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Recent advances of the simulation of X-ray radiation propagation through bone tissue
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Journal of Biomechanics 2006, Vol. 39 (Suppl 1)
to be an unsuitable method for the measurement of the elastic coefficients of the cortical bone tissue. Evaluated elastic constants are in line with literature values with literary values. Acknowledgement: This work was supported by the Ministry of Education project No. MSM 6840770012. 4715 Mo-Tu, no. 14 (P55) Compression and ultrasound testing of canine trabecular bone properties B.-A. Behrens 1, A. Bouguecha 1, T. Pressel 2, C.J. Wirth 2, A. MeyerLindenberg 3, I. Nolte 3. 1Institute of Metal Forming, University of Hannover,
Germany, 2Department of Orthopaedic Surgery, Medical University of Hannover, Germany, 3Small Animal Clinic, University of Veterinary Medicine Foundation Hannover, Germany Mechanical properties of canine trabecular bone are important for understanding normal and pathological biomechanics. They have to be known for assessing mechanical changes due to diseases and particularly for developing finite element models of the respective bone. Many studies have been published concerning mechanical properties of human trabecular bone but only few data about trabecular bone in dogs from different anatomic sites. In this study, cubic trabecular specimens from 8 dogs (16 samples) were cut from femoral heads, and specimen densities and elastic moduli were determined using compression testing and ultrasound. Thereby, for sonographic testing, an oscillation frequency of 2 MHz was chosen, and the ultrasound runtimes through the specimen were recorded. Thereafter, compression tests are followed. The Ringer's solution was used to minimize friction between the plates and the specimen. The upper plate was moving at a speed of 0.2mm/s while the lower plate remained fixed. The specimens were tested until destruction because we also intended to measure the yielding behaviour of the bone in addition to the elastic modulus. Elastic moduli were ranging from 6-11 GPa (average of 10 GPa) depending on testing direction. Moduli perpendicular to the main pressure trajectories obtained by compression testing were significantly (p <0.01) correlated with moduli obtained by ultrasound experiments but the moduli in the direction of the main trajectories did not show a significant correlation; other results show that this effect might be caused by the limited number of samples. 7454 Mo-Tu, no. 15 (P55) Recent advances of the simulation of X-ray radiation propagation through bone tissue M. Binkowski 1, Z. Kr612, Z. Wr6bel 1, H.-F. Zeilhofer2. 1Institute of Computer
Science, Department of Biomedical Computer Systems, University of Silesia, Sosnowiec, Poland, 2HFZ-Center of multidisciplinary research in cranio-maxillo-facial surgery, University of Basel, Basel, Switzerland In the paper we have presented an attempt at modelling the phenomenon of X-ray attenuation during propagation through tissue. This phenomenon is commonly used in medical imaging techniques. In the paper we have focused on X-ray computed tomography applied to the imaging of hard tissue, e.g. bone. A method from our previous research has been employed to study X-ray attenuation and used in the computer simulation of the phenomenon [1,2]. An X-ray device is simulated; it comprises three main parts: an X-ray source, a detector and the simulation space between them. Principal physical laws simplified due to the software requirements have been used to define the rules of X-ray propagation for the model. A three-dimensional model of bone tissue has been created. The data necessary to define virtual samples in the software have been acquired from a collection of real specimens, which have been scanned using proper tomography techniques. In particular, the head, mandible, and pelvis have been modeled according to the data from computed tomography, and a sample of bone according to the data from micro computed tomography. The only exception is the phantom dataset, which has been defined according to literature. The simulation results are sets of values, which represent the radiation intensity after propagation through the virtual samples. These numerical data are presented in the paper as gray-scale images, brightness of which is related to incident radiation intensity. Analyses have been performed for several types of virtual samples. The obtained results correspond to the original data used to define these samples, which proves that the presented model of X-ray attenuation can be legitimately used to calculate tomography projections. References [1] Binkowski M., Dyszkiewicz A., Wr6bel Z. The analysis of densitometry image of bone tissue based on computer simulation of X-ray radiation propagation through plate model. Comput Biol Med, the article has been accepted for publication.
Poster Presentations
[2] Binkowski M., Krol Z., Wrobel Z., Zeilhofer H.-E, Modelling of X-ray propagation in bone microstructure. Journal of Medical Informatics & Technologies 2005; 9: 75-82.
1.2 Bone Healing and Osteointegration 4322 Mo-Tu, no. 16 (P55) Torsional testing on a non-union model of fractured tibia of rabbit K.S.C. Kwong 1, C.C. Hui 1, X. Guo 1, J.C.'~ Cheng 2. 1Department of
Rehabilitation Sciences, Hong Kong Polytechnic University, HKSAR, China, 2Department of Orthopaedics & Traumatology, Chinese University of Hong Kong, HKSAR, China Introduction: Torsional testing was performed on rabbit tibiae to investigate the effect of extracorporeal shockwave (ESW) on healing of a non-union model of fractured tibia. ESW treated and control tibiae retrieved from sacrificed rabbits were tested, and radiographs were taken to observe the bony change. The results suggest that ESW could initiate the ossification process at the nonunion site, which demonstrated greater mechanical strength than the control. Methods: Osteotomy was performed on the right tibiae of 8 New Zealand White rabbits of 18 weeks old to establish a non-union model. The rabbits were equally divided into ESW treatment group and the control group. The treatment group received one session of 1000 shocks of ESW at 0.54 mJ/mm 2, delivered to the fracture site by a shockwave generator (Sonocur, Siemens). Torsional testing at a speed of 10 degree per minute was performed on the tibiae of the rabbits sacrificed at 10 weeks after treatment. The specimens were mounted onto a servohydraulic biaxial universal material testing machine (Bionix 858, MTS Systems) through the use of a pair of custom-made adaptors. Ultimate failure torque and the stiffness were obtained. Radiographs were taken biweekly for 10 weeks after treatment to examine the bony change at the fracture site. Results: Cracking of bone was found at the fracture site on all specimens when the ultimate failure torque was reached. The results of the ultimate failure torque and stiffness of the treatment group were both higher than the control group. Bony bridging was observed at around week 6 after ESW treatment while the fracture gap remained in the control group. Conclusion: ESW could induce healing of bone fracture in non-union cases. The increase in torsional strength and stiffness of the healing bone after treatment suggests that ESW might induce early remodeling of the callus and promote bridging at the non-union gap.
6571 Mo-Tu, no. 17 (P55) Effect of reindeer BMP on the healing of a critical size long bone defect T. Pekkarinen 1, T. J~ms~ 2, M. M ~ t t ~ 2, O. Hietala 1, P. Jalovaara 1.
1Department of Surgery, University of Oulu, Oulu, Finland, 2Department of Medical Technology, University of Oulu, Oulu, Finland Reindeer bone morphogenetic protein (BMP) extracts have been shown to effectively induce ectopic new bone formation in vivo. However, the bone healing capacity has not yet been evaluated. Here we investigated the effect of reindeer BMP on the healing of a long bone defect in rabbit radius. Implants contained 5mg or 10mg non-sterilized or 10mg gamma-sterilized reindeer BMP extract administered with collagen carrier. 70~tg rhBMP-2 with collagen carrier served as positive, and collagen and untreated defects as negative controls. NZW-rabbit with a 1.5cm critical size radius defect was used. Bone healing was evaluated after eight weeks by radiographs, pQCT and mechanical torsion tests. Bone formation (BF) was higher in all groups containing BMPs than in the untreated controls. BF was also significantly higher in the rhBMP-2 group and nearly significantly higher in the group treated with 10 mg non-sterilized reindeer BMP ( p = 0 . 0 6 1 ) w h e n compared to collagen controls. Bone union (BU) was significantly better in the non-sterilized BMP groups and rhBMP-2 group than in the untreated or collagen controls. New bone area at defect site was higher in all BMP implants than in the untreated defects, and also higher in the 10 mg non-sterilized reindeer BMP extract group and rhBMP-2 group when compared to collagen controls. Torsional stiffness was higher in the 10 mg non-sterilized BMP group than in the collagen group. Cross-sectional bone area measured by pQCT was higher in the rhBMP-2 group than in the collagen group. Mean bone density at the defect area was higher in the 10 mg non-sterilized BMP extract group than in the rhBMP-2 group. In conclusion, reindeer BMP improved effectively the healing of rabbit radius bone defect and was comparable with rhBMP-2. Only slight differences were found between the study groups in the mechanical properties, which was mainly due to the small sample size. Gamma sterilization of reindeer BMP extract reduced osteoinductivity slightly but not significantly.
Journal of Biomechanics 2006, Vol. 39 (Suppl 1)
to be an unsuitable method for the measurement of the elastic coefficients of the cortical bone tissue. Evaluated elastic constants are in line with literature values with literary values. Acknowledgement: This work was supported by the Ministry of Education project No. MSM 6840770012. 4715 Mo-Tu, no. 14 (P55) Compression and ultrasound testing of canine trabecular bone properties B.-A. Behrens 1, A. Bouguecha 1, T. Pressel 2, C.J. Wirth 2, A. MeyerLindenberg 3, I. Nolte 3. 1Institute of Metal Forming, University of Hannover,
Germany, 2Department of Orthopaedic Surgery, Medical University of Hannover, Germany, 3Small Animal Clinic, University of Veterinary Medicine Foundation Hannover, Germany Mechanical properties of canine trabecular bone are important for understanding normal and pathological biomechanics. They have to be known for assessing mechanical changes due to diseases and particularly for developing finite element models of the respective bone. Many studies have been published concerning mechanical properties of human trabecular bone but only few data about trabecular bone in dogs from different anatomic sites. In this study, cubic trabecular specimens from 8 dogs (16 samples) were cut from femoral heads, and specimen densities and elastic moduli were determined using compression testing and ultrasound. Thereby, for sonographic testing, an oscillation frequency of 2 MHz was chosen, and the ultrasound runtimes through the specimen were recorded. Thereafter, compression tests are followed. The Ringer's solution was used to minimize friction between the plates and the specimen. The upper plate was moving at a speed of 0.2mm/s while the lower plate remained fixed. The specimens were tested until destruction because we also intended to measure the yielding behaviour of the bone in addition to the elastic modulus. Elastic moduli were ranging from 6-11 GPa (average of 10 GPa) depending on testing direction. Moduli perpendicular to the main pressure trajectories obtained by compression testing were significantly (p <0.01) correlated with moduli obtained by ultrasound experiments but the moduli in the direction of the main trajectories did not show a significant correlation; other results show that this effect might be caused by the limited number of samples. 7454 Mo-Tu, no. 15 (P55) Recent advances of the simulation of X-ray radiation propagation through bone tissue M. Binkowski 1, Z. Kr612, Z. Wr6bel 1, H.-F. Zeilhofer2. 1Institute of Computer
Science, Department of Biomedical Computer Systems, University of Silesia, Sosnowiec, Poland, 2HFZ-Center of multidisciplinary research in cranio-maxillo-facial surgery, University of Basel, Basel, Switzerland In the paper we have presented an attempt at modelling the phenomenon of X-ray attenuation during propagation through tissue. This phenomenon is commonly used in medical imaging techniques. In the paper we have focused on X-ray computed tomography applied to the imaging of hard tissue, e.g. bone. A method from our previous research has been employed to study X-ray attenuation and used in the computer simulation of the phenomenon [1,2]. An X-ray device is simulated; it comprises three main parts: an X-ray source, a detector and the simulation space between them. Principal physical laws simplified due to the software requirements have been used to define the rules of X-ray propagation for the model. A three-dimensional model of bone tissue has been created. The data necessary to define virtual samples in the software have been acquired from a collection of real specimens, which have been scanned using proper tomography techniques. In particular, the head, mandible, and pelvis have been modeled according to the data from computed tomography, and a sample of bone according to the data from micro computed tomography. The only exception is the phantom dataset, which has been defined according to literature. The simulation results are sets of values, which represent the radiation intensity after propagation through the virtual samples. These numerical data are presented in the paper as gray-scale images, brightness of which is related to incident radiation intensity. Analyses have been performed for several types of virtual samples. The obtained results correspond to the original data used to define these samples, which proves that the presented model of X-ray attenuation can be legitimately used to calculate tomography projections. References [1] Binkowski M., Dyszkiewicz A., Wr6bel Z. The analysis of densitometry image of bone tissue based on computer simulation of X-ray radiation propagation through plate model. Comput Biol Med, the article has been accepted for publication.
Poster Presentations
[2] Binkowski M., Krol Z., Wrobel Z., Zeilhofer H.-E, Modelling of X-ray propagation in bone microstructure. Journal of Medical Informatics & Technologies 2005; 9: 75-82.
1.2 Bone Healing and Osteointegration 4322 Mo-Tu, no. 16 (P55) Torsional testing on a non-union model of fractured tibia of rabbit K.S.C. Kwong 1, C.C. Hui 1, X. Guo 1, J.C.'~ Cheng 2. 1Department of
Rehabilitation Sciences, Hong Kong Polytechnic University, HKSAR, China, 2Department of Orthopaedics & Traumatology, Chinese University of Hong Kong, HKSAR, China Introduction: Torsional testing was performed on rabbit tibiae to investigate the effect of extracorporeal shockwave (ESW) on healing of a non-union model of fractured tibia. ESW treated and control tibiae retrieved from sacrificed rabbits were tested, and radiographs were taken to observe the bony change. The results suggest that ESW could initiate the ossification process at the nonunion site, which demonstrated greater mechanical strength than the control. Methods: Osteotomy was performed on the right tibiae of 8 New Zealand White rabbits of 18 weeks old to establish a non-union model. The rabbits were equally divided into ESW treatment group and the control group. The treatment group received one session of 1000 shocks of ESW at 0.54 mJ/mm 2, delivered to the fracture site by a shockwave generator (Sonocur, Siemens). Torsional testing at a speed of 10 degree per minute was performed on the tibiae of the rabbits sacrificed at 10 weeks after treatment. The specimens were mounted onto a servohydraulic biaxial universal material testing machine (Bionix 858, MTS Systems) through the use of a pair of custom-made adaptors. Ultimate failure torque and the stiffness were obtained. Radiographs were taken biweekly for 10 weeks after treatment to examine the bony change at the fracture site. Results: Cracking of bone was found at the fracture site on all specimens when the ultimate failure torque was reached. The results of the ultimate failure torque and stiffness of the treatment group were both higher than the control group. Bony bridging was observed at around week 6 after ESW treatment while the fracture gap remained in the control group. Conclusion: ESW could induce healing of bone fracture in non-union cases. The increase in torsional strength and stiffness of the healing bone after treatment suggests that ESW might induce early remodeling of the callus and promote bridging at the non-union gap.
6571 Mo-Tu, no. 17 (P55) Effect of reindeer BMP on the healing of a critical size long bone defect T. Pekkarinen 1, T. J~ms~ 2, M. M ~ t t ~ 2, O. Hietala 1, P. Jalovaara 1.
1Department of Surgery, University of Oulu, Oulu, Finland, 2Department of Medical Technology, University of Oulu, Oulu, Finland Reindeer bone morphogenetic protein (BMP) extracts have been shown to effectively induce ectopic new bone formation in vivo. However, the bone healing capacity has not yet been evaluated. Here we investigated the effect of reindeer BMP on the healing of a long bone defect in rabbit radius. Implants contained 5mg or 10mg non-sterilized or 10mg gamma-sterilized reindeer BMP extract administered with collagen carrier. 70~tg rhBMP-2 with collagen carrier served as positive, and collagen and untreated defects as negative controls. NZW-rabbit with a 1.5cm critical size radius defect was used. Bone healing was evaluated after eight weeks by radiographs, pQCT and mechanical torsion tests. Bone formation (BF) was higher in all groups containing BMPs than in the untreated controls. BF was also significantly higher in the rhBMP-2 group and nearly significantly higher in the group treated with 10 mg non-sterilized reindeer BMP ( p = 0 . 0 6 1 ) w h e n compared to collagen controls. Bone union (BU) was significantly better in the non-sterilized BMP groups and rhBMP-2 group than in the untreated or collagen controls. New bone area at defect site was higher in all BMP implants than in the untreated defects, and also higher in the 10 mg non-sterilized reindeer BMP extract group and rhBMP-2 group when compared to collagen controls. Torsional stiffness was higher in the 10 mg non-sterilized BMP group than in the collagen group. Cross-sectional bone area measured by pQCT was higher in the rhBMP-2 group than in the collagen group. Mean bone density at the defect area was higher in the 10 mg non-sterilized BMP extract group than in the rhBMP-2 group. In conclusion, reindeer BMP improved effectively the healing of rabbit radius bone defect and was comparable with rhBMP-2. Only slight differences were found between the study groups in the mechanical properties, which was mainly due to the small sample size. Gamma sterilization of reindeer BMP extract reduced osteoinductivity slightly but not significantly.