Patent Number: 044184220
Section: description

BEST MODE FOR CARRYING OUT THE INVENTION Before passing more specifically to the details represented in the drawings, it should be noted that each described part is of essential importance for the invention, either in combination with the features of the claims or simply in itself. On an operating bed 20 there is resting a patient, in whose left femur there is implanted a locking nail 6 (indicated with dotted lines). A source 4 for X-rays is placed in a movable position with respect to the operating bed 20 and has a housing 21, including at the front an exit window 22. A receiver 23 is located in the beam path of the Rontgen generator 4, the receiver being operatively connected to a monitor 5 which is controlled through an image amplifier 24. Nail 6 is shown in FIG. 2 to include fastener holes 6-1 in the proximal end thereof and fastener holes 6-2 in the distal end thereof. Below the housing 21 of the generator is fixed an aiming gauge indicated generally with 25, which at its forward end has a reception socket 7 which is placed centrally with respect to the main beam path of the radiation socket 4. The aiming gauge 25 is illustrated in FIG. 3 in larger scale. It comprises a fork having two prongs 26 which are circularly formed in cross section. Plastic plugs 27 are inserted in the free extremities of the prongs 26, which at their projecting extremities are configured as points. The prongs 26 of the fork 25 are made by bending from an single elongated rod and thus are connected with each other through a circular portion 28. The center of the circular portion 28 is connected to a leg 29, preferably by welding. At the free end of the leg 29 a transverse portion 30 is welded thereto, extending in a plane perpendicular with respect to the plane defined by the prongs 26. The transverse portion 30 has a tubular shape and telescopically accommodates at the end thereof a tube 31 which in turn is crossed by reception socket 7. The retaining tube 31 is fixed inside the tube 30 with the aid of screws 33 and can be fixed at gradual distances in the tube 30. Reception socket 7 has a throughgoing staggered bore with the narrower part extending across the retaining tube 31. The reception socket serves to receive an aiming sleeve 32, that can be fixed in the socket 7 with the aid of a star shaped knob 34. FIG. 5 shows a support system for the aiming gauge 25 according to FIG. 3. It comprises a base plate 12 that is fixed on the underside of the housing 21 of the generator (FIG. 1) for example with the aid of screws. Pivotally connected to the base plate 12 through a hinge is a bracket plate 3. The hinge comprises a bushing bearing 13 welded to the base plate 12 and having a support rod 35 extending therethrough which in turn is mounted to be capable of rotation in two pivot bearings 36 and 37. The pivot bearings 36 and 37 are welded on the pivotable bracket plate 3. Sleeves 38 and 39 are welded on both sides of bracket plate 3 dimensions such and placed at such a distance that the fork prongs 26 of the aiming gauge 25 can be pushed into the sleeves 38, 39. This is done in the direction of arrow 40. On the pivotable bracket plate 3 two bearing blocks 41 and 42 are welded at a distance from each other for a shaft 43 carrying interlocking cams 8 at its extremities projecting from the bearing blocks 41 and 42, these cams are fixedly secured to the shaft for rotational movement therewith. The interlocking cams 8 are of eccentric form and partially extend through slots 44 in the bracket plate 3. In the position shown in FIG. 3, a portion of the cam extends through an opening, not shown, of the sleeves 38 and 39, in order to arrest the fork prongs 26 within the sleeves 38 and 39. If the shaft 43 is turned counterclockwise, the arresting mechanism is released. In the following the actuation of shaft 43 will be described and with that of the interlocking cams 8. The shaft 43 is extended through a crank arm 45 and is connected thereto in a way so as not to permit rotation therewith. A connecting rod is linked to the bifurcated crank arm 45, the connecting rod comprises two parts 46 and 47. Part 47 has a threaded portion, which can be screwed into a threaded bore of part 46. Part 47 is pivotally joined to the one extremity of crank arm 48 cooperating at its lower extremity with the crank shaft 50. Crank shaft 50 is rotatably received in the holes of bearing blocks 55 and 56. The eccentric plates 52 and 53 are connected rigidly to the crank shaft 50. The bearing blocks 55 and 56 are welded to the bracket plate 3. Annular portions 57 and 58 are secured to the ends of the crank shaft 50 for rotation therewith, the annular portions in turn are screwed onto a U-shaped bundle 9. It should be mentioned that spacer washers 60 and 61 are disposed between the bearing blocks 55 and 56 and the eccentric plates 52 and 53. It can be seen that connecting rod 46-47 is axially adjusted upon pivotal movement of the handle 9 through the crank shaft 50 and the crank arm 48 thus effecting rotation of shaft 43 and of the locking cams 8. In the position shown in FIG. 5 the eccentric plates 52 and 53 cooperate in a self-locking manner with resilient shoes 62 and 63, that are screwed on the upper side of the bracket plate 3 when the plate is viewed as in FIG. 5. The parts 46 and 47 of the connecting rod can be moved relative to each other. For this it is necessary to release part 47 from the crank arm 48, so that it can be rotated with respect to part 46. In this way it is possible to vary the tension with which the cams 8 urge against the prongs 26 of the aiming gauge 25. The base plate 12 extends beyond the bracket plate 3 at the opposite extremity thereof and retains at this end a locking mechanism 14, having a pawl 67 and an unlocking lever 68. With the bracket plate 3 a locking tongue 64 is connected, of which the part which is placed slightly beyond the edge of the bracket plate cooperates with pawl 67. Upon pivoting of bracket plate 3 towards the base plate 12 the locking tongue 64 trips automatically beneath pawl 67, so as to be able to be locked in the position illustrated in FIG. 5. The interlocking engagement can then be released by manual actuation of the unlocking lever 68. In the position shown in FIG. 5 the eccentric plates 52 and 53 are lying in close contact and under tension against the resilient shoes 62 and 63 so that the screws 65 and 66 compensate for possible existing clearances between plates 12 and 3, because the screws extend through plate 3 and are forced onto the base plate 12 by the eccentric plates 52 and 53. The adjusting screws 65 and 66 in the shoes 62 and 63 secure an exact adjustment. The aiming procedure starts with orienting the X-ray source 4 perpendicularly with respect to the axis of nail 6 and centering it on one of the holes 6-2 in the distal end of the nail 6. In this way the circular form of this hole appears on the monitor which image is overlapped with the image of the reception socket 7. This image must be checked after each operating step and if it is necessary be adjusted again. After having made the incision the aiming sleeve 32 inserted in socket 7 is moved adjacent the corticalis and fixed within its socket 7. Further working is now performed with the aid of the aiming sleeve.