Abstract:
A surgical instrument having at least one displacement element is provided for displacing bone parts. The apparatus includes an implantable, flat housing in which an adjusting device for the displacement element(s), embodied as bolts, is arranged. The adjusting device can be operated from outside the housing.

Description:
BACKGROUND OF THE INVENTION 
     The present invention relates to a surgical instrument for displacing bone parts, preferably however an instrument for the expansion of hardened parts. 
     In particular, the invention is intended for use in surgery on the jaw, to be employed in cases of atrophy, impacted teeth or shrinkage where it is necessary for the purpose of regeneration to separate bone parts and to raise them relative to adjacent bones or to enlarge the distance between the bone part and the bone. 
     In the known instruments of this type, the bone part is displaced by helical displacement, whereby however elements of the instrument project into the oral cavity of the patient to such a degree that the use of the known instruments is very disturbing to the patient and there is a risk of infection in the mucous membranes and skin exit locations. 
     The object of the invention is to avoid these disadvantages by an inventive construction of the apparatus. 
     SUMMARY OF THE INVENTION 
     This object is inventively achieved in accordance with the invention in that an implantable, flat housing is provided in which is located an adjusting device for at least one displacement element, or for two displacement elements that are mutually opposably movable, that can be operated from the exterior via an opening in the housing; the displacement element or elements are longitudinally displaceable bolts that act on counterbearings that are detachably attached to the bones. The bolts are expediently moved by a cone that travels longitudinally with the travel thereof being effected by a toothed wheel or toothed member that can be operated from the exterior and that meshes with a toothed rod attached to the cone. 
     The housing is preferably attached, for example by being screwed, to the bone or to the bone part to be displaced or raised. However, it is preferable to attach the housing to the actual bone rather than only to a part of the bone. 
     It is important that the displacement device be encapsulated in a housing that is implantable due to the flat shape of the housing. This arrangement of the instrument beneath the soft tissue ensures that the patient&#39;s discomfort is kept to a minimum. The instrument, in accordance with the invention, is thus patient-friendly and can be used on patients who previously could not tolerate or endure such a surgical procedure. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Additional details of the invention are explained with reference to the drawing, in which is illustrated an exemplary embodiment of the invention. 
     FIG. 1 is a plan view of an apparatus for the expansion of hardened parts in the region of the human jaw in the form of a flat housing with the cover removed, and enlarged in scale; 
     FIG. 2 is a cross-section taken along the line II—II in FIG. 1; and, 
     FIG. 3 is a cross-section taken along the line III—III in FIG.  1 . 
    
    
     DESCRIPTION OF PREFERRED EMBODIMENTS 
     An essential component of the instrument in accordance with the invention is a housing  1  that has a flat and rectangular contour and that is made of a material suitable for implantation, e.g. titanium. Preferably the dimensions thereof are about 3.5−5 cm×1.5−2.5 cm, with a thickness of about 1.5−3 mm; however, these dimensions can be altered if necessary for particular applications. This housing  1  should lie beneath the soft tissue directly on the bone. 
     The bone separation line, provided e.g. by a saw, is labeled  2 . The part of the bone to be lifted is labeled  3  and the actual bone is labeled  4 . In the present case the housing  1  should lie on the bone  4 . Provided for attaching the housing  1  are holes  5  with which the housing  1  can be screwed on. 
     The housing  1  comprises a lower part  6  and a cover  7 , whereby these parts engage in an exact fit. Although not shown, conventional locking elements can also be provided. The base of the lower part  6  is labeled  8  and the circumferential lateral walls of the lower part  6  are labeled  9 . 
     Provided in the base  8  and running lengthwise relative to the housing  1  is a central groove  10  into which engages a rib  11  of a symmetrical cone  12 , which in the extension of its longitudinal center axis has a rearwardly extending toothed rod  13  that meshes with a toothed wheel  15  borne on the base  8  by means of a pin  14 . This toothed wheel extends upward via a hub  16  that is borne in a round recess  17  in the cover  7 . The hub  16  also has at its free end a square keyhole  18 , which naturally can also be replaced by the frequently-used hexagonal keyhole. 
     Thus, when the housing  1  is closed, this square hole  18  is accessible from the outside. A suitable key can be inserted therein in order to turn the toothed wheel  15 , thereby moving the cone  12 . 
     Provided on both sides of the cone  12  in the lateral walls  9  are supports or bearings  19  for longitudinally displaceable bolts  20  that act upon abutments or counterbearings  21  that are outside the housing and that are securely screwed to the bone  3 ,  4 . 
     The ends of the bolts  20  which are located inside the housing  1  abut the lateral inclined surfaces of the cone  12 . Consequently, when the cone moves in the direction of the arrow  22 , the bolts  20  are outwardly displaced and thus the bone  3  is lifted or raised. 
     In order to avoid moving the cone  12  in opposition to the direction of the arrow  22 , reverse travel stops of any type can be provided that also must be releasable from the outside. However, these stops are not mandatory and it is possible to do without them if the cone incline itself inhibits reverse travel. 
     The bolts  20  can be either loose elements or components of the counterbearings  21 . However, it is important that when two bolts  20  are used there is an opposing movement for displacing the bone or parts thereof. 
     The adjusting device for the opposing bolts  20  is consequently hermetically sealed in the housing  1 . In addition, the adjusting device can also be actuated from the outside by simply turning the toothed wheel  15 . 
     It is furthermore important that the housing  1  is kept very flat. Therefore the movable elements  12 ,  13 ,  15  located therein are secured against undesired misalignment. The interior surfaces of the housing  1  constitute a stop for these elements. In addition, the bearings  19  provide secure bearing and guidance for the bolts  20 . 
     Instead of the symmetrical cone as illustrated in the drawing, it is also possible to use an asymmetrical cone (with different inclines). Furthermore, if the housing  1  is anchored or held appropriately, it is possible to provide only one effective adjusting element or one bolt  20 . Consequently, with reference to the drawing, one bolt  20  can be effective or can be omitted altogether. In this case a cone  12  that works only on one side would be sufficient. Finally, attaching the housing can be superfluous if the counterbearings  21  are anchored. 
     The specification incorporates by reference the disclosure of German priority document 199 34 889.8 of Jul. 24, 1999. 
     The present invention is, of course, in no way restricted to the specific disclosure of the specification and drawings, but also encompasses any modifications within the scope of the appended claims.