Periprosthetic Bone Remodeling after 12 Years Differs
in Cemented and Uncemented Hip Arthroplasties
Prakash Chandran MS, FRCS (Ortho),
Mohammed Azzabi MRCS,
Mark Andrews FRCS (Ortho), John G. Bradley FRCS
Received: 30 April 2011/Accepted: 4 October 2011/Published online: 21 October 2011
? The Association of Bone and Joint Surgeons1 2011
lead to differences in periprosthetic bone preservation
around cemented and uncemented hips in the long term?
The purpose of this study is to
compare the difference in periprosthetic bone density
between cemented Charnley total hip and uncemented
hydroxyapatite-coated Furlong1THAs at a minimum
followup of 12 years (mean, 16 years; range, 12–24 years).
We studied a cohort of 17 patients who had
bilateral THAs with a cemented Charnley THA on one side
and an uncemented Furlong1hydroxyapatite-coated THA
on the other side. At a minimum followup of 12 years,
Harris and Oxford hip scores were used to determine the
function, and dual-energy x-ray absorptiometry was used to
quantify bone mineral density adjacent to the prosthesis.
Different patterns of stress shielding may
The results of the dual-energy x-ray absorptiometry scan
for cemented and uncemented hips were analyzed using
paired-sample two-tailed t-tests. To compare the Harris hip
scores, a nonparametric Wilcoxon test was used.
Furlong1side in Gruen Zones 2, 3, 5, and 6 of the proximal
femur and DeLee and Charnley Zone 1 of the acetabulum. In
Bone density is better preserved around the
with the Charnley cemented stem.
Level of Evidence
Level III, therapeutic study. See
Guidelines for Authors for a complete description of levels
Periprosthetic bone behavior is complex and poorly under-
stood. Numerous studies have enumerated various patterns
of bone remodeling around cemented or uncemented hip
prostheses. There exists a major difference in bone remod-
eling between them [1, 8, 11, 13, 21]. Alterations of the
physiologic stresses around the hip contribute to the devel-
opment of subsequent adaptive remodeling to determine the
quality ofthe periprosthetic bone.Preoperative bonedensity
and mechanical characteristics of the implant, which
and the surface coating of the prosthesis determine the
Commonly, there is a loss of 10% to 45% of the peri-
prosthetic bone mass during the first years after THA.
Studies have suggested this bone loss is not necessarily
Each author certifies that he or she, or a member of their immediate
family, has no commercial associations (eg, consultancies, stock
ownership, equity interest, patent/licensing arrangements, etc) that
might pose a conflict of interest in connection with the submitted
All ICMJE Conflict of Interest Forms for authors and Clinical
Orthopaedics and Related Research editors and board members are
on file with the publication and can be viewed on request.
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. Chandran, M. Azzabi, M. Andrews, J. G. Bradley
Trauma and Orthopaedics, Scarborough General Hospital,
Scarborough, West Yorkshire, UK
P. Chandran (&)
15, Cresswell Close, Callands, Warrington,
North Cheshire WA5 9UA, UK
Clin Orthop Relat Res (2012) 470:1431–1435
and Related Research®
A Publication of The Association of Bone and Joint Surgeons®
progressive and some degree of restoration of bone density
around implants occurs usually by 2 years [13, 19]. How-
ever, some studies have shown up to 40% loss in average
bone mineral content inside the lesser trochanter and 28%
loss in average bone mineral content 4.8 cm distal to the
lesser trochanter in the medial cortex. The data suggest that
the loss in mineral content may progress and could account
for as much as a 50% decrease in bone mass in the long term
. The quality of periprosthetic bone determines the risk
of periprosthetic fracture and also defines the complexity of
revision surgery if needed. Better periprosthetic bone pres-
ervation can decrease the need for complex reconstruction.
uncemented hip prostheses do not make a direct comparison
between them. Studying the long-term difference in
periprosthetic bone density between the cemented or
uncemented hip prostheses could help in choosing the bone-
preserving prosthesis for hip arthroplasty.
Dual-energy x-ray absorptiometry (DEXA) scans have
been widely accepted as a reliable tool with high repro-
ducibility to quantify bone mineral density (BMD) changes
adjacent to a THA . It is a precise and an accurate
method of measurement for small changes in BMD around
femoral implants [4, 13–15, 26, 27].
We studied a cohort of patients who had bilateral THAs
with a cemented Charnley prosthesis on one side and an
uncemented hydroxyapatite (HA)-coated Furlong1(JRI
Limited, London, UK) prosthesis on the other side. The
aims of this study were (1) to compare the difference in
periprosthetic bone density between cemented Charnley
and uncemented HA-coated Furlong1prostheses at a
minimum followup of 12 years (range, 12–24 years); (2) to
assess if differences in periprosthetic bone density were
associated with differences in Harris or Oxford hip scores;
and (3) to compare radiographic signs of loosening.
Patients and Methods
Between 1980 and 1994, 22 patients had bilateral hip
arthroplasties with the cemented Charnley prosthesis on
one side and an uncemented Furlong1prosthesis on the
other side. The Furlong1prosthesis is fully HA-coated,
and the coating is applied by plasma spray with thickness
of 200 lm and bond strength of 40 Mpa. All surgeries were
performed by two senior authors (MA, JGB) using a sim-
ilar technique. At the time of study, five patients had died
and 17 were alive and were invited to participate in the
study. Seven of the patients were males. The mean age of
all patients at the time of assessment was 78 years (range,
62–93 years). The average time from cemented hip
arthroplasty to assessment was 18 years (range, 13–24
years), and the time from uncemented hip arthroplasty to
assessment was 14 years (range, 12–17 years) (Table 1).
We obtainedlocal and regional
We clinically assessed all patients by recording Oxford
and Harris hip scores. Standardized AP and lateral radio-
graphs were taken. The AP projection was centered on the
symphysis pubis and was taken at a standard distance of
1 m. We used Gruen zones  for the femoral component
and DeLee and Charnley  zones for the acetabular
component as references. The radiographs were assessed
for radiolucent lines, osteolysis, and endosteal bone for-
mation (spot welds) by one observer (PC); pedestal
formation was used to assess fixation and stability of the
uncemented stem (Fig. 1).
All patients had DEXA scans of both hips to determine
the quality of bone around the prosthesis. We collected
data regarding bone density and remodeling patterns. The
DEXA scanner used was a GE LUNAR prodigy ortho-
paedic scanner (GE Medical Systems Lunar, Milwaukee,
WI, USA), a narrow-angle fan-beam densitometer. We
used validated orthopaedic analysis software (GE Medical
Systems Lunar) solely to measure the periprosthetic bone
density excluding metal and cement artifacts; Gruen and
DeLee-Charnley zones were used as references and were
quantified in mg/cm2.
We analyzed the results from the DEXA scans using
paired-sample two-tailed t-tests. To compare the Harris hip
scores, a nonparametric Wilcoxon test was used. Pearson
correlations were done to examine the relationship between
the bone density measures (averaged for each zone) and the
Table 1. Comparative details of cemented and uncemented THAs*
Details Minimum MaximumMeanStandard
Age of patient at time of uncemented operation54.4 80.365.27.9
Age of patient at time of cemented operation38.479.459.69.9
Age of patient at time of scan61.692.777.88.9
Time between cemented operation and scan13.324.018.2 3.4
Time between uncemented operation and scan12.2 16.814.6 2.6
* Data in years.
1432Chandran et al. Clinical Orthopaedics and Related Research1
DEXA scans showed the BMD was significantly higher
acetabulum (Table 2). In all other zones, there was no
difference. Age was negatively correlated with bone density
in Gruen Zones 6 and 7 and acetabular Zones 2 and 3.
Comparison of Harris and Oxford hip scores showed no
statistically significant difference between the two hips
(p = 0.108).
All prostheses were well fixed, which included both
stems and the cups on either side. Radiographs showed
radiolucent lines in two Gruen zones in two cases around
the femur on the cemented Charnley prosthesis side. No
osteolysis, loosening, or migration of the prosthesis was
seen in any of the hips. In addition, 13 patients in the
Furlong1uncemented group showed endosteal bone for-
mation (spot welds), and pedestal formation was observed
Periprosthetic bone remodeling is complex and poorly
defined, particularly with relation to the different cemented
or uncemented prostheses currently in use. In our study, the
comparative results revealed better preservation of peri-
prosthetic bone with the uncemented HA-coated Furlong1
prosthesis in Gruen Zones 2, 3, 5, and 6 on the femoral side
Fig. 1 A bilateral THA with a cemented Charnley prosthesis on one
side and the uncemented HA-coated Furlong1uncemented prosthesis
on the other side is shown.
Table 2. Comparison of various zones between two sides (paired-samples t-test)
Zones Paired differences Significance
95% confidence interval of the difference
Z1 cemented –
?0.185 0.404 0.104
Z2 cemented –
Z3 cemented –
Z4 cemented –
Z5 cemented –
Z6 cemented –
?0.410 0.400 0.122
Z7 cemented –
CZ1 cemented –
CZ2 cemented –
CZ3 cemented –
Z = Gruen femoral zones; CZ = DeLee-Charnley acetabular zones.
Volume 470, Number 5, May 2012Periprosthetic Bone Remodeling in the Hip1433
and DeLee and Charnley Zone 1 on the acetabular side
when compared with the cemented Charnley prosthesis.
Our study has several limitations. It lacks the baseline
preoperative, postoperative BMD, and serial postoperative
measurements of bone density; these data would have
helped to identify longitudinal long-term changes resulting
from the implantation and subsequent remodeling and also
helped us to determine if the prosthesis has better preserved
or increased the BMD in the periprosthetic region. Our
primary aim was to compare the long-term difference in
periprosthetic bone density between the cemented and
uncemented HA-coated implants and the available data
helped us to make that comparison. The followup of the
patients who underwent cemented hip arthroplasties is
approximately 4 years longer than for the patients who had
the uncemented arthroplasties. Theoretically, the cemented
hip prostheses have been in place longer and therefore, it
might be expected that more bone was lost. Some studies
have shown remodeling in the periprosthetic region varies
with time and reaches homeostasis by approximately
2 years [1, 10] and few changes are expected later. Our
study involves observing long-term homeostasis in bone
remodeling and we believe the difference in timing of
implantation of cemented and uncemented implants would
not skew our results. Age has been found to negatively
correlate with bone densities in femoral Zones 6 and 7 and
acetabular Zones 2 and 3, suggesting older age is associated
with lower bone densities. The small sample size in our
study gives little power to detect such relationships. All
radiologic observations were made once by one observer
(PC), which could introduce interobserver and intraobserver
bias and adds to the limitation of the radiologic findings.
There are no long-term studies that directly compare
cemented and uncemented periprosthetic bone remodeling.
In the short term, up to 4 years , studies show that on the
femoral side, the cemented prosthesis induced bone mass
cortex and with the uncemented stem produced significant
bone resorption in the area of the lesser trochanter and in the
comparison, our study showed a different pattern of bone
remodeling with greater preservation of bone density in the
distal medial and the distal lateral cortex with the
Charnley cemented prostheses  have observed that at
1 year, there was a reduction in BMD of 6.7% in the calcar
region and an increase of 5.3% in the femoral shaft distal to
the tip of the implant . Studies with an uncemented
HA-coated prosthesis  showed that the BMD was lower
in Gruen Zones 1 and 7 and concluded prosthesis design
influences periprosthetic bone loss. Similar studies with
HA-coated ABG prostheses showed bone density values
averaged between 96% and 113.8% for Gruen Zones 1 to 6,
and in Zone 7, there was a decline to an average of 72.1% at
24 months . In contrast, one study  showed a 40%
loss of bone proximally and 49% distally at 7 to 14 years
. In our study with the HA-coated Furlong1prosthesis,
we observe preservation in the BMD in Gruen Zones 2, 3, 5,
bone density observed in our study could be the result of the
mechanical properties and load transmission characteristics
of the prosthesis . The femoral stems in the Furlong1
prosthesis transmit load largely in the metaphyseal-
suggesting a stress-related remodeling pattern for long-
On the acetabular side, the uncemented socket induced
bone resorption at the medial and caudal zones, and the
cemented socket showed significantly increased BMD in
the cranial zone . Other studies with the cemented
acetabular component observed the periacetabular bone
mass returned to baseline values at 2 years with a pattern
suggesting uniform transmission of load to the acetabulum
. Our study showed the BMD was better preserved in
DeLee and Charnley Zone 1 of the acetabulum. These
observations reflect the difference in load transmission of
the different socket designs suggesting a more uniform load
distribution with the Charnley cups as compared with the
screw-in design of the uncemented Furlong1cups, which
probably had a higher load transmission in Zone 1 .
HA coatings induce bony ingrowth onto the surface of
the prosthesis; its influence on the periprosthetic BMD is
not clear. Although a fully HA-coated stem is expected to
induce greater bone apposition, wider trabecular struts, and
more connectivity compared with half HA-coated stems
, or tapered corundum-blasted titanium stems , it is
not clear if the HA coating has any role in better preserving
bone stock, with studies showing good bony integration
with uncemented nonbioactive surface implants [7, 18].
With good survival of the HA-coated Furlong1cup and
stem , better preservation of periprosthetic bone would
potentially make revision surgery less complex and also
possibly decrease the risk of periprosthetic fracture.
Additional long-term studies of remodeling and peripros-
thetic bone density between cemented and uncemented
implants can help us understand preservation and behavior
of periprosthetic bone stock.
Bone density is better preserved around the uncemented
HA-coated stem in Gruen Zones 2, 3, 5, and 6 on the
femoral side and Zone 1 on the acetabular side compared
with the Charnley cemented stem.
biostatistics, University of York, for assistance with the statistical
We thank Dr Jeremy Miles, senior lecturer in
1434 Chandran et al.Clinical Orthopaedics and Related Research1
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