DE4332230C2 - Endoprosthesis, especially a hip endoprosthesis - Google Patents

Description

The invention relates to an endoprosthesis according to the Preamble of claim 1. In particular, here is a Hip endoprosthesis described to the patient then always is implanted if he is traumatized, physiologically, arthrotically or otherwise changed Hip joint suffers.

For implanting hip endoprostheses exist in essentially two process groups. On the one hand is this is the group of cementing processes in which a special bone cement produced, usually a polymethyl methacrylate, for a quick bond between the prepared marrow area and the prosthesis. On on the other hand, cementless processes are known which are associated with With the help of press fits, positive and frictional connection between bones and make prosthesis. In the latter process, the Prosthesis surface mechanically prepared so that a rough surface with craters and scratches arises or it becomes a three-dimensional surface structure in the form of Sintering, casting structures or plasma coatings generated. The can then be attached to these surface structures Partially grow bones. All of these procedures have Commonality that the implantation of the prosthesis The medullary canal of the bone has been largely cleared and must be drilled out, being measured on the Primary disease, many times more healthy tissue must be sacrificed. Since the invention is a Hip endoprosthesis that is cementless with the Thigh bone is interested here especially the related state of the art.  

DE 28 54 334 B2 describes a hip endoprosthesis cementless implantation described in a hole in the Femur is used. The prosthesis points a hollow shaft with cross holes, the Shank from the surgeon with cancellous substance which is replenished over time by the Cross holes can grow together with the bone. It will also mentioned a pressure compensation hole, which through the Reduce the insertion of the prosthesis into the internal bone pressure should.

In documents DE 37 15 000 C2, DE 31 20 147 A1, DE 87 12 607 U1 and DE 90 06 893 U1 are also used throughout Hip endoprostheses for cementless implantation described, which have a hollow shaft with cross holes for Growth of spongiosa substance is provided. At all mentioned hip endoprosthesis is before the final Implantation of a large-scale marrow preparation in the Thigh bone required. In detail, the Medullary canal cleared, drilled out and equivalent to later denture rasped positively. It will thereby increasing particles (blood, fat, osteoblasts, Koagel, Air, etc.) that are highly thromboactive. The extreme pressure build-up in the bone through the inserted Instruments and finally also through the prosthesis itself leads to the resulting medullary canal particles through the Vessels of the Volkmann canals from the interior of the market to the outside are directed to the periosteum. Because the peripheral Venous system on the femur almost an entire vein system has a direct connection to the heart because of the Pressure in connection with the medullary canal particles Thromboembolism is a risk.

DE 39 02 775 C2 already describes an upper femoral endoprosthesis with an insertion direction of thinning, the tube of the thigh bone, elastically deformable, hollow shaft from perforated slats and a joint head with neck, connected to the shaft. It is provided that the slats individually in the longitudinal direction are arranged, are united on the joint head side and themselves circumferentially to a circular or oval Add cross-section without connection. The slats should can be made so thin that they are in the Allow bone marrow to drive in. As a result, the cavity of the shaft immediately after installing the Prosthesis is filled out of the bone marrow and over the Perforations soon resulted in an intimate ingrowth. Around to bring about the described adjustment, should arranged around the circumference at least three slats and two will continue to be each other opposite stiffening slats recommended. It will aspired to be inside the stem of the prosthesis a new bone builds up, with the lamellae only one thin coating, as it were a lost formwork for the to form new bones. Such Thigh joint endoprosthesis has a comparative have complex shapes, and the intended Aus design as a lost formwork with cutting-like thin formation of the slats represents a specialized Construction with special demands on the Patient.

The object of the invention is to provide an endoprosthesis, in particular to provide hip endoprosthesis (HEP), the Features the disadvantages described above for the patient and minimize the operator's workload.  

The solution to the problem is characterized in claim 1. The Sub-claims relate to advantageous Refinements and training.

The stem of the prosthesis is made according to the other Embodiment of the invention with several axial bores provided and overall designed like a cutting tube, thus direct impact into the medullary canal of the Femur becomes possible.

To avoid the intra-medular pressure that arises during implantation, which according to measurements by ULRICH, WÖRSDÖRFER and HEINRICH (in "Orthopedics and Related Sciences", Vol.2 / 1991) of 2 mm Hg can rise to over 3800 mm Hg (5 bar), is the prosthesis with a system from Provide cross holes.

There is a plan at the proximal end of the prosthesis designed face to allow the impact lichen.

The advantages are in particular that the number of Work steps are reduced to a minimum, none large-scale marrow preparation requires more at all no healthy cancellous bone structure has to be sacrificed, none Medullary canal particles are released as well as all pressures the tube system can be derived to the outside.

The invention will be exemplified by the following Described drawings. Show it

Fig. 1 is a longitudinal sectional anterio-posterio,

. Figure 2 shows the medial-lateral view;

Fig. 3 is a view anterio-posterio;

FIG. 4 shows the enlarged section AA according to FIG. 3;

Fig. 5 shows the enlarged section B-B of FIG. 3.

The prosthesis 1 comprises according to FIGS. 1 to 3 three main sections, namely, the distal shaft 2, the proximal end 3 and the cone extension 11. A continuous axial bore 10 penetrates the distal shaft and the proximal end.

The distal shaft 2 is cylindrical in shape and has a hollow cross section according to FIG. 4. The shaft is from its lower shaft end 7 to the transition region (approximately in the region of the distal third) into the proximal end 3 , preferably with four slots 16 offset by 90 ° Mistake. To realize the cutting tube-like function of the shaft, the shaft end 7 tapers conically on its inside with a half opening angle of approximately 20 °.

Starting from the transition area in the middle of the entire prosthesis, the prosthesis widens towards the proximal end. A conical extension 11 for placing a joint ball extends at an angle of approximately 45 ° to the shaft axis (CCD angle 135 °). The prosthesis collar extends at an angle of approximately 55 to 60 ° with respect to the axis of the through axial bore 10 on one side of the prosthesis, the axes of the conical attachment, the collar and the through axial holes lying in one plane (see FIGS . 2 and 3). . The angles mentioned are to be adapted to the individual CCD angle values of the respective patient.

The side S of the prosthesis facing away from the cone shoulder 11 has a rectilinear contour K, while the contour on the side of the prosthesis facing it has an arcuate shape. The collar area protrudes on the side facing the shaft end 7 , so that a semi-ring-shaped stop surface 13 is created, which later lies against the thigh bone. There is a tapered transition area V between the cone shoulder 11 and the collar area 12 , which limits the area available for the interference fit between the cone shoulder and the joint head. On the side facing away from the collar area 12 , this transition area merges into the flat striking surface 4 , which is penetrated vertically by the axis of the continuous axial bore 10 , so that the striking forces when driving the prosthesis into the bone marrow are as good as possible with regard to the cutting action of the cutting-tube-like features, the cutting edges of which the direction of the axis of the axial bore 10 are oriented, can be implemented.

To increase the cutting tube-like effect, two additional axial bores 8 are made in the described embodiment of the invention in the proximal end on the side of the conical attachment (see FIG. 1). The widening of the prosthesis on this side takes place in such a way that correspondingly sharp edges 9 form. The axial bores also serve the purpose of being able to absorb cancellous substance when driven in, which displaces a not so large amount of this substance and thus reduces the pressure build-up. The wall thicknesses between the axial bores and between the axial bores and the outer walls of the prosthesis are, for. B. 3-4 mm. Furthermore, in order to improve the cutting action and reduce the displacement effect when the prosthesis is driven into the bone marrow according to FIGS. 3 and 5, depressions or grooves 14 on the front and back of the proximal end 3 down to the distal shaft 2 are incorporated.

In addition to the axial bores, the prosthesis contains a system of cross bores. In particular, there are the transverse bore 5 , which connect the axial bores 10 and 8 to the outer surface of the prosthesis, and the intermediate transverse bore 6 , which connects the axial bores to one another, and the transverse bore 15 , which is not connected to any of the axial bores, but forms a channel between the front and back of the proximal end 3 . This system of holes enables pressure relief during impact as well as subsequent bone and cancellous bone removal.

To ensure optimal biocompatibility as well one and also the required strength is considered Material preferably a titanium forged alloy used. This becomes the optimal cement-free Bone integration both in the cavities and outside provided with an appropriate bioactive coating, preferably with a pure titanium hydroxyl apatite Coating.

Claims (10)

1. Endoprosthesis, in particular a hip endoprosthesis with a distal and proximal end and a hollow shaft for the ingrowth of spongiosa substance, the prosthesis having a cutting-like distal shaft for driving into the bone marrow, characterized in that the prosthesis in addition to a continuous axial bore ( 10 ) has at least one has additional axial bore ( 8 ) and the outer contour of the shaft is designed such that the outer mouths of the additional axial bores ( 8 ) form as sharp as possible edges ( 9 ) which act as cutting edges. 2. Endoprosthesis according to claim 1, characterized in that the prosthesis from the distal to the proximal end Connection with lateral cutting edges expands. 3. Endoprosthesis according to claim 1 or 2, characterized in that the distal shaft ( 2 ) is designed like a cutting tube. 4. Endoprosthesis according to one of the preceding claims, characterized in that the proximal end ( 3 ) has a flat striking surface ( 4 ) so that the prosthesis can be driven directly into the medullary canal with the aid of a striking tool. 5. Endoprosthesis according to one of the preceding claims, characterized in that axial bores are connected via transverse bores ( 5 ) to the outer surface of the prosthesis. 6. Endoprosthesis according to one of the preceding claims, characterized in that the axial bores are interconnected by intermediate transverse bores ( 6 ). 7. Endoprosthesis according to one of the preceding claims, characterized in that the distal shaft ( 2 ) has a cylindrically shaped hollow cross-section which tapers conically at the inside of the shaft ( 7 ) on its inside. 8. Endoprosthesis according to one of the preceding claims, characterized in that the prosthesis shaft has at the distal end in the region of the distal lower third in the longitudinal direction, open at the distal end slots ( 16 ). 9. Endoprosthesis according to one of the previous ones Expectations, characterized, that the material is a titanium forged alloy. 10. Endoprosthesis according to claim 9, marked by a bioactive coating made of pure titanium hydroxyl apatite.