HK1108349B - Endoprosthetic elements for an ankle joint - Google Patents

Description

The present invention relates to a hip joint prosthesis component, namely a talus component and a tibial component inlay combination for a multi-piece hip joint prosthesis, and hip joint prostheses made from these components.

In view of the many reasons for a mobile solution for a painfully destroyed upper hip joint, it was only logical to look for solutions for other joints after the initial successes of hip and knee joint prosthetics, especially since a promising alternative in the sense of resection arthroplasty was not available for the joints directly affected by the body weight.

The first hip replacements were cemented metal-polyethylene joints, and the most famous of this generation, the St. George endoprosthesis, had a sledge-like talus component articulating with a downward congruent, i.e. concave, tibial component.

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It was found that the mechanical requirements and thus the high long-term survival rate can only be met by a hip joint prosthesis with an anatomically and biomechanically compatible design, implanted with minimal bone resection and carried free of the remaining ligaments and tendons.

The endoprostheses used today can be essentially divided into single and multi-axial two-component endoprostheses and three-component endoprostheses.

The three-component endoprosthesis generally consists of a tibial and a talus component and a glide core in between.

For example, a three-component prosthesis (HINTEGRA®; Newdeal SA, Vienne, France) with an anatomical tibial and talus component and a free-moving polyethylene (PE) glide core of ultra-high density (inlay) is known. The tibial component has a metal plate with tibial-shaped small anchorage pyramids and a ventral shield, which allows a screw fixation through two oval holes and prevents the growth of scar tissue and thus restriction of movement. The talus component has a shape similar to a cone with a medial lateral sliding radius. This side leads to the medial-medial and lateral edges of the PE guide.

Another example of a three-component prosthesis is shown in German patent DE 101 23 124.

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The tibial component of another well-known prosthesis (LINK S.T.A.R.®; Waldemar Link GmbH & Co. KG) consists of a metal plate with a highly polished flat articulation surface, which has two cylindrical fixation steps arranged backwards to anchor it in the tibial bone.

US patent 3,975,778 also reveals a prosthesis with a tibia and a talus component.

The present invention is intended to provide a spring joint prosthesis that prevents the slide from overhanging laterally and thus preventing the formation of an impingement.

In addition, a tapered prosthetic part should have an optimal fit with a simultaneous small bone resection.

One aspect of the invention concerns a tibial component-inlay combination for a multi-piece hip joint prosthesis, wherein the tibial component comprises a plate and a means of anchoring in the bone and the inlay has a planar tibial surface. According to the invention, on the side of the plate facing the inlay, a substantially central lift is provided and an exception is provided in the tibial surface of the inlay for lifting, wherein the exception is designed to allow rotation and AP sliding against the inlay of the tibial component and to prevent lateral movement of the inlay.

This prevents the glide core from overhanging laterally and thus preventing the formation of an impingement.

According to the invention, the lift is shaped like a spherical segment and the expansion is shaped like a segment of a cylinder with spherical segmented ends, with the axis of the cylinder oriented in the A/P direction.

The above embodiment provides for the inlay and the lifting in the tibial component plate, which is included in this embodiment. Another preferred embodiment is the reverse: it therefore concerns a tibial component-inlay combination for a multi-piece hip joint prosthesis, where the tibial component comprises a plate and a means of anchoring in the bone, and the inlay has a planar tibial surface, where the inlay facing the plate has a substantially central lifting, and the tibial surface of the inlay is included in this embodiment. The inlay is designed to prevent the lifting of a tibial component. The inlay is designed to be a red-blue segment and is designed to be placed in the direction opposite the end of the APG/PG.

Preferably, the means of anchorage in the bone shall comprise a ventral arched wedge.

Another subject matter of the invention concerns a three-piece hip joint prosthesis comprising the tibial component-inlay combination and a talus component of the invention.

The talus component has a bottom face facing the bony talus after implantation, the bottom face facing the bony talus being a concave spherical segment.

The concave design of the bottom of the talus component has been shown to allow for a particularly gentle preparation of the bone.

A means of anchoring the bone may be provided on the bottom of the concave spherical segment.

Preferably, the product consists of a centrally placed tubular stem and a ventral pen.

The following illustration illustrates the invention in greater detail, with Figures 1 and 2 illustrating a cross-section or view of an embodiment of the talus component, Figures 3, 4 and 5 illustrating a cross-section or view of an embodiment of the tibia component of a tibia component-inlay combination, and Figures 6, 7 and 8 illustrating a cross-section or view of an embodiment of the inlay of a tibia component-inlay combination, respectively.

Figure 1 shows a cut through an embodiment of talus component 1 as claimed 4. This element is usually made of biocompatible metal, e.g. CoCrMo according to ISO 5832/4. Reference number 2 refers to the cylindrical convex surface facing the inlay. Reference number 3 refers to the bottom of the element facing the talus, which is a concave spherical segment, which may be coated with, for example, tricalcium phosphate.

Fig. 2 shows a view of the bottom 3 of the talus component 1. In the central part of the bottom 3 there is a tubular stem 4 which is used for anchoring in the bone and, as shown, may be fitted with an inner wind. This is oriented towards the central radial of the spherical surface. To facilitate the insertion of the joint part, the tubular stem 4 is slanted so that the longer part is in front.

The ventral part of the tubular stem 4 is a metal pen 5 which, for example, has a diameter of about 3 mm and is placed parallel to the direction of the central stem 4 in the figure.

Figure 3 shows a side view of an embodiment of the tibia component 6 of a tibia component-inlay combination according to the invention. The tibia prosthesis element consists of e.g. a 3 mm thick metal plate 7 which carries on the side of the inlay a spherical segmented elevation 8 which forms a part for the necessary forced conduction of the polyinlay. The elevation 8 is essentially centrally provided on the underside 9 of the metal plate 7 as shown in Figures 4 and 5.

To increase the osseous integration area and to ensure the rotation of the tibial component 6, this is provided with a wedge 10 cranially. This wedge 10 is significantly flattened at its lower boundary side 11 to facilitate the insertion of the tibial component 6.

The longest revision wedge preferably has 2 holes for the locking bolts, the spherical section of the support 8 and the metal plate 7 can be fitted with a fastening mechanism for the modular tibia wedges.

Fig. 6 shows a view of the tibial surface 13 of PE inlay 12, which may be made, for example, of ISO 5834 chirula.

The tibial surface 13 consists of a planar surface, in the centre of which, in a longitudinal direction, i.e. A/R direction, a groove-shaped incision 14 is provided, which is formed as a cylindrical segment with spherical segments at the ends. This incision 14 can be seen from the cross-sections along the lines B-B and A-A of Figure 6 shown in Figures 7 and 8.

The surface 15 of the inlay 12 facing the talus component 1 is, as shown in Figure 7, the corresponding concave cylinder surface.

Figures 9 and 10 show the reverse embodiment, in which the exception is provided for in the tibia component rather than in the inlay. Figure 9 shows the exception with reference 8a in sheet 7 of the tibia component. The counterpart, i.e. the lifting which intervenes in the exception, is then provided for in inlay 12 as shown with reference 14a in Figure 10.

The outlet 8a in plate 7 may also be grooved, similar to the grooved outlet 14 of inlay 12 (Fig. 6), and even in the longitudinal direction, i.e. A/R direction.

Claims (4)

1. A tibia component-inlay combination for a multipart ankle joint prosthesis, wherein the tibia component (6) comprises a plate (7) and a means for anchoring in the bone and the inlay (12) has a planar tibial surface, wherein a substantially central elevation (8) is provided on the side of the plate (7) facing the inlay (12) and a recess (14) for the elevation (8) is provided on the tibial surface of the inlay (12), with the recess (14) being designed such that the inlay (12) is allowed to rotate and slide in an AP-direction relative to the tibia component (6) and a lateral movement of the inlay (12) is prevented, characterized in that the elevation (8) is in the shape of a spherical segment and the recess (14) is configured as a segment of a cylinder having an axis and spherical-segment-shaped ends, with the axis of the cylinder being oriented in the A/P-direction.
2. A tibia component-inlay combination for a multipart ankle joint prosthesis, wherein the tibia component (6) comprises a plate (7) and a means for anchoring in the bone and the inlay (12) has a planar tibial surface, wherein a substantially central recess (8a) is provided on the side of the plate (7) facing the inlay (12) and an elevation (14a) for said recess (8a) is provided on the tibial surface of the inlay (12), with the recess (8a) being designed such that the inlay (12) is allowed to rotate and slide in an AP-direction relative to the tibia component (6) and a lateral movement of the inlay (12) is prevented, characterized in that the elevation (14a) is in the shape of a spherical segment and the recess (8a) is configured as a segment of a cylinder having an axis and spherical-segment-shaped ends, with the axis of the cylinder being oriented in the A/P-direction.
3. A tibia component-inlay combination according to any of claims 1 to 2, characterized in that the means for anchoring in the bone comprises a ventrally curved wedge (10).
4. A three-part ankle joint prosthesis comprising a talus component, an inlay and a tibia component, characterized in that a combination according to any of claims 1 to 3 is provided as the tibia component and the inlay and that the talus component has a bottom side (3) facing the osseous talus after implantation and that the bottom side (3) facing the osseous talus is configured as a concave spherical segment.