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
