Abstract:
An intromedullary nail for the distraction of bone parts consists of two elements which can be moved relative to one another. At least one electrically operated driving element which is supplied by electrical energy to move the two elements relative to one another is connected to the medullary nail by at least one detachable plug-in element.

Description:
BACKGROUND OF THE INVENTION 
     The present invention relates to an active medullary nail for distraction of bone segments, comprising two elements, prosthesis, or the like, which can be moved relative to each other, with at least one electrically operated drive element. 
     Medullary nails of this type are known and available on the market in a very wide variety of forms and designs. It is becoming more and more common for electrical drive elements to be provided in the medullary nails in order to generate a distraction of two elements which are movable relative to each other. To do this, electrical connections are necessary for operating the medullary nail. 
     A disadvantage of the previously known connections is that these are embedded directly in the medullary nail and are often broken or damaged as a result of being moved many times if distraction takes place over a certain period of time, or as a result of external influences, for example movement of the limbs. 
     A further disadvantage is that these connections are removed following a specified distraction, for example by surgery or being cut through. Then, in the event of a renewed distraction, this connection has to be surgically connected up again, which is time-consuming. 
     It is an object of the present invention to make available an active medullary nail for distraction and also a medullary nail with optionally attached prostheses or the like, with which an electrical connection can be established in a very simple way. This is intended to fulfill the electrical, mechanical and hygiene requirements. 
     SUMMARY OF THE INVENTION 
     To achieve this object, the electrical energy can be delivered to the medullary nail via at least one detachable plug element. 
     A socket is provided in an opening preferably at one end of one of the two axially displaceable elements of the medullary nail. A plug element can be inserted there into an opening in order to establish an electrical connection for control and energy transmission. In this arrangement, completely standard plugs or plug connections can be used, as are described for example in DIN-ISO 5841-3. A bipolar design is preferred. A plurality of electrical signals can be transmitted. 
     It has proven particularly advantageous for at least one sealing lip element to be assigned to the plug element, preferably at the end. This sealing lip element is elastic and is preferably designed tapering outward. It closes off the opening of the socket completely and in an absolutely leaktight manner. In this way, no tissue fluid or the like can gain entry and damage the electrical connection between socket and plug element. 
     It is also advantageous in the present invention that the medullary nail be designed as a prosthesis and that after a desired period of distraction only the electrical plug connection be surgically removed. The opening can then be closed with a stopper or the like. Should further distraction prove necessary, the stopper can be surgically removed again and the plug then inserted there. This affords considerable advantages in particular in operating and handling active medullary nails of this type. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Further advantages, features and details of the invention will become apparent from the following description of preferred illustrative embodiments and from the drawing, in which: 
     FIG. 1 shows a diagrammatic view of an at least partially opened active medullary nail; 
     FIG. 2 a  shows an at least partial longitudinal section through the medullary nail according to FIG. 1; 
     FIG. 2 b  shows a cross section through the medullary nail along the line II—II according to FIG. 2 a;    
     FIG. 3 a  shows a partial longitudinal section through the medullary nail according to FIG. 1 as a further illustrative embodiment; 
     FIG. 3 b  shows a cross section through the medullary nail according to FIG. 3 a  along the line III—III; 
     FIG. 4 shows an at least partial longitudinal section through a further illustrative embodiment of a medullary nail according to FIG.  1 . 
    
    
     DETAILED DESCRIPTION 
     According to FIG. 1, an active medullary nail R 1  according to the invention has two elements  1 . 1 ,  1 . 2  which can be moved axially relative to each other. In the preferred illustrative embodiment, the element  1 . 1  can be displaced relative to the element  1 . 2 . Drive means (not shown here) such as gears, push rods, shape-memory drives or the like can move the element  1 . 1  relative to the element  1 . 2 . At least one electrical drive element  2  is preferably provided in the element  1 . 2  of the medullary nail R 1 . This drive element  2  communicates with a socket  4  of the element  1 . 2  via electrical connection lines  3 . The socket  4  is provided at the end face of the element  1 . 2  in the medullary nail. A plug element  6  can be inserted into the socket  4  through an opening  5 . Connected to the plug element  6  there are energy supply lines  7  which lead for example to an external power source. From there, energy can be introduced directly or indirectly, for example by induction. This energy is required for operating and controlling the drive element  2 . 
     To ensure that a desired distraction can take place over a certain period of time while the active medullary nail R 1  is in the bone, it is necessary to permanently establish an electrical connection. In this respect it has proven particularly advantageous to insert what is known as a plug element  6  into the end, particularly the end face, of the element  1 . 2 . Corresponding contact points  8  transmit electrical energy and/or electrical signals. 
     However, an important aspect of such connections is that for hygiene reasons there must be an absolutely leaktight and clean detachable connection point between medullary nail R 1  and plug element  6 . For this purpose, at least one sealing lip element  9 . 1 ,  9 . 2  is assigned to the plug element  6  and closes off in a detachable manner the opening  5  and thus the socket  4  of the element  1 . 2 . By this means it is possible to ensure that an electrical contact remains established in a detachable manner over long periods of time. 
     The outer sealing lip element  9 . 2  also ensures an optimum protection against buckling, which is of importance given the bending stresses which occur. 
     If, for example, the active medullary nail is a hip-joint endoprosthesis, as is shown partially in FIG. 4, or a knee-joint endoprosthesis, this too can be provided with a corresponding plug connection, as described above. In this way, a correction can be made for example after the operation by means of a corresponding distraction. This correction can be carried out over a fairly long period of the recovery process. If no further correction is then necessary, for example, only the plug element is removed from the opening  5  of the element  1 . 2 . If appropriate, the opening  5  is closed with a tight stopper or the like should correction be necessary again. In this way, prostheses designed as active medullary nails R 1  can be operated permanently and, after an appropriate distraction or correction of the bone, the electrical connections can be removed without difficulty. 
     Should a further correction prove necessary after a certain length of time, the plug element can be introduced again into the opening. An optionally fully implantable subcutaneous energy source, to which energy or corresponding signals are inductively fed, can then be implanted under the skin. The active medullary nail can be put back into operation in this way. 
     Also of importance is a radial sealing lip element  9 . 1 ,  9 . 2  which if appropriate bears on an inwardly projecting shoulder  10 . The sealing lip element  9 . 1 ,  9 . 2  is preferably designed tapering outward and lies tightly on an inner wall  11  of the socket  4  or element  1 . 2 . 
     It is also intended to provide an internal thread  12  inside the socket  4 , in which a corresponding external thread  13  of the plug element  6  engages in order to secure the plug element  6  in a detachable manner. However, locking connections or the like are preferably used. 
     As a means of securing against removal during operation, simple threaded pins or the like can be provided, as are indicated for example in FIG. 2 a . There, a corresponding securing element  14  passes radially through the element  1 . 2  as a threaded pin in order to detachably secure and clamp the plug element  6  which has been inserted in the socket  4 . This is also illustrated in the cross-sectional representation in FIG. 2 b.    
     FIGS. 3 a  and  3   b  show a further securing element  14  which engages in a corresponding groove  15  of the plug element  6  and thus axially secures the plug element  6  relative to the socket  4  of the element  1 . 2 . The securing element  14  can in this case be provided as a bolt or the like in order to prevent an axial movement of the plug element  6  relative to the socket  4 . No restriction is placed on the invention in this regard. 
     In the last illustrative embodiment according to FIG. 4, it will be seen that plug elements  6  can also be inserted, in the manner described above, as active medullary nails R 2  in any desired prostheses, hip joint endoprostheses. This is intended also to lie within the scope of the present invention. 
     LIST OF REFERENCE LABELS 
     
       
         
               
             
               
               
             
           
               
                   
               
               
                 List of reference labels 
               
               
                   
               
             
             
               
                   
               
             
          
           
               
                 1 
                 Element 
               
               
                 2 
                 Drive element 
               
               
                 3 
                 Connection line 
               
               
                 4 
                 Socket 
               
               
                 5 
                 Opening 
               
               
                 6 
                 Plug element 
               
               
                 7 
                 Connection line 
               
               
                 8 
                 Contact point 
               
               
                 9 
                 Sealing lip element 
               
               
                 10 
                 Shoulder 
               
               
                 11 
                 Inner wall 
               
               
                 12 
                 Internal thread 
               
               
                 13 
                 External thread 
               
               
                 14 
                 Securing element 
               
               
                 15 
                 Groove 
               
               
                 R 1   
                 Active medullary nail 
               
               
                 R 2   
                 Active medullary nail