DE202004016353U1 - Meta-diaphysic femoral neck implant, comprising specifically shaped pedicle partially covered with net - Google Patents

Abstract

The slightly tapering implant (1) has a wider upper (2, 5) and a narrow lower area (7), both forming an obtuse angle. The upper area (5) has an egg-shaped cross section and is covered with netting (6). The lower segment (7) has an oval cross section and a smooth outer surface for an easy insertion into the prepared bone. A slightly bent adapter (3) can be joined to the upper end (2) in order to add a ball joint (4).

Description

The The present invention relates to a meta-diaphyseal endoprosthesis for an artificial one Hip joint.

at damage in the hip joint area are you trying so much natural Retain bone material as possible. Therefore, it appears with relatively minor damage, such as hip joint necrosis, as inappropriate, a replacement for the then by resection of large areas to create resected joint ball. Then usually come so-called long-stem endoprostheses are used. With such damage that nevertheless affect the patient, For this reason, so-called femoral neck endoprostheses are increasingly coming used where the prosthetic stem is only in the metaphysis and the epiphysis lies. The use of such an implant, as is known, for example, from EP-A-0 878 176, in the event of complications after a long period of wear, the withdrawal the already mentioned and known long-stem endoprostheses. In the Implantation of the femoral neck endoprosthesis is a priori less resection of the femoral neck made than this the implantation of a long-stem endoprosthesis is the case. In the event of the rest of the femoral neck can now be replaced be resected to one extent as from the outset when implanting a long-stem endoprosthesis, whereby the endoprosthetic supply of the endoprostheses by one Cycle extended can be. damage like a head necrosis justify such a careful one Procedure not always.

Therefore, according to the DE 102 18 801 B3 a joint cap implant has been proposed, the use of which can reduce the resection during implantation to a minimum, while the head damage can nevertheless be eliminated. The cap implant consists of a cap modeled on the shape of the joint ball with a molded plug-in cone protruding from the pole area to the concave open side, and of a fixation aid running around the inside of the cap. After preparation of the natural joint ball head, the cap is placed on the remaining head by milling. For this purpose, after milling the natural joint head, a hole is made in its pole area, into which the plug-in cone can be placed.

The use of the endoprostheses mentioned should again be based on the resection images of the femur 1 are explained.

1a shows the resection image of the femur when the mentioned cap implant according to the DE 102 18 801 B3 is implanted. The femoral neck as such is essentially preserved as a whole. Only the ball joint head has been shaped by a milling cutter so that the cap implant can be placed on the rest of the head.

1b shows a resection image as it is generated before using a femoral neck endoprosthesis according to EP-A-0 878 176, the so-called cut prosthesis. Here the natural ball-and-socket joint head has been completely resected, but the femoral neck has been completely preserved.

1c shows a classic resection image of a femur that has been prepared for the implantation of a typical long-stem endoprosthesis. One can clearly see that the femoral neck and, of course, the natural ball joint head have been completely resected.

Now there are indications where the choice of the most appropriate Endoprosthesis is not easy. Individual patients play here space conditions a role but also a possible one Uncertainty on the part of the patient who does not adhere to the Operator's specifications for behavior after surgery persists, such as one Week to maintain bed rest before loading the hip joint. In particular when implanting a femoral neck endoprosthesis is the initial one stability limited in the first days after the operation.

In such patients and indications, a resection pattern is appropriate 2 he wishes. This resection image is a compromise between the resection images according to the 1b and 1c , A rest of the femoral neck is therefore preserved.

task The present invention is a meta-diaphyseal endoprosthesis specify which function as a meta-diaphyseal endoprosthesis in a residual femoral neck Fulfills, but an increased stability across from offers the classic femoral neck endoprosthesis.

This problem is solved by a meta-diaphyseal endoprosthesis, which has a stem that can be implanted without cement in the upper area of a femur below the greater trochanter, with the proximal end of which an adapter for receiving an artificial joint ball can be connected, the outside of the stem being partially, namely in the proximal area is covered with an open-meshed three-dimensional network structure. In this respect, these features correspond to the features of the cut prosthesis mentioned. According to the invention, however, it is also provided that the stem in the distal region has a smooth surface for contact with the lateral inner cortex in the diaphyseal region of the Femurs.

Opposite the Cut prosthesis, the endoprosthesis according to the invention has no step, which is directed caudally. The relief takes place predominantly rather than due to the introduction of forces into the cortex the application of the distal area of the stem to the inner cortex in the diaphyseal Area. The endoprosthesis according to the invention is sufficient so further down into the medullary canal compared to the Cut prosthesis in which the wear is primarily in the area of the already mentioned level takes place, into the cancellous bone.

by virtue of the open-mesh three-dimensional provided in the proximal area The network endoprosthesis according to the invention is implanted without cement, because in this spatial network structure and through it bone trapezoids wax in and so for long-term stability to care.

According to one advantageous development provides that the stem in the proximal The area is egg-oval in cross-section and oval in the distal area is, the transition runs continuously from the egg-oval to the oval cross-section. The latter characteristic ensures that there are no steps in the stem. This Continuing education ensures that the endoprosthesis with a positive fit sitting in the medullary canal. It is optimally the course of Adam's Adjusted bow.

According to one yet another advantageous development is provided that in distal region of the stem a coupling device is provided is to which a stem extension part with a smooth surface can be coupled. By coupling a stem extension part becomes the contact area of the endoprosthesis on the lateral inner cortex, causing the contact pressure is reduced under load. In practice it can be provided that the endoprosthesis is different with a whole number long handle extension parts is delivered so that the surgeon during the operation a Handle extension part suitable for individual patient requirements choose can.

According to one special development is provided that the longitudinal axis of the distal area of the stem and the longitudinal axis of the proximal area of the stem an angle α im Include a range of 145 ° <α <160 °. This Angle corresponds essentially to the CCD angle, i.e. the center-collum-diaphyseal angle or collodiaphyseal angle. This measure serves to optimize the Form closure of the endoprosthesis in the medullary canal.

The Invention is based on exemplary embodiments according to the drawing figures explained in more detail. in this connection shows:

3 schematically the endoprosthesis according to a first embodiment,

4 the endoprosthesis according to 3 , shown schematically in the unloaded state sitting in a resected femur,

5 a second embodiment of the endoprosthesis, and

6 the endoprosthesis according to 5 , implanted in a resected femur.

3 shows the implantable stem 1 the endoprosthesis with its proximal end 2 of the proximal area 5 , on the distal side of his distal area 7 followed. The distal area 7 is opposite the proximal area 5 bent. The longitudinal axes of the two areas 5 and 7 enclose an angle α in the range from 145 ° to 160 °.

The proximal area 5 is with an open-meshed three-dimensional network structure 6 busy.

With the proximal end 2 of the stem 1 is an adapter 3 , shown here as an angled double cone, connectable. The adapter 3 can be an artificial joint ball 4 take up.

Schematic next to the stem 1 are the cross-sections of the stem, once in the proximal area 5 and once in the distal area 7 , As can be clearly seen, the cross section in the proximal area is egg-oval, in the distal area 7 oval. This shape creates an optimal shape closure between the stem 1 and the medullary canal in the femur.

The distal area 7 is not otherwise provided with a spatial network structure. As a result, the threadability of the stem 1 relieved in the medullary canal.

The distal area 7 lies down as in 4 hinted at the inner cortex 1 of the femur 11 on. This contact initiates the forces exerted by the hip joint under load into the inner cortex 10 ,

The 5 and 6 show a second embodiment of the endoprosthesis. However, only the differences from the first embodiment described above will be discussed below.

In the distal area 7 of the stem 1 is a coupling device 8th intended. In the illustrated embodiment, the coupling device is tung 8th shown as an inner bore with thread. With the coupling device 8th is a stem extension part 9 connectable. The stem extension part 9 has a smooth surface, as does the distal area 7 of the stem 1 , By extending the stem 1 through the stem extension part 9 the contact surface to the inner cortex 10 increased, which reduces the surface pressure accordingly.

1

stalk

2

proximal The End

3

adapter

4

joint ball

5

proximal Area

6

Dimensional network structure

7

distal Area

8th

coupling device

9

Stem extension part

10

Innenkortikalis

11

femur

Claims (4)

Meta-diaphyseal endoprosthesis for an artificial hip joint, comprising - a stem that can be implanted without cement in the upper area of a femur below the greater trochanter ( 1 ), with its proximal end ( 2 ) an adapter ( 3 ) to hold an artificial joint ball ( 4 ) is connectable, the handle outside partially, namely in the proximal area ( 5 ) with an open-meshed three-dimensional network structure ( 6 ) is occupied, the distal area ( 7 ) with a smooth surface for contact with the lateral inner cortex in the diaphyseal area of the femur. Endoprosthesis according to claim 1, wherein the stem ( 1 ) in the proximal area ( 5 ) egg-oval in cross-section and in the distal area ( 7 ) is oval, with the transition from the oval to the oval cross-section being continuous. Endoprosthesis according to claim 1 or 2, in which in the distal region ( 7 ) of the stem ( 1 ) a coupling device ( 8th ) is provided, to which a stem extension part ( 9 ) can be coupled with a smooth surface. Endoprosthesis according to one of claims 1 to 3, in which the longitudinal axis of the distal region ( 7 ) of the stem ( 1 ) and the longitudinal axis of the proximal area ( 5 ) of the stem ( 1 ) enclose an angle α in the range of 145 ° <α <160 °.