DE102004051431B3 - Meta-diaphysiar end prothesis for artificial hip joint has support whose outside edge is covered with a meshed net structure with smooth surface at distal end for laying on femur - Google Patents

Abstract

The prothesis has a support (1) which can be implanted in the upper femur underneath the trochanter. An adapter (3) to take an artificial hip ball (4) can be connected to its proximal end (2). The outside edge of the support is partly covered with an open-meshed three-dimensional net structure (6) whose distal area (7) has a smooth surface to lay on the lateral inner corticalis in the diaphysiar area of the femur.

Description

The The present invention relates to a metaphyseal endoprosthesis for an artificial one Hip joint.

For injuries in the hip joint area, efforts are made to retain as much natural bone material as possible. Therefore, with relatively small lesions, such as hip joint necrosis, it appears inappropriate to provide replacement for the then resected joint ball by resecting large areas. Usually then so-called long-stemmed endoprostheses are used. In the case of such damages, which nevertheless affect the patient, so-called femoral neck endoprostheses are increasingly used for this reason, in which the prosthesis stem lies only in the metaphysis and the epiphysis. The use of such an implant, as is known for example from the EP 0 878 176 A2 , allows, in the case of complications after a long period of time, the withdrawal to the already mentioned and known long-stemmed endoprostheses. In the implantation of the femoral neck endoprosthesis from the outset a lower resection of the femoral neck is made than is the case with the implantation of a long-stemmed endoprosthesis. In the event of replacement becoming necessary, the remainder of the femoral neck can now be resected to the extent that it would be from the outset for implantation of a long-stemmed endoprosthesis, thereby extending the endoprosthetic restoration of the endoprostheses by one cycle. However, damage such as head necrosis does not always justify such a cautious approach.

Therefore, according to the DE 102 18 801 B3 a joint cap implant has been proposed, in which application the resection can be minimized during implantation, whereby the head damage can nevertheless be eliminated. The cap implant consists of a cap reproduced in the shape of the joint ball with an integrally formed plug-in cone projecting from the pole region to the concave open side as well as a fixation aid circulating inside the cap. The cap is set after preparation of the natural ball joint head by milling on the remaining residual head. For this purpose, after the milling of the natural condyle, a bore is made in its pole region into which the conical plug can be placed.

The use of the endoprostheses mentioned is to be repeated on the basis of resection images of the femur on the basis of 1 be 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 remains essentially as a whole. Only the ball joint head has been shaped by a 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 the EP 0 878 176 A2 , the so-called cut denture. Here the natural ball 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-stemmed endoprosthesis. It can be clearly seen that the femoral neck and, of course, the natural ball joint head has been completely resected.

Now There are indications where the choice of the most appropriate Endoprosthesis is not easy. Here patient-individual play space conditions a role but also a possible one Uncertainty on the part of the patient, who does not care about the Specifications of the surgeon for the behavior after the operation holds, such as a Week bed rest before stress on the hip joint. Especially in the implantation of a femoral neck endoprosthesis is the initial stability Limited in the first days after surgery.

In such patients and indications is a resection picture according to 2 he wishes. This resection picture is a compromise between the resection pictures according to the 1b and 1c , A remainder of the femoral neck is thus preserved.

A hip joint endoprosthesis, which deals with the outlined theme, is known from the DE 297 05 200 U1 , This is an endoprosthesis is described, whose stem shape allows a great deal of freedom in the choice of the resection length of the femoral neck, since the stem can be more or less inserted into the intramedullary space of the femur before its lower end by striking the cortical bone of the diaphyseal or metaphyseal area that sets a limit. However, the insertion depth is determined from the outset by a so-called neck support or collar, which lays against the resection of the residual thigh neck. This speaks in advance of a cemented implantation, even if the stem surface is formed for an intimate connection with the natural bone tissue or is roughened or provided with a hydroxyapatite coating. This is sufficient for a cementless fixation of the pedicle in the femur. The stability of the seat in the intramedullary space is impaired.

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

Is solved this task by a meta-diaphyseal endoprosthesis, the one cementless in the upper part of a femur below the trochanter majors implantable stem has, with its proximal end an adapter for holding an artificial Joint ball is connectable, the stem outside partially, namely in proximal region with an open-meshed three-dimensional spatial network structure is occupied. in that regard, these characteristics are consistent with the characteristics of mentioned cut prosthesis. However, according to the invention Furthermore provided that the stem in the distal region has a smooth surface for Attachment to the lateral cortex in the diaphyseal area of the femur.

Opposite the Cut-prosthesis does not show the endoprosthesis according to the invention which is directed to caudal, up. The reduction is predominantly instead of due to the introduction of forces into the cortex the abutment of the distal portion of the pedicle to the internal cortex in the diaphyseal Area. The endoprosthesis according to the invention is sufficient so further down into the medullary canal of the femur compared to the Cut prosthesis, in which the reduction primarily in the field of already mentioned stage takes place, into the cancellous bone.

by virtue of the open-mesh three-dimensional in the proximal area Raumnetzstruktur the endoprosthesis according to the invention is implanted without cement, there in this spatial network structure and through it bone trabeculae grow in and so on a long-term stability to care.

According to one advantageous development is provided that the stem in the proximal Region oval in cross section and oval in the distal region is, the transition from the egg oval to the oval cross-section runs steadily. Latter feature ensures that there are no steps in the stalk These Continuing education ensures that the endoprosthesis form-fitting sitting in the medullary canal. It is optimally the course of Adam's Bow adapted.

According to one Yet another advantageous embodiment is provided that in distal portion of the stem provided a coupling device is to which a stem extension part with a smooth surface can be coupled. By coupling a stem extension part becomes the contact surface the endoprosthesis on the lateral inner cortical increases, causing the contact pressure is reduced under load. In practice, can be provided that the endoprosthesis with a whole number different long stem extension parts is delivered so that the surgeon during the surgery one after patient-specific requirements suitable stem extension part choose can.

According to one special training is provided that the longitudinal axis of the distal portion of the pedicle and the longitudinal axis of the proximal portion of the stem an angle α im Range of 145 ° <α <160 °. This Angle corresponds essentially to the CCD angle, ie center-collum diaphyseal angle or collodiaphysis angle. This measure serves to optimize the Form closure of the endoprosthesis in the medullary cavity.

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

3 FIG. 2 schematically the endoprosthesis according to a first embodiment, FIG.

4 the endoprosthesis according to 3 , shown schematically as unloaded 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 region 5 , distal to its distal region 7 followed. The distal area 7 is opposite the proximal region 5 bent. The longitudinal axes of the two areas 5 and 7 include an angle α in the range of 145 ° to 160 °.

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

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

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

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

The distal area 7 settles, as in 4 indicated to the internal cortex 1 of the femur 11 at. This contact is followed by the introduction of the forces exerted by the hip joint under load into the internal 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 8th shown as an internal 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 well as the distal area 7 of the stem 1 , By extending the stem 1 through the stem extension part 9 the abutment surface is attached to the inner cortex 10 increases, whereby the surface pressure is reduced 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 pedicle implantable without cement in the upper area of a femur below the greater trochanter ( 1 ), with its proximal end ( 2 ) an adapter ( 3 ) for receiving an artificial joint ball ( 4 ), wherein the outside of the stem is partially, namely in the proximal region ( 5 ) with an open-mesh three-dimensional spatial network structure ( 6 ), whose distal region ( 7 ) is formed with a smooth surface for engagement with the lateral inner cortical bone in the diaphyseal area of the femur. Endoprosthesis according to claim 1, in which the stem ( 1 ) in the proximal region ( 5 ) in cross section egg oval and in the distal region ( 7 ) is formed oval, wherein the transition from the egg-oval to the oval cross section is continuous. Endoprosthesis according to claim 1 or 2, wherein 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 region ( 5 ) of the stem ( 1 ) include an angle α in the range of 145 ° <α <160 °.