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 .
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 , embodied as bolts , is arranged . the adjusting device can be operated from outside the housing .