Characteristics and mechanical properties of acrylolpamidronate-treated strontium containing bioactive bone cement.
ABSTRACT The aim of the present study was to determine the influence of surface treatment on the mechanical properties of strontium-containing hydroxyapatite (Sr-HA) bioactive bone cement. Previously we developed an injectable bioactive cement (SrHAC) system composed of Sr-HA powders and bisphenol A diglycidylether dimethacrylate (Bis-GMA). In this study, the Sr-HA powder was subjected to surface treatment using acrylolpamidronate, a bisphosphonate derivative, which has a polymerizable group, to improve the interface between inorganic filler and organic matrix by binding Sr-HA and copolymerizing into the matrix. After surface treatment, the compression strength, bending strength, and stiffness of the resulting composites were defined by using a material testing machine (MTS) according to ISO 5833. The fracture surface of the bone cement specimen was observed with a scanning electron microscope. Invitro cytotoxicity of surface-treated SrHAC was also studied using a tetrazolium-based cell viability assay (MTS/pms) on human osteoblast-like cells, the SaOS-2 cell line. Cells were seeded at a density of 10(4)/mL and allowed to grow in an incubator for 48 h at 37 degrees C. Results indicated that after surface treatment, the compression strength and stiffness significantly improved by 22.68 and 14.51%, respectively. The bending strength and stiffness of the bioactive bone cement also showed 19.06 and 8.91% improvements via three-point bending test. The fracture surface micromorphology after compression and bending revealed that the bonding between the resin to surface-treated filler considerably improved. The cell viability indicated that the treated particles were nontoxic and did not inhibit cell growth. This study demonstrated a new surface chemistry route to enhance the covalent bonds between inorganic fillers and polymer matrix for improving the mechanical properties of bone cement. This method not only improves the overall mechanical performance but also increases osteoblastic activity.
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ABSTRACT: A paired biomechanical study of pedicle screws augmented with bone cement in a human cadaveric and osteoporotic lumbar spine model. OBJECTIVES.: To evaluate immediate strength and stiffness of pedicle screw fixation augmented with a novel bioactive bone cement in an osteoporotic spine model and compare it with polymethylmethacrylate (PMMA) cement. A novel bioactive bone cement, containing nanoscale particles of strontium and hydroxyapatite (Sr-HA), can promote new bone formation and osteointegration and provides a promising reinforcement to the osteoporotic spine. Its immediate mechanical performance in augmenting pedicle screw fixation has not been evaluated. Two pedicle screws augmented with Sr-HA and PMMA cement were applied to each of 10 isolated cadaveric L3 vertebrae. Each screw was subjected to a toggling test and screw kinematics were calculated. The pedicle screw was subjected to a pullout test until failure. Finally, the screw coverage with cement was measured on computed tomographic images. Screw translations in the toggling test were consistently larger in the Sr-HA group than in the PMMA group (1.4 ± 1.2 mm vs. 1.0 ± 1.1 mm at 1000 cycles). The rotation center was located closer to the screw tip in the Sr-HA group (19% of screw length) than in the PMMA group (37%). The only kinematic difference between Sr-HA and PMMA cements was the screw rotation at 1000 cycles (1.5° ± 0.9° vs. 1.3° ± 0.6°; P = 0.0026). All motion parameters increased significantly with more loading cycles. The pullout force was higher in the PMMA group than the Sr-HA group (1.40 ± 0.63 kN vs. 0.93 ± 0.70 kN), and this difference was marginally significant (P = 0.051). Sr-HA cement covered more of the screw length than PMMA cement (79 ± 19% vs. 43 ± 19%) (P = 0.036). This paired-design study identified some subtle but mostly nonsignificant differences in immediate biomechanical fixation of pedicle screws augmented with the Sr-HA cement compared with the PMMA cement.Spine 04/2012; 37(17):E1030-7. · 2.16 Impact Factor
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ABSTRACT: There is accumulating evidence that strontium (Sr)-containing bioceramics have positive effects on bone tissue repair. The aims of the present study were to evaluate the osteoconductivity of Sr-doped bioactive glass (BG) particles implanted in rat tibia bone marrow, and characterize the neoformed bone tissue by SEM-energy-dispersive X-ray microanalysis. Melt-derived BGs were prepared from a base 45S5 BG. Sr-doped glass (45S5.6Sr) was prepared using 6 wt % SrO as a substitute for the CaO. Histological analysis using undecalcified sections showed that new lamellar bone had formed along the surface of both 45S5 and 45S5.6Sr BG particles within 4 weeks. To evaluate osteoconductivity, affinity indices were calculated. At 30 days after implantation, 45S5 and 45S5.6Sr BGs had almost identical affinity indices (88% +/- 7% and 87% +/- 9%; p > 0.05). Strontium was not detected in the neoformed bone tissue surrounding 45S5.6Sr BG particles. These results indicate that 45S5.6Sr BG particles are osteoconductive when implanted inside the intramedullary canal of rat tibiae, and no alterations in bone mineralization, in terms of Ca/P ratio, were observed in the neoformed bone tissue around 45S5.6Sr BG particles.Journal of Biomedical Materials Research Part A 02/2009; 92(1):232-7. · 2.83 Impact Factor
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ABSTRACT: Strontium (Sr) has become more attractive for orthopaedic applications as they can simultaneously stimulate bone formation and prevent bone loss. A Sr-containing bioactive bone cement (Sr-BC) has been designed to fix osteoporotic bone fracture. Sr is a trace element, so the safety of containing Sr is concerned when Sr-BC is implanted in human body. The preclinical assessment of biocompatibility of Sr-BC was conducted according to ISO 10993 standards. MTT assay showed that this bioactive bone cement was non-toxic to mouse fibroblasts, and it met the basic requirement for the orthopaedic implant. The three independent genetic toxicity studies including Ames, chromosome aberration and bone marrow micronucleus assays demonstrated absence of genotoxic components in Sr-BC, which reassured the safety concerns of this novel bone cement. The muscle implantation results in present study were also encouraging. The acute inflammation around the cement was observed at 1week post-implantation; however, no significant difference was observed between control and Sr-BC groups. These responses may be attributed to the presence of the foreign body, but the tissue healed after 12weeks implantation. In summary, the above preclinical results provide additional assurance for the safety of this implant. Sr-BC can be used as a potential alternative to the traditional bone cement.Materials science & engineering. C, Materials for biological applications. 12/2013; 33(8):5100-5104.
CHARACTERISTICS AND MECHANICAL PROPERTIES OF ACRYLOLPAMIDRONATE TREATED
STRONTIUM CONTAINING BIOACTIVE BONE CEMENT
ZY Li1, C Yang2, WW Lu1, B Xu2, WM Lam1, GX Ni1, SA Abbah1, F Yang1, KMC Cheung1 and KDK Luk1
1Department of Orthopaedics and Traumatology, The University of Hong Kong, Hong Kong, China
2Department of Chemistry, Hong Kong University of Science and Technology, Hong Kong, China
Previously we developed an injectable strontium-containing
hydroxyapatite bioactive bone cement (Sr-HAC) system
composed of Sr-HA powders and bisphenol A
diglycidylether dimethacrylate (Bis-GMA) . The outcome
of clinical trials for vertebroplasty was very satisfactory with
a lower setting temperature, good osteointegration and with
no evidence of toxicity . However, the Sr-HAC was
primarily designed for osteoporotic bone fracture and has
not yet been optimized for other orthopaedic applications
such as total hip replacement surgery, implant augmentation
etc, which require the improved mechanical properties.
The aim of the present study was to determine the influence
of surface treatment on the mechanical properties and
biocompatibility of Sr-HA bioactive bone cement.
The Sr-HA powder was subjected to surface treatment using
acrylolpamidronate, a bisphosphonate derivative which has a
polymerizable group, to improve the interface between
inorganic filler and organic matrix by binding Sr-HA and
copolymerizing into the matrix. After surface treatment, the
compression strength, bending strength and stiffness (Fig. 1)
of the resulting composites were defined by using a material
testing machine (MTS) according to ISO 5833. The fracture
surface of the bone cement specimen was observed with a
scanning electron microscope (SEM). In vitro cytotoxicity of
surface treated SrHAC was also studied using a tetrazolium
based cell viability assay (MTS/pms) on human
osteoblast-like cells, the SaOS-2 cell line. Cells were seeded
at a density of 104/ml and allowed to grow in an incubator
for 48hrs at 37°C.
Fig.1: Bending test curves of original Sr-HAC
RESULTS AND DISCUSSION
After surface treatment, the compression strength and
stiffness significantly improved by 22.68% and 14.51%,
respectively. The bending strength and stiffness of the
bioactive bone cement also showed 19.06% and 8.91%
improvements via three-point bending test.
The fracture surface micromorphology after compression
and bending revealed that the bonding between the resin to
surface treated filler considerably improved. Results of the
morphology after compression suggest that there was better
integration between acrylolpamidronate treated SrHAC (Fig.
2B) than pristine SrHAC (Fig. 2A). The increase in the
compressive strength and stiffness can be explained by the
Sr-HA treatment with acrylolpamidronate, which promoted
a better adhesion between the Sr-HA filler and the Bis-GMA
matrix . For untreated Sr-HA bone cement, a typical
smooth Type I brittle fracture surface was observed (Fig.
2C), which meant that there was no or little plastic
deformation when bending, while a rougher Type II/III
brittle fracture surface was observed in treated Sr-HA bone
cement (Fig. 2D). The morphology of treated SrHAC after
bending testing showed that the fracture surface was much
more jagged, irregular, and rough (Fig. 2D). As a result, the
bending strength and stiffness of the bioactive bone cement
Fig. 2: SEM micrographs of the Sr-HAC fracture surface
The cell viability indicated that the treated particles were
nontoxic and did not inhibit cell growth.
This study demonstrated a new surface chemistry route to
enhance the covalent bonds between inorganic fillers and
polymer matrix for improving the mechanical properties of
bone cement. This method not only improves the overall
mechanical performance, but also increases osteoblastic
1. Li YW, et al. J Biomed Mater Res 52, 164-170, 2000.
2. Cheung KM, et al. Spine 30, S84-S91, 2005.
3. Mekraldi S, et al. J Bone Miner Res 20, 1365-1371, 2005.
This study was partially supported by Hong Kong ITF Fund