MXPA98003429A - Femur component for a cad endoprotesis - Google Patents

Abstract

The present invention relates to a femur component for a hip endoprosthesis with a distal end intended for insertion into the medullary space of the femur, a proximal flange section with a neck, whereby in the main flange section it can be attached a spherical head, a shank section with a longitudinal axis, and a length L that lies between the flange section and the end, and a circumferential groove in the third proximal to the shank section that joins the flange section

Description

COMPONENT OF FÉMOR FOR A HIP ENDOPROTESIS.

The invention relates to a femur component for a hip endoprosthesis, according to the definition in claim 1. One of the problems with bonded femur components is that the bone attachment inserted in the medullary nail can be displaced in a manner next after implantation of the prosthesis stem only with application of increasing force; this constitutes a major component if a distal medullary space retainer device is used. A further problem is that the femur component in relation to the prosthesis rod must be emptied too much to provide space for bonding with the bone. According to the sequential procedure, the rod is currently inserted into the femur bed which is already filled with bone cement. Accurate and quiet rest during the polymerization process is very problematic and can lead to inhomogeneous formation of the cement coating and excessive local stress concentrations within the hardened bone cement. For this, US Pat. No. 5,133,772 to HACK et al., A femur component according to this class, is already known. With these known femur components, the filling of the bone cement is done via one or more internal channels which are fused from the neck of the prosthesis in a circumferential groove through the interior of the rod. In the case of this known femur component, the application of cement is considered to be very little directed locally to the proximal range to achieve a load transfer to the femur as physiologically as possible. The internal channels lead to mechanical weakening of the implant in the range of the application of the cement ring because the cannulation weakens the cross section of the prosthesis stem. The long curved cannulation within the prosthesis limits the application of normally viscous bone cement in a very short period of time for polymerization. It is this elapsed period over which the danger of an oversized friction resistance of the application of bone cement in the cannulae consists. This can lead to a qualitative damage of the polymerized proximal cement ring. Finally, the interior channels also contain the danger of obstruction. The standard cemented systems so far lead to very little insertion due to the strength in the femur as the insertion of loaded is ensured on the whole but mainly the distal stem of the prosthesis and therefore is not physiological. This can lead to a proximal resorption of the bone and later to instability of the prosthesis. This is where the invention provides solutions. The invention is based on the task of producing a femur component for a hip endoprosthesis which can be fixed on a compact homogeneous cement surface area within the femur, whereby an extensive physiological load distribution in the section is achieved of proximal stem and which extensively eliminates the danger of a bent rod tip, The invention solves the proposed problem with a femur component having the features of claim 1. The invention combines the advantages of a cement anchor similar to the better primary stability through a good initial closure together with the proximal anchor and therefore a physiological load of the femur. By means of an adapted surgical technique, respectively, the preparation of the implant bed of precise positioning of the uncemented systems can be achieved by means of the femur component according to the invention that allows a minimum free space of the femur. Additional advantageous embodiments of the invention are characterized in the dependent claims. The advantages obtained by means of the invention are essentially those sought by means of a femur component according to the invention which local application of cement in the proximal section of the femur which is possible for a relevant period of time of polymerization. The invention and the additional embodiments of the invention are discussed in more detail in the following by means of partially schematic representations of some embodiments of the invention.

The figures show: Figure 1 is a perspective representation of the femur component according to the invention; and Figure 2 is a side view of the femur component according to Figure 1. The femur component shown in Figure 1 and 2 for a hip endoprosthesis provides a distal end 1 intended for insertion into the medullary space of the femur, a proximal flange section 2, with a neck 3, a shaft section 4 with a longitudinal axis 5 and a length L that is located between the flange section 2 and the end 1, and a circumferential groove 6 provided in the proximal third which is joined in the flange section 2. The slot 6 is connected to the proximal zone 8 of the flange section 2 by means of 2 or more channels 7 running in the direction of the longitudinal axis 5 of the surface of the flange section 2. In Figure 2 a channel 7 of previous placement is observed. A corresponding channel is also provided on the back side. The channels 7 provide an average cross-sectional area constituting 8 to 120 mm2, preferably 15 to 50 mm2.

The groove 6 suitably provides an average depth with an amount of 0.5 to 6.0 mm, preferably 1 to 4 mm respectively, of 2-40% of the width of the flange section 2 measured in the medial-lateral direction. The average height of the groove 6 suitably constitutes 10 to 50 mm, preferably 15 to 35 mm measured in the direction of the longitudinal axis 5, respectively 5-25% of the length L. The volume of the groove 6 adequately constitutes 500 to 10,000 mm3 , preferably 2,000 to 6,000 mm3. The average cross section of the rod section 4 in the slot 6 interval advantageously constitutes 50 to 500 mm 2, preferably 100 to 300 mm 2. The center of the slot 6 provides a distance to the distal end of the shaft 1 with an amount of 60 to 250 mm, preferably 100 to 200 mm and to the distal end of the neck 3 with an amount of 15 to 100 mm, preferably 30 to 60 mm . The proximal limit 10 of the slot 6 provides an average measured distance to the distal limit 11 of the proximal zone 8 of the flange section 2 with an amount of 2 to 18 mm, preferably 5 to 10 mm. The proximal limit 10 of the slot 6 provides a distance measured laterally to the distal limit 11 of the proximal zone 8 of the flange section 2 with an amount of 5 to 50 mm, preferably 15 to 35 mm.

The average cross section of the rod section advantageously constitutes 25 to 120 mm2, preferably 40 to 80 mm2 in its distal third which includes the end 1. In the proximal third of the rod section 4, which joins the section 2 of the rim not through the slots 9, can be additionally installed to the slots 7. The advantage of these additional slots or ridges 9 is in the form of a fixation compound between the prosthesis and the femur that is achieved therewith. the improvement of primary stability in the sense of an uncemented prosthesis. This leads to an additional macroscopic spongy anchor (which acts additionally with the cement anchor) which improves the torque capacity (stability against rotation, protection against rotation) of the prosthesis. The additional grooves of the flanges 9 also produce an additional guide and thus an exact locational positioning of the prosthesis during the hardening process. In the proximal half of the femur component is included a flange section 2 and the proximal part of the rod section 4 but without the groove 6 a microstructure is proposed which provides an average surface roughness with an amount of 5 μm to 1000 μm, preferably 10 μm to 600 μm. Since the entire proximal part is used for the introduction of force from the implant to the bone and a proximal area above the cement ring is provided for purposes of support and guidance especially in this area, an optimization of bone growth and therefore bone integration follows by means of a corresponding surface quality. Advantageously, this proximal half of the femur component (without the slot 6) is provided at least partially with a coercion of a bioactive material, preferably hydroxyapatite. The microscopic anchoring that can be achieved with it - as superposition to the macroscopic anchor - improves implant adhesion and bone integration and thus long-term stability. If the coating is of a bioactive material, this leads to an improvement in primary stability. In the neck 3, a spherical head is connected in a known manner. It is noted that in relation to this date, the best method known by the applicant to carry out the aforementioned invention, is the conventional one for the manufacture of the objects to which it relates. Having described the invention as above, property is claimed as contained in the following:

Claims (17)

RE-VPIDICACY

1. A femur component for a hip endoprosthesis with a distal end intended for insertion into the medullary space of the femur, a proximal flange section with a neck, whereby in the main flange section a spherical head, a cross section can be joined of rod with a longitudinal axis, and a length L lying between the flange section and the end, and a circumferential groove in the third proximal to the rod section that joins the flange section, the component is characterized in that the groove is joined to the proximal zone of the flange section via two channels on the surface of the flange section.

2. The femur component according to claim 1, characterized in that they are additionally provided to the channels, grooves or fins which do not pass through, in the proximal third of the rod section which is joined in the flange section.

3. The femur component according to claim 1 or 2, characterized in that the proximal half of the femur component preferably the flange section includes providing a microstructure.

4. The femur component according to one of claims 1 to 3, characterized in that the proximal half of the femur component, preferably the flange section includes at least partially providing a coating with a bioactive material, preferably with hydroxyapatite.

5. The femur component according to one of claims 1 to 4, characterized in that the groove provides an average depth constituting between 0.5 and 6.0 mm, preferably between 1 and 4 mm.

6. The femur component according to one of claims 1 to 4, characterized in that the groove provides an average depth with an amount of 2-40% of the width of the flange section measured in the medial-lateral direction.

7. The femur component according to one of claims 1 to 6, characterized in that the groove provides an average height in the direction of the longitudinal axis constituting between 10 to 50 mm, preferably 15 to 35 mm.

8. The femur component according to one of claims 1 to 6, characterized in that the groove provides an average height in the direction of the longitudinal axis with an amount of 5-25% of the length L.

9. The femur component according to one of claims 1 to 8, characterized in that the volume of the groove constitutes 500 to 10,000 mm3, preferably 2,000 to 6000 mm3.

10. The femur component according to one of claims 1 to 9, characterized in that the average cross-sectional area of the rod section in the range of the groove constitutes 50 to 500 mm2, preferably 100 to 300 mm2.

11. The femur component according to one of claims 1 to 10, characterized in that the center of the groove provides a distance to the end of the distal rod constituting 60 to 250 mm, preferably 100 to 200 mm.

12. The femur component according to one of claims 1 to 10, characterized in that the center of the groove provides a distance to the distal end of the neck constituting 15 to 100 mm, preferably 30 to 60 mm.

13. The femur component according to one of claims 1 to 12, characterized in that the average cross-sectional area of the rod section in its distal third, which includes the end, constitutes 25 to 120 mm2, preferably 40 to 80 mm2 .

14. The femur component according to one of claims 3 to 13, characterized in that the microstructure provides an average surface roughness constituting 5 μm to 1000 μm, preferably 10 μm to 600 μm.

15. The femur component according to one of claims 1 to 14, characterized in that the channels provide an average cross-sectional area constituting 8 to 120 mm2, preferably 15 to 50 mm2.

16. The femur component according to one of claims 1 to 15, characterized in that the proximal limit of the slot provides a distance measured medially to the distal limit of the proximal area of the flange section constituting 2 to 18 mm, preferably 5 to 10 mm.

17. The femur component according to one of claims 1 to 16, characterized in that the proximal limit of the groove provides a distance measured laterally to the distal limit of the proximal area of the flange section which constitutes 5 to 50 mm, preferably 15 to 35 mm. A femur component is provided for a hip endoprosthesis having a distal end (1) intended for introduction into the medullary space of the femur, a proximal flange section (2), with a neck (3) a section (4) of rod between the flange section (2) and the end (1) with a longitudinal axis (5) and a length (L), and a peripheral groove (6) in the proximal third of the section (4) of the rod which it joins the flange section (2). The groove (6) is connected to the proximal zone (8) of the flange section (2) via two channels (7) on the surface of the flange section (2). The channels (7) facilitate the local application of cement in the proximal region of the femur. They also allow excess bone cement, present in the medullary space of the femur when the femur component is implanted, to escape.