WO2009152548A1

WO2009152548A1 - An acetabular component

Info

Publication number: WO2009152548A1
Application number: PCT/AU2008/000897
Authority: WO
Inventors: Lindsay Laird
Original assignee: Atlax Pty Ltd As Trustee For Atlax Trust
Priority date: 2008-06-20
Filing date: 2008-06-20
Publication date: 2009-12-23

Abstract

An acetabular component for a hip replacement prosthesis is disclosed including a generally concave inner surface which in use accommodates the head of a femoral component; the inner surface includes a trough for accumulating synovial fluid during use. An acetabular component with an inner surface further including an arrangement of depressions is also disclosed.

Description

AN ACETABULAR COMPONENT

Technical Field

The present invention relates to the field of medical prosthetics and particularly relates to an acetabular component for use in a prosthetic hip replacement.

Background to the Invention

A standard hip replacement operation consists of replacing both sides of the hip joint. The socket (acetabulum) of the pelvis is reamed out and an acetabular component inserted. The top of the thigh bone (femur) is usually removed and replaced with a stem component inserted into the medullary cavity of the femur and this has a prosthetic head component which then articulates with the cup of the acetabulum.

There are various types of stem components which may be cemented in place, or others that are uncemented with various treatments on the surface of the stem to maintain stability of the stem. The neck of the prosthesis may or may not be modular.

The head component in most modern stem-type femoral components is modular. The head size may vary and be matched with the liner size of the acetabular component. The head may be made of mertal or ceramic.

In a resurfacing hip replacement design the femoral head is shaped and not removed. A metal or ceramic cap and short stem is placed over the re- shaped femoral head and fixed in place; this then articulates with the acetabular component.

Acetabular components are mostly modular. They consist of a metal hemispherical shell with or without fins, spikes and options for screws etc, and a liner of metal, ceramic, polyethylene or combination which then locks into the shell. The diameter of the articulating surface closely matches that of the femoral head component.

In the case of a liner made from metal or ceramic, a so called hard-on-hard articulation, the liner is manufactured to be extremely smooth to articulate with the femoral component. In hard-on-hard articulations there is a specific slight miss -match in the diameter of each component to allow some fluid circulation between the two components.

It is known that contact between the articulating surfaces can generate wear- products which may lead to osteolysis and ultimately to failure of the replacements. There remains a continued need for improved prostheses which have increased resistance to wear.

Summary of the Invention

In a first aspect the present invention provides an acetabular component for a hip replacement prosthesis including: a generally concave inner surface which in use accommodates the head of a femoral component; the inner surface includes a trough for accumulating synovial fluid during use.

The trough may have an average depth of between 0.5 to 1.5 mm. The trough may have an average depth of about lmm.

The trough may occupy between 5% and 25% of the area of the inner surface. The trough may occupy between 10% and 20% of the area of inner surface. The trough may occupy about 15% of the area of the inner surface. The trough may flare outwardly in a direction towards the edge of the inner surface.

The trough may include a bulbous end region disposed away from the edge of the inner surface.

The inner surface may further include an arrangement of depressions. The arrangement of depressions may include an array of dimples. The dimples may be approximately 2mm in diameter.

The arrangement of depressions may include a network of channels or slots. The arrangement of depressions may occupy between 20% and 95% of the area of the inner surface.

The arrangement of depressions may occupy between 40% and 90% of the inner surface.

The arrangement of depressions may occupy about 85% of the inner surface. The arrangement of depressions may be approximately lmm in depth. The component may be in the form of a liner for insertion into an acetabular shell. The component may be formed from ceramic or metal.

In a second aspect the present invention provides an acetabular component for a hip replacement prosthesis including: a generally concave inner surface which in use accommodates the head of a femoral component; and wherein the inner surface further includes an arrangement of depressions.

Brief Description of the Drawings

An embodiment of the present invention will now be described, by way of example only, with reference to the accompanying drawings, in which:

Figure 1 is an underside perspective view of an acetabular liner according to an embodiment of the invention;

Figure 2 is a cross section view of the liner of figure 1, the cross section being taken through the middle of the trough; Figure 3 is a side view of the liner of figure 1 ; and Figure 4 is an underside view of the liner of figure 1.

Detailed Description of the Preferred Embodiment Referring to figure 1, an acetabular component is shown in the form of acetabular liner 10. The liner 10 has a generally concave inner surface 12 which in use accommodates the head of a femoral component. Inner surface 12 includes a trough 14 which in use accumulates synovial fluid.

The trough has a generally constant depth of approximately lmm with smoothly blended edges to the surrounding surface. The trough occupies approximately 15% of the surface area of the inner surface 12.

The inner surface 12 further includes an arrangement of depressions in the form of dimples (not shown). The dimples are approximately 2mm in diameter and have a depth of approximately lmm. The edges of the dimples present a very smooth transition to the surrounding surface. The arrangement of dimples occupies the remaining 85% of the area of inner surface 12.

The acetabular liner 10 is manufactured in metal or ceramic; a so called hard- on-hard articulation.

The liner locks into an acetabular shell by either a morse-taper lock or a locking ring in the shell component in the usual fashion. When fitted to patient, the trough is aligned caudally.

The liner is matched with a femoral head component of appropriate size which may also have dimples, channels or slots, or have a conventional smooth articulating surface. During walking, when the leg is non-weight bearing, the two components of the hip replacement very slightly come apart allowing synovial fluid to accumulate in the trough 14, and then as the heel- strike and weight bearing occurs, the synovial fluid is circulated to the dimples. This circulation of fluid decreases the contact of the surfaces on each other and therefore decreases wear on the components. Further, the circulation of fluid flushes the joint of abrasive particles. This flushing action is enhanced by way of the trough 14 extending to the edge of the liner. Further, the trough 14 flares outwardly at the edge of the liner still further enhancing the flushing of particles.

Trough 14 includes a bulbous end portion 16 to enhance accumulation of synovial fluid.

In the embodiment described above, the trough was approximately lmm in depth. In other embodiments the trough may be from 0.5mm to 1.5mm in depth. In the embodiment described above the trough occupied approximately 15% of the area of the inner surface of the liner. In other embodiments the trough may occupy between 5% and 25% of the inner surface.

In the embodiment described above the arrangement of depressions was provided in the form of an arrangement of dimples. In other embodiments the depressions may be provided in the form of a series of interconnected channels or slots. The channels or slots may be approximately lmm in depth and width.

In the embodiment described above the arrangement of depression occupied the remaining 85 % of the area of the inner surface not occupied by the trough. In other embodiments, only a portion of the remaining inner surface is occupied by the arrangement of depressions. The arrangement of depressions may occupy between 20% and 95% of the inner surface.

In the embodiment described above, the liner was formed from ceramic or metal as part of a hard-on-hard articulation. In other embodiments the liner may be formed from a softer material such as polyethylene.

Any reference to prior art contained herein is not to be taken as an admission that the information is common general knowledge, unless otherwise indicated.

Finally, it is to be appreciated that various alterations or additions may be made to the parts previously described without departing from the spirit or ambit of the present invention.

Claims

1. An acetabular component for a hip replacement prosthesis including: a generally concave inner surface which in use accommodates the head of a femoral component; the inner surface includes a trough for accumulating synovial fluid during use.

2. An acetabular component according to claim 1 wherein the trough has an average depth of between 0.5 to 1.5 mm.

3. An acetabular component according to any preceding claim wherein the trough has an average depth of about lmm.

4. An acetabular component according to any preceding claim wherein the trough occupies between 5% and 25% of the area of the inner surface.

5. An acetabular component according to any preceding claim wherein the trough occupies between 10% and 20% of the area of inner surface.

6. An acetabular component according to any preceding claim wherein the trough occupies about 15% of the area of the inner surface.

7. An acetabular component according to any preceding claim wherein the trough flares outwardly in a direction towards the edge of the inner surface.

8. An acetabular component according to any preceding claim wherein the trough includes a bulbous end region disposed away from the edge of the inner surface.

9. An acetabular component according to any preceding claim wherein the inner surface further includes an arrangement of depressions.

10. An acetabular component according to claim 9 wherein the arrangement of depressions includes an array of dimples.

11. An acetabular component according to claim 10 wherein the dimples are approximately 2mm in diameter.

12. An acetabular component according to claim 9 wherein the arrangement of depressions includes a network of channels or slots.

13. An acetabular component according to any one of claims 9 to 12 wherein the arrangement of depressions occupies between 20% and 95% of the area of the inner surface.

14. An acetabular component according to any one of claims 9 to 12 wherein the arrangement of depressions occupies between 40% and 90% of the inner surface.

15. An acetabular component according to any one of claims 9 to 12 wherein the arrangement of depressions occupies about 85% of the inner surface.

16. An acetabular component according to any one of claims 9 to 15 wherein the arrangement of depressions are approximately lmm in depth.

17. An acetabular component according to any preceding claim which is in the form of a liner for insertion into an acetabular shell.

18. An acetabular component according to any preceding claim which is formed from ceramic or metal.

19. An acetabular component for a hip replacement prosthesis including: a generally concave inner surface which in use accommodates the head of a femoral component; and wherein the inner surface further includes an arrangement of depressions.

20. An acetabular component according to claim 19 wherein the arrangement of depressions includes an array of dimples.

21. An acetabular component according to either of claims 19 or 20 wherein the arrangement of depressions are approximately lmm in depth.

22. An acetabular component according to any one of claims 19 to 21 wherein the arrangement of depressions includes a network of channels or slots.

23. An acetabular component according to any one of claims 19 to 22 wherein the arrangement of depressions occupies between 20% and 95% of the area of the inner surface.

24. An acetabular component according to any one of claims 19 to 22 wherein the arrangement of depressions occupies between 40% and 90% of the inner surface.

25. An acetabular component according to any one of claims 19 to 22 wherein the arrangement of depressions occupies about 85% of the inner surface.

26. An acetabular component according to any one of claims 19 to 25 which is in the form of a liner for insertion into an acetabular shell.

27. An acetabular component according to any one of claims 19 to 26 which is formed from ceramic or metal.

28. An acetabular component according to any one of claims 19 to 27 wherein the inner surface further includes a trough for accumulating synovial fluid during use.

29. An acetabular component according to claim 28 wherein the trough has an average depth of between 0.5 to 1.5 mm.

30. An acetabular component according to claim 28 wherein the trough has an average depth of about lmm.

31. An acetabular component according to any one of claims 28 to 30 wherein the trough occupies between 5% and 25% of the area of the inner surface.

32. An acetabular component according to any one of claims 28 to 30 wherein the trough occupies between 10% and 20% of the area of inner surface.

33. An acetabular component according to any one of claims 28 to 30 wherein the trough occupies about 15% of the area of the inner surface.

34. An acetabular component according to any one of claims 28 to 33 wherein the trough flares outwardly in a direction towards the edge of the inner surface.

35. An acetabular component according to any one of claims 28 to 33 wherein the trough has a bulbous end region disposed away from the edge of the inner surface.