DE2645101A1 - Hip prosthesis with cup-shaped ball socket - with self-tapping thread interrupted by upwards tapering free grooves - Google Patents

Abstract

Hip joint internal prosthesis comprises a ball cup-shaped joint socket to be implanted in the acetabulum (3). In the lower region of the outer wall of the socket is a self-tapping thread (1) which is interrupted by four or more free grooves (2) which taper upwardly. Pref. there are four or more vertical blind holes (4) in the edge of the joint socket. The socket does not need to be made of metal or plastic, and the prosthesis cannot weaken or pierce the cortex of the acetabulum facing away from the operating area. The socket also facilitates surgical procedures during implantation. The height of the cup-shaped socket can be slightly less than its radius, which increases the pivot.

Description

Hip joint endoprosthesis part

The invention relates to a hip joint endoprosthesis part with in the human acetabular bone to implant the acetabulum. These sockets have so far been made of metal or plastic and are either with Bone cement or anchored in the acetabular bone by screwing. they have the Disadvantage that they often weaken or weaken the cortex of the acetabular bone. even partially pierced, which of course the entire hip joint prosthesis endangered, if not completely unusable. Since acetabular cup endoprostheses usually are implanted in connection with femoral neck endoprostheses as total endoprostheses, lead the - different material combinations metal-plastic because of the material-related high coefficient of friction inevitably leads to inadmissibly high wear rates. the The resulting abrasion particles are partially toxic, but lead in any case they lead to inflammation in the zones of the bone adjacent to the prosthesis and thus to easing.

The invention is based on the object of a hip joint endoprosthesis part to create the socket of which does not have to be made of metal or plastic which is designed in such a way that it covers the cortex of the facing away from the surgical field Acetabular bone in which this socket is to be implanted, on none The case can weaken or even pierce. The joint socket is also intended to be a simplification of the operative measures during the implantation.

According to the invention this is achieved in that the joint socket a has spherical shape and in the lower part of its outer jacket with a self-tapping thread is provided, which goes up by four or more rejuvenating free minutes is interrupted.

The outer jacket of the socket joint according to the invention runs approximately equidistantly to the inner spherical cap, which corresponds approximately to a hemisphere and its diameter again by the diameter of the joint heads given for anatomical reasons is fixed. It has been found that when using high-strength ceramics the required wall thickness of the joint socket leads to a low overall height of the socket, with an implanted joint socket the most extensive intactness of the above lying cortex of the hip bone guaranteed. The height of the dome can be something be less than the radius thereof. This increases the swivel range of the in this The joint socket of the joint head is larger.

The spherical shape brings the further advantage of a machining technology optimally achievable spherical conformity of the cavity of the acetabular bone and the shell of the implant with it. This in turn results in an improved Pressure distribution on the hip joint socket, the local stress peaks and thus Inappropriate tissue overloads as well as the tissue irritation caused by this, which can lead to bone loss and thus loosening of the implant.

Due to that lying within the spherical surface, rising with it downwards Thread depth pressed in and free minutes tapering upwards through vertical interrupted thread is an improved self-tapping effect that also then to a secure, low-tension seat of the joint socket within the acetabular bone leads when the surgeon, for example, out of time constraints (spinning heart failure of the patient) do not pay attention to the final accuracy when creating the bone cavity can. The work of the surgeon is also facilitated by the fact that the inventive The joint socket takes up less space than conventional acetabular cups.

According to a further idea of the invention are in the joint socket edge four or more vertical blind holes are provided, in which a corresponding four or more protruding pins equipped tool engages, by means of which the socket can be screwed into the recess of the acetabulum. The absolutely slip-proof tool engagement created in this way contributes to error-free operation Procedure of the operation at.

The socket according to the invention can be according to its novel Shape design, apart from the stated advantages, without difficulty a ceramic material without strength-increasing inserts (so-called full ceramic) produce; the material stresses in different load cases of the with it built-up hip joint endoprostheses are so far below the maximum values that that a previously unattained safety factor can be adhered to.

In the drawing, an embodiment of the invention is shown, on the basis of which this invention will be explained in more detail below. They show: Fig. 1 shows a partial sectional side view of a joint socket according to the invention, FIG. 2 shows the Top view, FIG. 3 the bottom view of the same and FIG. 4 the longitudinal section through the outer part of an acetabular bone with an implanted joint socket according to the invention.

According to Fig.l, the joint socket is in the lower region of the outer jacket the self-tapping thread 1 incorporated, the circumferential through the four is interrupted by 90 ° offset from each other free minutes 2, which are shown in FIG taper upwards. The one not covered with thread 1 (only indicated in Fig. 2) Part of the outer shell of the joint socket is spherically arched and lies with it Area, as can also be seen in FIG. 4, in a form-fitting manner on the corresponding area of the hollowed acetabular bone 3. From Fig.l it can also be seen that the height H of the dome is smaller than the radius r.

According to Figure 3, four blind holes are in the lower edge of the joint socket 4 incorporated, the engagement of a corresponding number of pins of a allow equipped wrench, by means of which the joint socket screwed into the cavity of the Htiftpfannenkbone 3 largely adapted to its shape earth can.

In Figure 4, the spherical joint head 4 is also the rest second partial prosthesis, not shown, anchored in the femur. It can also be seen from FIG. 4 that the joint socket has a vertical body axis has been used. This position is for the initiation of joint loading in the acetabular bones 3 as well as for the stress on the material of the entire Endoprosthesis particularly cheap. From Figure 4 it can also be seen that the inventive Joint socket with the upper smooth part of its outer jacket fully immersed in the bone material and is located on the overlying cortical zone of the acetabular bone 3 supports.

List of drawing positions 1 thread 2 free groove 3 acetabular bone 4 blind hole

Claims (2)

A n p r ü c h e (i) Hip joint endoprosthesis part with in the acetabular bone joint socket to be implanted, in that the Joint socket has a spherical cap-shaped shape and in the lower region of its Outer jacket is equipped with a self-tapping thread (1) through four or more upwardly tapering free minutes (2) is interrupted. 2. Hip joint endoprosthesis part according to claim 1, characterized in that g e k e It is not stated that there are four or more vertical blind bores in the edge of the joint socket (4) are provided.