Download - Strontium Ranelate Enhances Callus Strength More Than PTH 1-34 in an Osteoporotic Rat Model of Fract
Strontium Ranelate Enhances Callus Strength More ThanPTH 1-34 in an Osteoporotic Rat Model of Fracture Healing
Bjoern Habermann • Konstantinos Kafchitsas •
Gavin Olender • Peter Augat • Andreas Kurth
Received: 6 May 2009 / Accepted: 26 October 2009 / Published online: 4 December 2009
� Springer Science+Business Media, LLC 2009
Abstract Treatment of an underlying disease is often
initiated after the occurrence of an osteoporotic fracture.
Our aim was to investigate whether teriparatide (PTH 1-34)
and strontium ranelate affect fracture healing in ovariec-
tomized (OVX) rats when provided for the first time after
the occurrence of an osteoporotic fracture. We combined
the model of an OVX rat with a closed diaphyseal fracture.
Sixty Sprague Dawley rats were randomly assigned to four
groups. Fracture healing in OVX rats after treatment with
pharmacological doses of strontium ranelate and PTH 1-34
was compared with OVX and sham-treated control groups.
After 28 days, the femur was excised and scanned by micro
computed tomography and the callus evaluated, after which
biomechanical torsional testing was performed and torque
and toughness until reaching the yield point were analyzed.
Only treatment with strontium ranelate led to a significant
increase in callus resistance compared to the OVX control
rats, whereas both PTH 1-34 and strontium ranelate
increased the bone volume/tissue volume ratio of the
callus. The PTH 1-34–increased trabecular bone volume
within the callus was even higher compared to sham. As for
the callus tissue volume, the increase induced by strontium
ranelate was significant, contrary to the changes induced by
PTH. Callus in strontium ranelate–treated animals is more
resistant to torsion compared with OVX control rats. To
our knowledge, this is the first report of the enhancement of
fracture healing by strontium ranelate. Because both
treatments enhance bone and tissue volume within the
callus, there may be a qualitative difference between the
calluses of PTH 1-34– and strontium ranelate–treated OVX
rats. The superior results obtained with strontium ranelate
compared to PTH in terms of callus resistance could be the
consequence of a better quality of the new bone formed
within the callus.
Keywords OVX rats � Osteoporosis � Fracture healing �PTH � Strontium ranelate
Osteoporosis leads to a reduction of the trabecular structure
in cancellous bone and to an increase in bone fragility. As a
result of these structural changes, a higher incidence of
bone fractures after inadequate trauma occurs in those
patients. In addition to the treatment of the fracture, it is
essential to initiate adequate treatment of the underlying
disease, i.e., osteoporosis. Because in most cases osteopo-
rosis is diagnosed at the time of fracture occurrence,
information on the influence of antiosteoporotic drugs on
fracture healing is essential.
Strontium ranelate has proven its efficacy in reducing
the risk of vertebral, nonvertebral, and hip fracture in
women with postmenopausal osteoporosis [1, 2]. This
efficacy of strontium ranelate is independent of baseline
risk factors [3] and is maintained during 5 [4] and even
B. Habermann (&) � K. Kafchitsas � A. Kurth
Department of Orthopaedics and Orthopaedic Surgery,
University Medical Center of the Johannes Gutenberg University
Mainz, Langenbeckstrasse 1, 55131 Mainz, Germany
e-mail: [email protected]
K. Kafchitsas
e-mail: [email protected]
A. Kurth
e-mail: [email protected]
G. Olender � P. Augat
Biomechanical Research Laboratory, Traumacenter Murnau,
Murnau, Germany
e-mail: [email protected]
P. Augat
e-mail: [email protected]
123
Calcif Tissue Int (2010) 86:82–89
DOI 10.1007/s00223-009-9317-8
8 years [5]. Strontium ranelate has a dual mode of action
[6, 7]. In vitro, it increases bone formation by enhancing
preosteoblast replication, differentiation, and activity [8–
10] and decreases bone resorption by inhibiting osteoclast
differentiation, activity and stimulating osteoclast apopto-
sis [10–13]. In vivo, strontium ranelate increases bone
strength in intact rats or totally prevents its decrease in
ovariectomized (OVX) rats as a result of its positive effects
on microarchitecture and intrinsic bone quality [14, 15].
Teriparatide (PTH 1-34) has anabolic effects on bone
and increases bone strength [16–19]. A continuous infusion
of PTH 1-34 has catabolic effects, whereas its intermittent
administration has anabolic effects on bone formation. In
osteoporotic women, its intermittent administration leads to
an increase in bone mineral density (BMD) and a reduction
in vertebral and nonvertebral fracture incidence [20]. It was
shown in nonosteoporotic rats that daily administration of
PTH 1-34 enhances fracture healing [21]. Furthermore,
PTH 1-34 enhances callus formation in young, aged, and
OVX rats [22–25].
As the population ages, the prevalence of osteoporotic
fractures increases. Although most fractures heal, approx-
imately 5 to 10% are associated with impaired healing,
including delayed healing or nonunion. Fracture healing is
a long and difficult process, which includes a first phase of
inflammation and resorption and a second phase of bone
formation. Considering the poor quality and quantity of
bone in the elderly, there is a potential for the use of
pharmaceutical agents to enhance fracture healing.
The purpose of the present study was to determine the
effect of two antiosteoporotic treatments on fracture heal-
ing in osteoporotic OVX rats 28 days after fracture
occurrence. PTH, which has been proven to influence
fracture healing in OVX rats [24], was taken as a control
treatment. Strontium ranelate, which acts on both resorp-
tion and formation, is a good candidate to enhance fracture
healing. We combined the rat model of a closed, stan-
dardized diaphyseal fracture of the femur, as introduced by
Bonnarens and Einhorn [26], with the model of a post-
ovariectomy osteopenic rat, mimicking postmenopausal
bone loss [27].
Materials and Methods
Forty-five animals were ovariectomized at the age of
12 weeks, and a further 15 underwent sham operation. At
the age of 24 weeks, osteopenia in the OVX rats was
diagnosed by means of dual-energy x-ray absorptiometry
(DXA). Then, in all animals, a standardized mid-diaphy-
seal fracture was induced. Under general anesthesia
(100 mg ketanest [Ketavet], 1 mg midazolam [Dormicum],
and 10 mg xylazine [Rompun], i.p.), a 0.8-mm Kirschner
wire was introduced into the left femoral canal through a
medial parapatellar incision and arthrotomy of the knee.
After closing the wound, a mid-diaphyseal fracture was
produced by using a falling weight of 650 g over a three-
point bending mechanism. In all groups, the drop height of
the weight was 14 cm and induced by lateral loading. The
fracture was radiographically documented. In all cases, a
straight mid-diaphyseal fracture was induced. The animal
experiments were approved by the Regierungspraesidium
Darmstadt, Germany.
At the time of fracture, the animals were divided into
four groups. Group 1 was the sham control group, and
groups 2, 3, and 4 were the OVX treatment groups. Groups
1 and 2 were treated with NaCl 0.9% s.c. daily, group 3
was treated with 600 mg/kg/d strontium ranelate (pur-
chased from Servier Deutschland GmbH) p.o. daily, and
group 4 received 20 lg PTH 1-34 (purchased from Lilly
Deutschland GmbH) three times a weeks.c. (equivalent to a
dose of 20 lg/kg/d). The fracture was radiographically
documented. The dose of 600 mg/kg/d of strontium rane-
late leads to a blood strontium concentration close to the
human exposure after a therapeutic dose of 2 g/d [15]. The
dose of 20 lg/kg/d PTH 1-34 leads to higher human
therapeutic exposure but is a pharmacological dose used in
rats. The rats were liberated to calcium-reduced food and
water ad libitum (EF R/M, Sniff GmbH). They were killed
after 28 days and the left femurs were immediately
excised, wrapped in NaCl-soaked gauze, and frozen at
-80�C.
The samples were then scanned by MicroCT 80 by
Scanco Medical, Zurich, Switzerland. The whole bone
was scanned, and 600 slices 40 lm in thickness were
placed through the former fracture area. The center of
the fracture callus was defined manually as the point
where the previous organization of the cortical bone in
the fracture area was nearly inexistent. One hundred
slices of 40 lm were placed above and below. The
threshold for calluses was 155–320, whereas it was 320–
1000 for cortical bone and 155–210 for bone marrow.
The evaluation of the data focused on outer callus con-
tour, cortical contour, and marrow contour, as well as
cortical thickness and polar moment of inertia. BMD,
tissue volume (TV), bone volume (BV), and the BV/TV
ratio were recorded. BMD was achieved by measuring
mean voxel values. Mean voxel values (1/mm) could be
equalized to the bone mineral content when the scan was
calibrated for bone. The manufacturer’s software package
was used for image processing and data evaluation
(version 4.04).
After embedding the samples in methylmethacrylate
cement (Technovit, Heraeus Sulzer, Wehrheim, Germany),
torsion testing on the bones was carried out with the axial-
torsional 8874 system by Instron (Darmstadt, Germany).
B. Habermann et al.: Strontium Ranelate Enhances Callus Strength 83
123
Between the different steps of preparation, each specimen
was kept immersed in physiological solution to avoid
drying of the bone that could affect the biomechanical
properties. The speed of torsional testing was 1 degree per
second. Biomechanical testing recorded the modulus of
rigidity and torque until failure. The torque was expressed
in Nm. The yield point indicated the point between the
elastic and plastic phase. At this point, initial microfrac-
tures could be seen. The toughness in terms of the bone’s
resistance to fracture was measured in J/m3. Before anal-
ysis of the biomechanical data, the values were normalized
by combining them with the lower body weight of the sham
group [28].
Data were collected in Excel (Microsoft). All data were
expressed as the mean ± standard deviation. For statistical
analysis, we used one-way analysis of variance, and
P \ 0.05 was considered significant. Sigma Stat (SPSS)
was used.
Results
DXA
Ovariectomy led to a significant reduction in BMD in the
lumbar spine after 12 weeks (-22.07%, P \ 0.05).
Biomechanical Testing
In the OVX group, a huge and significant decrease in
resistance to torsional load was observed compared to the
sham group (OVX -33.16%, P \ 0.001) (Fig. 1; Table 1).
Treatment with strontium ranelate significantly
improved the mechanical properties of the callus when
compared to the OVX control group, while the improve-
ment induced by the treatment with PTH 1-34 did not reach
significance (strontium ranelate ?43.8%, P \ 0.05; PTH
?20.2%, P [ 0.05). Treatment with strontium ranelate or
PTH 1-34 also improved the mechanical properties of the
callus compared to the sham control group but did not
reach significance (strontium ranelate ?30.19%, P [ 0.05;
PTH 1-34 ?7.01%, P [ 0.05).
In all groups, mechanical testing to the yield point
showed no significant differences.
Micro Computed Tomography of the Fracture Callus
Ovariectomy led to a nonsignificant increase in the callus
tissue volume (mm3) when compared to the sham group
(?11.7%; P [ 0.05) and to a nonsignificant decrease in the
callus bone volume (mm3) (-1%, P [ 0.05). As for the
BV/TV ratio, ovariectomy significantly decreased the rel-
ative content of bone in callus (-7.7%; P \ 0.05) (Fig. 2).
The OVX rats showed a significant decrease in BMD
compared to the sham rats (-19.6%; P \ 0.05), which can
be interpreted as a lower BMD (Table 2 and Fig. 3).
PTH 1-34 and strontium ranelate both showed a sig-
nificant increase in bone volume of the callus when com-
pared to OVX control rats (strontium ranelate ?46.3%,
P \ 0,01; PTH 1-34 ?31.9%, P \ 0.05) with no signifi-
cant difference between the two treatments. As for the
callus tissue volume, the increase induced by strontium
ranelate was significant compared to OVX, whereas PTH
induced no change (strontium ranelate ?32.4%, P \ 0.01,
PTH 1-34 ?6.1%, P [ 0.05); the difference between both
drugs was significant (strontium ranelate vs. PTH, ?24.8%,
P \ 0.01). In both the PTH 1-34– and strontium ranelate–
treated animals, BV/TV was significantly increased com-
pared to the OVX control rats (strontium ranelate ?12.2%,
P \ 0.05; PTH 1-34 ?25.6%, P \ 0.001) (Fig. 2). The
BV/TV of the PTH-treated rats was even higher than in the
sham rats (?10.2%, P \ 0.05). Strontium ranelate and
PTH 1-34 both showed a nonsignificant increase in the
bone mineral content (strontium ranelate ?2.5%, P [ 0.05;
PTH 1-34 ?9.8%, P [ 0.05). The difference between them
was also not significant.
Discussion
Osteoporotic fractures in formerly untreated patients
mostly lead to increased morbidity and mortality. The risk
of being bedridden and experiencing further fractures is
increased. Adequate and evidence-based medication for
osteoporosis needs to be initiated. It is unknown whether
certain osteoporotic drugs impair fracture healing or
enhance it, so that patients may experience earlier mobility.
Besides vitamin D and calcium administration, bisphos-
phonates, estrogen, raloxifen, strontium ranelate, and PTH
1-34 are commonly used antiosteoporotic drugs. Up to
now, only preclinical data provided information on the
0
1
2
3
4
5
6
7
8
*
#
SHAM OVX OVX+ PTH 1-34 OVX +Strontium
Ranelate
Fig. 1 Torsion to bone fracture (J/m3). * P \ 0.05 compared to
sham. # P \ 0.05 compared to ovariectomy (OVX)
84 B. Habermann et al.: Strontium Ranelate Enhances Callus Strength
123
impact of the therapeutic agents on fracture healing.
Clinical trials with antiosteoporotic agents focusing on the
outcome of the fracture healing and not on the incidence of
osteoporotic fractures will be necessary.
The OVX rat is a model commonly used to mimic
osteoporosis-induced bone loss. Shortly after ovariectomy,
the changes in bone are close to those observed in human
postmenopausal bone loss. Bonnarens and Einhorn [26]
introduced the model of a standardized closed diaphyseal
fracture, which has been used in many studies since. The
advantage of a closed fracture is that the initial environ-
ment is unchanged and not influenced, as it would be after
an open osteotomy. Combining both models is interesting
to study the impact of an agent on fracture healing in an
osteoporotic environment.
Many previous publications have studied fracture heal-
ing in osteoporotic rats, with diverse outcomes [29–34].
One reason for these diverse outcomes is most certainly the
type of fracture used. These can be differentiated as closed
and open fractures, as well as the type of fixation and the
location, i.e. tibia, femur, or mandibula. Furthermore, there
have been recent reports on fracture models that use the
metaphysis [35, 36]. Such models are interesting because
metaphyseal fractures are probably the most common
fractures encountered in a clinical osteoporosis situation.
The problem with such fractures is the mechanical evalu-
ation of their stability and the reproducibility. The diaph-
yseal fracture in animal experiments is also a well-
established method, easy to standardize, and, after ex-
planting the bone, is suited to mechanical testing. However,
the advantage of a closed fracture as it was used in our
study is that the initial environment is unchanged and not
influenced, as it would be after an open osteotomy. Nev-
ertheless, another reason for a diverse outcome is the use of
different endpoints. Endpoints in the literature vary
between 3 and 18 weeks [21, 22, 29–33, 37]. As described
by Schmidmaier et al. [38], fracture healing in rats runs
through the same phases as it does in any other mammal.
At day 21, the endochondral ossification phase is almost
complete, and the remodeling phase has started [38, 39].
Therefore, we were of the opinion that any impact on
healing would be detectable at day 28.
Table 1 Biomechanical data of fracture callusa
Characteristic Sham OVX OVX ? PTH OVX ? strontium ranelate
Torsional load (J/m3) 5.31 ± 0.96 4.02 ± 1.46* 4.44 ± 1.26 5.39 ± 1.68#
Yield point 0.06 ± 0.06 0.26 ± 0.48 0.11 ± 0.06 0.05 ± 0.04
OVX ovariectomized, PTH teriparatidea Data are presented as mean ± SD
* P \ 0.05 compared to sham# P \ 0.05 compared to OVX
0
0.1
0.2
0.3
0.4
0.5
0.6
SHAM OVX OVX+ PTH 1-34 OVX + Strontium Ranelate
*#
###*
Fig. 2 Callus bone volume/tissue volume. * P \ 0.05 compared to
sham. # P \ 0.05 compared to ovariectomy (OVX). ### P \ 0.01
Table 2 Micro computed tomography data of fracture callusa
Characteristic Sham OVX OVX ? PTH OVX ? strontium ranelate
Callus tissue volume (mm3) 210.19 ± 46.38 234.87 ± 60.46 249.2 ± 4332* 311.18 ± 607***,##,$$
Callus bone volume (mm3) 83.77 ± 27.24 82.95 ± 29.68 109.43 ± 30.89 *,# 121.37 ± 31.04*,##
Callus bone volume/tissue volume 0.39 ± 0.05 0.35 ± 0.05* 0.43 ± 0.06*,### 0.39 ± 0.043#
Bone mineral content of the callus 546.72 ± 57.62 457.27 ± 74.12*** 501.96 ± 45.6* 468.63 ± 59.24*
OVX ovariectomized, PTH teriparatidea Data are presented as mean ± SD
* P \ 0.05; ** P \ 0.01; *** P \ 0.001 compared to sham# P \ 0.05; ## P \ 0.01; ### P \ 0.001 compared to OVX$$ P \ 0.01 compared to PTH
B. Habermann et al.: Strontium Ranelate Enhances Callus Strength 85
123
The primary question addressed in this study was whe-
ther PTH 1-34 and strontium ranelate impact on fracture
healing at endpoint. An impact on fracture healing, be it
either an enhancement or a decrease, is evaluated by
assessing the biomechanical properties of the callus.
Whereas many authors use a three-point bending test [29–
32, 34], there are some reports on the torsional testing [40,
41] that we used. In torsional testing, the initial collapse of
the bony structure is not so much influenced by where the
main load is applied but by the structure of the whole bone
itself. The fracture callus is not homogenous, and a three-
point bending test cannot be representative of the whole
callus biomechanical competence. In addition to mechan-
ical testing, micro computed tomography (lCT) has the
ability to reconstruct the fracture site in 3D and provide
information on remodeling status.
The present results confirm those of previous studies
showing that ovariectomy impairs fracture healing in rats
[24, 42–44], affecting trabecular bone formation and min-
eralization. The OVX group showed a significant decrease
in callus resistance to torsional testing, reflecting a weaker
callus strength and thus validating the model. The lCT
data in our study clearly show that ovariectomy affects the
callus, as previously demonstrated [24, 42–44]. Although
there were no significant differences in the volume of the
callus between the sham and OVX rats, ovariectomy led to
a larger callus. Furthermore, the bone and mineral content
of this callus were considerably and significantly reduced
Fig. 3 a Horizontal slice through fracture callus of an ovariecto-
mized (OVX) Sprague Dawley (SD) rat treated with placebo. bHorizontal slice through fracture callus of an OVX SD rat treated with
strontium ranelate. c Horizontal slice through fracture callus of an
OVX SD rat treated with teriparatide
86 B. Habermann et al.: Strontium Ranelate Enhances Callus Strength
123
in the OVX rats. A significant reduction in BMD 12 weeks
after ovariectomy was confirmed by the DXA data. These
results reflect the inhibition of trabecular bone formation
and the reduction of mineralization in the later stages of
fracture healing in the OVX rat model.
PTH 1-34 (20 lg/kg/d) OVX-treated rats did not show a
significant increase in their callus resistance compared to
the OVX control rats. It had been previously demonstrated
that PTH enhances bone repair in rats. Preclinical studies
have shown a dose-response relationship from 10 to
800 lg/kg/d in the administration of PTH, with higher
doses being more potent for enhancement of fracture
healing by increasing BV/TV, bone callus volume, and
finally callus resistance [45]. But the doses used in many of
these studies were much higher than the recommended
equivalent human doses. Many studies in normal and old
rats have now clearly shown that even at dosages more in
line with those corresponding to clinical exposure (5 to
10 lg/kg/d), PTH enhances fracture healing. Only one
study in OVX rats with low-dose PTH 1-84 (15 lg/kg/d)
showed that this agent is effective in enhancing fracture
healing, improving both callus formation and resistance as
assessed by a three-point bending test, whereas we used
torsional testing [24]. A recent report in a rat cortical defect
model showed that PTH at a clinically relevant dose is not
sufficient to substantially enhance cortical bone repair over
5 weeks [46]. The dose of 20 lg/kg/d used in our study is
an intermediate one when considering previous published
studies. Even if in the present study PTH did not signifi-
cantly increase the resistance of the callus, it significantly
influenced its remodeling. The callus volume tended to
increase, and the within-callus BV/TV was significantly
enhanced. Indeed, as an anabolic agent, PTH has been
shown to enhance callus formation by the early stimulation
of proliferation and differentiation of osteoprogenitor cells
[47].
Treatment with strontium ranelate (600 mg/kg/d leading
to a blood strontium concentration close to the human
therapeutic exposure) led to a significant increase in callus
resistance compared to the OVX control rats. The increase
in stability even exceeded the results of the sham group,
although not significantly. The strontium ranelate effects
on callus remodeling were expressed by a significant
increase in BV/TV and volume of the callus. The BV/TV
of the callus in strontium ranelate OVX-treated rats was
identical to that of the sham rats, suggesting that strontium
ranelate is able to restore a level of bone remodeling
approaching that of a normal rat. Strontium ranelate has
been proven to have a dual mechanism of action in vitro,
acting on both osteoclasts and osteoblasts. It can be thus be
hypothesized that this drug could decrease the first phase of
bone resorption while improving the second phase of bone
formation by promoting the differentiation of bone marrow
cells present at the callus site. Indeed, strontium ranelate
was shown to promote stromal cell differentiation at the
very first stage, but also during latter stages, during
osteoblast differentiation [9, 10].
Whereas both PTH 1-34 and strontium ranelate
increased the volume of trabecular bone within the callus,
only strontium ranelate improved the resistance to torsional
testing. The BV/TV of the PTH-treated rats was even
higher compared to sham rats, but with no subsequent
increase in mechanical resistance. As a consequence, there
may be a qualitative difference between the calluses of
PTH 1-34 and strontium ranelate-treated OVX rats. Indeed,
in an OVX fracture rat model, the callus of PTH-treated
OVX rats remained more porous than in the sham rats,
showing that even if PTH treatment induced increased
amounts of bone tissue in the callus, this bone has still the
altered mechanical properties induced by ovariectomy [24].
As an anabolic agent, PTH increases bone remodeling and
improves microarchitecture. However, the relatively huge
increase in bone remodeling induced by such an agent
could induce an overall decrease in the maturation of
collagen fibers and lead to a poorer intrinsic bone quality.
This has been shown recently in OVX rats receiving PTH
by a decrease in trabecular bone hardness [48]. Strontium
ranelate has been shown to improve bone remodeling,
leading to better microarchitecture and intrinsic tissue
quality in intact and OVX rats [14, 15]. This difference of
effect of both drugs on intrinsic bone quality associated
with a higher callus volume primarily after treatment with
strontium ranelate could explain the better resistance of the
callus after treatment with strontium ranelate compared to
PTH 1-34. A histology study would be required to establish
the exact mechanism of action of both drugs in this model.
Moreover, this study is limited by the fact that analysis was
performed only at endpoint. Nevertheless, the aim was to
study and compare the enhancement of fracture healing
between two drugs at a defined time point and not to study
the acceleration or delay of healing, which would have
required the assessment of different time points.
In conclusion, this is the first report on the enhancement
of fracture healing with strontium ranelate. The callus in
strontium ranelate–treated animals is even more resistant to
torsion in comparison to OVX and sham-untreated animals
and even to those treated with PTH 1-34. PTH did not
significantly enhance the resistance of the callus vs. OVX,
despite a significant increase in the BV/TV ratio within the
callus. The superior results obtained with strontium rane-
late compared to PTH could be the consequence of a better
quality of the new bone formed within the callus. Stron-
tium ranelate might be taken into consideration in order to
enhance fracture repair.
B. Habermann et al.: Strontium Ranelate Enhances Callus Strength 87
123
Acknowledgments The study was supported by Elsbeth Bonhoff
Stiftung. No direct funding from any pharmaceutical company was
received.
References
1. Reginster JY, Seeman E, De Vernejoul MC, Adami S, Compston
J, Phenekos C, Devogelaer JP, Curiel MD, Sawicki A, Goemaere
S, Sorensen OH, Felsenberg D, Meunier PJ (2005) Strontium
ranelate reduces the risk of nonvertebral fractures in postmeno-
pausal women with osteoporosis: treatment of peripheral osteo-
porosis (TROPOS) study. J Clin Endocrinol Metab 90:2816–2822
2. Meunier PF, Roux C, Seeman E, Ortolani S, Badurski JE, Spector
TD, Cannata J, Balogh A, Lemmel EM, Pors-Nielsen S, Rizzoli
R, Genant HK, Reginster JY (2004) The effects of strontium
ranelate on the risk of vertebral fracture in women with post-
menopausal osteoporosis. N Engl J Med 350:459–468
3. Roux C, Reginster JY, Fechtenbaum J, Kolta S, Sawicki A,
Tulassay Z, Luisetto G, Padrino JM, Doyle D, Prince R, Far-
dellone P, Sorensen OH, Meunier PJ (2006) Vertebral fracture
risk reduction with strontium ranelate in women with postmen-
opausal osteoporosis is independent of baseline risk factors.
J Bone Miner Res 21:536–542
4. Meunier PJ, Roux C, Ortolani S, Diaz-Curiel M, Compston J,
Marquis P, Cormier C, Isaia G, Badurski J, Wark JD, Collette J,
Reginster JY (2009) Effects of long-term strontium ranelate
treatment on vertebral fracture risk in postmenopausal women
with osteoporosis. Osteoporos Int 20:1663–1673
5. Reginster JY, Bruyere O, Sawicki A, Roces-Varela A, Fardellone
P, Roberts A, Devogelaer JP (2009) Long-term treatment of
postmenopausal osteoporosis with strontium ranelate: results at
8 years. Bone 45:1059–1064
6. Marie PJ (2005) Strontium ranelate: a novel mode of action
optimizing bone formation and resorption. Osteoporos Int
16(suppl 1):S7–S10
7. Marie PJ (2006) Strontium ranelate: a physiological approach for
optimizing bone formation and resorption. Bone 38:S10–S14
8. Canalis E, Hott M, Deloffre P, Tsouderos Y, Marie PJ (1996) The
divalent strontium salt S12911 enhances bone cell replication and
bone formation in vitro. Bone 18:517–523
9. Zhu LL, Zaidi S, Peng Y, Zhou H, Moonga BS, Blesius A, Du-
pin-Roger I, Zaidi M, Sun L (2007) Induction of a program gene
expression during osteoblast differentiation with strontium rane-
late. Biochem Biophys Res Commun 355:307–311
10. Bonnelye E, Chabadel A, Saltel F, Jurdic P (2008) Dual effect of
strontium ranelate: stimulation of osteoblast differentiation and
inhibition of osteoclast formation and resorption in vitro. Bone
42:129–138
11. Baron R, Tsouderos Y (2002) In vitro effects of S12911–2 on
osteoclast function and bone marrow macrophage differentiation.
Eur J Pharmacol 450:11–17
12. Takahashi N, Sasaki T, Tsouderos Y, Suda T (2003) S 12911–2
inhibits osteoclastic bone resorption in vitro. J Bone Miner Res
18:1082–1087
13. Hurtel AS, Mentaverri R, Caudrillier A, Cournarie F, Wattel A,
Kamel S, Terwilliger EF, Brown EM, Brazier M (2008) The
calcium-sensing receptor is involved in strontium ranelate-
induced osteoclast apoptosis: new insights into the associated
signalling pathways. J Biol Chem 284:575–584
14. Ammann P, Badoud I, Barraud S, Dayer R, Rizzoli R (2007)
Strontium ranelate treatment improves trabecular and cortical
intrinsic bone tissue quality, a determinant of bone strength. J
Bone Miner Res 22:1419–1425
15. Bain SD, Jerome C, Shen V, Dupin-Roger I, Ammann P (2009)
Strontium ranelate improves bone strength in ovariectomized rat
by positively influencing bone resistance determinants. Osteo-
poros Int 20:1417–1428
16. Ejersted C, Andreassen TT, Oxlund H, Jørgensen PH, Bak B,
Haggblad J, Tørring O, Nilsson MHL (1993) Human parathyroid
hormone (1–34) and (1–84) increase the mechanical strength and
thickness of cortical bone in rats. J Bone Miner Res 8:1097–1101
17. Wronski TJ, Yen CF, Qi H, Dann LM (1993) Parathyroid hor-
mone is more effective than estrogen or bisphosphonates for
restoration of lost bone mass in ovariectomized rats. Endocri-
nology 132:823–831
18. Mosekilde L, Danielsen CC, Søgaard CH, McOsker JE, Wronski
TJ (1995) The anabolic effects of parathyroid hormone on cor-
tical bone mass, dimensions and strengthassessed in a sexually
mature, ovariectomized rat model. Bone 16:223–230
19. Andreassen TT, Oxlund H (2000) The influence of combined
parathyroid hormone and growth hormone treatment on cortical
bone in aged ovariectomized rats. J Bone Miner Res 15:2266–
2275
20. Neer RM, Arnaud CD, Zanchetta JR, Prince R, Gaich GA,
Reginster JY, Hodsman AB, Eriksen EF, Ish-Shalom S, Genant
HK, Wang O, Mitlak BH (2001) Effect of parathyroid hormone
(1–34) on fractures and bone mineral density in postmenopausal
women with osteoporosis. N Engl J Med 344:1434–1441
21. Skripitz R, Aspenberg P (2004) Parathyroid hormone—a drug for
orthopedic surgery? Acta Orthop Scand 75:654–662
22. Andreassen TT, Ejersted C, Oxlund H (1999) Intermittent para-
thyroid hormone (1–34) treatment increases callus formation and
mechanical strength of healing rat fractures. J Bone Miner Res
14:960–968
23. Holzer G, Majeska RJ, Lundy MW, Hartke JR, Einhorn TA
(1999) Parathyroid hormone enhances fracture healing. A pre-
liminary report. Clin Orthop 366:258–263
24. Kim HW, Jahng JS (1999) Effect of intermittent administration of
parathyroid hormone on fracture healing in ovariectomized rats.
Iowa Orthop J 19:71–77
25. Andreassen TT, Fledlius C, Ejersted C, Oxlund H (2001)
Increases in callus formation and mechanical strength of healing
fractures in old rats treated with parathyroid hormone. Acta
Orthop Scand 72:304–307
26. Bonnarens F, Einhorn TA (1984) Production of a standard closed
fracture in laboratory animal bone. J Orthop Res 2:97–101
27. Waynforth HB (1980) Experimental and surgical techniques in
the rat. Academic Press, New York, pp 161–163
28. Muller W (1975) A method for the comparison of morphomet-
rical data on skeletal muscles in young rats of different ages and
body weights. Histochemistry 43:241–248
29. Giannoudis P, Tzioupis C, Almali T, Buckley R (2007) Fracture
healing in osteoporotic fractures: is it really different? A basic
science perspective. Injury 38(suppl 1):S90–S99
30. Melhus G, Solberg LB, Dimmen S, Madsen JE, Nordsletten L,
Reinholt FP (2007) Experimental osteoporosis induced by ovar-
iectomy and vitamin D deficiency does not markedly affect
fracture healing in rats. Acta Orthop 78:393–403
31. Namkung-Matthai H, Appleyard R, Jansen J, Hao Lin J, Maas-
tricht S, Swain M, Mason RS, Murrell GA, Diwan AD, Diamond
T (2001) Osteoporosis influences the early period of fracture
healing in a rat osteoporotic model. Bone 28:80–86
32. Yingje H, Ge Z, Yishen W, Ling Q, Hung WY, Kwoksui L,
Fuxing P (2007) Changes of microstructure and mineralized tis-
sue in the middle and late phase of osteoporotic fracture healing
in rats. Bone 41:631–638
33. Wang JW, Li W, Xu SW, Yang DS, Wang Y, Lin M, Zhao GF
(2005) Osteoporosis influences the middle and late periods of
88 B. Habermann et al.: Strontium Ranelate Enhances Callus Strength
123
fracture healing in a rat osteoporotic model. Chin J Traumatol
8:111–116
34. McCann RM, Colleary G, Geddis C, Clarke SA, Jordan GR,
Dickson GR, Marsh D (2008) Effect of osteoporosis on bone
mineral density and fracture repair in a rat femoral fracture
model. J Orthop Res 3:384–393
35. Sturmer EK, Seidlova-Wuttke D, Sehmisch S, Rack T, Wille J,
Frosch KH, Wuttke W, Sturmer KM (2006) Standardized bend-
ing and breaking test for the normal and osteoporotic metaphy-
seal tibias of the rat: effect of estradiol, testosterone and
raloxifene. J Bone Miner Res 21:89–96
36. Tezval M, Stuermer EK, Sehmisch S, Rack T, Stary A, Stebener
M, Konietschke F, Stuermer KM (2009) Improvement of tro-
chanteric bone quality in an osteoporosis model after short-term
treatment with parathyroid hormone: a new mechanical test for
trochanteric region of rat femur. Osteoporos Int. [Epub ahead of
print]. doi:10.1007/s00198-009-0941-y
37. Kubo T, Shiga T, Hashimoto J (1999) Osteoporosis influences the
late period of fracture healing in a rat model prepared by ovari-
ectomy and low calcium diet. J Steroid Biochem Mol Biol
68:197–202
38. Schmidmaier G, Wildemann B, Melis B, Krummrey G, Einhorn
A, Haas N, Raschke M (2004) Development and characterization
of a standard closed tibial fracture model in the rat. Eur J Trauma
30:35–42
39. Hadjiargyrou M, Lambardo F, Zhao S, Ahrens W, Joo J, Ahn H,
Jurman M, White DW, Rubin CT (2002) Transcriptional profiling
of bone regeneration: insight into the molecular complexity of
wound repair. J Biol Chem 277:30177–30182
40. Drosse I, Volkmer E, Seitz S, Seitz H, Penzkofer R, Zahn K,
Matis U, Mutschler W, Augat P, Schieker M (2008) Validation of
a femoral critical size defect model for orthotopic evaluation of
bone healing: a biomechanical, veterinary and trauma surgical
perspective. Tissue Eng Part C Methods 1:79–88
41. Mark H, Rydevik B (2005) Torsional stiffness in healing frac-
tures: influence of ossification: an experimental study in rats.
Acta Orthop 3:428–433
42. Hill EL, Kraus K, Labierre KP (1995) Ovariectomy impairs
fracture healing after 21 days in rat. Trans Orthop Res Soc
20:230
43. Tsahakis PJ, Martin DF, Harrow ME, Kiebzak GM, Meyer RA Jr
(1996) Ovariectomy impairs femoral fracture healing in adult
female rats. Trans Orthop Res Soc 21:264
44. Walsh WR, Sherman P, Howlet CR, Sonnabend DH, Ehrlich MG
(1997) Fracture healing in a rat osteopenia model. Clin Orthop
342:218–227
45. Barnes GL, Kakar S, Vora S, Morgan EF, Gerstenfeld LC, Ein-
horn TA (2008) Stimulation of fracture-healing with systemic
intermittent parathyroid hormone treatment. J Bone Joint Surg
Am 90(suppl 1):120–127
46. Komatsu DE, Brune KA, Liu H, Schmidt AL, Han B, Zeng QQ,
Yang X, Nunes JS, Lu Y, Geiser AG, Ma YL, Wolos JA,
Westmore MS, Sato M (2009) Longitudinal in vivo analysis of
the region-specific efficacy of parathyroid hormone in a rat cor-
tical defect model. Endocrinology 4:1570–1579
47. Nakajima A, Shimoji N, Shiomi K, Shimizu S, Moriya H, Ein-
horn TA, Yamazaki M (2002) Mechanisms for the enhancement
of fracture healing in rats treated with intermittent low-dose
human parathyroid hormone (1–34). J Bone Miner Res 11:2038–
2047
48. Brennan TC, Rizzoli R, Ammann P (2009) Selective modification
of bone quality by PTH, pamidronate or raloxifene. J Bone Miner
Res 24:800–808
B. Habermann et al.: Strontium Ranelate Enhances Callus Strength 89
123