SYMPOSIUM: PAPERS PRESENTED AT THE ANNUAL MEETINGS OF THE HIP SOCIETY
Second-generation Modular Acetabular Components Provide
Fixation at 10 to 16 Years
Paul F. Lachiewicz MD, Elizabeth S. Soileau BSN
Published online: 21 June 2011
? The Association of Bone and Joint Surgeons1 2011
metal-coated acetabular components had high rates of
wear, pelvic osteolysis, and liner dissociation. Second-
generation components were designed to reduce the inci-
dence of these problems but it is unclear whether the
changes achieved these goals.
We asked the following questions:
(1) Is the risk of revision surgery for loosening, wear, or
liner dissociation low with the second-generation acetab-
ular component? (2) Is the rate of pelvic osteolysis low? (3)
Can the liner be exchanged without bone cement?
We retrospectively reviewed prospectively col-
lected data from 99 patients (118 hips) undergoing THAs
with one second-generation modular titanium acetabular
component with routine screw fixation and conventional
polyethylene. The minimum followup was 10 years (mean,
12 years; range, 10–16 years). We obtained Harris hip
scores and examined radiographs for loosening and
At last followup, all acetabular components were
well fixed and no titanium shell had been revised or
removed. No liner had dissociation. At most recent
followup, the mean Harris hip score was 89. We observed
pelvic osteolysis in eight hips (7%). There were three
reoperations for dislocation (head-liner exchange only) and
three loose femoral components revised. Two liners (at 11
and 14 years) were exchanged for wear-pelvic osteolysis.
This second-generation modular titanium
fiber-metal-coated acetabular component with screw fixa-
tion had no loosening, no liner dissociation, and a low rate
of pelvic osteolysis at 10 to 16 years. Liner exchange is
practical without use of cement. We continue to use this
component with highly crosslinked polyethylene liners.
Level of Evidence
Level IV, therapeutic study. See
Guidelines for Authors for a complete description of levels
The first and second versions of an uncemented titanium
fiber-metal-coated acetabular component (HGP-I and
HGP-II; both Zimmer, Warsaw, IN) with screw fixation
had a locking mechanism composed of three (HGP-I) or
three to five (HGP-II) sets of thin metal ‘‘tines’’ that were
bent to hold the polyethylene liner [1, 5, 11, 12, 20, 25–27].
This so-called polyethylene locking mechanism was a
major factor implicated in backside wear of the liner,
pelvic osteolysis in 17% to 23%, broken ‘‘tines,’’ and
catastrophic liner dislodgement with inability to safely
replace the liner (without shell removal) without bone
cement [7, 28, 31]. The HGP-II component did not have a
polished inner surface, had a locking mechanism of three to
five sets (dependent on shell size) of metal ‘‘tines’’ fabri-
cated of pure titanium (not titanium alloy), and was thicker
to permit 6.5-mm screws that had a bulbous head.
One of the authors (PFL) is a member of the speakers’ bureau of
Zimmer, and his institution received research support from Zimmer
for a different study.
Each author certifies that his or her institution approved the human
protocol for this investigation, that all investigations were conducted
in conformity with ethical principles of research, and that informed
consent for participation in the study was obtained.
P. F. Lachiewicz (&), E. S. Soileau
Chapel Hill Orthopedics Surgery and Sports Medicine,
101 Conner Drive, Suite 200, Chapel Hill, NC 27514, USA
Clin Orthop Relat Res (2012) 470:366–372
The so-called ‘‘second-generation’’ titanium fiber-metal-
coated acetabular component (Trilogy; Zimmer) was
introduced in 1994 with several notable modifications from
the earlier versions . The polyethylene locking mech-
anism was redesigned to include a locking ring that grasped
the entire periphery of the liner, two metal antirotation tabs
to match cutouts on the liner, and a polar inset for the polar
tab of the polyethylene liner. This design was intended to
permit liner exchange without the use of bone cement. The
inner surface of the component was also highly polished
titanium and was designed for improved polyethylene liner
congruity. These changes were introduced to minimize
rotation of the polyethylene liner in the metal shell,
decrease or eliminate backside wear, and prevent liner
dislodgement. It was hoped that these design features
would result in a clinically low incidence of acetabular
component revision for loosening or wear, radiographic
pelvic osteolysis, and eliminate liner dislodgement at fol-
lowup times greater than 10 years. Two studies with this
acetabular component [8, 9] at minimum 4 years to mean
5.7 years followup reported only one loose component and
one case of osteolysis. We previously reported this device
in 93 patients (112 hips) at 7 to 13 years followup (mean,
9.5 years) and found no loosening or dissociation and only
two cases of pelvic osteolysis .
We asked the following questions: (1) Is the rate of
revision surgery for loosening, wear osteolysis, or liner
dissociation low at longer followup? (2) Is the rate of
pelvic osteolysis low at 10 to 16 years with this component
and conventional polyethylene liners? (3) Can the polyeth-
ylene liner be exchanged without bone cement?
Patients and Methods
We retrospectively reviewed prospectively collected data
from all 219 patients having 250 primary THAs between
March 1994 and December 1999. All patients had the
second-generation titanium fiber-metal acetabular compo-
nent (Trilogy, multihole; Zimmer), and no other acetabular
component was implanted during this time. Ninety-three of
these 219 patients were previously reported . No other
acetabular component was used during the study period.
Also during this time, 14 of these patients (14 hips) were
included in a prospective, randomized study comparing the
rate of dislocation between a 28-mm and 22-mm head size
. Of the original 219 patients, 87 patients (97 hips) had
died and 33 patients (35 hips) were lost before 10 years
followup. Telephone contact only was made with 10
patients (11 hips) of the ‘‘lost’’ group and they had not had
any additional surgery on the hip. These exclusions left 99
patients (118 hips) with a minimum followup of 10 years
(mean, 12 years; range, 10–16 years). There were 56
female patients (66 hips) and 43 male patients (52 hips)
with a mean age of 59.3 years (range, 22–81 years). The
mean patient weight was 77 kg (range, 44–115 kg), the
mean height was 170 cm (range, 150–188 cm), and
the mean body mass index 26.7 kg/m2(range, 16.5–38.6
kg/m2). The preoperative diagnosis was osteoarthritis in 75
hips, osteonecrosis in 19, rheumatoid arthritis in 13, and
other diagnoses in nine.
All surgery was performed by one surgeon (PFL) using
previously reported techniques . The femoral compo-
nent was cemented in 73 hips and uncemented in 45 hips
with the decision based on patient age and bone quality.
The femoral head size was 28 mm in 83 hips, 22 mm in 18
hips, 26 mm in 16 hips, and 32 mm in one hip. The deci-
sion on head size was based on both the outer diameter of
the acetabular component  and a desired minimum
polyethylene thickness of 7 mm. The conventional poly-
ethylene liners  had a mean thickness of 9.4 mm
(range, 7.2–13.3 mm).
Patients were mobilized on the first or second postop-
erative day, either full (cemented femur) or partial
(uncemented femur) weightbearing, with a walker or
crutches for 6 weeks. No formal physiotherapy was
Patients were routinely examined and had radiographs at
6 weeks, 6 months, 1 year, and annually (or biannually) in
two outpatient facilities. The patients were clinically pro-
spectively followed using the Harris hip score 
preoperatively and at routine postoperative intervals by one
clinical research nurse (ESS). AP pelvis radiographs and
true lateral radiographs were routinely obtained in the
recovery room. Standardized supine AP radiographs cen-
tered over the pubis and frog-lateral radiographs were
performed at each followup visit with technicians specifi-
cally trained for these radiographs with similar patient and
tube positioning . The radiographs were reviewed (by
both authors at the same time) for pelvic osteolysis, ace-
tabular radiolucent lines, and component shift or migration
using the method described by Massin et al. . The
acetabular abduction angle, measured on the 6-week
postoperative pelvic radiograph, was a mean 42.8? (range,
30?–55?). Acetabular radiolucent line thickness and loca-
tion were described using the method of DeLee and
Charnley . Pelvic osteolysis was described using the
method of Maloney et al. . Oblique pelvic radiographs
and computerized axial tomography were not performed.
Survivorship analysis of the entire cohort was performed at
10 and 15 years with three end points or definitions of
failure: shell removal, reoperation only for wear or oste-
olysis, and revision of the hip arthroplasty for any reason
(including femoral loosening, recurrent dislocation, and
Volume 470, Number 2, February 2012 Second-generation Acetabular Component367
There were no reoperations for acetabular component
loosening, migration, or polyethylene liner dissociation. No
acetabular titanium shell has been removed for any reason.
There were no apparent insertional fractures of the ace-
tabulum intraoperatively. The mean preoperative Harris hip
score for the entire cohort was 53.2 points (range, 21–81
points) and the mean postoperative hip score was 89.3
points (range, 57–100 points).
We observed pelvic osteolysis in eight hips (7%), and
these included the two patients who had revision for oste-
olysis. In six hips, a lesion was noted in one acetabular zone
and in two hips, a lytic lesion was noted in two zones. In one
patient, the pelvic osteolytic lesion was noted on the 8-year
followup radiograph, whereas in the other seven hips, the
lesion was first noted on the 10- to 15-year followup radio-
graph. Acetabular radiolucent lines were seen in 15 hips (15
patients). In 14 hips, it was in one zone only, in Zone 1 or
Zone 3, and less than 1 mm in thickness. In one hip, there
were radiolucent lines less than 1 mm thick in two zones.
Eight patients (7%) had a reoperation. Three patients
with cemented femoral components were revised for
aseptic loosening. The polyethylene liner was routinely
exchanged at the time of femoral component revision.
Three patients had reoperations for recurrent posterior
dislocations (one each with a 28-mm, 26-mm, and 22-mm
femoral head). These patients had exchange of the poly-
ethylene liner with increase in size of the femoral head.
Two of these patients had no additional dislocations at 11
and 6 years, respectively. One patient had an increase of
the femoral head from 28 to 36 mm at 11 years but has had
two anterior dislocations in the 3 years after the liner-head
exchange. There were two reoperations (1.7%) for symp-
tomatic pelvic osteolysis-polyethylene wear. These two
patients had mild groin pain, presumably as a result of hip
synovitis. One patient had liner exchange with grafting of
osteolysis by another surgeon at 11 years and one patient
had liner exchange without grafting at 14 years. Both
patients had relief of symptoms at 2 years postoperatively.
The 10- and 15-year survival for the acetabular shell was
100%. With failure defined as reoperation for wear or
osteolysis, the 10-year survival rate was 100% and the
15-year survival rate was 93.4% (95% confidence interval,
72.36% to 98.75%) (Fig. 1). With failure defined as any
reoperation, the 10-year survival rate was 94.33% (95%
confidence interval, 90.13% to 96.77%) and the 15-year
survival rate was 88.15% (95% confidence interval,
69.47% to 95.20%) (Fig 2).
The results of uncemented acetabular components at fol-
lowup times of 10 years and longer are dependent on a
number of implant factors, including fixation ingrowth
surface, adjuvant fixation, polyethylene fabrication, and poly-
ethylene liner locking mechanism. This second-generation
Fig. 1 Survivorship curve with the end
point of revision (liner exchange only)
for wear or osteolysis.
368 Lachiewicz and Soileau Clinical Orthopaedics and Related Research1
unique polyethylene locking mechanism and a polished,
more congruent inner surface. In our previous report of 111
hips at 7 to 13 years, we noted no loosening or dissociation,
. We asked the following questions: (1) Is the risk of
revision surgery for loosening, wear, or liner dissociation
low with the second-generation acetabular component? (2)
Is the rate of pelvic osteolysis low? (3) Can the liner be
exchanged without bone cement?
This study has several limitations. First, we had no
control group comparing these patients with the second-
generation component with those having the first two
versions of the first-generation titanium fiber-metal ace-
tabular component. Second, 87 patients (39%) had died and
33 patients (15%) were lost to followup before 10 years.
However, this is to be expected in a 10-year followup
study. Third, we did not perform oblique pelvic radio-
graphs or computerized axial tomography and the rate of
pelvic osteolysis might be underestimated. Fourth, poly-
ethylene wear measurements  using digital techniques
with computerized edge detection [2, 16, 23, 29] were not
performed, because we did not have digital radiography. In
our previous study , we reported a difference in the rate
of polyethylene wear between the two types of standard
polyethylene (irradiated in air and irradiated in nitrogen
gas) used with this component, and we did not repeat the
analysis for this study. Fifth, we had a single observer for
our radiographic findings and had no way to assess the
reliability of our findings. A final limitation is that we did
not measure the size of the osteolytic lesions on the plain
radiographs, because we believe this would be unreliable.
A number of studies reported 10-year results of first-
generation uncemented acetabular components [1, 3, 4, 10,
lack of consistency in defining the cohorts, differences in
followup time, and lack of survivorship data using the three
end points defined in this study. In addition, none of the
reported components is considered a second-generation
the question of whether the design changes solved the prob-
shell revision and osteolysis. Our findings are similar to the
two short-term followup studies of this second-generation
component. Della Valle et al. reported the minimum 4-year
results of 308 acetabular components (77% without screws)
. Only one component was revised for aseptic loosening
of the patients in that study (64 years) was greater than the
study, 65 hips followed for a mean of 5.7 years, Della Valle
118 hips with the second-generation titanium fiber-metal
(range, 10–16 years), there were only two hips (1.8%)
revised for symptomatic polyethylene wear and osteolysis
and there were eight hips (7%) with pelvic osteolysis.
Fig. 2 Survivorship curve with the end
point of revision for any reason (fem-
oral component loosening, recurrent
dislocation, and wear osteolysis).
Volume 470, Number 2, February 2012 Second-generation Acetabular Component369
Table 1. Uncemented acetabular component survival
Kawamura et al. 
Udomkiat et al. 
Della Valle et al. 
Archibeck et al. 
Garcia-Rey et al. 
Grobler et al. 
minimum 10 (NS)
Claus et al. 
minimum 10 (13.7)
minimum 10 (12)
Bojescul et al. 
Lachiewicz (current study)
94.3 (10 years)
100 (10 years)
100 (10 years)
88.2 (15 years)
100 (15 years)
93.4 (15 years)
HG-I = Harris-Galante I; HG-II = Harris-Galante II; Trilogy, all Zimmer, Warsaw, IN; PCA = porous-coated anatomic, Howmedica Osteonics, Rutherford, NJ; AML = anatomic medullary
locking; Duraloc 300, Duraloc 500, all DePuy, Warsaw, IN; Arthropor, Joint Medical Products, Stamford, CT; APR = anatomic porous replacement, Sulzer Orthopedics, Austin, TX;
NS = not stated in article.
370Lachiewicz and SoileauClinical Orthopaedics and Related Research1
Liner exchange for wear, recurrent dislocation, or at the
time of femoral revision was effectively performed without
cement in eight hips of this cohort. While we again note the
difficulty of comparing the various series (Table 1), these
rates appear improved from the historical results with the
first two versions of the titanium fiber-metal acetabular
Based on our observations, we question the need for new
acetabular components with more expensive coatings,
different polyethylene locking mechanisms, or monoblock
(nonmodular) designs. Loosening did not occur with this
titanium-fiber metal-coated component fixed with screws.
Pelvic osteolysis was still seen with this acetabular com-
ponent but at a very low rate at 10 to 16 years. However,
this cohort used ‘‘conventional’’ polyethylene liners. The
author continues to use this acetabular component for pri-
mary THAs but now uses highly crosslinked polyethylene
liners in all patients.
radiographic measurements, Mr Rich Sloane for performing the sur-
vival analysis, and Mr Stephen Perlman for assistance with the
We thank Dr John Hubbard for assistance with
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372 Lachiewicz and SoileauClinical Orthopaedics and Related Research1