SYMPOSIUM: PAPERS PRESENTED AT THE ANNUAL CLOSED MEETING OF THE
INTERNATIONAL HIP SOCIETY
THA Using Metal-on-Metal Articulation in Active Patients
Younger Than 50 Years
Christian P. Delaunay MD, Franc ¸ois Bonnomet MD,
Philippe Clavert MD, Philippe Laffargue MD,
Henri Migaud MD
? The Association of Bone and Joint Surgeons 2008
expectancies and of patients who are younger and more
active is the longevity of their total hip arthroplasty. We
retrospectively reviewed 83 cementless total hip arthro-
plasties in 73 patients implanted with metal-on-metal
articulation. All patients were younger than 50 years old
(average age, 41 years) at the time of the index procedure,
and 80% of the patients had an activity level graded 4 or 5
when measured with the system of Devane et al. A 28-mm
cementless titanium acetabular components. At the most
recent followup (average, 7.3 years), the average Merle
d’Aubigne ´-Postel score improved from a preoperative 11.1
points to 17.4 points. We observed no radiographic evi-
dence of component loosening. Ten acetabular components
had lucency limited to one zone. The 10-year survivorship
with the end point of revision (ie, exchange of at least
one prosthetic or bearing component) was 100% (95%
confidence interval, 90%–100%). Metasul bearings with
The main concern of patients with longer life
cementless acetabular components remain promising in
this high-risk younger patient population. However, addi-
tional followup strategies are recommended to determine
any possible long-term deleterious effects associated with
the dissemination of metallic ions.
Level of Evidence: Level IV, therapeutic study. See the
Guidelines for Authors for a complete description of levels
As a result of the general increase in longevity in the older
population and the expansion of surgical indications,
Improvements in manufacturing processes have led to the
near elimination of catastrophic component fracture
resulting from corrosive and noncorrosive fatigue. Conse-
quently, from the overall successful outcome of primary
THA, a dramatic reduction in the conservative application
of these surgical procedures has resulted in a growing
application of THA in younger and more active individu-
als. The rate of THA performed in ‘‘younger’’ patients, as
reported in various national registries, ranges from less
than 4% in patients younger than 45 years old up to 15% in
patients younger than 55 years old [2, 5, 15, 26, 44, 50].
The primary concern of patients with longer life
expectancies and of patients who are younger and more
active is the longevity of their THA. Annual reports of the
Swedish Hip Arthroplasty Registry [15, 36] consistently
document among patient-related risk factors young age (ie,
younger than 50 years) substantially reduces the survival of
all types of primary THAs. The Maurice E. Mu ¨ller
Research Center in Orthopaedic Surgery at the University
of Bern reported the risk of aseptic stem loosening
One author (CD) certifies that he has received payments or benefits
from a commercial entity (Zimmer-GmbH, Winterthur, Switzerland)
related to this work.
Each author certifies that his or her institution has approved or waived
approval for the human protocol for this investigation and that all
investigations were conducted in conformity with ethical principles of
C. P. Delaunay (&)
Department of Orthopaedic Surgery, Clinique de l’Yvette, 67-71
route de Corbeil, 91160 Longjumeau, France
F. Bonnomet, P. Clavert
Ho ˆpital Hautepierre, CHRU de Strasbourg, Strasbourg, France
P. Laffargue, H. Migaud
Ho ˆpital Salengro, CHRU de Lille, Lille, France
Clin Orthop Relat Res (2008) 466:340–346
increases by 1.8% for each year of age reduction at the time
of index surgery .
High activity level is highlighted worldwide as the
major factor affecting prosthetic reconstruction durability
as a result of conventional polyethylene (PE) wear. Even in
a center of excellence, cemented fixation of the THA using
low friction arthroplasty (LFA), considered worldwide as a
gold standard, cannot achieve a long-lasting outcome. In
patients younger than 50, the best results have been
reported with the Kerboull cemented hip, providing
85.4% ± 5% survival at 20 years . At worst, in patients
younger than 40 years of age, the Wrightington survival
was 76% at 20 years and none of the cups with a wear rate
greater than 0.2 mm per year survived 25 years .
However, activity level varies considerably between
patients of the same age class (body mass index, type of
work, sports, leisure activities) [10, 51]. Moreover,
younger candidates for THA are not normally active as a
result of the etiology of their disease (eg, juvenile arthritis,
avascular necrosis, or developmental dysplasia of the hip)
. Obviously, cemented fixation of low-friction torque
metal-on-PE THA in younger active patients does not
achieve the goal of longevity.
We hypothesized cementless fixation and hard-on-hard
bearings could improve THA survival in a highly active
Materials and Methods
We retrospectively reviewed data from 73 patients (83
hips) from three orthopaedic centers on all THAs per-
formed in active patients younger than 50 years old
between 1995 and 2004. All patients had a cementless
primary THA with 28-mm metal-on-metal (MoM) bear-
ings. To reduce patient-related bias (eg, bone quality,
functional needs) and surgery-related technical difficulties
(eg, anatomic deformity, previous surgery), we excluded
patients with high dysplasia (greater than Crowe II),
rheumatoid arthritis, and juvenile arthritic hips, and those
with a low activity level. Among the 73 patients, there were
58 male and 15 female patients (gender ratio 4:1) with an
average age at surgery of 40.7 years (range, 23–49 years).
Twenty-eight patients were graded Charnley A, 42
Charnley B (10 bilateral), and three Charnley C. One
patient with a Merle d’Aubigne ´-Postel score  of 17
points after the first postoperative year was lost to fol-
lowup. For the 82 hips with available information at the
latest followup (minimum, 2 years; average, 7.3 years;
range, 2–10.4 years), using the classification of Devane
et al.  preoperative activity level was Grade 3 in 15
patients, Grade 4 in 31 patients, and Grade 5 in 27. The
preoperative surgical diagnoses included aseptic necrosis
in 35 hips (42%), secondary arthritis in 29 hips (dysplasia
Crowe I and II, 23; posttrauma, four; Legg-Calve ´-Perthes
disease, two), and osteoarthritis in 19 hips. Previous sur-
gery was noted in 12 hips (14.5%): five fracture internal
fixations (four of the femoral neck and one acetabulum),
three core decompressions, two shelf procedures, one
femoral osteotomy, and one Chiari pelvic osteotomy. By
surgical site location, the patient contribution to the study
was 40 in Lille (Center A) by three surgeons, 24 in
Longjumeau (Center B), and 19 in Strasbourg (Center C)
by one surgeon in each of these two last centers.
The first author and all coauthors were the five operating
surgeons (CD in Center A; HM, PL in Center B; and FB, PC
in Center C). Sixty-four THAs were performed through a
posterolateral approach (in Centers A and B), whereas 19
were operated on through a transgluteal approach (Center
C). In all cases, a Zweymu ¨ller-Alloclassic-SL femoral
component was implanted without cement (Zimmer, Win-
terthur, Switzerland). The MoM bearings were composed of
forged, high-carbide cobalt-chromium alloy Protasul-21
WF (ISO 5832–12, MetasulTM; Zimmer). All acetabular
components were titanium metal-backed components from
the same manufacturer (Zimmer) and implanted without
cement. However, the acetabular components were of two
different profiles: 59 were hemispheric press-fit cups (40 of
the Armor1 design with titanium mesh and one or two
additional screws in Center B, and 19 of the press-
fit hydroxyapatite1 design without screws in Center C)
and 24 were conical threaded rings (Alloclassic-CSF1 in
Center A) (Fig. 1). All PE liners for the three designs were
made in GUR 1020 resin sterilized by gamma radiation in
nitrogen (ex-Chirulen1; Ticona, Oberhausen, Germany).
The capture mechanism was of the ‘‘snap-fit fastened’’ type
for all three designs, with antirotation devices by additional
two thin bottom spikes for the press-fit HA cup or by pegs
engaging in metallic shell rim grooves (two for the Armor
cup and four for the CSF threaded cup).
Each author clinically and radiographically reviewed
their own patients. Clinical results were graded according
to the Merle d’Aubigne ´-Postel scoring system with a
maximum of 18 points . Radiographic results for the
femoral component were described according to Gruen
 and for the acetabular component according to DeLee
and Charnley  on anteroposterior radiographs. Femoral
component stability and osseointegration were assessed
according to the method described by Engh et al. 
(calcar atrophy, spot welds, stress shielding, and pedestal).
Wear was measured according to the method described by
Livermore et al. .
Survivorship analysis was conducted according to the
Dobbs life table with 95% confidence intervals calculated
with the Wilson quadratic method as recommended by
Dorey and Korn .
Volume 466, Number 2, February 2008THA Using Metal-on-Metal Articulation 341
The 10-year survivorship for the end point of THA com-
ponent revision for any cause was 100% (95% confidence
interval [CI], 89.6%–100%). These data indicated our
hypothesis about the beneficial effect of cementless THA
implant fixation and hard-on-hard metallic bearings
remained thus far valid (Table 1).
The mean Merle d’Aubigne ´-Postel score increased from
a preoperative 11.1 points (range, 6–15 points) to a
postoperative 17.4 points (range, 14–18 points). Osseoin-
tegration was confirmed by radiographic evidence of
periprosthetic spot welds in 51 hips and calcar atrophy in
53 hips. For both acetabular and femoral component pro-
files, there was no radiographic evidence of osteolysis or
loosening in any observed hips. Nevertheless, 10 cases had
radiographic evidence of nonprogressive acetabular com-
ponent lucency limited to only one zone. Bearing wear was
undetectable. Seventy THAs (83%) were graded A
(Fig. 2), 11 THAs (14%) were graded B, two THAs were
graded C (each had a reoperation, see subsequently), and
none were graded D.
We reoperated on two Grade C THAs for unexplained
pain. In one patient (one hip), lateral pain was judged to
be from trochanteric bursitis. Transosseous nodes about
the trochanteric posterior margin were identified and
resected 9 years after the index THA resulting in relief of
pain. In the other patient (one hip), groin pain from
impingement between the cup rim and the psoas tendon
was surgically relieved 5.7 years after the index THA by
tendon release. In these two hips with a secondary surgical
procedure, we observed no visual evidence of macro-
scopic metallosis. For the end point of hip reoperation for
any cause, the 10-year survivorship was 96.4% (95% CI,
Complications included one intraoperative nondis-
placed, incomplete fracture of the greater trochanter, which
was detected on postoperative immediate radiographic
control. The patient was treated with protected weight-
bearing with no adverse postoperative effect on the
outcome. There were no deep infections but two early
superficial infections. We treated one late dislocation from
a violent fall 7.6 years post-THA surgery with closed
reduction; the patient had no recurrence or further adverse
Fig. 1A–C Three
components used in the study
press-fit acetabular component
with titanium fiber-mesh and
threaded acetabular component;
and (C) the press-fit hydroxyap-
atite acetabular component with
342Delaunay et al.Clinical Orthopaedics and Related Research
events. One patient who was 45 years old at the time of the
index surgery died 8 years postoperatively of complica-
tions related to severe alcohol addiction.
A report from the Swedish Hip Registry confirmed the
deleterious effect of young age on THA longevity using
any end point . In its last electronic issue, the proba-
bility of revision for second-generation cemented implants
in patients younger than 50 years was approximately 14%
and 20% at 10 and 13 years, respectively . Our survival
rate of 0% at 10 years with cementless MoM articulating
THA components suggests improvement in THA outcome
in the young and active patient population.
Nevertheless, no definitive conclusions about outcomes
in the younger patient can be drawn before at least a
minimum 10-year followup, and the minimum 2-year and
mean 7.3-year followup of this study is too short to draw
definite conclusions. Our study was also retrospective and
used three cup designs. Although we did not separately
analyze the three cup designs, none were revised for
aseptic loosening and the few complications were not
specifically associated with a particular design.
Femoral component fixation in younger, more active
patients continues to be debated. Ten-year survival rates
greater than 90% have been achieved in patients younger
than 50 years either with Charnley or Charnley-Kerboull
cemented femoral components using the first-generation
cementing technique [24, 29, 30, 49, 59] and with other
cemented femoral components using the second-generation
technique . However, in the younger, more active THA
population, continued optimum outcomes beyond 10 years
have not been achieved with the so-called gold standard
Charnley LFA. In patients younger than 50 years, the LFA
survival rate has been reported as 86% at 15 years ,
74.3% at 20 years in Wroblewski et al. , and 60% at
30 years in the Johnston Iowa series . The results
deteriorate even more in patients younger than 40 years
(76% survival at 20 years) mainly as a result of excessive
Table 1. Dobbs life table and 95% confidence intervals for the end point ‘THA component revision for any cause’ (n = 83 hips)
Examined Withdrawn DeadRevisionNumber
Number of hips
0–1 83000 8383 100%95.58% 100%
1–282100 8382.5100% 95.55%100%
2–380200 8281100% 95.47%100%
3–474600 8077100% 95.25%100%
4–5 67700 74 70.5100% 94.83%100%
5–6 61600 6764100% 94.34%100%
6–75830061 59.5100%93.94% 100%
7–853 500 5856 100%93.58% 100%
8–9421110 5448100%92.59% 100%
9–1024 1800 42 33100% 89.57%100%
10–118 1400 24 17100%81.57% 100%
Fig. 2 This 8.4-year postoperative followup radiograph shows a
primary Alloclassic-SL femoral component and CSF-threaded ace-
tabular component with 28-mm Metasul bearings. The patient is an
active (Grade 5 of Devane et al. ) truck driver who was 46 years
old at the time of the index surgery.
Volume 466, Number 2, February 2008THA Using Metal-on-Metal Articulation 343
PE wear with an average annual rate of 0.11 and 0.12 mm
For the same patient population, modern cementless
femoral components in use since the late 1980s also
showed promising results with 10-year survival rates reg-
ularly greater than 95% with hydroxyapatite-coated [6, 52],
porous-coated , or grit-blasted [1, 55] implants. In a
multicenter study of 1419 primary THAs in active patients
younger than 50 years of age, the 10-year survival rate was
greater than 97% for the cemented Charnley-Kerboull
(polished steel alloy) and for five cementless stems . At
an equivalent 10-year followup, there is still no clear
advantage of one technique for femoral component fixation
in the young and active patient population, but there is no
longer an advantage for cementing as it was repeatedly
stated over the last two decades. Although our results are at
a mean followup of 7.3 years (minimum 2 years), we
report 100% survival of all cementless femoral components
implanted for this study.
On the acetabular side, comparative analyses of the
large database of the Research Center in Orthopaedic
Surgery of the University of Bern reported 10-year survi-
vorship of uncemented press-fit (96.9%) and threaded
(96.7%) titanium acetabular component designs .
Interestingly, the hazard ratio in the incidence of radio-
graphic signs of loosening, adjusted for age and gender,
was nearly twofold better for threaded titanium cups (0.16)
than for press-fit titanium acetabular components (0.29),
with cemented conventional PE acetabular components
being defined as the reference level (1.00). This observa-
tion was also confirmed in the Finnish Arthroplasty
Register, in which the risk of revision for aseptic loosening
in patients younger than 55 years of age operated on for
primary osteoarthritis was three times higher for all-PE
cemented acetabular components than for press-fit porous-
coated uncemented acetabular components . A similar
conclusion was drawn from the meta-analysis of the
international literature conducted by Migaud et al. .
We observed similar radiographic evidence of stable ace-
tabular component fixation in a younger, more active
In the younger, more active patient population, the
introduction of cementless acetabular component fixation
seemed promising. However, the intuitive advantages with
the early design of cementless acetabular components may
have been offset by an increased rate of conventional
modular PE liner revisions resulting from deficient locking
mechanisms, thin PE, and subsequent PE wear [21, 42].
These facts are confirmed by US investigations on patients
younger than 50 years of age using the Harris-Galante I
press-fit cup (HG I; Zimmer, Warsaw, IN). In two series,
efficient primary fixation with adjuvant screws and osseo-
integration into the titanium fiber-mesh led to survival of
98% or higher at 10 years, but overall results were marred
by periprosthetic osteolysis (observed in 20% and 23% of
hips) and substantial PE wear (average annual rate 0.15 and
0.19 mm, respectively), and the 10-year survival rate of
80.7% in the Mayo Clinic series [7, 18]. However,
McAuley et al.  reported on a cohort of patients
50 years and younger. The survival rate for six different
(± 3.86%) and 60% (± 9.8%) at 10 and 15 years, respec-
tively, which was mainly the result of thin conventional PE
liners . Despite the in vitro superior tribology of
alumina-on-alumina articulating surfaces , we turned
our interest to the MoM combination. Twenty-eight milli-
meter, forged, high-carbide ([C], 0.2%–0.25%) CoCr alloy
femoral articulations were introduced in France in 1994 at
the senior author’s (CD) institution (Metasul; Zimmer,
ex-Centerpulse, Winterthur, Switzerland) . The compo-
nent was CE-marked in 1995 and FDA-cleared in 1998. In
the general population, cementless fixation of Metasul-
layered acetabular components was achieved with various
component configurations [11, 35, 45]. Other MoM com-
binations, with low carbon CoCr alloys, demonstrated poor
wear properties . This has been the case with the low-
carbon ([C], 0.05–0.08) Sikomet SM21 (Sikov, Medizin-
technik, Austria) in which disappointing results of survival
rates of 93% at 6 years and 91% at 7 years were reported
[33, 41]. In patients younger than 50 years old, provided
osseointegration of the acetabular component is achieved,
our results of Metasul MoM THA survival remains similar
to other independent reports at 5 years (100%) and at
7 years (100%) [31, 39]. These data indicated satisfactory
midterm results can be obtained in younger and more
active patients with high-carbon Metasul 28-mm articular
bearing surfaces across a variety of cementless shell pro-
files, including microporous threaded cups [12, 48].
Metallic wear particles are markedly smaller than PE
wear particles and can easily disseminate in the whole body
before urinary excretion [10, 28]. Therefore, MoM bearing
surfaces are associated with the potential risk of systemic
dissemination of metallic ions. This is particularly true for
young, active patients who could be exposed to higher
levels of ions for longer periods of time. Measured sys-
temic metal levels can be used to monitor MoM hip
arthroplasties, but the methodology is demanding and
controversy remains with respect to analytic techniques,
units, and acceptable range level . More interestingly,
blood or serum cobalt and chromium ion levels are not
markedly affected by patient activity [11, 25]. Addition-
ally, carcinogenic concern is loosing argumentative
consistency as epidemiologic data are reported in the
Nordic population . However, temporary increases in
hematopoietic cancers were observed . In addition,
Type IV hypersensitivity reactions have been described
344Delaunay et al.Clinical Orthopaedics and Related Research
around failed MoM THAs that were unknown with non-
metallic bearing surfaces [8, 58]. Better knowledge of the
exact frequency and clinical consequences of these obser-
vations deserves ongoing extensive research. In the
authors’ opinion and according to the current knowledge,
the use of all types of MoM bearings either in conventional
THA or with surface replacement arthroplasty must be
weighed against these potential risks, particularly in
younger individuals. Renal insufficiency and patients with
allergic disposition are certainly not recommended candi-
dates . For women of reproductive age, transplacental
transfer of metallic ions remains controversial [4, 60].
However, from our experience, standard cementless THAs
with 28-mm MoM articulating surfaces have the advanta-
ges of a variety of known standard surgical techniques, are
proven regarding component design and fixation method-
ology, remove conventional PE from the bearing profiles,
and eliminate the adverse issues encountered with early
results of hip resurfacing products (femoral neck fracture).
Improving longevity and long-term outcome of THA in
younger and more active patients remains a challenge. So
far, the cementless grit-blasted titanium Alloclassic-SL
straight taper was well adapted to the standard femoral
configuration selected according to the inclusion criteria.
No difference in fixation quality to the host bone could be
observed among the three types of cementless acetabular
components, despite the fact two were not hydroxyapatite-
coated and one was a threaded ring. From our experience,
the Metasul bearing surface remains promising as an option
in the young and more active patient population. Addi-
tional followup is necessary to determine any possible
long-term deleterious effects associated with metallic ion
tribution in translation and editing of the manuscript.
We thank Robert Eberle for his valuable con-
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