DE9313233U1 - Endoprosthesis - Google Patents

Description

The invention relates to an endoprosthesis with a pin tapering towards its free end, a joint head and a joint head recess tapering inwards.

Such endoprostheses are known, for example, from DE-OS 32 47 726, in which a pin is integrally formed on the proximal end of a shaft and is designed as a plug-in cone that can be inserted and fixed into a corresponding conical bore in the head. This known two-part design of head and shaft has the advantage of flexible adaptation of head and shaft dimensions to the respective patient data with comparatively reduced storage. It is sufficient to connect the head with the appropriate diameter to the corresponding length and diameter.

WWR/JOE/nr

suitably selected shaft in order to achieve a dimensioning of the artificial joint that is adapted to the patient. If several shaft sizes and several head sizes are kept ready during the operation, the surgeon can quickly and reliably select the appropriate head/shaft combination during the operation.

Despite this quick and clear combination of prosthetic head with other prosthetic parts, the adaptation to the patient data that is possible as a result is not always sufficient to ensure, for example, the satisfactory function of an artificial joint.

In addition to the dimensions of the appropriate head size and the dimensions of the other prosthetic parts, the angle that the head axis, which runs through the center of the head around the joint head recess, forms with the other prosthetic parts is particularly patient-dependent. This angle, which is measured in joint endoprostheses with a shaft between the shaft axis and the head axis crossing it and is called the CCD angle in hip joint endoprostheses, is on average around 126° in the natural femur, for example, with a range of variation between 115° and 140°. Furthermore, the antetorsion or retrotorsion angle of the head and the distance between the head and shaft vary depending on the patient.

From DE-PS 36 00 804, a hip joint endoprosthesis with a shaft, a spherical head and an anchoring part for anchoring the head to the shaft is known, in which the anchoring part has a plug-in cone at the head and shaft ends, which can be anchored in a cone hole on the head and proximal end of the shaft. The longitudinal axis of the plug-in cone on the shaft and the longitudinal axis of the plug-in cone on the head on the anchoring part intersect at a predetermined angle 0<ß<50°. The separate connecting part between the head and shaft enables adaptation to a desired CCD angle.

realized.

The object of the invention is to further develop an endoprosthesis of the type mentioned at the outset in such a way that the endoprosthesis can be easily adapted to the individual patient requirements regardless of the selected size of the prosthesis head and the other prosthesis parts.

This object is achieved in the endoprosthesis of the type mentioned at the beginning according to the invention by a coupling element which contains a recess which receives the pin with a clamping fit and a pin section which can be inserted into the joint head recess with a clamping fit.

After selecting the head size and suitable additional prosthetic parts, an endoprosthesis that can be easily adapted to the individual patient data can be created by choosing a suitable coupling element if these parts are held in position with the appropriate size gradation. The selection of a suitable coupling element allows the distance and, if necessary, a predetermined angular arrangement of these prosthetic parts to be selected independently of the joint head and the other prosthetic parts. Storage remains manageable and the selection of the parts required to create the individually adapted endoprosthesis is relatively clear and simple for the surgeon - even during an operation.

Particularly preferably, the pin and the recess of the coupling element as well as the joint head recess and the pin section are rotationally symmetrical, whereby the pin or pin section can be inserted into the recess of the coupling element or into the joint head recess with a clamping fit, regardless of its rotational position about its rotation axis. This enables a continuous fine adjustment of the relative position of the head and the rest

Prosthetic parts possible.

The pin and the recess of the coupling element as well as the joint head recess and the pin section are preferably designed as plug-in cone connections, which represent particularly simple and self-locking connections.

In an alternative embodiment, the pin and the recess of the coupling element as well as the joint head recess and the pin section have elliptical or polygonal sections. Such sections can be used for indexing in order to enable the arrangement of the joint head only in predetermined relative angular positions to the other prosthetic parts.

Particularly preferably, the longitudinal axes of the recess of the coupling element and the pin section, which run through the center of gravity of the boundary surfaces facing away from the joint, are arranged offset from one another. Depending on the requirements of the individual patient data, they can enclose a predetermined angle 0<a<50° or can also be arranged offset parallel to one another. By including a predetermined angle α between these longitudinal axes, for example, in the case of endoprostheses with a shaft, both a desired angle between the shaft axis and the axis running through the center of the head and the joint head recess as well as a desired retrotorsion or antetorsion angle of the head relative to the shaft can be achieved. If the longitudinal axes of the recess and the pin section of the coupling element are offset parallel, then a twisting of the coupling element on the pin due to its eccentricity leads to an offset of the pin section of the coupling element that can be inserted into the joint head, running transversely to the pin axis.

If the longitudinal axes of the pin section and the recess of the coupling element intersect in the direction facing away from the joint head,

If the longitudinal axes of the pin section and the recess of the coupling element intersect inside the joint head, then when the coupling element is rotated on the pin, movement transverse to the longitudinal axis of the recess is avoided at the end of the coupling element facing away from the joint head.

If the recess of the coupling element extends into the pin section of the coupling element or even through the coupling element, and the coupling element can be inserted into the joint head recess with a clamping fit over its entire axial length, a particularly space-saving embodiment is realized, in which the movement of the head is, however, restricted when the coupling element is rotated on the pin.

In order to prevent rotation between the pin and the recess of the coupling element as well as between the pin section of the coupling element and the joint head recess, in a preferred embodiment of the invention a projection engages in a corresponding recess.

Advantageously, the pin and the joint head recess also form a clamping fit, so that a prosthesis consisting of a shaft and joint head can be formed even without a coupling element.

In the following, embodiments of the invention are explained in more detail with reference to the drawings.

Show it:

Fig. 1 a joint endoprosthesis with a coupling element between the joint head and a shaft; and

Fig. 2a-2g Cross sections and perspective views of various embodiments of the coupling element.

The joint endoprosthesis 1 shown in Figure 1 has a shaft 2, the distal end of which is broken away and at the proximal end of which a pin 8 is arranged, which has the shape of a conical section tapering towards the free end. The axis of the pin 8 forms an angle ß with the shaft axis 3.

An inwardly tapering recess 22 of a coupling element 20 is placed on the pin 8 at the proximal end of the shaft 2, forming a firm friction or clamping connection. The outer contour of the coupling element 20 is designed as a conical pin section 24, which can be anchored in a corresponding recess 32 of a joint head 30 with a clamping fit. The recess 22 extends into the conical pin section 24. The axis 23 of the recess 22 intersects with the axis 25 of the pin section 24 and forms a predetermined angle α with it, which can be between 0 and 50°.

The axis 25 of the pin section 24 of the coupling element 20 intersects the shaft axis 3 at the angle 7, for which the following applies for the embodiment shown in the figure:

γ = a + ß.

In the embodiment shown, the joint head 30 is spherical and flattened at its shaft-side end. The inwardly tapering conical recess 32 is arranged centrally in the shaft-side end surface 34, the axis 25 of which is identical to the axis of rotation of the conical pin section 24 of the coupling element 20 and runs through the center of the joint head 30.

In Figures 2a to 2g, various coupling elements 20 with different angles α between the longitudinal axes 23, 25 of the recess 22 or the pin section 24 of the coupling element 20 are shown.

The conical recess 22 in Figures 2a-c extends into the conical pin section 24 of the coupling element 20, whereby the coupling element 20 takes on the form of a plug-in sleeve closed on one side. The included angles α between the longitudinal axes 23, 25 of the plug-in cones 22, 24 are different in Figures 2a to 2c. The coupling element 20 shown in Figure 2c merely causes the head to be spaced apart from the shaft by a predetermined amount, the angle a - 0°.

Figure 2d shows a coupling element 20 in which a conical recess 22 extends completely through the coupling element 20, the axis 23 of which intersects the axis 25 of the outer cone 24, for example, at an angle α = 10°, the coupling element has the shape of a sleeve that is open on both sides.

Figure 2e shows a coupling element 20 with a conical pin section 24, which continues on the shaft side into a cylindrical section 24a. A tapered recess 22 extends inwards from the shaft-side boundary surface 21 of the coupling element 20, which ends in front of the conical pin section 24, and whose axis of rotation 23 intersects the axis of rotation 25 of the outer cone 24 at an angle α.

Figure 2f shows a perspective view of a coupling element 20 with a conical pin section 24 and a conical recess 22, with the rotation axes of the cones intersecting at a predetermined angle. A projection 26 is provided on the pin section 24, which fits into a corresponding recess in the joint head (not shown) to prevent rotation.

engages. On the inner front side of the recess 22, a rectangular recess 27 is provided, into which a corresponding projection on the shaft (not shown) engages.

Figure 2g shows a coupling element 20 in the form of a pyramid section with a hexagonal cross section and a hexagonal base area of an inwardly tapering recess 22.

Claims (19)

Expectations 1. Endoprosthesis with a pin tapering towards its free end, a joint head and a joint head recess tapering inwards, characterized by a coupling element (20) which has a recess (22) receiving the pin (8) with a clamping fit and a
Clamping fit into the joint head recess (32) and includes a pin portion (24). 2. Endoprosthesis according to claim 1, characterized in that the pin (8) and the recess (22) of the coupling element (29) are rotationally symmetrical. 3. Endoprosthesis according to claim 1 or 2, characterized in that the joint head recess (32) and the pin section (24) are rotationally symmetrical. 4. Endoprosthesis according to one of the preceding claims,
characterized in that the pin (8) and the recess (22) of the coupling element (20) are conical. 5. Endoprosthesis according to one of the preceding claims,
characterized in that the joint head recess (32) and the pin portion (24) are conical. 6. Endoprosthesis according to claim 1, characterized in that the pin (8) and the recess (22) of the coupling element (20) have polygonal sections. 7. Endoprosthesis according to claim 1 or 6, characterized in that the joint head recess (32) and the pin section (24) have polygonal sections. 8. Endoprosthesis according to claim 1, characterized in that the pin (8) and the recess (22) of the coupling element (20) have elliptical sections. 9. Endoprosthesis according to claim 1 or 8, characterized in that the joint head recess (32) and the pin section (24) have elliptical sections. 10. Endoprosthesis according to one of the preceding claims, characterized in that the longitudinal axes (23, 25) of the recess (22) of the coupling element (20) and of the pin section (24), which run through the respective center of gravity of the boundary surfaces on the head side or facing away from the joint head, are offset from one another. 11. Endoprosthesis according to claim 10, characterized in that the longitudinal axes (23, 25) of the recess and of the pin section of the coupling element enclose a predetermined angle 0<a<50°. 12. Endoprosthesis according to claim 10 or 11, characterized in that the longitudinal axes (23, 25) of the recess (22) and of the pin section (24) of the coupling element (20) are offset in parallel. 13. Endoprosthesis according to one of the preceding claims, characterized in that the longitudinal axes (23, 25) of the pin section (24) and the recess (22) of the coupling element (20) intersect in the boundary surface of the recess facing away from the joint head. 14. Endoprosthesis according to one of the preceding claims, characterized in that the longitudinal axes (23, 25) of the pin section (24) and the recess (22) of the coupling element (20) intersect inside the joint head. 15. Endoprosthesis according to one of the preceding claims, characterized in that the recess (22) in the coupling element (20) extends into the pin portion (24) of the coupling element. 16. Endoprosthesis according to one of the preceding claims, characterized in that the recess (22) of the coupling element (20) extends through the coupling element (20). 17. Endoprosthesis according to one of the preceding claims, characterized in that the entire outer contour of the coupling element can be inserted into the joint head recess with a clamping fit. 17. Endoprosthesis according to one of the preceding claims, characterized in that to prevent rotation between the pin (8) and the recess (22) of the coupling element (20) a projection engages in a corresponding recess (27). 18. Endoprosthesis according to one of the preceding claims, characterized in that a projection (26) engages in a corresponding recess to prevent rotation between the pin section (24) of the coupling element (20) and the recess (32) of the joint head (30). 19. Endoprosthesis according to one of the preceding claims, characterized in that the pin (8) and the joint head recess (32) form a clamping fit.