DE9103574U1 - Kit for a hip joint prosthesis - Google Patents

Description

EFFNER & SPREINE 15 March 1991

Asset Management GmbH
D-IOOO Berlin 33

EF41.G6

Kit for a hip joint prosthesis

Description

The invention relates to a kit for a hip joint prosthesis of the type specified in the preamble of claim 1.

Such kits for hip joint prostheses are known from DE 40 08 563 Al and from EP 0 382 429 A2 and

EF41.G6 Sheet 2

consist of a prosthetic shaft with a neck, a spherical prosthetic head with a blind bore and an intermediate element that can be inserted between the prosthetic shaft and the prosthetic head.
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However, with these kits, only the distance of the position of the center of the joint ball in relation to a fixed point of the center axis of the shaft neck can be changed.

The invention is based on the object of developing the intermediate element in a kit for a hip joint prosthesis of the type mentioned at the beginning in such a way that the center of the joint ball can also be displaced laterally in relation to the center axis of the shaft neck of the prosthesis.

This also makes it possible to easily adjust the CCD angle of the hip joint prosthesis without having to keep a large number of prosthesis shafts with differently aligned prosthesis necks on hand.

This object is achieved with the characterizing features of claim 1.

The invention is based on the knowledge that the position (of the center) of the joint ball can be changed not only by changing the shaft direction by selecting a different shaft with a prosthetic neck running in a different direction, but can also be influenced subsequently by a suitable intermediate piece if it is provided with the measures described here.

EF41.G6 Sheet 3

A particularly advantageous feature of the invention is that with just a few different intermediate elements, an almost infinite number of adjustment options can be achieved in three dimensions by appropriate rotation. In addition, the distance between the center of the joint ball and the prosthesis shaft can be varied using intermediate elements that have different distances.

Now only a small number of simple intermediate elements need to be kept in stock instead of a large number of different shaft prostheses with varying neck shapes. A change or alignment is also possible with an implanted shaft later or during reoperations. In the case of the first implantation, the doctor therefore does not need to take any special care with the final position of the prosthesis, but can concentrate completely on achieving optimal stability of the prosthesis seat. Only then is a geometric measurement carried out and the final position of the joint ball determined and adjusted using the intermediate elements according to the invention.

In addition, the intermediate elements according to the invention can also be used to adapt connections of the joint ball and prosthesis neck that have different dimensions. This is particularly advantageous for cone connections of different standards.

0 The intermediate element according to the invention can be provided either with a through hole or with a blind hole.

EF41.G6 Sheet 4

which is not centric and/or at an angle to the longitudinal axis of the intermediate element.

In a first preferred embodiment of the intermediate element according to the invention, the outer contours of the intermediate element and the blind hole in the intermediate element are conical, so that the intermediate element can be inserted into the corresponding conical hole in the prosthesis head and placed on the conical neck of the prosthesis. The blind hole runs at an angle to the longitudinal axis of the intermediate element, whereby the longitudinal axis of the intermediate element coincides with the longitudinal axis of the prosthesis head. Before the operation, the patient's CCD angle is determined and the intermediate element to be used is then prepared. During the operation, however, a different connecting part can also be used at any time if the situation requires it. Such an intermediate element can be inserted into the prosthesis head in different rotational positions depending on requirements, so that different CCD angles, corresponding to the number of rotational positions, can be produced with a single intermediate element. For orientation, the rotation positions are marked together with the CCD angle that can be generated thereby on the intermediate element and a counter-marking on the prosthesis head.

In a further preferred embodiment of the intermediate element according to the invention, the longitudinal axis of the bore runs parallel but offset to the longitudinal axis of the connecting part. If the connecting part and the bore are conical, such a connection can

EF41.G6 Sheet 5

The attachment part can also be inserted into the prosthesis head in different rotational positions, whereby again different CCD angles can be produced using an intermediate element, depending on the number of rotational positions. These positions and the CCD angles that can be produced are clearly indicated on the elements, together with the counter marking.

In an advantageous development of the intermediate element according to the invention, it has a bore that connects the proximal end face of the intermediate element with the inner contour of the connecting part, which is designed as a blind bore. The bore is at least partially provided with an internal thread and facilitates the removal of an intermediate element inserted in a prosthesis head when an instrument with an external thread that engages the internal thread of the bore is inserted into the bore and pulled out of the prosthesis head together with the intermediate element.

In an advantageous development of the kit according to the invention, it comprises a large number of connecting parts, which have different lengths, so that with a single prosthesis shaft with an arranged neck, the distance between the prosthesis head and the prosthesis neck can be varied. The length of the intermediate element and therefore the achievable distance also affects the CCD angle that can be produced. The CCD angle value listed on the intermediate element has been calculated taking this fact into account.

Using a table listing the achievable CCD angles for intermediate elements of different lengths,

EF41.G6 Sheet 6

the surgeon can easily read the intermediate element to be used (in the above context, the term "CCD angle" is always understood as a variable vectorial spatial direction).
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Other advantageous developments of the invention are characterized in the subclaims or are described in more detail below together with the description of the preferred embodiment of the invention using the figures. They show:

Figure 1 shows a section through a hip joint prosthesis assembled with the elements of the kit according to the invention with a first embodiment of an intermediate element arranged between the prosthesis shaft and the prosthesis head,

Figure la is a section through the intermediate element according to Figure 1,
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Figure 2 shows a section through another assembled hip joint prosthesis with a second embodiment of an intermediate element ,

Figure 2a shows a section through the intermediate element according to Figure 2,

Figure 3 shows a section through another assembled hip joint prosthesis with a third embodiment of an intermediate element and

EF41.G6 Sheet 7

Figure 3a shows a section through the intermediate element according to Figure 3.

The hip joint prosthesis shown in Figure 1 consists of a prosthesis shaft 1, which has a conical neck 3, a spherical prosthesis head 6, which has a conical blind bore 8, and a conical intermediate element 10, which is inserted between the prosthesis shaft 1 and the prosthesis head 6. Both the prosthesis shaft 1 and the prosthesis head 6 are part of the standard version of the kit and can be assembled into hip joint prostheses with different CCD angles using a number of differently designed intermediate elements 10, which are described in more detail below.

In the case of the connecting part 10 shown in Figures 1 and 1a, its outer contour 12 corresponds to the inner contour 9 of the blind hole 8 of the prosthesis head 6. It also has a conical hole 17 into which the conical neck 3 of the prosthesis shaft 1 can be inserted. The conical hole 17 of the intermediate element 10 is designed as a continuous hole, the longitudinal axis 19 of which runs at an angle to the longitudinal axis 11 of the intermediate element 10. The intermediate element 10 accordingly has a changing wall thickness over its length. The blind hole 8 in the prosthesis head 6 and the intermediate element 10 have been dimensioned in such a way that the remaining wall thickness of a hole 17 in the intermediate element 10, which runs at the maximum required angle to the longitudinal axis 11 of the intermediate element 10, is sufficient to be able to maintain the required stability of the intermediate element 10. The CCD angle that occurs when inserting a known connector

EF41.G6 Sheet 8

The angle of the end part with a centrally arranged bore corresponds to the fixed angle of the prosthesis shaft axis 2 to the prosthesis neck axis 4, since the prosthesis neck axis 4 coincides with the longitudinal axis of the prosthesis head 7, and can be increased or reduced using the non-centric design of the bore 17 of the intermediate element 10 shown in Figure 1. If the longitudinal axis of the prosthesis shaft 1 is formed at an angle of 126° to the longitudinal axis 4 of the prosthesis neck 3, since this angle corresponds to the most frequently naturally occurring CCD angle in humans, the range of naturally occurring CCD angle variations from approximately 115° to 140° can be completely covered using intermediate elements 10 alone, which enable a reduction or increase in the CCD angle by 15°.

The second embodiment of the intermediate element 10 according to the invention shown in Figures 2 and 2a differs from the first embodiment according to Figure 1 in that the intermediate element is longer and the conical bore 17 is designed as a blind bore, wherein it has a proximal end face 18 which extends perpendicular to the longitudinal axis 19 of the blind bore 17.

Figures 3 and 3a show a third embodiment of the intermediate element 10 according to the invention. The conical intermediate element 10 has a blind hole 17 which is also conical, but whose longitudinal axis 19 runs parallel at a distance from the longitudinal axis 11 of the connecting part 10. A continuous hole 17 which extends perpendicularly to the proximal end face 14 of the intermediate element 10

EF41.G6 Sheet 9

The continuous bore 20 extends from the proximal end wall 18 of the conical blind bore 17 to the proximal end face 14 of the intermediate element 10. The bore 20 has an internal thread 21 at the proximal end. By using an instrument which has an external thread which can engage in the internal thread 21, the removal of a very firmly seated intermediate element 10 from the prosthesis head 6 can be made considerably easier.

The invention is not limited in its implementation to the preferred embodiments given above. Rather, a number of variants are conceivable which make use of the solution presented even in fundamentally different embodiments.
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Claims (8)

EF41.G6 Sheet 10 Claims 1. Kit for a hip joint prosthesis consisting of a prosthesis shaft (1) with a neck (3) for receiving a joint ball (6), an intermediate element (10) which can be inserted between the prosthesis shaft (1) and the joint ball (6) and whose outer contour (12) corresponds to the inner contour (9) of the blind bore (8) and whose inner contour (13) corresponds to the outer contour (5) of the prosthesis neck (3), characterized, that the longitudinal axes (11 and 19) of the inner and outer contours (9 and 13) of the intermediate element form an angle other than 0° with one another and/or run parallel to one another or are arranged spatially skewed. 2. Kit according to claim 1, characterized in that the neck (3) of the prosthesis shaft (1) and the blind bore (8) of the ball joint (6) on the one hand and/or the outer contour (12) and the inner contour (13) of the intermediate element (10) designed as a bore (17) on the other hand are each designed in a circular cone shape in mutual adaptation. 3. Kit according to claim 2, characterized in that the conical cross-section of the neck (3) of the prosthesis shaft (1) and the blind bore (8) of the EF41.G6 Sheet 11 ball (6) is larger than the conical cross-section of the outer contour (12) and the inner contour (13) of the intermediate element (10) formed by the bore (17). 4. Kit according to one of claims 1 to 3, characterized in that the intermediate element (10) has an end wall (16). 5. Kit according to claim 4, characterized in that the end wall (16) has a bore (20) passing vertically through it. 6. Kit according to claim 5, characterized in that the through hole (20) is at least partially provided with an internal thread (21). 7. Kit according to one of the preceding claims, characterized in that the distal end face (15) of the intermediate element (10) has markings (22) for the respective rotation positions and/or corresponding angle information. 8. Kit according to one of the preceding claims, characterized by various intermediate elements (10) of different lengths and different EF41.G6 sheet chen angles or distances of the longitudinal axes of inner and outer contour.