AU704200B2

AU704200B2 - Femur component for a hip endoprosthesis

Info

Publication number: AU704200B2
Application number: AU37693/95A
Authority: AU
Inventors: Lutz Claes; Andre Gaechter; Lothar Kinzl; Robert Jun Mathys; Peter Studer
Original assignee: Mathys Medizinaltechnik AG
Current assignee: Synthes Bettlach GmbH
Priority date: 1995-11-09
Filing date: 1995-11-09
Publication date: 1999-04-15
Anticipated expiration: 2015-11-09
Also published as: ATE250903T1; AU3769395A; WO1997017041A1; EP1011541B1; KR19990067423A; EP1011541A1; DE59510804D1

Abstract

The femur component for a hip endoprosthesis has a distal end (1) destined for introduction into the femur medullary space, a proximal shoulder section (2) with a neck (3), a shaft section (4) between the shoulder section (2) and end (1) with longitudinal axis (5) and length (L), and a peripheral groove (6) in the proximal third of the shaft section (4) which merges into the shoulder section (2). The groove (6) is linked to the proximal zone (8) of the shoulder section (2) via two channels (7) on the surface of the shoulder section (2). The channels (7) facilitate local application of cement in the proximal region of the femur. They also allow excess bone cement, present in the femur medullary space when the femur component is implanted, to escape.

Description

bedding during the process of polymerisation is very problematic and may lead to inhomogenous formation of the cement coating and Localise excessive stress concentrations within the hardened bone cement.

A ILemur component is described in US 5,133,772 HACK et al. With this femur component the fill in of the bone cement is realized via one or more internal channels which merge from the neck of the prosthesis into a circumferential groove through the interior of the shaft. In case of this femur component the application of cement is though too little locally directed to the proximal range to reach a transfer of loading to the femur as physiological as possible.

The interior channels lead to a mechanical weakening of the implant in the range of the appliancing cement ring because the cannulation weakens the cross-section of the shaft of the prosthesis. The long and bending cannulation within the prosthesis limits the application of normally viscous bone cement on a very short period of time for polymerisation. Is this period passed over the danger of an oversized friction resistance of the appliancing bone cement in the cannulas consists; this can lead to a qualitative impairment of the polymerized proximal cement ring. Finally the interior channels also contain the danger of obstruction.

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X 'o The standard cemented systems do not permit a purposeful insertion of the femur. This can lead to a proximal resorption of the bone and a later instability of the prosthesis.

Here the invention shall offer remedy. The invention is based on the task to produce a femur component for a hip endoprosthesis which is fixable over a compact homogeneous cement surface zone within the femur, therewith reaching an extensive physiologic load distribution in the proximal shaft section and extensively eliminating the danger of a varus tip over.

According to the invention there is provided a femur component for a hip endoprosthesis for insertion into a femur medullary space, the component including a proximal end, a distal end, a neck adjacent the proximal end, a proximal zone adjacent the neck, a shoulder section adjacent the proximal zone, a shaft section with a longitudinal axis and a length extending between the shoulder section and the distal end, and a circumferential groove in the shaft 15 section adjacent the shoulder section, wherein, the groove is linked to the proximal zone via two channels on the surface of the shoulder section.

The invention combines the advantages of a cement anchoring like better primary stability through the initial good form closure together with the proximal anchoring and therewith physiological loading of the femur.

By means of an adapted surgical technique respectively preparation of the bed of the implant the fitting exactness of noncemented systems can be reached by means of the femur component according to the invention what allows a 25 minimum clearing of the femur.

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Further advantageous embodiments characterized in the dependent claims.

of the invention are The reached advantages by means of the invention are essentially to be seen therein that by means of the femur component according to the invention a local application of cement in the proximal section of the femur is possible during a relevant time period of polymerisation.

The invention and further embodiments of the invention are discussed in more detail in the following by means of the partially schematic representations of some embodiments of the invention.

The figures show: Fig. 1 a perspectival representation of the femur component according to the invention; and Fig.2 a lateral view of the femur component according to fig.l.

The femur component shown in fig. 1 endoprosthesis provides a distal end 1 insertion into the femur medullary space, section 2 with a neck 3, a shaft section 4 and 2 for a hip destined for the a proximal shoulder with a longitudinal axis 5 and a length L lying between the shoulder section 2 and the end 1, and a circumferential groove 6 provided at the proximal third which merges into the shoulder section 2.

The groove 6 is connected to the proximal zone 8 of the shoulder section 2 via two or several channels 7 that run in the direction of the longitudinal axis 5 of the surface of the shoulder section 2. In fig. 2 an anterior lying channel 7 is to be seen. A corresponding channel is also provided posterior.

The channels 7 provide an average cross-section area amounting to 8 to 120 mm 2 preferably to 15 to 50 mm 2 The groove 6 suitably provides an average depth with an amount of 0,5 to 6,0 mm preferably of 1 to 4 mm respectively of 2 of the width of the shoulder section 2 measured in medio-lateral direction.

The average height of the groove 6 suitably amounts to 10 to 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 suitably amounts to 500 to 10'000 mm 3 preferably 2'000 to 6'000 mm 3 The average cross-section of the shaft section 4 in the range of the groove 6 advantageously amounts to 50 to 500 mm 2 preferably 00 to 300 mm 2 100 to 300 mm -6- The center of the groove 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 amount of 15 to 100 mm preferably 30 to 60 mm.

The proximal boundary 10 of the groove 6 provides a medial measured distance to the distal boundary 11 of the proximal zone 8 of the shoulder section 2 with an amount of 2 to 18 mm preferably 5 to 10 mm. The proximal boundary 10 of the groove 6 provides a laterally measured distance to the distal boundary 11 of the proximal zone 8 of the shoulder section 2 with an amount of 5 to 50 mm preferably 15 to 35 mm.

The average cross-section of the shaft section advantageously amounts to 25 to 120 mm 2 preferably 40 to 80 mm 2 in its distal third which includes the end 1.

in the proximal third of the shaft section 4 which merges into the shoulder section *0 2 ribs 9 can be installed additionally to the channels 7. The advantage of these additional ribs 9 is in the form locking compound between prosthesis and femur reached therewith to the improvement of the primary stability in the sense of a noncemented prosthesis. This leads to a further (acting additionally to the 20 cement anchoring) macroscopic spongy anchoring which improves the torquing loading capacity (stability against rotation, protection against rotation) of the prosthesis.

o if L I I V^ IP The additional grooves of ribs 9 also produce an additional guidance and therewith an exact locational positioning of the prosthesis during the setting process.

In the proximal half of the femur component including the shoulder section 2 and the proximal part of the shaft section 4 but without groove 6 a microstructure is intended which provides an average surface roughness with an amount of 5 Mm to 1000 Mm preferably of 10 Mm to 600 Mm. Since the whole proximal part is used to the force introduction from the implant to the bone and a proximal zone above the cement ring is provided for purposes of support and guidance especially in this zone an optimization of the boney growing and therewith a boney integration follows by means of a corresponding surface quality. Advantageously this proximal half of the femur component (without groove 6) is at least partially provided with a coating of a bioactive material preferably hydroxylapatite. The microscopic anchoring reachable therewith as superposition to the macroscopic anchoring improves the adherence of the implant and boney integration and therewith the long term stability. If the coating is of a bioactive material this leads to an improvement of the primary stability.

At the neck 3 a spherical head is attachable in a known manner.

I

THE CLAIMS DEFINING THE INVENTION ARE AS FOLLOWS: 1. A femur component for a hip endoprosthesis for insertion into a femur medullary space, the component including a proximal end, a distal end, a neck adjacent the proximal end, a proximal zone adjacent the neck, a shoulder section adjacent the proximal zone, a shaft section with a longitudinal axis and a length extending between the shoulder section and the distal end, and a circumferential groove in the shaft section adjacent the shoulder section, wherein, the groove is linked to the proximal zone via two channels on the surface of the shoulder section.

2. A femur component according to claim 1, including ribs which are provided in the shoulder section.

3. A femur component according to claim 1 or 2, wherein half of the femur i5 component adjacent the proximal end provides a microstructure.

4. A femur component according to any one of claims 1 to 3, wherein half of •".the femur component adjacent the proximal end is coated with a bioactive S. material.

5. A femur component according to claim 4, wherein the bioactive material is 0 hydroxylapatite.

6. A femur component according to any one of claims 1 to 5, wherein the groove has an average depth of between 0.5 and 6.0 mm.

7. A femur component according to claim 6 wherein the average depth is between 1.0 and 4.0 mm.

25 8. A femur component according to any one of claims I to 5, wherein the groove has an average depth equivalent to 2 to 40% of a width of the shoulder 0 section measured in a medio-lateral direction.

9. A femur component according to any one of claims 1 to 8, wherein the groove has an average height in the direction of the longitudinal axis of between 10 to 50 mm.

Claims

11. A femur component according to any one of claims 1 to 8, wherein the groove has an average height in the direction of the longitudinal axis equivalent to 5 to 25% of the length of the shaft section.

12. A femur component according to any one of claims 1 to 11, wherein the volume of the groove is between 500 to 10'000 mm 3

13. A femur component according to claim 12 wherein the volume of the groove is between 2000 to 6000 mm 3

14. A femur component according to any one of claims 1 to 13, wherein the average cross-sectional area of the shaft section in the groove is between 50 to 500 mm 2 A femur component according to claim 14, wherein the average cross- sectional area of the shaft section in the groove is between 100 to 300 mm 3 15 16. A femur component according to any one of claims 1 to 15, wherein a 6 length from a center of the groove to the distal end amounts to 60 to 250 mm.

17. A femur component according to claim 16, wherein the length from the .oll center of the groove to the distal end amounts to 100 to 200 mm. •°o

18. A femur component according to any one of claims 1 to 10, wherein a length from a center of the groove to the neck amounts to 15 to 100 mm.

19. A femur component according to claim 18 wherein the length from the center of the groove to the neck amounts to 30 to 60 mm. •20. A femur component according to any one of claims 1 to 12, wherein the average cross-sectional area of the shaft section along a third of its length 25 adjacent the distal end amounts to 25 to 120 mm 2

21. A femur component according to claim 20, wherein the average cross- sectional area of the shaft section along the third of its length adjacent the distal end amounts to 40 to 80 mm 2 *°6

22. A femur component according to claim 3, wherein the microstructure provides an average surface roughness amounting to 5ptm to 600jim.

23. A femur component according to claim 22, wherein the average surface -,roughness amounts to 10gm to 600gm. VT Ui 'd

24. A femur component according to any one of claims 1 to 14, wherein the channels have an average cross-sectional area of between 8 to 120 mm 2 A femur component according to claim 24, wherein the channels have an average cross-sectional area of the channels is between 5 to 50 mm 2

26. A femur component according to any one of claims 1 to 15, wherein a proximal boundary of the groove provides a medially measured distance to a distal boundary of the proximal zone of the shoulder section that amounts to 2 to 18 mm.

27. A femur component according to claim 26, wherein the proximal boundary of the groove provides a medially measured distance to the distal boundary of the proximal zone of the shoulder section that amounts to 5 to 10 mm.

28. A femur according to any one of claims 1 to 16, wherein a proximal boundary of the groove provides a laterally measured distance to a distal boundary of the proximal zone of the shoulder section which amounts to 5 to mm.

29. A femur according to claim 27, wherein the proximal boundary of the groove provides a laterally measured distance to the distal boundary of the o proximal zone of the shoulder section which amounts to 15 to 35 mm.

30. A femur component substantially as hereinbefore described with reference 20 to the illustrations. o*« DATED: 8 January 1999 PHILLIPS ORMONDE FITZPATRICK Attorneys for: MATHYS MEDIZINAL TECHNIK AG C:\WINWORD\TONIA\BF\SPECI'37693.DOC Abstract: The femur component for a hip endoprosthesis has a distal end destined for introduction into the femur medullary space, a proximal shoulder section with a neck a shaft section between the shoulder section and end with longitudinal axis and Length and a peripheral groove in the proximal third of the shaft section which merges into the shoulder section The groove is linked to the proximal zone of the shoulder section via two channels on the surface of the shoulder section The channels (7) facilitate local application of cement in the proximal region of the femur. They also allow excess bone cement, present in the femur medullary space when the femur component is implanted, to escape.