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External mechanical microstimuli improve osseointegration of titanium implants in rat proximal tibiae
S126
Abstracts
images of bone biopsies (obtained, e.g., by electron microscopy) with functional images of the mechanical properties. This article is part of a Special Issue entitled ECTS 2012. Disclosure of interest: None declared.
doi:10.1016/j.bone.2012.02.388
PP200 Effect of specimen size on microCT measurements of cortical porosity F. Particelli⁎, M. Montesi, L. Mecozzi, D. De Pasquale, F. Baruffaldi Laboratorio di Tecnologia Medica, Istituto Ortopedico Rizzoli, Bologna, Italy Abstract: Micro-CT imaging has become fundamental in morphometric investigation of bone. The accuracy of bone measurements can be influenced by a segmentation method that, through a threshold value, separates “bone” from “non bone” in the reconstructed grayscale datasets. In order to validate the characterization of human cortical bone microarchitecture using micro-CT, cortical porosity was compared with that obtained through histological examination [1,2]. Since studies often compare samples with a range of different sizes, the accurate measurement in specimens of unequal size is important. The aim of this work was to compare microtomographic and histological analyses of cortical bone biopsies of two different sizes, and to investigate how porosity is affected by errors when a different threshold value is applied. Sixteen cortical bone biopsies (8 with a diameter of 3 mm (group A) and 8 with a diameter of 1.5 mm (group B)) taken from the human femoral diaphysis were firstly included in PolyMethaMethylAcrylate (PMMA), examined by micro-CT and then the porosity was calculated through the dedicate software. Secondly, the cortical bone biopsies embedded in PMMA were sectioned to thin slices, observed at the microscope and then the porosity was determined through the microscope software. From each sample, the cross section image obtained by micro-CT and the corresponding slice obtained by histology were compared, and different threshold values for the two groups were found. The porosities calculated by the two techniques were highly correlated (R2 = 0.93 for 3 mm diameter and R2 = 0.98 for 1.5 mm diameter). No statistically significant differences were shown between micro-CT and histology. Moreover, calculating porosity of group B using the threshold value obtained for the group A the difference d and the mean percentage difference d% found in the comparison are indicated in Table 1. Although with the little number of samples, this preliminary study confirmed that micro-CT analyses is a reliable method for the morphometrical characterization of cortical tissues. Moreover, these results demonstrate that, halving the diameters of cortical bone biopsies, a little difference in threshold value introduce a very small error in the porosity measurements. Table 1 d
SD
MicroCT threshold group A—threshold group B Porosity (%) 0.87 0.13
d%
SD
13.61
4.0
This article is part of a Special Issue entitled ECTS 2012. Disclosure of interest: None declared. References [1] Particelli et al. 2011, J Microsc. doi: 10.1111/j.1365-2818.2011.03573.x. [Epub ahead of print]. [2] Perilli E. et al. 2007, J Microsc 225:192-20. doi:10.1016/j.bone.2012.02.389
PP201 External mechanical microstimuli improve osseointegration of titanium implants in rat proximal tibiae G. Zacchettia,⁎, A. Wiskottb, J. Cugnonic, I. Botsisc, M. Piccininic, P. Ammanna a Division of Bone Disease, Dep. of Rehabilitation and Geriatrics, Switzerland b Laboratory of biomaterials, School of Dentistry, University of Geneva, Geneva, Switzerland c Laboratory of Applied Mechanics and Reliability Analysis, École Polytechnique Fédérale de Lausanne, Lausanne, Switzerland
Abstract: A poor osseointegration of endosseous implants is the cause of early implant failure compromising the outcome of a surgical intervention both in dentistry and orthopedics. The aim of this work was to measure the effect of external mechanical microstimuli of controlled magnitude on implant osseointegration in rat proximal tibiae. Increasing loads were selected and the dose-dependent effect on parameters of implant osseointegration was examined. 40 female rats 6 months old were operated at the right tibiae by transcutaneous insertion of two stepped titanium cylindrical implants, 1 mm and 0.8 mm in diameter, respectively. The loaded implant (LI) was fixed into the trabecular bone of the secondary spongiosa whereas the anchorage implant was inserted 8 mm distally, encompassing both cortical surfaces. After 2 weeks rats were assigned to 4 groups (Non Stimulated= NS; 1N, 2N 3N), and further underwent a daily external mechanical loading during 4 weeks. Parameters of bone architecture were analyzed ex-vivo by microcomputerized tomography (μCT) on a circular band of 0.5 mm around the LI as well as in a region located up to 1 mm away from the LI, along the axis of the force. Ultimate Strength (US) was measured by a pull-out test as indicator of implant osseointegration. Increasing loading did not significantly modify BV/TV around the LI; still trabecular BV/TV was increased in the vicinity of the LI in 1N rats and decreased in 3N rats, while Cortical Thickness (Ct.Th) significantly increased in the 3N group. 2N rats displayed a significant increase of the pull-out force necessary to loosen the implant compared to NS, corresponding to the load having a partial effect on trabecular and cortical bone near LI. We hypothesize that bone ingrowths within the etched implant surface may improve implant anchorage. In conclusion, the in-vivo mechanical loading of implants induces loaddependent modifications in bone microarchitecture and improves implant osseointegration in rat tibiae. The histomorphometric analysis of bone growing on the implant surface is necessary to further explain the mechanism of implant osseointegration.
BV/TV Ct.Th (mm) US (N)
NS
1N (750 με)
2N (1500 με)
3N (2250 με)
0.15 ± 0.02 0.44 ± 0.01 39.57 ± 2.23
0.20 ± 0.02 0.43 ± 0.01 40.82 ± 3.12
0.17 ± 0.02 0.43 ± 0.01 46.63 ± 2.21*
0.14 ± 0.02# 0.46 ± 0.01# 43.81 ± 3.41
Average ± SEM; #p b 0.05 vs 1N; *p b 0.05 vs NS. This article is part of a Special Issue entitled ECTS 2012. Disclosure of interest: None declared. doi:10.1016/j.bone.2012.02.390
PP202 Effects of PEMF and sulfurous mineral water on bone in experimental osteoporosis G. Stefanovskia,⁎, T. Popovića, M. Stefanovskib a Rheumatology-osteoporosis, Institute for Physical Medicine and Rehabilitation, Banja Luka, Bosnia and Herzegovina b Balneology, Institut for Balnelogy, PMR Mlječanica, Koz. Dubica, Bosnia and Herzegovina Abstract: Introduction: Sulfurous mineral water is used in the treatment of skeletal disorders. Electric and magnetic fields could modify the behavior of bone cells. Aim of study: The aim of our study was to evaluate the influence of PEMF and sulfurous mineral water “Mljecanica” on bone in a model of estrogen-deficient osteoporosis. Material and methods: Fourteen-weeks-old bilaterally ovariectomized female Wistar rats (n = 21) were randomly assigned to three groups: OVX + PEMF + SW (n = 7), OVW + SW (n = 7) and OVX control (n = 7). The accommodation condition (temperature 22°–24 °C) and feeding were the same for all groups. After six weeks OVX+PEMF + SW rats were supplied with sulfurous mineral water ad libitum and exposed to PEMF Kosmag 60 (40 Hz, 10 mT, 45 min) during four weeks, 5 days per week. OVX + SW rats were supplied with sulfurous water ad libitum, during four weeks, 5 days per week. OVX animals were drinking taped water ad libitum. After four weeks animals were sacrificed. At the end of the four-week period biochemical analyses: osteocalcin (OC), alkaline phosphatase (AP), calcium (Ca) and phosphorus (P) were evaluated. The histological analyses of left tibia were studied by routine light microscope. Biomechanical properties were studied on TOMI 2001. Results: Statistically significant increase of OC (p b 0.05) and statistically significant decrease of Ca and AP (p b 0.01) were obtained in OVX+PEMF + SW compared to OVX-control group. The increase of same parameters in OVX + SW group was not significant in comparison with that of OVX group. Histological observation in OVX+PEMF + SW showed growth of young chondrocytes in the central zone and cartilage on peripheral parts. The trabecules were thicker, still disconnected, with bone marrow in between. OVX + SW showed the growth of young chondrocytes in the central zone of bone and their migration to peripheral parts. Biomechanical analyses of the left femur on banding and torsion in experimental groups showed better quality of bone. Conclusions: This study shows that sulfurous water, used in experimental osteoporosis, induces the reparing mechanism of osteoporotic bone. In group OVX+ PEMF + SW we observed synergic effect on calcium level and positive impacts on the mechanical properties of bone. Treatment with PEMF and sulfurous water decreased bone fragility.
Abstracts
images of bone biopsies (obtained, e.g., by electron microscopy) with functional images of the mechanical properties. This article is part of a Special Issue entitled ECTS 2012. Disclosure of interest: None declared.
doi:10.1016/j.bone.2012.02.388
PP200 Effect of specimen size on microCT measurements of cortical porosity F. Particelli⁎, M. Montesi, L. Mecozzi, D. De Pasquale, F. Baruffaldi Laboratorio di Tecnologia Medica, Istituto Ortopedico Rizzoli, Bologna, Italy Abstract: Micro-CT imaging has become fundamental in morphometric investigation of bone. The accuracy of bone measurements can be influenced by a segmentation method that, through a threshold value, separates “bone” from “non bone” in the reconstructed grayscale datasets. In order to validate the characterization of human cortical bone microarchitecture using micro-CT, cortical porosity was compared with that obtained through histological examination [1,2]. Since studies often compare samples with a range of different sizes, the accurate measurement in specimens of unequal size is important. The aim of this work was to compare microtomographic and histological analyses of cortical bone biopsies of two different sizes, and to investigate how porosity is affected by errors when a different threshold value is applied. Sixteen cortical bone biopsies (8 with a diameter of 3 mm (group A) and 8 with a diameter of 1.5 mm (group B)) taken from the human femoral diaphysis were firstly included in PolyMethaMethylAcrylate (PMMA), examined by micro-CT and then the porosity was calculated through the dedicate software. Secondly, the cortical bone biopsies embedded in PMMA were sectioned to thin slices, observed at the microscope and then the porosity was determined through the microscope software. From each sample, the cross section image obtained by micro-CT and the corresponding slice obtained by histology were compared, and different threshold values for the two groups were found. The porosities calculated by the two techniques were highly correlated (R2 = 0.93 for 3 mm diameter and R2 = 0.98 for 1.5 mm diameter). No statistically significant differences were shown between micro-CT and histology. Moreover, calculating porosity of group B using the threshold value obtained for the group A the difference d and the mean percentage difference d% found in the comparison are indicated in Table 1. Although with the little number of samples, this preliminary study confirmed that micro-CT analyses is a reliable method for the morphometrical characterization of cortical tissues. Moreover, these results demonstrate that, halving the diameters of cortical bone biopsies, a little difference in threshold value introduce a very small error in the porosity measurements. Table 1 d
SD
MicroCT threshold group A—threshold group B Porosity (%) 0.87 0.13
d%
SD
13.61
4.0
This article is part of a Special Issue entitled ECTS 2012. Disclosure of interest: None declared. References [1] Particelli et al. 2011, J Microsc. doi: 10.1111/j.1365-2818.2011.03573.x. [Epub ahead of print]. [2] Perilli E. et al. 2007, J Microsc 225:192-20. doi:10.1016/j.bone.2012.02.389
PP201 External mechanical microstimuli improve osseointegration of titanium implants in rat proximal tibiae G. Zacchettia,⁎, A. Wiskottb, J. Cugnonic, I. Botsisc, M. Piccininic, P. Ammanna a Division of Bone Disease, Dep. of Rehabilitation and Geriatrics, Switzerland b Laboratory of biomaterials, School of Dentistry, University of Geneva, Geneva, Switzerland c Laboratory of Applied Mechanics and Reliability Analysis, École Polytechnique Fédérale de Lausanne, Lausanne, Switzerland
Abstract: A poor osseointegration of endosseous implants is the cause of early implant failure compromising the outcome of a surgical intervention both in dentistry and orthopedics. The aim of this work was to measure the effect of external mechanical microstimuli of controlled magnitude on implant osseointegration in rat proximal tibiae. Increasing loads were selected and the dose-dependent effect on parameters of implant osseointegration was examined. 40 female rats 6 months old were operated at the right tibiae by transcutaneous insertion of two stepped titanium cylindrical implants, 1 mm and 0.8 mm in diameter, respectively. The loaded implant (LI) was fixed into the trabecular bone of the secondary spongiosa whereas the anchorage implant was inserted 8 mm distally, encompassing both cortical surfaces. After 2 weeks rats were assigned to 4 groups (Non Stimulated= NS; 1N, 2N 3N), and further underwent a daily external mechanical loading during 4 weeks. Parameters of bone architecture were analyzed ex-vivo by microcomputerized tomography (μCT) on a circular band of 0.5 mm around the LI as well as in a region located up to 1 mm away from the LI, along the axis of the force. Ultimate Strength (US) was measured by a pull-out test as indicator of implant osseointegration. Increasing loading did not significantly modify BV/TV around the LI; still trabecular BV/TV was increased in the vicinity of the LI in 1N rats and decreased in 3N rats, while Cortical Thickness (Ct.Th) significantly increased in the 3N group. 2N rats displayed a significant increase of the pull-out force necessary to loosen the implant compared to NS, corresponding to the load having a partial effect on trabecular and cortical bone near LI. We hypothesize that bone ingrowths within the etched implant surface may improve implant anchorage. In conclusion, the in-vivo mechanical loading of implants induces loaddependent modifications in bone microarchitecture and improves implant osseointegration in rat tibiae. The histomorphometric analysis of bone growing on the implant surface is necessary to further explain the mechanism of implant osseointegration.
BV/TV Ct.Th (mm) US (N)
NS
1N (750 με)
2N (1500 με)
3N (2250 με)
0.15 ± 0.02 0.44 ± 0.01 39.57 ± 2.23
0.20 ± 0.02 0.43 ± 0.01 40.82 ± 3.12
0.17 ± 0.02 0.43 ± 0.01 46.63 ± 2.21*
0.14 ± 0.02# 0.46 ± 0.01# 43.81 ± 3.41
Average ± SEM; #p b 0.05 vs 1N; *p b 0.05 vs NS. This article is part of a Special Issue entitled ECTS 2012. Disclosure of interest: None declared. doi:10.1016/j.bone.2012.02.390
PP202 Effects of PEMF and sulfurous mineral water on bone in experimental osteoporosis G. Stefanovskia,⁎, T. Popovića, M. Stefanovskib a Rheumatology-osteoporosis, Institute for Physical Medicine and Rehabilitation, Banja Luka, Bosnia and Herzegovina b Balneology, Institut for Balnelogy, PMR Mlječanica, Koz. Dubica, Bosnia and Herzegovina Abstract: Introduction: Sulfurous mineral water is used in the treatment of skeletal disorders. Electric and magnetic fields could modify the behavior of bone cells. Aim of study: The aim of our study was to evaluate the influence of PEMF and sulfurous mineral water “Mljecanica” on bone in a model of estrogen-deficient osteoporosis. Material and methods: Fourteen-weeks-old bilaterally ovariectomized female Wistar rats (n = 21) were randomly assigned to three groups: OVX + PEMF + SW (n = 7), OVW + SW (n = 7) and OVX control (n = 7). The accommodation condition (temperature 22°–24 °C) and feeding were the same for all groups. After six weeks OVX+PEMF + SW rats were supplied with sulfurous mineral water ad libitum and exposed to PEMF Kosmag 60 (40 Hz, 10 mT, 45 min) during four weeks, 5 days per week. OVX + SW rats were supplied with sulfurous water ad libitum, during four weeks, 5 days per week. OVX animals were drinking taped water ad libitum. After four weeks animals were sacrificed. At the end of the four-week period biochemical analyses: osteocalcin (OC), alkaline phosphatase (AP), calcium (Ca) and phosphorus (P) were evaluated. The histological analyses of left tibia were studied by routine light microscope. Biomechanical properties were studied on TOMI 2001. Results: Statistically significant increase of OC (p b 0.05) and statistically significant decrease of Ca and AP (p b 0.01) were obtained in OVX+PEMF + SW compared to OVX-control group. The increase of same parameters in OVX + SW group was not significant in comparison with that of OVX group. Histological observation in OVX+PEMF + SW showed growth of young chondrocytes in the central zone and cartilage on peripheral parts. The trabecules were thicker, still disconnected, with bone marrow in between. OVX + SW showed the growth of young chondrocytes in the central zone of bone and their migration to peripheral parts. Biomechanical analyses of the left femur on banding and torsion in experimental groups showed better quality of bone. Conclusions: This study shows that sulfurous water, used in experimental osteoporosis, induces the reparing mechanism of osteoporotic bone. In group OVX+ PEMF + SW we observed synergic effect on calcium level and positive impacts on the mechanical properties of bone. Treatment with PEMF and sulfurous water decreased bone fragility.