In addition to these hooking means ( FIGS. 3 ,  4  and  5 ), the hooks or stirrups can have a point  26  ( FIG. 15 ) which will pierce the bone so as better to immobilize it. Moreover, it is preferable to place a tubular crosspiece  329  between the hooks  235  and  236  so as to avoid any sliding of the bone by opening of the hooks from gripping, thereby permitting obtaining a very effective encircling of the bone. 
     The third embodiment of the distraction device  3  comprises: 
     An adjustment device  300  which comprises a central means  31  itself comprised by a small frame  310  (smaller than the dimension for example of a domino), in which freely turns on an axle a small wheel  311  which can be toothed, centered on said frame  310  and having at one of the ends of its axle a means  312  for rotating it with the desired amplitude. This means can be a hole permitting the engagement of a male key with six flats  321 , or any other equivalent means, its only requirement being to be received without projection in said frame  310 . 
     In this frame will be positioned on each rib of the wheel  311  two rods  35  and  36  which will be moved in translation as required thanks to the adjustment means  31  located on the frame  310  and accessible by a mini-tool  321 . The two rods  35  and  36  can have a channeled portion followed by a screw-threaded portion which permits very easily engaging symmetrically the screw-threaded portions to the channeled portion, permitting thereafter the systematic engagement in the wheel  311 . Before proceeding to the final adjustment, upon engagement of the rods, the mini-tool can be engaged in the adjustment device  31  to start the distraction which will take place then in a semi-automatic manner and will proceed by using the mini-tool to perfect the adjustment. This operation is of course after having hooked the previously described hooking means to the bones. In this embodiment, the blocking of the adjustment device  31  takes part by tightening the two screws  341  and  342  located on the frame  310 . On the other hand, a small cover constituted by a vertical plate  330  located between the two rods, or a plate that is pierced to let them pass, closes the frame by avoiding introduction particularly of tissue into the frame, without interfering with the movement of the rods  35  and  36  in translation by the toothed wheel operated by the surgeon. 
     In the third embodiment of the distraction device  3 , it is also possible to correct a deformation that can develop in a three-dimensional space. 
     To obtain such a result, there are emplaced preferably within the distraction device  3 
         a new hooking means of the stirrup type  333     rods  35  and  36  with bendable or deformable ends  38  and  39 , this new stirrup  333  has a tightening screw  3330  disposed in an enlargement  3331  forming a portion of the body of the stirrup, as well as two small holes  3332  and  3333  permitting access to a specific gripper  3334  whose jaws can be positioned in the holes to be able to raise the rib or the bone and to bring the rod  35  or  36  to be threaded on said hooking means  333 . This manipulation is made possible the ends of the rods  38  and  39  are deformable as needed. Once the distraction device  3  is emplaced, the screws  3330  are tightened, the hooks are brought together or spaced apart by the desired distance and the central adjustment means  300  is tightened by the adjustment screws  341  and  342 . This manipulation is without risk to the child, because the bending to measure of the ends of the rods  38  and  39  permits pure translatory movement, rendered impossible with rods that are straight and rigid over all the length.       

     Moreover, there is no possible error of manipulation because the tightening screw  3330  disposed in the enlargement  3331  cannot be lost, which thus permits, thanks to the means previously described, correcting a three-dimensional deformation without risk of error. 
     Thanks to the means previously described in the preferred embodiment No. 3, it is possible to proceed to a mechanical mounting on the bones or the ribs which can be carried out easily in the following way:
         we start by positioning the stirrup  333  with its rod  35  about the bone without gripping it with the screw  3330 , which permits rotation of the assembly about the bone which thereby permits threading the two rods  35  and  36  with their adjustment means  31 , which are caused to slide to the ends  38  and  39 .       

     With the help of the adjustment means  31 , the second rod (for example  36 ) is brought into the hooking means  333  pre-positioned on the second rib which is not necessarily the nearest one; this emplacement is possible thanks only to the ends  38  and  39  which can be bent to measure, of the rods  35  and  36 , which permit reaching a position in practically all difficult cases encountered. Once the adjustments have been determined, it remains only to carry out the tightening of the various means of the distraction device  3 . 
     The three embodiments of the distraction device  1 ,  2 ,  3  thus permit, thanks to the means for using them, previously described, to straighten the bones of a child, without thereby finally blocking it, because straightening the skeleton of a child, without thereby finally blocking it, because it suffices to carry out a small intervention to have access easily to the distraction device, which permits following the development of this skeleton by correcting the deformations whilst permitting the child to grow. In embodiments  2  and  3 , the structure of the hooking devices is perfectly interchangeable, and not specific except for the first embodiment. The third embodiment is distinguished however the most from the prior art. 
     Finally, all the devices which are used in any embodiment, comprise adjustment or hooking means that can be adapted to any shape of bones; they will be produced of materials that are biocompatible with the human body. As is known at present, the preference is toward unoxidizable metals: stainless steel, titanium alloys or other metals of high strength, insensitive to corrosion by the human body; composite materials of high strength and biologically compatible can also be envisaged. Given their small size, all these means can be assembled in “assembly kits”; these kits being present in chests used during an operation. All these new devices give to this invention a great advance as to technical devices already used for the care of malformations which will be able to be treated without impeding growth, with simple devices.