AU696248B2

AU696248B2 - Orthopedic prosthesis

Info

Publication number: AU696248B2
Application number: AU24757/95A
Authority: AU
Inventors: Dawn M Ryan; Jeff Schryver; Jeff Shea
Original assignee: Smith and Nephew Inc
Current assignee: Smith and Nephew Inc
Priority date: 1994-05-09
Filing date: 1995-05-05
Publication date: 1998-09-03
Anticipated expiration: 2015-05-05
Also published as: CA2190029A1; WO1995030389A1; EP0758873A4; JPH09511668A; AU2475795A; EP0758873A1

Description

WO 953O3~9PCTUS95/0571 0 "ORTHOPEDIC PROSTOZES" The present invention relates to orthopedic prosthetic joint devices for implantation into or replacement of a joint of the human or animal body.

A number of commercially available prosthetic devices for implantation into a patient's joint or for total joint replacement include a metallic part and a plastics liner forming at least in part, the articulating surface of the joint. IVor example, in 1. Patent No. 4,828,565 there is provided a cotyliodal component for a non-cemented hip prosthesis. The component has two parts, a titanium hemispherical shell and a cuP, of polymer which is engaged into it.

other patents and patent applications which describe acetabular cups include European Patent Application No. 212,087 published April 3, 1987, wherein mtetallic pins project from the surface of the cup and contain holes in which tissue may grow.

In European Patent No. 341,298 published novernber 8, 1989, an acetabular cup has a metal outer shell and a pl1astic body for retaining the hip joint head.

The use of a combination of a plastics liner and a base member is also a feature of other joint prostheses such as those for implantation into the shoulder or knee. One example of a tibial prostheis which has a plate or insert forming an SUBSTITUTE SHEET (RULE 26) 11V) PEI( 0|11I'473-M 195 Onn articulating surface for the joint is described in US Patent No. 4462120.

The present invention provides an improved glenoid or tibial orthopedic joint prosthesis comprising: a prosthesis body having a first body surface for engaging a patient's joint and a second body surface, and a polymeric liner that lines the prosthesis body at the second body surface during use, the liner having first and second surfaces, the second surface defining an articulating surface that is positioned to receive and articulate with a separate joint prosthesis articulating member, the first surface of the liner defining a non-articulating surface that is positioned on the opposite side of the liner from the second surface; wherein said second body surface of the prosthesis body has a polished surface..

The prosthesis body thus has a non-articulating polished surface that receives the plastic liner, for retarding liner debris generation. The polished surface has a roughness of preferably less than eight microinches, more preferably less than four microinches, for example between one and four microinches. Most preferably, the polished surface is mirrorlike.

Preferably, the polymeric liner is formed of polyethylene UHMWPE).

The combination of the polymeric liner and orthopedic base with mirrored or polished surface finish provides numerous advantages. First, it provides a low friction and low abrasion surface for ,-stributing the contact forces between the liner and the prosthesis body shell.

This reduces the abrasive generation of polymeric debris resulting from motion between the liner and the body.

This motion may come from a variety of mechanisms which include Poisson volumetric distortion of the polymer resulting in localized expansion and contraction of the surface of the P l\J'IT1 I 12170 95 1 As5i 9 -3liner against the body as a result of loading the liner, and the micro-motion which occurs from forces on a liner within and around the confines of the prosthesis body interior.

Micro-motion can occur in a knee prosthesis as a tibial tray liner receives force generated by a femoral prosthesis. A shoulder or glenoid component also has force transmitted at the joint to a plastic liner of the glenoid metallic component.

A mirror finish additionally allows the use of optical non-contact inspection of the second body surface of the prosthesis body for checking the geometric correctness of the surface.

10 The use of non-contact optical inspection methods allow complete checking ot whole two and three dimensional surfaces at one time.

S.

The usual method of optical three-dimensional inspection is to project a regular pattern of i: light onto the surface which is to be inspected. The resultant two dimensional projection of 15 the scene may be used to give highly accurate total surface measurement. Distortions in the Sregular pattern indicate distortions in the part surface and indicate deviations from the desired part geometry. This method is ineffective on highly smooth surfaces since the projected light of the regular pattern bounces off the measurement target and no two dimensional mapping is possible.

According to an aspect of the invention, therefore, there is provided a kit comprising the orthopedic joint prosthesis in which the polished second body surface of the prosthesis body acts as a mirror, and grid means. The surface mirror may be used as a lens to view the grid means, which may be in the form of a grid drawn on a wi4te sheet of paper or a series of concentric rings. Distortions in the viewed image then are a result of distortions of the lens and hence the surface which is desirel to be measured. It is thereby possible to inspect the quality of the polished surface of the prosthesis body.

The method of inspection may be both by trained human inspectors and by image analysis p,0 performed by capturing the reflected image by a video camera, digitizing the image, and i- P ,']'l;WIl'lill24757 95a1 I 1'/1S -4using computer analysis to measure the amount of deviation of the pattern from the allowed surface geometry tolerance.

The advantages of this mirror surface is therefore to provide non-contact, and therefore nondestructive (non-scratching), measurement of the polished second body surface of the prosthesis body. The inspection methods require a surface which allows a reflective resolution sufficient to provide adequate reflective image quality for analysis. Current Vo inspection limits require a surface roughness of less than eight microinches to accomplish S: this quality of resolution.

BRIEF DESCRIPTION OF THE DRAWINGS: Various embodiments of an orthopedic joint prosthesis in accordance with the present invention will now be described by way of example only with reference to the accompanying 15 drawings, in which like parts are given like reference numerals, and wherein: Figure 1 is a top view of a glenoid component; 2 Figure 2 is a bottom view of the glenoid component of Figure 1; Figure 3 is an elevational view of the glenoid component of Figure 1; Figure 4 is a side view of the glenoid component of Figure 1; Figure 5 is a bottom view of a tibial component; Figure 6 is an elevational view of the tibial component taken along lines 9-9 of Figure Figure 7 is a sectional view taken along line 10-10 of Figure l' olI'R lll211477 9. 191 1 V 5 NI Figure 8 is an elevational view of the tibial component of Figures 5 to 7 in use; Figure 9 is a side view of an asymmetric tibial component; Figure 10 is a top view of the asymmetric tibial component of Figure 9; Figure 11 is an elevational view of the asymmetric tibial component of Figure 9; Figure 12 is a bottom view of the asymmetric tibial component of Figure 9; Figure 13 is a schematic diagram of the grid used to inspect the polished surface for distortions; Figure 14 illustrates a second embodiment of a test grid pattern used to inspect a mirror-like surface portion of the prosthesis body of the present invention; *<0 Figure 15 is a schematic diagram of a test grid showing no surface defects; and Figure 16 is schematic diagram showing local defects for a polished surface that has been inspected using the grid.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT: Figures 1-4 illustrate a glenoid prosthesis 10. The glenoid prosthesis 10 includes a component 41 that can cooperate with a humeral component (not shown). The use of glenoid components as part of a total shoulder system can be seen for example in Smith Nephew Richards publication entitled "Cofield Total Shoulder System Surgical Technique", and in US Patent 5,108,396, incorporated herein by reference. The glenoid component 41 has a bone ingrowth surface 42 that can be, for example, a plurality of metallic sintered beads 43. Bone

S

ingrowth surface 42 is attached to the patient's bone tissue with bone cement and screws for

I

I' 0I10,1lllV2,1751 91M I'm l'Ivll -6example as described more fully in the Cofield Total Shoulder System Surgical Technique and in US Patent 5,108,396.

Surface 44 is a mirror surface that receives a polyethylene or like insert (not shown) that provides an articulating surface for articulating with a humeral component. Thus, the mirror surface 44 is a non-articulating surface that engages the rear or non-articulating surface of the polyethylene insert. The glenoid component can include a stem 45 and cylindrical hollow sleeves 46 that accommodate bone screws. Annular shoulder 47 projects away from mirror surface 44, defining a structure that can hold the polyethyler 0 insert during use.

Figures 5-8 illustrate tibial prosthesis 10'. The tibial prosthesis 10' includes a tibial C component 48 having a stem 49 that occupies a surgically formed opening in the patient's tibia and a tray 51. The distal side of tray 51, from which the stem 49 projects, registers against the patient's proximal tibia, once surgically shaped to receive tibial component 48.

15 Tibial component 48 has a mirror surface 50 that receives polymeric insert 52 (see Figure 11). Mirror surface 50 is provided on the proximal side of tray 51.

o C During use, polymeric insert 52 articulates with femoral component 53. Femoral component 53 is attached to the patient's femur 54 (as shown in Figure 11), articulating against polymeric insert 52 that is supported upon the mirror surface 50. Surface 50 is the proximal surface of tray 51. Thus, the mirror surface is a non-articulating surface that engages the rear or distal surface of the polymeric insert 52. The proximal surface of polymeric insert 52 is an articulating surface that receives a polished metallic articulating surface of femoral component 53.

Figures 9-12 illustrate an asymmetric tibial prosthesis 10". Prosthesis 10" includes an asymmetric tibial component 56 that has a bone engaging surface 57 that engages the proximal, surgically prepared surface of the patient's tibia. the opposing surface from bone engaging surface 57 is a proximal, mirror surface 58 that receives a polymeric insert (not 0 shown). Peripheral shoulder 59 and mirror surface 58 define non-articulating surfaces that oFks 11 91 191 W )103 -7receive the polymeric insert, much in the same fashion that polymeric insert 52 is held with tray 51 at surface 50. An opening 60 allows tibial component 56 to be attached to the patient's tibia using a bone screw, for example.

It should be understood that the attachment of a polyethylene or polymeric insert to a tibial component (such as tray 51), or to an asymmetric tibial component (such as component 56) is per se known in the art. Such inserts are shown and described in the Smith Nephew Richards publication entitled "Genesis Total Knee System Surgical Technique" published in S1992 and incorporated herein by reference. However, the present invention provides an improvement that features a polished, preferably mirror surface portion in combination with a polymeric insert as aforedescribed as part of an overall prosthesis.

as Figures 13-16 illustrate grid charts 200, 205 that can be drawn on a white sheet of paper, for example, and used to inspect the polished surface of the glenoid and tibial components for 4 S 15 defects. In Figure 13, a grid 200 is in the form of a plurality of concentric rings 201, 202, 203, etc. A central opening 204 allows the user to visually inspect the polished surface 16 of the component when the flat grid 200 is placed on top of the component with the print of a i chart 200 facing the mirror like polished surface. In this fashion, the user simply views the lined pattern of the concentric rings 201-203 of grid chart 200 as reflected off the mirror surface of the component.

In Figure 14, a generally rectangularly shaped test grid 205 is shown. In Figure 15, a reflective pattern for the test grid 205 is shown as pattern 206, showing no defects. In Figure 16, another test grid pattern reflection 207 is shown that notes two local defects 208, 209.

Figure 13 illustrates a method of inspection that may be used by trained human inspectors, simply looking through the central opening 204. When such human inspection is employed, the inspector simply looks through the opening 204 when the grid chart 200, 205 is placed against the polished surface of the component.

P VII'rttIIu~'/ 11H1U45 A91WiA/ -8- Another method of inspection may be by image analysis performed by capturing the reflected image with a video camera, digitizing the image and using computer analysis to measure the amount of deviation of the pattern from the allowed surface geometry tolerance. Thus, the polished surface defines a mirror that is used as a lens to view a two dimensional pattern such as the grid patterns 200, 205 drawn for example on a white sheet of paper. Distortions in the viewed image are then z tsult of distortions of the lens surface and hence the surface which is desired to be measured.

SBecause many varying anc' different embodiments may be made within the scope of the inventive concept herein taught, and because many modifications may be made in the o: embodiments herein detailed in accordance with the descriptive requirement of the law, it is I to be understood that the details herein are to be interpreted as illustrative and not in a limiting sense.

04 S 15 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

1. A glenoid or tibial orthopedic joint prosthesis comprising: a prosthesis body having a first body surface for engaging a patient's joint and a second body surface, and a polymeric liner that lines the prosthesis body at the second body surface during use, the liner having first and second surfaces, the second surface defining an articulating surface that is positioned to receive and articulate with a separate joint prosthesis 10 articulating member, the first surface of the liner defining a non-articulating surface that is positioned on the opposite side of the liner from the second surface; wherein said second body surface of the prosthesis body has a polished surface.

2. An orthopedic joint prosthesis according to claim 1 wherein said polished surface has 15 a roughness of less than eight microinches.

3. An orthopedic joint prosthesis according to claim 1 or claim 2, wherein the polished surface has a roughness of less than four microinches. a a

4. An orthopedic joint prosthesis according to any one of claims 1-3, wherein the polished surface has a roughness of between one and four microinches.

An orthopedic joint prosthesis according to any one of claims 1 to 4, wherein said polished surface is mirror-like.

6. An orthopedic joint prosthesis according to any one of the preceding claims, wherein said polymeric liner is formed of polyethylene.

7. An orthopedic joint prosthesis according to any one of the preceding claims, wherein l r \35^4 saiC g!enoid prosthesis comprises a glenoid component including a stem and cylindrical 11 PF Iti(l I IIiII/ 'A VA Mm/uN4 hollow sleeves for accommodating bone screws.

8. An orthopedic prosthesis according to any one u: claims 1 to 6, wherein said tibial prosthesis comprises a tibial component having st'm for implantation into a tibia and a tray attached to the stem, said polished surface being provided on the tray.

9. An orthopedic joint prosthesis according to claim 8, wherein said tibial prosthesis is an asymmetric tibial prosthesis.

10. An orthopedic joint prosthesis according to any one of the preceding claims further comprising means for connecting the liner to the prosthesis body such that the non-articulating surface of said liner is adjacent to and in contact with the polished second body surface of the ,prosthesis body. 15

11. An orthopedic joint prosthesis according to claim 10, wherein said means comprises an annular shoulder which projects away from the polished second body surface of the S' prosthesis body and defines a structure which holds the polymeric insert during use.

12. An orthopedic joint prosthesis according to claim 10, wherein said means comprise projections on a surface of the polymeric liner and complementary grooves on said non articulating surface which engage said projections.

13. An orthopedic joint prosthesis according to claim 10, wherein said means comprises a peripheral shoulder adjacent to said polished second body surface.

14. An orthopedic joint prosthesis according to claim 1 and substantially as herein described with reference to the accompanying drawings. A kit comprising the orthopedic joint prosthesis of claim 5 and grid means for SN inspecting the polished second body surface for defects.

P 4o1(0,>)'llli\i 1197 W I r 11

16. A kit according to claim 15 wherein the grid means is grid comprised of a plurality of concentric rings.

17. A kit according to either claim 15 or claim 16 wherein the surface mirror defines a lens to view the grid.

18. A kit according to claim 15 and substantially as herein described with reference to the accompanying drawings. 00 10 DATED this 15th day of JULY 1998 Smith Nephew, Inc. By DAVIES COLLISON CAVE Patent Attorneys for the applicant *0 0