AU2017219133B2

AU2017219133B2 - Medical Device

Info

Publication number: AU2017219133B2
Application number: AU2017219133A
Authority: AU
Inventors: Warwick J.M. Bruce
Original assignee: Smith and Nephew PLC; TJ Smith and Nephew Ltd
Current assignee: TJ Smith and Nephew Ltd
Priority date: 2008-11-05
Filing date: 2017-08-28
Publication date: 2019-01-24
Anticipated expiration: 2029-11-05
Also published as: AU2017219133A1; AU2015261563A1

Abstract

H:\jl1\Inte oven\NRPortbl\DCC\JLL\8932494_I.docx-24/11/2015 Abstract An implant, comprising: a head having a central axis; and a stem having a stem axis, wherein the head central axis and the stem axis are not co-linear. A method for resurfacing a femoral head, comprising the steps of: providing an implant according to the present invention; and implanting the implant with reference to the centre of the femoral neck. WO 2010/052461 PCT/GB2009/00261 1 z z pw xEr w \ I- I Lti ED) zicm a:0 SUSITT HET.UL 6

Description

Medical Device

This application is related to Australian Patent Application No. 2009312593, the entire content of which is incorporated herein by reference.

The present invention relates to medical devices, particularly hip implants.

Known femoral head resurfacing designs have the stem axis and the femoral head axis concurrent. That is, the stem axis and the femoral head axis are co-linear (see Figure 1 A). Femoral anatomy varies significantly between patients. The centre of the femoral neck is often not the centre of the femoral head. Consequently, mismatches can occur when a femoral head is resurfaced with a conventional resurfacing design. Such mismatches mean that known resurfacing designs do not reproduce the natural biomechanics and stability of the joint. This can lead to many problems for the patient, ranging from discomfort to pain and ultimately to failure, necessitating revision surgery.

With known femoral head resurfacing designs there is also little intra-operative flexibility in positioning the centre of the femoral head once the stem has been prepared. Consequently, the mismatches cannot be rectified and the above problems are encountered.

According to an aspect ofthe present invention, there is provided an eccentric resurfacing head.

According to an aspect ofthe present invention, there is provided an implant, comprising: a head having a central axis; and a stem having a stem axis, wherein the head central axis and the stem axis are not co-linear.

According to an aspect ofthe present invention, there is provided an implant for resurfacing a femoral head, comprising: a head having a central axis; and a stem having a stem axis, wherein the head central axis and the stem axis are not co-linear.

PCT/GB2009/002611

2017219133 28 Aug 2017

WO 2010/052461

According to an aspect of the present invention, there is provided an implant, comprising: a head having a bearing surface centre; and a stem having a stem axis, wherein the stem axis is offset compared to the head bearing surface centre.

According to an aspect of the present invention, there is provided an implant for resurfacing a femoral head, comprising: a head having a bearing surface centre; and a stem having a stem axis, wherein the stem axis is offset compared to the head bearing surface centre.

According to an aspect of the present invention, there is provided a resurfacing femoral head and stem, wherein the stem axis is offset compared to the bearing surface centre.

According to an aspect of the present invention, there is provided an implant comprising a head having a bearing surface and a recess inside the head with a stem, the stem and recess having an axis, wherein the stem/recess axis and the head axis are offset from each other.

According to an aspect of the present invention, there is provided an implant for resurfacing a femoral head, comprising a head having a bearing surface and a recess inside the head with a stem, the stem and recess having an axis, wherein the stem/recess axis and the head axis are offset from each other.

According to an aspect of the present invention, there is provided an implant, comprising: a head having an external surface defining a bearing surface, the bearing surface having a centre, and an internal surface defining a recess within the head; and a stem disposed on the internal surface of the head and having a stem axis, wherein the stem axis is offset compared to the head bearing surface centre.

I I:\saf\Interwoven\NRPortbl\DCC\SAF\l 6501292_ I .docx-21/02/2018

2017219133 21 Feb 2018

According to an aspect ofthe present invention, there is provided an implant for resurfacing a femoral head, comprising: a head having an external surface defining a bearing surface, the bearing surface having a centre, and an internal surface defining a recess within the head;

and a stem disposed on the internal surface ofthe head and having a stem axis, wherein the stem axis is offset compared to the head bearing surface centre.

According to an aspect ofthe present invention, there is provided an implant, comprising: a head having an external surface defining a bearing surface, the bearing surface having a centre, and an internal surface defining a recess within the head; and a stem disposed on the internal surface of the, head and having a stem axis, wherein the stem axis is offset compared to the head bearing surface centre, and wherein the stem and the internal surface are concentric.

According to an aspect ofthe present invention, there is provided an implant for resurfacing a femoral head, comprising: a head having an external surface defining a bearing surface, the bearing surface having a centre, and an internal surface defining a recess within the head; and a stem disposed on the internal surface ofthe head and having a stem axis, wherein the stem axis is offset compared to the head bearing surface centre, and wherein the stem and the internal surface are concentric.

Specifically, the present invention provides a femoral implant for resurfacing a femoral head comprising: a head comprising an external bearing surface having a centre and defining a head axis passing through the centre, and an internal surface defining a recess within the head and a recess axis; and a stem extending from the internal surface of the head and having a stem axis, characterised in that the stem and the head are integral to provide a onepiece implant, and wherein the stem axis is offset and parallel to the head axis and co-axial to the recess axis such that the internal surface ofthe head remains symmetric in use.

The offset between the stem axis and the head bearing surface centre may be any suitable amount. The offset may be an integer or non-integer amount. The offset may be in the range 1-10 mm. The offset may be in the range 1-5 mm. The offset may be in the range 1-3 mm. The offset may be around 1 mm. The offset may be around 2 mm. The offset may be around 3 mm.

I I:\saf\Interwoven\NRPortbl\DCC\SAF\l 6501292_ 1 .docx-21/02/2018

2017219133 21 Feb 2018

Preferably, the internal geometry of the head remains symmetric., which may be achieved by thickening one wall of the head (see Figure 1 B). This allows the surgeon to prepare the bone and then decide where to position the centre of the bearing.

Preferably, the implant is a monobloc/single part comprising a head and a stem.

An advantage associated with an integral monobloc head and stem construction is that they are mechanically superior to two-component embodiments. For example, a two component device has fretting interfaces which can lead to wear. In contrast, a single component device does not have fretting interfaces and is therefore more resistant to wear.

Implants according to the present invention may comprise one or more bone ingrowth surfaces.

Implants according to the present invention may be made of any suitable material. The implant may comprise metal. The implant may comprise metal alloy. The implant may comprise stainless steel. The implant may comprise titanium. The implant may comprise cobalt chrome.

According to the present invention, there is provided a method of implantation, comprising the steps of: providing an implant according to the present invention; and implanting the implant into a body.

WO 2010/052461

PCT/GB2009/002611

2017219133 28 Aug 2017

According to the present invention, there is provided a method for resurfacing a femoral head, comprising the steps of: providing an implant according to the present invention; and implanting the implant with reference to the centre of the femoral neck.

An advantage associated with referencing the centre of the neck of the femur is that the risk of neck fracture is minimised or eliminated.

In use, the implant may be cemented.

In use, the implant may not be cemented.

Implants according to the present invention allow the surgeon final control on. the bearing centre of the hip. This is important in restoring the natural biomechanics and stability of the joint.

Reference will now be made, by way of example, to the accompanying drawings, in which:

Figures 1A and 1B show cross-sections of a known femoral head resurfacing implant and a femoral head resurfacing implant according to an embodiment of the present invention, respectively;

Figures 2A and 2B show a top plan view and a cross-section view of a femoral head resurfacing implant according to another embodiment of the present invention, respectively;

Figures 3A and 3B show a top plan view and a cross-section view of a femoral head resurfacing implant according to another embodiment of the present invention, respectively; and

Figures 4A, 4B and 4C show cross-sections of a known femoral head resurfacing implant, the embodiment shown in Figure 2B and the embodiment shown in Figure 3B, respectively.

I I:\saf\Interwoven\NRPortbl\DCC\SAF\l 6501292_ 1 .docx-21/02/2018

2017219133 21 Feb 2018

As shown in Figures IA and 4A, for known femoral head resurfacing implants (10) the femoral head axis (6) and the stem axis (7) are co-linear. That is, the stem (5) is concentric to the head (4) centre. As shown in Figures 1 B, 2A, 2B, 3A, 3B, 4B and 4C, for femoral head resurfacing implants (1-3) in accordance with the present invention, the femoral head axis (6) and the stem axis (7) are offset such that they are not co-linear. As shown in Figure 1 B, implants (1) according to an embodiment of the present invention comprise a stem (5) that is eccentric to the articulating surface (8) but concentric to the internal profile (9). Figures 2A, 2B and 4B show an implant (2) having an offset of approximately 1 mm. Figures 3A, 3B and 4C show an implant (3) having an offset of approximately 2 mm.

For example, the embodiment shown in Figure 4A may have a head external diameter of around 50 mm, an offset of 0 mm, and be coupled with a cup having a diameter of around 56 mm. The embodiment shown in Figure 4B may have a head external diameter of around 52 mm, an offset of around 1 mm, and be coupled with a cup having a diameter of around 58 mm. The embodiment shown in Figure 4C may have a head external diameter of around 54 mm, an offset of around 2 mm, and be coupled with a cup having a diameter of around 60 mm.

The reference in this specification to any prior publication (or information derived from it), or to any matter which is known, is not, and should not be taken as an acknowledgment or admission or any form of suggestion that that prior publication (or information derived from it) or known matter forms part of the common general knowledge in the field of endeavour to which this specification relates.

Throughout this specification and the claims which follow, unless the context requires otherwise, the word comprise, and variations such as comprises and comprising, will be understood to imply the inclusion of a stated integer or step or group of integers or steps but not the exclusion of any other integer or step or group of integers or steps.

Claims

Claims

1. A femoral implant for resurfacing a femoral head comprising:

a head comprising an external bearing surface having a centre and defining a head axis passing through the centre, and an internal surface defining a recess within the head and a recess axis; and a stem extending from the internal surface of the head and having a stem axis, characterised in that the stem and the head are integral to provide a one-piece implant, and wherein the stem axis is offset and parallel to the head axis and co-axial to the recess axis such that the internal surface of the head remains symmetric in use.
2. An implant according to claim 1, wherein the offset is in the range of 1-3mm.
3. An implant according to claim 1 or 2, wherein the stem extends downwardly beyond the external bearing surface of the head.