CH712549A2 - Shank 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 portion of the shaft (1) which is substantially complementary to the course of the proximal, lateral cortical bone of a femur into which the shaft (1) is to be inserted is formed. The concave curvature of the medial side (4) in the proximal portion of the shaft (1) is substantially complementary to the course of the proximal medial limb bone portion of the femur. To adapt to the size of the thigh, the shaft (1) can be provided in different sizes. A distal portion (7) of the shaft (1) is straight, and in the longitudinal bore (5) a rod (2) is received with a protruding from the distal end of the longitudinal bore (5) tip (8).

Description

Description: [0001] The invention relates to a stem for a hip joint prosthesis, wherein a lateral side of the stem is convexly curved in a proximal portion of the stem and a medial side of the stem is concavely curved in a proximal portion of the stem, and the stem is a continuous longitudinal bore from the proximal to the distal end.

In this document, the position and direction designations used in the anatomy usually for describing the position, the position and the course of individual structures are used to designate structures, sections and sides of the shaft. These anatomical position and direction designations are best suited relative to the human or animal body and thus to the definition of the shaft with respect to its installation position in the body. In particular, the following anatomical names are used:

Proximal: towards the body center or running.

Distal: Located away from the body center or running.

Medial: located towards the center.

Lateral: located to the side.

Anterior: lying in front.

Posterior: lying back.

Orthograd: in physiologically normal movement or flow direction:

Retrograde: contrary to the physiologically normal movement or flow direction [0003] Furthermore, the terms metaphysis and diaphysis are used in this document. The metaphysis is a proximal bone portion of the long bones (e.g., femurs), whereas the diaphysis is a distal bony portion.

Conventionally, stems for hip joint prostheses transmit forces to the distal (diaphyseal) portion of the femur. This leads to oscillations in the dynamic power transmission because the femur is not loaded in the proximal (metaphyseal) section. Reactions of the cooking (hypertrophy) up to loosening of the prosthesis can be the consequence. Furthermore, due to the lack of or insufficient force transmission of the previous shafts, the vitality of the bone in the epiphysis (end portion of the femur) may be lost. It has been shown that a constant dynamic load is required to maintain bone vitality.

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

Another fundamental problem for hip prosthesis wearers with weak, porotic bone or after traumatic events is that they may suffer femoral stem fractures that are below the distal end of the prosthesis. Prosthetic care for such cases is often very difficult. The common surgical procedure is usually done over a long-flat plating with a long bone plate and cortical screws. The disadvantage here is in principle that the operation can not be performed covered, because the bone must be exposed for the creation of the plate. Conflicts between prosthesis, plate and screw can lead to the failure of the Ostheosynthese because sufficient stability can not be achieved.

The search for other solutions, in particular, in a covered manner, i. without the exposure of the femur bone to perform the treatment of the fracture leads to the creation of a connection between the prosthesis and a retrograde introduced intramedullary nail to achieve a new stability of prosthesis and femur bone.

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 introduced, which establishes a connection between the prosthesis and a retrograde introduced into the prosthesis intramedullary nail. It is proposed to adapt the prosthesis tip and the proximal head of the intramedullary nail to each other, as far as the dimensioning and design of the prosthesis tip permit at all. This creates a conical or truncated pyramidal connection between the prosthesis and the intramedullary nail or the prosthesis tip. At first glance, this solution seems to be sufficiently stable.

However, extensive tests and experiments have shown that this compound is not sufficiently stable according to AT 502 137, when a stronger force is effective for a long time. These disadvantages could be overcome by the hip prosthesis disclosed in AT 514114 A1. However, in this hip prosthesis, the preparation of the conical or truncated pyramidal connection between stem and stem tip or intramedullary nail has proven to be cumbersome and thus expensive, and there have occasionally been concerns about tightness at the transition between stem and stem tip.

There is therefore still a need for a shaft for a hip joint prosthesis, which serves as a prevention prosthesis for the provision of care in future femoral shaft fractures, and which avoids the disadvantages of the above-mentioned prostheses.

The present invention solves the stated object in that the convex curvature of the lateral side in the proximal portion of the shaft is substantially complementary to the course of the proximal, lateral cortical bone of a femur, in which the shaft is to be inserted, is formed that the concave Curvature of the medial side in the proximal portion of the shaft is formed substantially complementary to the course of the proximal medial calf-carotene bone of the femur, wherein to adapt to the size of the thigh, if necessary, the shaft is provided in different sizes, that a distal portion of the shaft straight is formed, and that in the longitudinal bore a rod is received with an outstanding from the distal end of the longitudinal bore tip.

By the convex curvature of the lateral side of the shaft in a proximal portion of the advantage is achieved that a power transmission is ensured on the metaphyseal part of the femur. It is particularly advantageous that by maintaining the dynamic load of this area bone reactions such as hypertrophy are avoided, and the vitality of the proximal thigh bone is maintained.

By this anchoring position at the proximal shaft end of the shaft has a small longitudinal extent, which has the advantage that a simple, arcuate implantation is made possible, which can be performed using all modern minimally invasive surgical procedures. In particular, the stem shape 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 formation of the distal portion, a large shaft volume is realized. In this case, it is particularly advantageous in addition to the large volume of the prosthesis shaft, that this extends distally axially to the shaft axis, whereby the possibility is created to form a longitudinal bore in the shaft, which receives a rod with a tip. This is inserted orthograde in the chart, the tip of this rod protrudes at the distal end of the shaft end.

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

A further advantageous feature of the shank according to the invention is that femoral stem fractures occurring after implantation can be supplied. In this case, the rod is removed from the shaft and instead an intramedullary nail orthograde or retrograde introduced into the longitudinal bore of the shaft. This type of treatment of femoral stem fractures allows a covered supply of the fracture without extensive exposure of the bone.

Advantageous embodiments of the inventive shaft and alternative embodiments will be explained in more detail by way of example with reference to the figures.

Fig. 1 shows a schematic representation of an inventive shaft 1 for a hip joint prosthesis in the medio-lateral plane with an inserted rod 2. Fig. 2 shows a schematic representation of an inventive shaft 1 for a hip joint prosthesis in the anterio-posterior plane with 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, which has an elongated rod 2 with transverse openings.

Fig. 1 and Fig. 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 portion, and a medial side 4 of the shaft is concavely curved in a proximal portion. This shaping of the shaft 1 ensures that a force transmission to the metaphyseal part of the femur after implantation is ensured. For this purpose, the convex course of the curvature on the lateral side 3 in the proximal portion is formed substantially complementary to the course of the proximal, lateral cortex of a femoral bone in which the shaft 1 is inserted.

The concave curvature of the medial side 4 in the proximal portion of the shaft 1, however, is formed substantially complementary to the course of the proximal, medial limb bone portion of the femur.

Claims (17)

To perform an adjustment to different sized femurs, the shaft 1 is provided in different sizes. The shaft 1 further 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 portion 7 of the shaft 1 is formed straight, whereby an increased shaft volume in the distal portion 7 of the shaft 1 is realized. This allows the attachment of a continuous longitudinal bore 5 from the proximal to the distal end of the shaft 1. In this, the rod 2 is inserted orthogradally, wherein the rod tip 8 protrudes from the distal end of the shaft 1. In an alternative embodiment variant, the rod 2 can be introduced into the longitudinal bore 5 in a retrograde manner. 3 shows a schematic view of a shaft 1 according to the invention in an alternative embodiment variant, with a rod 2 extended in comparison to FIGS. 1 and 2. In the distal section of the rod 2, which extends out of the longitudinal bore 5 of the shaft 1 emerges, transverse openings 10 are attached, which serve to fix the rod 2 in the femur. This embodiment of the rod 2 is used in particular in 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. This is done, if necessary, by exchanging the short rod 2 introduced by way of example in the first implantation, shown by way of example in FIG. 1 and FIG. 2, by the longer rod 2 shown in FIG. 3, with formed transverse openings 10 at the distal end. This results in the advantage that a revision prosthesis can be replaced by this variant of the shaft 1, for which purpose rods 2 are provided in different lengths. The rod 2 is fixed for anchoring in the shaft 1 in a preferred embodiment shown in Fig. 1 in a proximal portion of the longitudinal bore 5. This fixation is realized by means of non-positive or positive connection 9 and can be done for example by a screw connection. As a result, the compound 9 is designed releasably, whereby the possibility is created to subsequently replace the rod 2 by a longer rod 2, or to fix an orthograde or retrograde intramedullary nail for the treatment of Femurschaftbrüchen in the shaft 1. The releasable positive or non-positive connection 9 between rod 2 and shaft 1 is realized in an alternative embodiment shown in FIG. 3 at the distal portion of the shaft 1. The rod 2 has in a preferred embodiment, as shown in Fig. 1 and Fig. 3, a head 6, which is arranged sunk in the proximal end of the shaft 1. As a result, no portion of the rod 2 protrudes from the proximal end of the shaft 1. In a preferred embodiment, the longitudinal bore 5 has a circular or polygonal cross section. This is, as shown in Fig. 1 and Fig. 3, constant along its axial extent. In an alternative embodiment, the longitudinal bore 5 tapers from its proximal end 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. This, in a preferred embodiment, may in turn be constant over the entire length of the rod 2, as shown in FIGS. 1 and 3, or may taper from the proximal to the distal end in an alternative embodiment variant. The distal portion 7 of the shaft 1 is designed in a preferred embodiment shown in FIGS. 1 and 2 such that it tapers towards its distal end. This facilitates implantation by minimally invasive methods. Rejuvenation may occur both in the medio-lateral, anterior-posterior, and medial to lateral directions, as well as in any combination of the foregoing. claims A stem (1) for a hip joint prosthesis, wherein a lateral side (3) of the stem (1) is convexly curved in a proximal portion of the stem (1) and a medial side (4) of the stem (1) in a proximal portion the shaft (1) has 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 portion of the shaft (1) in Essentially complementary to the course of the proximal, lateral cortical bone of a femur into which the shaft (1) is to be inserted, is formed that the concave curvature of the medial side (4) in the proximal portion of the shaft (1) is substantially complementary to the course of the proximal , medial limb bone portion of the femur is formed, wherein, to adapt to the size of the thigh, if necessary, the shaft (1) ready in different sizes That is, a distal portion (7) of the shaft (1) is formed straight, and a rod (2) is received in the longitudinal bore (5) with a tip (8) projecting from the distal end of the longitudinal bore (5) , Second shaft (1) according to claim 1, characterized in that the rod (2) is fixed in a proximal portion of the longitudinal bore (5). 3. shaft (1) according to claim 2, characterized in that the rod (2) in the proximal portion of the longitudinal bore (5) is releasably fixed, in particular by means of non-positive or positive connection (9). 4. shaft (1) according to any one of the preceding claims, characterized in that the rod (2) in a distal portion of the longitudinal bore (5) is releasably fixed, in particular by means of non-positive or positive connection (9). 5. shaft (1) according to any one of the preceding claims, characterized in that a proximal head (6) of the rod (2) in the shaft (1) is arranged sunk. 6. shank (1) according to any 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) along its axial extent has a constant cross-section. 8. shaft (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 any 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) along its axial extent has a constant cross-section. 11. Shaft (1) according to claim 9, characterized in that the rod (2) tapers from its proximal end to its distal end. 12. shaft (1) according to any one of the preceding claims, characterized in that the rod (2) in its from the distal end of the longitudinal bore (5) protruding portion transverse openings (10). 13. shank (1) according to one of the preceding claims, characterized in that rods (2) of different lengths are provided. 14 shaft (1) according to any one of the preceding claims, characterized in that the rod (2) orthograde and / or retrograde in the longitudinal bore (5) can be inserted. 15 shaft (1) according to any one of the preceding claims, characterized in that it tapers in its distal portion (7) seen in the medio-lateral plane to the distal end. 16 shaft (1) according to any one of the preceding claims, characterized in that it tapers in its distal portion (7) seen in the anterio-posterior plane to the distal end. 17 shaft (1) according to any one of the preceding claims, characterized in that its cross-section in its distal portion (7) tapers from the medial to the lateral side.