CH712549B1 - Shank for a hip joint prosthesis and a set of items with stems for a hip joint prosthesis. - Google Patents

Abstract

A shaft (1) according to the invention for a hip joint prosthesis with a continuous longitudinal bore (5) from the proximal to the distal end has a convex curvature of the lateral side (3) in the proximal section of the shaft (1), which is essentially complementary to the course of the proximal, lateral cortex of a femur into which the shaft (1) is to be inserted. The concave curvature of the medial side (4) in the proximal section of the shaft (1) is essentially complementary to the course of the proximal, medial calcar bone section of the femur. To adapt to the size of the thigh, the shaft (1) can be provided in different sizes. A lateral side of a distal section (7) of the shaft (1) is straight, and a rod (2) with a tip (8) protruding from the distal end of the longitudinal bore (5) is received in the longitudinal bore (5).

Description

The invention relates to a shaft for a hip joint prosthesis, wherein a lateral side of the shaft is convexly curved in a proximal portion of the shaft and a medial side of the shaft is concave in a proximal portion of the shaft, and the shaft has a continuous longitudinal bore from having proximal to the distal end.

The invention further relates to a set of articles with a plurality of shafts provided in different sizes for a hip joint prosthesis and a plurality of rods provided in different sizes.

In this document, the position and directional designations used in anatomy to describe the position, the location and the course of individual structures are used to designate structures, sections and sides of the shaft. These anatomical position and directional designations are most suitable relative to the human or animal body and thus to define the shaft in relation to its installation position in the body. In particular, the following anatomical terms are used: Proximal: located or running towards the center of the body. Distal: located or running away from the center of the body. Medial: towards the center. Lateral: lying to the side. Anterior: lying down. Posterior: lying behind. Orthograde: in the physiologically normal direction of movement or flow. Retrograde: against the physiologically normal direction of movement or flow

Furthermore, the terms metaphysis and diaphysis are used in this document. The metaphysis is a proximal section of the long tubular bones (e.g. thighbones), whereas the diaphysis is a distal section of bone.

Traditionally, hip joint prosthesis stems transmit forces to the distal (diaphyseal) portion of the femur. This leads to vibrations in the dynamic power transmission because the thighbone is not loaded in the proximal (metaphyseal) section. This can result in reactions from boiling (hypertrophy) to loosening of the prosthesis. Furthermore, the lack of or inadequate power transmission of the previous shafts can result in the loss of vitality of the bone in the epiphysis (end section of the thigh bone). It has been shown that a constant dynamic load is necessary to maintain the vitality of the bones.

DE 20 2014 102 059 U1 describes a basic solution to the above-mentioned problem by providing a shaft for a hip joint prosthesis, the lateral side of which is convexly curved at least in the distal section of the shaft. In a preferred embodiment of this shaft, its medial side is curved concavely at least in the proximal section. This design made it possible to shorten the shaft significantly compared to the conventional shafts. Due to the shortened design, this shaft is suitable for implantation using minimally invasive surgery. This shaft has proven itself in practice, but has the disadvantage that, due to its curvature in the distal section, the prosthesis shaft axis does not run axially to the femoral shaft axis.

Another fundamental problem for hip prosthesis wearers with weak, porothic bone or after traumatic events is that they can suffer femoral shaft fractures that lie below the distal end of the prosthesis. Prosthetic fitting in such cases is often very difficult. The most common surgical method is usually carried out using long plating with a long bone plate and cortical screws. In principle, it is disadvantageous that the operation cannot be carried out under cover because the bone has to be exposed in order to place the plate. Conflicts between prosthesis, plate and screw can lead to failure of the ostheosynthesis because sufficient stability cannot be achieved.

The search for other solutions, especially in order to covertly, ie without exposing the femur bone to carry out the treatment of the fracture, leads to the establishment of a connection between the prosthesis and a retrograde inserted intramedullary nail in order to renew the stability of the prosthesis and femur bone to reach.

Such an idea is based on the Austrian patent AT 502 137, which discloses an axial bore in the prosthesis through which a lag screw can be inserted, which establishes a connection between the prosthesis and an intramedullary nail inserted retrograde into the prosthesis. It is proposed to adapt the prosthesis tip and the proximal head of the intramedullary nail to one another, insofar as the dimensions and design of the prosthesis tip allow this at all. This creates a conical or truncated pyramid-shaped connection between the prosthesis and the intramedullary nail or the tip of the prosthesis. At first glance, this solution appears to be sufficiently stable.

However, detailed tests and experiments have shown that this connection according to AT 502 137 is not sufficiently stable when a stronger force is effective over a long period of time. These disadvantages could be overcome by the hip prosthesis disclosed in AT 514114 A1. However, with this hip prosthesis, the production of the conical or truncated pyramid-shaped connection between the shaft and the shaft tip or intramedullary nail has proven to be complex and thus expensive, and there were occasional concerns about the tightness at the transition between shaft and shaft tip.

There is therefore still a need for a shaft for a hip joint prosthesis, which serves as a preventive prosthesis for the provision of care in the event of any future femoral shaft fractures, and which avoids the disadvantages of the above-mentioned prostheses. The present invention achieves the stated object by providing a shaft for a hip joint prosthesis with the features of claim 1 and by providing a set of objects with a plurality of shafts according to the invention provided in different sizes for a hip joint prosthesis and a plurality of rods provided in different sizes.

The convex curvature of the lateral side of the shaft in a proximal section has the advantage that force transmission to the metaphyseal part of the femur is ensured. It is particularly advantageous here that by maintaining the dynamic loading of this area, bone reactions such as hypertrophy are avoided and the vitality of the proximal thigh bone is maintained.

Through this anchoring position at the proximal end of the shaft, the shaft has a small longitudinal extent, which has the advantage that a simple, arcuate implantation is made possible, which can be carried out using all modern minimally invasive surgical methods. In particular, the shape of the shaft ensures that implantation is possible via the anterior approach without severing tendons and muscles.

Due to the advantageous shape of the shaft, in particular the straight design of a lateral side of the distal section, a large shaft volume is realized. In addition to the large volume of the prosthesis shaft, it is particularly advantageous that it runs distally axially to the shaft axis, which creates the possibility of forming a longitudinal bore in the shaft which receives a rod with a tip. This is inserted orthogonally into the shaft, with the tip of this rod protruding from the shaft end at the distal end.

The rod can be inserted into the shaft in different lengths, which results in an indication of a weakened, partially destroyed, reduced or otherwise damaged bone, the advantage of using the rod used to support the bone and thereby replace a revision prosthesis. For this purpose, the tip of the rod can, if necessary, be anchored in the thighbone by means of a transverse lock.

Another advantageous property of the shaft according to the invention is that femoral shaft fractures that occur after implantation can be treated. The rod is removed from the shaft and an intramedullary nail is inserted into the longitudinal bore of the shaft in an orthograde or retrograde position. This type of treatment of femoral shaft fractures allows a covered treatment of the fracture without extensive exposure of the bone.

Advantageous embodiments of the shaft according to the invention and alternative design variants are explained in more detail below with reference to the figures. Figure 1 shows a schematic representation of a shaft 1 according to the invention for a hip joint prosthesis in the medio-lateral plane with an inserted rod 2. Figure 2 shows a schematic representation of a shaft 1 according to the invention for a hip joint prosthesis in the anterio-posterior plane with an inserted rod 2. FIG. 3 shows a schematic representation of a shaft 1 according to the invention for a hip joint prosthesis in the medio-lateral plane with an inserted rod 2 in an alternative embodiment variant, which has an elongated rod 2 with transverse openings.

Figure 1 and Figure 2 show a schematic view of a shaft 1 according to the invention for a hip joint prosthesis in a preferred embodiment. As shown in FIG. 1, a lateral side 3 of the shaft 1 is convexly curved in a proximal section, and a medial side 4 of the shaft is concavely curved in a proximal section. This shaping of the shaft 1 ensures that force is transmitted to the metaphyseal part of the femur after the implantation. For this purpose, the convex course of the curvature on the lateral side 3 in the proximal section is essentially complementary to the course of the proximal, lateral cortex of a femur into which the shaft 1 is inserted. The concave curvature of the medial side 4 in the proximal section of the shaft 1, on the other hand, is essentially complementary to the course of the proximal, medial calcar bone section of the femur.

In order to adapt to thigh bones of different sizes, the shaft 1 is provided in different sizes.

The shaft 1 also has an inserted rod 2 which has a rod tip 8 which protrudes from the distal end of the shaft 1. For this purpose, a distal section 7 of the shaft 1 is straight, as a result of which an increased shaft volume is realized in the distal section 7 of the shaft 1. This enables a through longitudinal bore 5 to be made from the proximal to the distal end of the shaft 1. The rod 2 is inserted orthogonally into this, with its rod tip 8 protruding from the distal end of the shaft 1. In an alternative embodiment, the rod 2 can be inserted retrograde into the longitudinal bore 5.

Figure 3 shows a schematic view of a shaft 1 according to the invention in an alternative embodiment, with a compared to Figure 1 and Figure 2 elongated rod 2. In the distal portion of the rod 2, which emerges from the longitudinal bore 5 of the shaft 1 are Transverse openings 10 attached, which are used to fix the rod 2 in the thigh bone. This embodiment of the rod 2 is used in particular when there is an indication of a weakened, partially destroyed, reduced or otherwise damaged bone in order to support the bone by means of the inserted rod 2. If necessary, this is done by exchanging the short rod 2, which was introduced during the first implantation and shown by way of example in FIG. 1 and FIG. 2, for the longer rod 2 shown in FIG. 3, with formed transverse openings 10 at the distal end. This has the advantage that this variant of the shaft 1 can replace a revision prosthesis, rods 2 of different lengths being provided for this purpose.

For anchoring in the shaft 1, the rod 2 is fixed in a preferred embodiment variant shown in FIG. 1 in a proximal section of the longitudinal bore 5. This fixation is realized by means of a force-fit or form-fit connection 9 and can be done, for example, by a screw connection. This makes the connection 9 detachable, which makes it possible to subsequently replace the rod 2 with a longer rod 2, or to fix an orthograde or retrograde intramedullary nail for the treatment of femoral shaft fractures in the shaft 1. The releasable form-fitting or force-fitting connection 9 between rod 2 and shaft 1 is implemented in an alternative embodiment variant shown in FIG. 3 on the distal section of shaft 1.

In a preferred embodiment variant, as shown in FIG. 1 and FIG. 3, the rod 2 has a head 6 which is arranged sunk in the proximal end of the shaft 1. As a result, no section of the rod 2 protrudes from the proximal end of the shaft 1.

In a preferred embodiment variant, the longitudinal bore 5 has a circular or polygonal cross section. As shown in FIG. 1 and FIG. 3, this is constant along its axial extent. In an alternative embodiment variant, the longitudinal bore 5 tapers from its proximal to its distal end.

The rod 2 also has a circular or polygonal, adapted to the longitudinal bore 5 of the shaft 1, cross section. In a preferred embodiment, this can in turn, as shown in FIG. 1 and FIG. 3, be constant over the entire length of the rod 2, or in an alternative embodiment it can taper from the proximal to the distal end.

The distal section 7 of the shaft 1 is designed in a preferred embodiment shown in Figure 1 and Figure 2 such that it tapers towards its distal end. This facilitates the implantation using minimally invasive methods. The tapering can take place both in the medio-lateral, the anterio-posterior plane, and from the medial to the lateral side, as well as in any combination of the above.

Claims (18)

1. Shaft (1) for a hip joint prosthesis, a lateral side (3) of the shaft (1) being convexly curved in a proximal section of the shaft (1) and a medial side (4) of the shaft (1) being curved in a proximal section of the shaft (1) is concavely curved, the shaft (1) having a continuous longitudinal bore (5) from the proximal to the distal end, characterized in that the convex curvature of the lateral side (3) in the proximal section of the shaft (1) in the Essentially complementary to the course of the proximal, lateral cortex of a femur into which the shaft (1) is to be inserted, the concave curvature of the medial side (4) in the proximal section of the shaft (1) is essentially complementary to the course of the proximal , medial calcar bone portion of the thigh bone is formed that a lateral side of a distal portion (7) of the shaft (1) is straight, and that in the longitudinal bore (5) Rod (2) is received with a tip (8) protruding from the distal end of the longitudinal bore (5). 2. Shank (1) according to claim 1, characterized in that the rod (2) is fixed in a proximal section of the longitudinal bore (5). 3. Shank (1) according to claim 2, characterized in that the rod (2) is releasably fixed in the proximal section of the longitudinal bore (5), in particular by means of a non-positive or positive connection (9). 4. Shank (1) according to one of the preceding claims, characterized in that the rod (2) is releasably fixed in a distal section of the longitudinal bore (5), in particular by means of a force-fitting or form-fitting connection (9). 5. Shank (1) according to one of the preceding claims, characterized in that a proximal head (6) of the rod (2) is arranged sunk in the shank (1). 6. Shank (1) according to one of the preceding claims, characterized in that the longitudinal bore (5) has a circular or polygonal cross section. 7. Shank (1) according to claim 6, characterized in that the longitudinal bore (5) has a constant cross section along its axial extent. 8. Shank (1) according to claim 6, characterized in that the longitudinal bore (5) tapers from its proximal end to its distal end. 9. Shank (1) according to one of the preceding claims, characterized in that the rod (2) has a circular or polygonal cross section. 10. Shank (1) according to claim 9, characterized in that the rod (2) has a constant cross section along its axial extension. 11. Shaft (1) according to claim 9, characterized in that the rod (2) tapers from its proximal end to its distal end. 12. Shank (1) according to one of the preceding claims, characterized in that the rod (2) has transverse openings (10) in its section protruding from the distal end of the longitudinal bore (5). 13. Shank (1) according to one of the preceding claims, characterized in that the rod (2) can be inserted orthograde into the longitudinal bore (5). 14. Shank (1) according to one of claims 1 to 7 or 9 to 12, characterized in that the rod (2) can be inserted retrograde into the longitudinal bore (5). 15. Shaft (1) according to one of the preceding claims, characterized in that it tapers towards the distal end in its distal section (7) as seen in the medio-lateral plane. 16. Shaft (1) according to one of the preceding claims, characterized in that it tapers towards the distal end in its distal section (7) as seen in the anterio-posterior plane. 17. Shank (1) according to one of the preceding claims, characterized in that its cross section tapers in its distal section (7) from the medial to the lateral side. 18. Set of objects, characterized by a plurality of shafts (1) provided in different lengths for a hip joint prosthesis according to one of the preceding claims and, for each of said shafts (1), a plurality of rods (2) provided in different lengths.