Patent Number: 044184220
Section: summary

TECHNICAL FIELD The invention refers to a distal aiming device for the nail setting of bones. BACKGROUND ART In a common orthopedic technique for repairing broken or shattered bones, an elongated metal pin or nail is inserted along the central portion of the bone. The nail strengthens the bone and holds the parts of the bone together. Such a technique is often used in repairing the femur, the bone that connects the pelvis with the knee, or the tibia, one of the bones that connects the knee with the ankle. To insure that the parts of the bones are maintained together and in the correct position, transverse fasteners extend through the bone and the pin at each end. The pin contains holes at each end for this purpose. In the surgical procedure, the bone is reamed out and the pin inserted along the central portion. However, once the pin is lodged in the bone, a problem arises. How does the surgeon know where to drill the fastener holes in the bone so that they will line up with the preestablished holes in the pin, thus permitting insertion of the fasteners? For the proximal end of the pin, that is, the end nearest the point of insertion, a jig may be fastened to the exposed end of the pin. The jig extends along the bone and positions aiming sleeves that provide the necessary guide to the drill. However, the problem is more difficult for the distal end of the pin, that is, the end buried in the bone. Jigs connected with the pin have been used to aim at the distal perforations or bores in the locking pin. However, due to the curved shape of bones, such as the femur, and the danger that the pin might twist during setting of the pin, the known device is not well suited. DISCLOSURE OF THE INVENTION The fundamental object of the invention is thus to provide an aiming device for pin or nail setting at the distal end of the pin wherein the aiming procedure can be made in a rapid manner, surely, and without complications. This problem is solved such that socket means for the aiming sleeve is attached to a housing for an X-ray source and positioned at a distance from the exit window of the ray source and substantially coaxial to the main beam path of the ray source. The aiming procedure using the invention starts with placing the X-ray source, i.e. its beam path, perpendicularly to the longitudinal axis of the pin or nail and centering it with respect to a distal hole or bore of the pin or nail. The X-ray image occuring in receiver means is for example transmitted from the receiver means to a monitor through a multiplier, whereupon the hole of the pin or nail inclusive other parts can be seen on the monitor screen. By changing the position of the aiming device and/or the position of the patient, the image of the hole can be brought into an overlapping position with the socket of the aiming sleeve, so that the axis of the aiming sleeve is coaxial with the axis of the hole. After making an incision, the aiming sleeve for the femur or the tibia, is inserted in the socket and moved up to the corticalis and fixed in this position. All the other steps, such as incision, making bores, tightening of the screws and so on can be made by means of the aiming sleeve. It is, in addition, possible to make a check after each operative phase and if necessary to again adjust the aiming device. For mechanical reasons and in order to achieve a simple and suitable adjustment, it is preferred to use a receiving bushing or socket in which the aiming sleeve is slidably received and which can be fixed in selected positions. The socket for the aiming sleeve is fixed to the housing of the X-ray source through an appropriate retaining means, so that it may be placed at a distance from the exit window of the source within the main beam path. A particular embodiment of the invention provides for this reason that the socket for the aiming sleeve is slidably mounted with respect to the housing. The sliding support of the sleeve enables the operator to adjust the desired distance with respect to the leg of the patient. The retaining means for the socket of the aiming sleeve can be designed in any suitable way. An additional embodiment of the invention provides in this respect fo the aiming sleeve socket to be mounted on bifurcated support means and two bushes fixed to the housing to accommodate the fork ends of prongs. By means of the bifurcated support the aiming sleeve socket can be continuously adjusted. In order to maintain the adjusted position of the socket, another embodiment of the invention provides that the housing of the X-ray source arranged thereat has at least one arresting adjusting element that fixes the fork in a selected position. In order to fix the fork on the housing another embodiment of the invention provides on the housing of the X-ray source a bracket carrying the bushes for the fork prongs. In order to have as little obstruction as possible, the fork is fixed on the bottom side of the housing. To facilitate the insertion of the fork, which is preferably made of sterilizeable material, an additional embodiment of the invention provides that the bracket be composed of a base plate connected rigidly to the housing and a bracket plate retaining the bushes and pivotally supported at the base plate. For the insertion of the fork the pivotable bracket plate is pivoted downwards and thereafter pivoted back again to its starting position. So that the plate remains in its working position, another embodiment of the invention provides that on the base plate there is a hand operated locking mechanism and the pivotable bracket plate includes a locking portion that can be brought into interlocking engagement with the locking device. The locking means is suitably designed such that the interlocking portion becomes automatically arrested when the plate is pivoted back into its working position. Other advantageous embodiments of the invention are described below.