Abstract:
A device for straightening and stabilizing the vertebral column, particularly for stabilizing broken vertebrae, includes a supporting implant which is plastically expandable by internal pressure. The supporting implant can be placed into the interior of a vertebral body which has been fractured under compression or between adjacent vertebral bodies. A pressure balloon to which pressure fluid can be admitted may be arranged in the interior of the supporting implant for producing the internal pressure.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    1. Field of the Invention  
           [0002]    The present invention relates to a device for straightening and stabilizing the vertebral column, particularly for stabilizing broken vertebrae.  
           [0003]    2. Description of the Related Art  
           [0004]    Devices for straightening and stabilizing broken vertebrae are known to be used. These devices include a catheter which can be inserted into the interior of the vertebra through a duct drilled into the pedicle of the broken vertebra. A pressure line pushed through the catheter into the interior of the vertebra has at the end thereof an expandable pressure balloon which makes it possible to expand once again and return into its original shape a vertebra which has been compressed and possibly broken. The balloon which has subsequently been decompressed and pulled out together with the pressure line leaves a hollow space into which a bone filler material can be introduced through the catheter.  
         SUMMARY OF THE INVENTION  
         [0005]    It is the primary object of the present invention to provide a novel device for stabilizing the vertebral column, particularly for straightening and stabilizing broken vertebrae, which makes it possible to achieve a higher degree of stabilization more quickly than by using the known devices, wherein the required operation is simpler.  
           [0006]    In accordance with the present invention, the device for straightening and stabilizing the vertebral column is characterized by a supporting implant which is plastically expandable by internal pressure.  
           [0007]    Such a supporting implant, which is preferably provided for being arranged in the interior of a vertebral body fractured under compression or also, for example, after an intervertebral disc resection for arrangement between adjacent vertebral bodies, can be easily moved to the implantation location because of its small dimensions. After the expansion has been effected, a preliminary stabilization is ensured immediately because the supporting implant maintains its final shape obtained during the plastic expansion. A filler material which is initially present in liquid form can be introduced under slight pressure into the created hollow space and can harden in the hollow space. Because of the action of the supporting implant, it is not necessary to wait until the filler material has hardened completely.  
           [0008]    While mechanical tools for producing the internal pressure are conceivable, a preferred embodiment of the invention provides for a device which produces the internal pressure by means of a pressure fluid.  
           [0009]    The pressure fluid can be introduced directly into the supporting implant, which requires that the supporting implant and the supply connections are pressure tight. However, in accordance with a preferred embodiment, a pressure balloon is provided which is arranged in the interior of the supporting implant and into which the pressure fluid can be introduced.  
           [0010]    The expandable supporting implant may include a weakened wall, or a wall which is perforated in the manner of expanded metal and/or folded in the manner of a bellows.  
           [0011]    This type of supporting implant can be expanded with relatively low internal pressure, wherein the stability of the expanded implant is reduced by the weakened or folded portions, however, the implant can still carry out a sufficient supporting function.  
           [0012]    The wall of the expandable supporting implant may have weak portions and/or folds arranged in such a way that the supporting implant expands into a desired shape. For example, if such a supporting implant is arranged between adjacent vertebrae, the desired shape is approximately that of a parallelepiped.  
           [0013]    In accordance with a preferred embodiment of the invention, the expandable supporting implant has an oblong shape so that it is suitable for being arranged at the implantation location by means of a catheter or a guide sleeve. In particular, the expandable supporting implant, and possibly the pressure balloon, may be placed in the manner of a stocking on a pressure line which can be introduced through the guide sleeve, wherein the pressure balloon is arranged between the supporting implant and the pressure line and, in the non-expanded state, forms a hose-type sleeve which surrounds the pressure line and which is connected at its ends in a pressure-tight manner by being placed around the circumference of the pressure line.  
           [0014]    The pressure fluid is preferably not compressible, and a device for measuring the supplied amount of pressure fluid is provided. This makes it possible to control the degree of expansion through the supplied quantity.  
           [0015]    In accordance with another advantageous embodiment of the invention, a monitoring device is provided which monitors changes over time of the fluid pressure and the supplied fluid quantity so that the pressure application can be interrupted when predetermined relative values of these changes are exceeded. Such a monitoring device prevents fluid which is under high pressure from being released into the body when the supporting implant is destroyed, for example, as a result of a material defect.  
           [0016]    The various features of novelty which characterize the invention are pointed out with particularity in the claims annexed to and forming a part of the disclosure. For a better understanding of the invention, its operating advantages, specific objects attained by its use, reference should be had to the drawing and descriptive matter in which there are illustrated and described preferred embodiments of the invention.  
       
    
    
     BRIEF DESCRIPTION OF THE DRAWING  
       [0017]    In the drawing:  
         [0018]    [0018]FIG. 1 is a schematic sectional view of a device according to the invention with a supporting implant placed on a pressure line;  
         [0019]    [0019]FIG. 2 is an illustration of a detail of the supporting implant of FIG. 1;  
         [0020]    [0020]FIG. 3 is an illustration, on a smaller scale, showing the device of FIG. 1 inserted into a broken and compressed vertebral body;  
         [0021]    [0021]FIG. 4 shows the vertebral body of FIG. 3 which has been expanded by means of the device of FIG. 1; and  
         [0022]    [0022]FIG. 5 is an illustration of another embodiment of the supporting implant which can be used in a device of the invention.  
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0023]    [0023]FIG. 1 of the drawing shows a guide sleeve  1  and a pressure line  2  extending through the guide sleeve  1 , wherein the pressure line  2  is provided with an opening  3  for releasing a pressure fluid.  
         [0024]    An elastic hose-type sheath  4  is placed in the manner of a stocking and flush at the ends thereof on the circular cylindrical pressure line  2 . The sheath  4  is glued in a pressure-tight manner at its ends to the circumference of the pressure line  2  at  5  and  6 . Instead of providing a glued connection, it would also be possible to press the elastic sheath  4  at the ends thereof by means of rings against the pressure line.  
         [0025]    A hollow-cylindrical supporting implant  7  is placed around the elastic sheath  4 . As can be seen in FIG. 2, the cylindrical wall  8  of the implant  7  is a mesh-like material with openings  9 , wherein wires of the mesh extend at an acute angle relative to each other. The wall  8  can be tangentially expanded in the manner of expanded metal in the direction of double arrow  21 , so that the supporting implant  7  is radially expanded.  
         [0026]    At its end opposite the sheath  4  or the supporting implant  7 , the pressure line  2  is in connection with a schematically illustrated device  10  for supplying an incompressible pressure fluid  11 , wherein this device  10  includes a pressure cylinder  12  and a piston  13 . The piston  13  may be movable manually, preferably by means of a screw-type pressure gauge, or by means of a motor drive.  
         [0027]    Reference numeral  14  denotes a schematically illustrated control and monitoring device which includes a pressure indicator  16  and a display  17  for the supplied quantity of pressure fluid.  
         [0028]    The manner of operation of the device is shown in FIGS. 1 and 2 and shall now be explained in connection with FIGS. 3 and 4.  
         [0029]    For stabilizing a broken vertebra, initially a duct  18  is drilled through the pedicle  20 , wherein a catheter and a drilling tool extending through the catheter can be used for this purpose. As shown in FIGS. 3 and 4, the guide sleeve  1  is now placed in the duct  18  and the pressure fluid  2  with the supporting implant  7  can be forwardly pushed into the interior of the compressed vertebra which has compression folds at  19 .  
         [0030]    The incompressible pressure fluid  11  is pressed by means of the device  10  into the pressure line  2 , the pressure fluid  11  emerges from the opening  3  and the elastic sheath  4  is expanded into a balloon. The expanding sheath or balloon  4  expands the supporting implant  7 , as illustrated in FIG. 4, wherein the wall  8  of the supporting implant  7  is plastically deformed in the direction of arrow  21  shown in FIG. 2 and the acute angles between the mesh wires at  17  are widened.  
         [0031]    The quantity of supplied pressure fluid during the expansion can be read at the display  17  of the control and monitoring device  14  and, thus, the extent of the achieved expansion can be determined. The expansion or supply of pressure fluid is stopped when a predetermined value of the supplied pressure fluid quantity has been reached.  
         [0032]    The control and monitoring device  14  further ensures that the application of pressure is stopped immediately if the balloon  4  ruptures during the expansion, for example, due to a material defect, and pressure fluid is released from the vertebra; this is the case when the supplied pressure fluid quantity increases significantly over time, while the pressure stays constant or increases only slightly.  
         [0033]    After the required expansion has been achieved, the pressure fluid is withdrawn through the opening  3  which is located near the lowest point of the balloon  4 . The pressure line  2  with the empty pressure balloon or the empty sheath  4  can now be pulled back through the guide sleeve  1 .  
         [0034]    The plastically deformed supporting implant  7  maintains its shape and supports the vertebra in such a way that it maintains the shape shown in FIG. 4 and the damage shown at  19  can heal. A filler material is introduced into the interior of the supporting implant.  
         [0035]    [0035]FIG. 2 is a cross-sectional view of another embodiment of a supporting implant  7   a  according to the invention. The supporting implant  7   a  has in its wall  8   a  folds  22 , wherein the folds on opposite sides have different lengths, so that the expanded implant has a rectangular shape in cross-section.  
         [0036]    In the embodiment described above, a salt solution containing an x-ray contrast agent is used as the pressure fluid.  
         [0037]    Of course, two of the above-described supporting implants can be and are usually inserted into a broken vertebra, wherein ducts are drilled in both pedicles for inserting a catheter.  
         [0038]    While specific embodiments of the invention have been shown and described in detail to illustrate the inventive principles, it will be understood that the invention may be embodied otherwise without departing from such principles.