external wear of the polyethylene socket in cemented ... - Bone & Joint

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of the socket. It is suggested that, in some cases, changes at the bone-cement junction are secondary to socket loosening and abrasion against the bone of the ...
EXTERNAL

WEAR

OF THE

IN CEMENTED B. M.

TOTAL

WROBLEWSKI,

M.

LYNCH,

From

We examined

59 cemented

POLYETHYLENE HIP

ARTHROPLASTY

J. R. ATKINSON,

Wrightington

high density

polyethylene

SOCKET

D.

Hospital,

DOWSON,

G.

H.

ISAAC

Wigan

sockets

removed

at revision

hip

arthroplasty.

Of

these 19 showed areas of wear between the outside of the socket and the acetabular bone. This was associated with lack of acrylic cement in those areas and was also related to the depth of the wear on the articulating

of the socket. It is suggested that, in some cases, changes at the bone-cement junction are secondary to socket loosening and abrasion against the bone of the acetabulum, rather than to particles migrating from the metalpolyethylene interface. It is therefore important that impingement of the neck of the femoral stem on the edge of the cup be avoided and that, when the socket is inserted, it is not in direct contact with the bone. surface

reaction to orthopaedic after total hip arthroplasty

Tissue products

ly studied,

and the changes

have

thought

been

the articulating

(HDP)

tissue

granulation

include

have

may

and bone resorption.

phagocytosis

and

articulating part of the socket which migrate, but instead be secondary to loosening of the components the resulting abrasion of the HDP socket against

polyethylene have been

of the

may and the

acetabulum.

that

Vernon-

late The

wear particles on previously reported

1979).

(Wroblewski

The during

of

acetabular from the

considered that by foreign-body

tissue was important and that be due to excessive bone necrosis.

effects cartilage

undesirable

suggested

ofcemented to wear products

develop and lead to sequence of events

; the possible

and Freeman (1977) also of the bone-cement interface

granulomatous loosening could

this

(1976)

Semlitsch

of the implant

Roberts invasion

that

particles from polyethylene

seen at the bone-cementjunction components may not be due

bone and

foreign-body

socket

to be due to migrating of the high density

junction

cup.

loosening

bone

at the bone-.cement

surface

Willert

may

implants and wear have been extensive-

detailed

examination arthroplasties

revision

of

sockets produced

has

removed

evidence of an HDP

wear may occur between the outside and the bone (Isaac et al. 1986). The purpose of paper is to point out that, in some cases, the changes

B. M. Wroblewski, M. Lynch, Centre for

WN9

FRCS,

FRCS, Senior Hip Surgery,

9EP,

Consultant Orthopaedic Wrightington

Orthopaedic Registrar Hospital,

Surgeon Wigan,

Lancashire

England.

J. R. Atkinson,

G. H. Isaac, D. Dowson,

Senior

Lecturer,

Research Professor

ment of Mechanical University of Leeds,

Department

of Metallurgy

Fellow, Department of Metallurgy and Director, Institute of Tribology, Engineering Leeds LS2

9JT,

Depart-

England. Fig. 1

Requests

for

reprints

©

1987 British 0301-620X/87/l022

VOL.

69-B,

No.

should

Editorial $2.00

1, JANUARY

be Society

1987

sent

to Mr

of Bone

B. M. and

Joint

Wroblewski. Surgery

Evidence of erosion of the socket against large area with no acrylic cement, and deep polyethylene.

the acetabulum pitting on the

: there is a surface of the

61

62

B. M. wROBLEwSKI,

MATERIAL Fifty-nine

sockets

AND

from

M. LYNCH,

J. R. ATKINSON,

METHOD

Charnley

low friction

arthroplas-

Wear within an HDP socket after total hip arthroplasty is a time-related phenomenon (Charnley 1979): as the metal head bores for itself a new, roughly cylindrical channel, the angular range of movement becomes

Of the 59 sockets,

19 (32.2%) showed areas where there on the outer aspect of the socket, with obvious erosion of the HDP caused by movement against the bone ofthe acetabulum (Fig. 1). The extent of this

cement

external

socket

wear

was

classified

into

three

progressively restricted, neck of the stem on the

greater

than

in diameter, usually shallow discrete deep pits (Fig. 1).

but occasionally

with

Medium:

deep

than

.

Extensive

Discrete,

5 mm

Small:

erosion

Pits

well

with

each

area

directly

localised

pits,

not

size not

pinpoint

more

than

I. Clinical

details

of 19 patients

and

findings

after

related 1986).

to the depth

revision

of total

Sex

77

F

OA

8

9

54

F

OA

10

10

1 2

hip arthroplasties

Years

Months

Reason Loose

.

3

71

M

Trauma

4

70

F

Perthes’

5

80

M

Protrusio

6

76

M

7

75

8

11

disease

(Wroblewski

It is to be expected that, once impingement and loosening has occurred, any part ofthe outer aspect of the socket which is not fully covered by the cement and is in

Follow-up Age

wear

2 mm

Original diagnosis

Case

of socket

1985b,

deep. Table

for revision cup

Internal socket wear (mm)

External socket erosion

3.13

Small

Fractured loose cup

stem,

0.48

Small

Fractured loose cup

stem,

1.04

Small

10

3

Loose

cup

2.64

Medium

11

9

Loose

cup

2. 1

Small

OA

12

4

Fractured loose cup

3.8

Small

M

OA

10

Loose

cup

3.6

Small

64

F

OA

13

Loose

cup

4.32

Large

9

31

F

RA

12

Loose

cup

2.4

Medium

10

65

F

Congenital with OA

Loose

cup

0.38

Small

11

74

F

Protrusio

I2

76

M

13

67

14

acetabuli

dysplasia

acetabuli

6

9

stem,

7

6

Loose

cup

3.6

Large

OA

7

3

Loose

cup

1.08

Small

M

OA

11

7

Loosecup

2.35

Large

71

F

OA

13

5

Loose

cup

1.32

Small

15

65

M

OA

10

Loose cup

3.35

Large

16

69

M

OA

8

Loose

cup

1.5

Small

17

77

M

Segmental

Loose

cup

0.2

Large

18

69

M

OA

3.2

Large

0.16

Small

necrosis

10

3

9

4

Fractured loose

19 OA, RA,

57 osteoarthritis rheumatoid

M

OA

1

of the This

more

in diameter. of almost

leading to impingement rim of the deepened socket.

block to movement, confirmed by both clinical and theoretical studies (Wroblewski l985a), results in shock loading and subsequent loosening of the socket. It has also been found that the incidence of socket migration is

groups: Large 5 mm

and the surface

DISCUSSION

RESULTS no acrylic

G. H. ISAAC

The clinical details of the 19 patients measurements of wear on the articulating inner are summarised in Table I.

ties were available for study. Visual examination and scanning electron microscopy were carried out (Isaac et al. 1986). No cases of deep sepsis were included.

was

D. DOwSON,

9

stem,

cup

Loose cup

arthritis

THE

JOURNAL

OF BONE

AND

JOINT

SURGERY

EXTERNAL

direct

contact

with

WEAR

acetabular

OF THE

bone

against this bone. Wear particles cup and cement together will lead associated with HDP granulomata

POLYETHYLENE

will

move

SOCKET

and

wear

plus movement of the to the type of changes (Wroblewski 1979).

Examination of the original anteroposterior radioof the 19 arthroplasties showed that in 12 cases there had been at least one area with no cement between the cup and the bone while in another three cement graphs

was only

thickness

likely to precede further supported internal erosion. in

socket

Thus three

when groups

1 mm.

within

twofold.

is

components reduce the

the

extent

of external

socket

the depth of socket wear was considered an average wear of 1 .83 mm was

Firstly,

the femoral subluxation

neck would

and the margin of the cup or of increase the forces involved, and it

has been suggested that cement particles to enter arthoplasty

Once occurred

in some

cases

loosening

of

this the

mechanism

may

articulating part (Isaac et al. 1986).

the

the bone-cement

socket

junction

or

the

becomes

allow of

stem part

the

changes

of the

“joint cavity” and any volume and pressure changes, causing migration of particles, will now involve all parts of that cavity. Repeated pumping action and mechanical abrasion of the outside of the HDP socket could thus

VOL.

69-B,

No.

1, JANUARY

1987

in

technique

possibility

the with

the

which

design

will

impingement

of

of

the

postpone

or

or wear

at the

possibility

that

the

the acetabular

socket

makes

direct

bone.

REFERENCES

Oiarnley J. Low friction arthrop/asty of the Berlin etc : Springer-Verlag, 1979:320-31.

GH,

Isaac

JR,

Atkinson

cement Charnley

in

MAR.

prostheses. basis ofjoint

hip : theory

and

practice.

D, Wroblewski

performance arthroplasties.

D, Freeman

replacement The scienufic

Medical,

Dowson

long-term low friction

Vernon-Roberts

BM. The role premature failure Med 1986,15(l):19-22.

and Eng

The

tissue

In : Swanson replacement.

response

SAy,

to total

joint

MAR,

eds.

Freeman

Tunbridge

of of

Wells : Pitman

1977:86-129.

Willert

H-G, Semlitsch M. Reactions of the articular capsule artificial joint prostheses. In : Williams D, ed. Biocompatibiity implant materials. Tunbridge Wells: Pitman Medical, 1976:40-8.

Wroblewski

cartilage.

has

junction and even

will be of benefit. Secondly, the design and of insertion of the acetabular cup should

articulation technique preclude contact

any

or of

associated with small erosions on the outside of the socket; wear was an average of 2.52 mm when erosions were medium-sized; and an average of 2.73 mm when the erosions were large (if the rather exceptional Case 17 is excluded, this average becomes 3.38 mm).

During load-bearing, deflection and deformation of the components occurs, resulting in changes in the volume of and the pressure within the cavity containing the implant. Any particles contained within the “synovial” (or rather bursal) fluid are free to migrate according to these changes. Any episode of impingement between

63

ARTHROPLASTY

canal.

the medullary conclude,

is

of

HIP

then, that the changes at the bonecementjunction ofthe acetabulum, hitherto attributed to wear products migrating from the articulating surface may, in a proportion of cases, be secondary to socket loosening. The implications of these findings are We

of the socket

and

loosening

TOTAL

explain some of the changes at the bone-cement of the acetabulum, at the neck of the femur

changes at the bone-cementjunction by the correlation between the depth wear

That

IN CEMENTED

Wroblewski friction

BM.

Wear

J Bone

BM.

of Joint

Direction

arthroplasty.

high-density Surg and

[Br] rate

J Bone

polyethylene

bone

and

l979;6l-B:498-500. of socket

Joint

on

to of

Surg

wear [Br]

in Charnley

1985a;67-B

low-

:577-61.

Wroblewski BM. Charnley low friction arthroplasty in patients under the age of4O years. In : Sevastik J, Goldie I, eds. The young patient with degenerative hip disease. Stockholm : Almqvist & Wiksell, l985b:l97-20l.

Wroblewski arthroplasty.

BM. FifteenClin

to 21-year Orthop;1986;21

results

ofthe

1 :30-5.

Charnley

low-friction