MXPA00003315A - Bone fixation device - Google Patents

Abstract

A bone fracture fixation device comprises an intramedullary nail (1) with a distal end (2), a proximal end (3) and a central axis (4). An intramedullary nail head (10) can be set and fixed on the proximal end (3) of the intramedullary nail (1) and has at least one bore (11;13) which extends transversely to the central axis (4) for form-fittingly receiving at a stable angle bone fixation means (12, 14). At least one threaded bore (8;29) is provided between the distal end (2) and the proximal end (3) of the intramedullary nail (1).

Description

DEVICE FOR FIXING BONES DESCRIPTION OF THE INVENTION The invention relates to a device for fixing bone fractures in accordance with the preamble of claim 1. In the case of the fractured head of the tibia, it is a question of reconstructing a fractured surface bearing loads. The tibia is the only bone in the body that presents a continuous transition of a cubic bone with a joint surface that supports loads to a tubular bone. In the area of the head of the tibia, the load forces that act axially on the proximal articulation surfaces of the tibia are continuously transformed into a load for a tubular bone. For these circumstances there are still no particular implants. An ideal load support for the head of the tibia should satisfy these special circumstances. The state of the art knows various straight plates and angulated plates as well as intramedullary blocks for the treatment of fractures of the head of the tibia. However, all these implants are designed for young and strong bone, since until now it was primarily to treat fractures caused by accidents (accidents in sports, work and transit). Conditioned by the increasing age of the population, and also by the activity of the older population, it is now necessary to also deal with fractures of porous bones to a greater extent. Osteoporosis represents a growing problem in the health sector. The proportion of people older than 80 years increases remarkably, so that fractures with osteoporosis also increase markedly; in this, fractures of the proximal and distal tibia, of the proximal and distal femur, but also of the proximal humerus and the distal forearm, stand out. Current osteosynthetic implants belonging to the state of the art are only unsuitable for use in porous bones with their thin corticalis and spongiosa qualitatively worse. Correct replacement is often difficult in the case of a thin corticalis. The fixation or restraint of the fracture, which is replaced, often presents considerable problems in the porous bone because the osseous anchoring of the implants is difficult. But for the treatment of proximal tibial fractures, and in particular fractures of the head of the tibia, there are no really optimized implants, neither for young and strong bones nor for porous bones. There are only several lightly modified plates and intramedullary nails. All the plates are fixed to the bone with screws after the replacement of the fracture. As non-axial implants, these plate systems are always exposed to a certain bending stress. With plates and screws it is not possible to achieve, or only in a very limited way, a stable angular fixation that is required in the case of fractures of joints or fractures near the joints. Intramedullary nails can not be applied «in the case of fractures of the joints and only in a limited way in the case of fractures near the joints. From W094 / 13219 a modular intramedullary nail is known which is constituted by an intramedullary nail and a sleeve that can be telescopically drilled on its proximal end. The cap remains axially slidable so that the bone fixation element can pass both through openings provided in the cap as well as an oblong hole in the intramedullary nail. With this it is impossible to achieve a secure fixation between the intramedullary nail and the cap. The bone fixation element can not be pulled angularly stable to the socket. EP-B 544,868 discloses a bone screw with a threaded screw head, the thread pitch of the thread of the screw head being smaller than that of the thread of the screw rod. This differential screw is provided to be screwed directly into a fractured bone; there is no use at all with which the screw head is screwed to an implant. EP 0 118 778 discloses a locking pin with an elongated hollow body that at the front end is rounded and has an insertion end with a widening. In addition, at least two transverse bores are provided in the body to receive a bone screw in each case. The profile of the section of the body is annularly closed on its circumference. EP 0 447 824 FRIGG discloses another locking pin made of solid material. In this case the proximal end part has an area of the section configured in trigonal form in both the anterior and posterior half, and in its entirety is approximately square. The distal end part has an area of the section that in the anterior half is approximately trigonal and in the posterior half it is approximately hemispherical. This special construction of the intramedullary nail according to the invention produces on the one hand a high stability of rotation in the spongy proximal part of the tibia and on the other hand an adaptation as optimal as possible to the geometry of the medullary cavity in the distal corticoid part of the tibia. Another locking nail is known from DE 43 41 677 SCHROEDER. The nail body is rounded at the anterior distal end and has a proximal insertion end. Transverse holes are provided in the nail body to house a bone screw in each case. In addition, the nail body is made of solid material and has a funnel-shaped opening on at least one side of each transverse bore. It is in this that the invention wants to remedy. The invention is based on the problem of creating a bone fixation device with which the following fractures can be optimally treated also in the case of osteoporosis: 1. Tibia fractures of the tibia - Fractures of the proximal shaft of the tibia ipsilateral fractures of the head of the tibia < 2 . Fractures of the head of the tibia Fractures of the medial and lateral tibia plateau - Fractures of the dorsal joint parts of the proximal tibia Fractures ipsilateral of the tibia rod 3. Analogous fractures in the distal and proximal femur (and to satisfy this the following conditions): - it offers a stable fixation, even in the case of osteoporosis, through an optimal biomechanical (axial) position, and a stable angular fixation, as well as a large seating surface between the bone and the implant, - simple and safe in its management (for example, by -eventing a posterior access in the case of dorsal-proximal fractures of the head of the tibia; it is applicable for the left and right tibia, as well as for the medial and lateral plateaus of the Furthermore, the invention is based on the problem of grabbing a bone fragment by means of a bone screw extending transverse to the axis of the intramedullary nail, and being able to attract it to the nail. intramedullary, whereby an interfragmentary pressure can be generated. In general, the invention solves the imposed task with a device having the features of claim 1. An intramedullary nail at the head of the tibia is biomechanically found in an optimal position as an axial implant. The intramedullary nail is fixed by bolts in the medullary space of the tibia. If the intramedullary nail is additionally attracted against the ventral corticalis, then the seating surface between the porous bone and the implant is increased, thereby reducing the contact forces. With bolts screwed in an angularly stable manner to the intramedullary nail the bone of the tibia can be reconstructed. The intramedullary nail with screws of the head of the tibia screwed in an angularly stable manner biomechanically adopts the function of an intramedullary angular plate. In this way, the advantages of an axial implant (intramedullary nail) are combined with the advantages of an angularly stable implant (angle plate). Contrary to known bone synthesis systems, in the case of the implant according to the invention, the load support is first introduced in a biomechanical position and anchored to the intact bone. The fracture is then replaced against this firmly anchored load carrier and is fixed in an angularly stable manner. Because the fixation of the fracture in an angularly stable manner takes place in the firmly anchored load carrier, bone quality (porosity) is of secondary importance.

A preferred development of the invention consists in providing the intramedullary nail both in the area of the distal end and also of the proximal end, at least one bore extending transverse to the central axis, in order to be able to block the intramedullary nail. The head of the intramedullary nail has a bore, conveniently at least two or more bores whose axes can be parallel or divergent, and in which a threading can be provided. The bone fixation element to be inserted into the head of the intramedullary nail is preferably a bone screw with threads on the head and the screw shaft, the bone screw preferably having an uninterrupted central channel. The thread near the head of the screw preferably has a smaller pitch than the thread of the screw rod. Preferably between the two differential threads an unthreaded segement is provided. In this way it is possible to attract a bone fragment grasped with this screw in order to produce an intrafragmentary pressure. The point of this bone screw is preferably self-tapping self-tapping. This simplifies the course of the operation. Instead of the bone screw, a blade or plate can also be used with bone fixation elements. The blade or plate is preferably split or drilled with a thread in order to accommodate bolts or screws. In this way it is possible to achieve an angularly stable intramedullary screwdriving. The invention and the improvements of the invention are explained below in more detail on the basis of the partially schematic representations of several exemplary embodiments. They show: Figure 1 a longitudinal section through the device according to the invention implanted in the bone, with an intramedullary nail head for screws of the head of the tibia; 2 shows an enlarged perspective view of the head of the intramedullary nail of FIG. 1, rotated through 90 °; 3 shows an enlarged perspective view of the screw for the head of the tibia of FIG. 1; 4 shows a perspective view of a device according to the invention implanted in the bone, with an intramedullary nail head for a cruciform intramedullary plate for the head of the tibia; 5 shows a perspective view of an intramedullary nail head with a cross-shaped groove; 6 shows a perspective representation of a device according to the invention according to FIG. 4 implanted in the bone in its final condition; and Figure 7 a perspective representation of a bone plate of the head of the tibia, for a variant of the device according to Figure 4. The device according to the invention shown in Figure 1 comprises a known intramedullary nail 1 with a distal end 2, a proximal end 3, and a central axis 4. The intramedullary nail 1 is slightly curved, and the distal end 2 has a blunt configuration. In the region of the distal end 2, two bores 6 are provided which extend transverse to the central axis 4, into which locking bolts can be inserted. A threaded bore 8 extending in the anterior-posterior direction (corresponding approximately to the plane of the drawing) is provided between both bores 6, which serves to accurately position the intramedullary nail 1 within the medullary space of the bone. proximal end 3 two holes 7 are provided which extend transverse to the central axis 4, inside which other locking bolts can be inserted. With a third bore 29 threaded in an anterior-posterior direction the intramedullary nail can be attracted to the ventral corticalis 31. This allows a precise placement of intramedullary nail 1 in the medullary space. As shown in more detail in figure 2, the head 10 of the intramedullary nail has the shape of a cylinder cut obliquely, the oblique surface 23 being crossed by three adjacent holes 11 which may have parallel or divergent axes. In all the bores 11 of the head 10 of the intramedullary nail a thread 15 is provided to be able to receive bone screws 12 (FIG. 3) having a screw head 16 with a corresponding thread 7. The bone screws 12 have a screw shank 18 with two threaded segements 19 and 17. The pitch of the thread 19 at the tip 20 of the screw is greater than that of the thread 17 near the head of the screw. The bone screws 12 also have an uninterrupted central channel 22 through which guide wires can be pushed. Between both threads 17; 19 an unthreaded segment 21 is provided. The tip 20 of the screw has self-tapping and self-cutting configuration. Other holes 26, 27 are provided on the oblique surface 23 in order to be able to detachably fix the usual pointing mechanisms of the intramedullary nail. As shown in Figures 1 and 2, the head 10 of the intramedullary nail can be mounted with its cylindrical bore 33 on a correspondingly cylindrical pivot 32 of the proximal end 3 of the intramedullary nail 1. In the pivot 32 longitudinal grooves or grooves 24 may be provided which fit into corresponding elements (grooves or grooves) inside the bore 33, in order to secure both parts 1, 10 against rotation. The final axial fixation of both parts 1, 10 can also be effected by introducing a fixing screw into the transverse bore 35 of the head 10 of the intramedullary nail. In another embodiment of the invention shown in FIG. 4, a cruciform blade 14 having a slot 24 for receiving bolts or screws is provided as a bone fixing element in place of the bone screw 12. To house this blade 14 the head 10 of the intramedullary nail is also modified with respect to the embodiment according to figures 1 and 2. As shown in figure 5, the head 10 of the intramedullary nail for this variant is provided instead of the three bores 11, a single cruciform groove 13 admitted at a certain depth within the oblique surface 23. A further modification in this embodiment of the head 10 of the intramedullary nail is that a pivot 38 is provided instead of a cylindrical bore 33 (Figure 2); correspondingly the associated intramedullary nail 1 has a perforation 39 instead of a pivot. The cruciform blade 14 can slide into the cruciform slot 13 until its head 25 is flush with the oblique surface 23, so that the position shown in Fig. 6 is reached. Instead of the blade 14 one can also use a bone sheet 36 - shown in figure 7 - which has threaded bores 37 which can be distributed in the sheet 36 in a different manner. The head 25 has the same configuration as that of the blade 14, in such a way as to guarantee an angular and stable insertion of the bone plate 36 into the cruciform recess 13 (FIG. 4).

Claims (14)

1. CLAIMS 1. Device for fixation of bone fractures comprising an intramedullary nail with a distal end, a proximal end and a central axis, where A) at the proximal end of the intramedullary nail an intramedullary nail head is provided that has at least a bore or slot extending transverse to the central axis for the holloWly stable and shapely engaging housing of the associated bone fixation elements; and that B) at least one threaded bore is provided in the area of the distal end, this device being characterized by the fact that C) as bone fixing elements the device further comprises at least one bone screw with a screw head and a threaded rod shank; and that D) the head of the screw has a thread whose pitch is smaller than that of the thread of the screw shank. Device according to claim 1, characterized in that the head of the intramedullary nail is configured as a separate element that can be removably mounted and fixed on the proximal end of the intramedullary nail. 3. Device according to. Claim 1, characterized in that the head of the intramedullary nail is formed in one piece with the intramedullary nail. Device according to one of claims 1 to 3, characterized in that the intramedullary nail has at least one bore extending transversely to the central axis in the area of the distal end. Device according to one of claims 1 to 4, characterized in that the intramedullary nail has at least one hole extending transversely to the central axis in the region of the proximal end. Device according to one of claims 1 to 5, characterized in that at least three holes are provided in the head of the intramedullary nail. Device according to claim 6, characterized in that the bores have divergent axes. Device according to claim 6, characterized in that the bores have parallel axes. Device according to one of claims 1 to 8, characterized in that the bore of the head of the intramedullary nail is threaded. Device according to claim 1, characterized in that the bone fixing element is a bone screw with a threaded screw head, wherein a central uninterrupted channel is preferably provided in the bone screw. Device according to claim 1, characterized in that an unthreaded rod segment is provided between both threads. Device according to one of claims 1 to 11, characterized in that the tip of the bone screw has self-drilling and self-cutting configuration. Device according to one of claims 1 to 12, characterized in that the bone fixing element is a blade or a sheet that preferably has a slot or a threaded hole for receiving bolts or screws. Device according to one of claims 1 to 13, characterized in that another threaded bore is provided in the area of the proximal end.