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Bone quality after osteonecrosis of the rat femoral head
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Journal of Biomechanics 2006, Vol. 39 (Suppl 1)
In this study, three human bones of the same person, femur, tibia and fibula, amputated due to non-pathological reason were examined. Studies in microstructure and mechanical properties were conducted. Microscopical results showed that the density of a Haversian system is the lowest in fibula whereas it is the highest in tibia. Mechanical tests were carried out by using a Vickers indenter attached to an Instron Universal Testing Machine. Nanoindentation was performed using the Hysitron nanoindenter. Several different mechanical tests such as hardness measurements, relaxation and loading-unloading tests were performed. Although hardness is varying on each bone depending on the anatomical region time after operation working in the favor of increase. Hysteresis loop of "loading-unloading" cycle corresponds energy absorption capacity. Results were obtained during relaxation tests. This research showed that tibia is superior comparing with the other two, whereas fibula is the weakest in terms of mechanical strength. Although it needs more detailed structural analysis to make a judgement, it is clear that according to our study, the density of Haversian channels is operative primarily. 4407 Mo-Tu, no. 40 (P55) Bone quality after osteonecrosis of the rat femoral head G. Yamako 1, R. Takano 2, K. Tokunaga 2, N. Endo 2, T. Hara 3. 1Graduate
School of Science and Technology, Niigata University, Niigata, Japan, 2Division of Orthopaedic Surgery, Niigata University, Niigata, Japan, 3Faculty of Engineering, Niigata University, Niigata, Japan The morbidity of osteonecorsis of the femoral head (ION) has grown rapidly. The death of osteocytes for ION could lead to the structural failure and the hip joint distruction. An essential ION treatment is to prevent collapse of a degeneration site in the femoral head with necrosis. Therefore, it is crucial to demonstrate the mechanism of the femoral head collapse. The biomechanical and structural degeneration of the cancellous bone after ION has been few documented, while regenerating processes of the bone tissue have been shown to lead the structural degeneration. The purpose of this study is to evaluate the trabecular architecture, the mineralization of bone and the mechanical property in the regenerating cancellous bone region after ION. ION was surgically induced in the left femoral head of a young wister rat. After 7, 21 and 42 days postoperation, the metaphysis cancellous bone was scanned on micro CT system. To measure bone mineral density (BMD) using micro CT, we developed a phantom containing K2HPO4 solutions of known concentrations. Histomorphometry analysis was performed using the parallel plate model to measure bone volume (BVF), trabecular thickness (Tb. Th), trabecular number (Tb. N), and trabecular space (Tb. Sp). The apparent modulus of the cancellous bone structure was calculated by voxel based FE model simulating an uniaxial loading condition. The analyzed data showed that significant decreasing in BMD, BVF, Tb. Th and apparent modulus on day 7 after induction of traumatic ischemia. These findings quantitatively revealed that the trabecular bone of regeneration site after ION could transiently decrease in the structural and mechanical strength. This suggests that bone tissues after ION regenerates by pathological bone repair that could lead to collapse of the femoral head even in human ION. 4132 Mo-Tu, no. 41 (P55) Effect of chemical sterilization on mechanical properties of human cortical bone and patellar tendon allografts M.E. Zobitz, P.M. Huddleston, D.B. Jones. Orthopedic Biemechanics
Laboratory, Mayo Clinic, Rochester, MN, USA Although musculoskeletal allografts are increasingly being utilized in a variety of orthopedic procedures, they pose the serious risk of disease transmission as highlighted by the death of a young patient after receiving a contaminated allograft [1]. Gamma irradiation has been widely used to minimize this risk, but it weakens musculoskeletal allografts [2]. The BioCleanse ® (Regeneration Technologies Inc., Alachua, FL) tissue sterilization process is a fully-automated, low-temperature chemical sterilization process that has been validated to consistently eliminate bacteria, bacterial spores, fungi, and viruses and renders allograft tissue sterile. The purpose of this study was to determine if the BioCleanse ® process alters the mechanical properties of cortical bone and patellar tendon allografts, compared to untreated control. Cortical bone specimens (n=178, age range 29-62) were machined into cylindrical geometries. Destructive testing was performed in axial compression, diametral compression, shear, and three-point bending. Bi-lateral bone-patellar tendon-bone specimens (n = 40, age range 19-88) were harvested and tested in a linear manner. Creep testing was performed by applying 1000 cycles of loading (50-250 N) followed by a test to failure. For each testing method, the effect of treatment on the ultimate strength and tendon creep was statistically analyzed. For the cortical bone specimens, among the four testing modes there were no significant differences between the Control and BioCleanse ® treated specimens. In the patellar tendon allografts there was, similarly, no significant differ-
Poster Presentations
ence in tendon creep or ultimate strength between Control and BioCleanse ® treated groups. The clinical significance of these findings is that the chemical sterilization process does not have an adverse effect on the biomechanical properties of cortical bone or patellar tendon allografts. References [1] Kainer MA, et al. N Engl J Med. 2004; 25: 2564-7. [2] Pelker RR, et al. Clin Orthop. 1983; 174: 54-7.
4641 Mo-Tu, no. 42 (P55) Behavior of cortical bone under loading in micro level; an experimental and FEM study A.R. Heidari 1, M.R. Eslami 2, A.R. Arshi 3, E. Mallakin 3. 1Fracture Lab,
Biomedical Engineering Faculty, Amir Kabir University, Tehran, Iran, 2ASME Mem., Mechanical Engineering Faculty, Amir Kabir University, Tehran, Iran, 3Biomedical Engineering Faculty, Amir Kabir University, Tehran, Iran Behavior of cortical bone in micro level has great effects on micromechanics of this tissue so bone researchers are focusing on smaller and smaller size scales. The objective of this research was to develop a detailed Finite Element Composite micromechanical model for haversian cortical bone. This model has made as an n-layered cylinder with internal stresses by real dimensions. Cement line, Osteon Layers, Interstitial Bone, Volkmann Canals and other porosities are included. In this study, the simultaneous effect of static and dynamic loading on stress distribution has taken into account. Solutions obtained by applying uniform macroscopic stresses to the boundaries of model. The results showed a maximum value of stress near haversian canal. In the next step, several samples obtained from bovine bone according to standards by machinery. Fracture tests done by INSTRON machine, and SEM pictures obtained from fracture surfaces. The figures showed cracks are in same orientation and same spots that software had marked as maximum stress spots. References [1] Braidotti P., Branca F. P., Sciubba E., Stagni L. An elastic compound tube model for single osteon. J Biomechanics 1995; 28(4): 439-444. [2] Guo X. R., Liang L. C., Goldestein S. A. Micromechanics of osteonal cortical bone fracture. J Biomechanics engineering 1998; 120:112-117. [3] Hogan H. A. Micromechanics modeling of haversian cortical bone properties. J Biomechanics, 1992; 25(5): 549-556. [4] Lakes R. S., Nakamura S., Behiri T. C., Bonfield W. Fracture mechanics of bone with short cracks. J Biomechanics 1990; 23(10): 967-975. [5] Melvin J. W. Fracture mechanics of bone. J Biomechanical Engineering 1993; 115: 549-554. [6] Fergal J., Taylor D., T. Clive Lee. The effect of bone microstructure on the initiation and growth of microcracks, Bone 2001; 28(2): 215-219.
5547 Mo-Tu, no. 43 (P55) High hydrostatic pressure as an alternatve sterilization method to irradiation or autoclaving of tumor-afflicted bone? P. Diehl 1, E. Steinhauser 1, J. Schauwecker 1, M. Schmitt 2, U. Magdolen 1, R. Gradinger 1, W. Mittelmeier 3 . 1Orthopedic Surgery, Technical University ef
Munich, Munich, Germany, 2Obstetrics and Gynecology, Technical University of Munich, Munich, Germany, 3 Orthopedic Surgery, University of Restock, Restock, Germany Introduction: In orthopedic surgery, sterilization of bone used for reconstruction of osteoarticular defects caused by malignant tumors is carried out in different ways. At present, to devitalize tumor-bearing osteochondral segments, extracorporal irradiation or autoclaving is used. Both methods have substantial disadvantages, e.g. loss of biomechanical and biological integrity of the bone. As an alternative approach, high hydrostatic pressure (HHP) treatment of bone is a new technology, now being used in preclinical testing to inactivate tumor afflicted bone without alteration of biological properties of bone. The aim of this study was to investigate the influence of HHP on bone, tendons, and cartilage. Method: Freshly resected human cortical bone chips and trabecular bone cylinder from femoral bones, 19 paired Achilles tendons harvested from both limbs of pigs and cylindric osteochondral segments of 20 bovine femoral condyles were subjected to HHP of 0, 300 and 600MPa (10min, RT). The biomechanical properties of the trabecular and cortical bone specimens were tested by a load-to-failure compression and a four-point-bending test. Tendons were exposed to a uniaxial tensile test until failure and cartilage was evaluated by a repetitive ball indention test. Testing parameters were Young's modulus (N/mm 2) and strength (N/mm2). For morphological investigations samples of tendons were labelled immunhistologically with HE, collagen I and versican, samples of cartilage with aggrecan and link-protein. Results: No significant difference was observed between the bone, tendons and cartilage treated at HHP of 300 to 600 MPa and the controls, regarding strength and Young's modulus. The biomechanical results were confirmed by
Journal of Biomechanics 2006, Vol. 39 (Suppl 1)
In this study, three human bones of the same person, femur, tibia and fibula, amputated due to non-pathological reason were examined. Studies in microstructure and mechanical properties were conducted. Microscopical results showed that the density of a Haversian system is the lowest in fibula whereas it is the highest in tibia. Mechanical tests were carried out by using a Vickers indenter attached to an Instron Universal Testing Machine. Nanoindentation was performed using the Hysitron nanoindenter. Several different mechanical tests such as hardness measurements, relaxation and loading-unloading tests were performed. Although hardness is varying on each bone depending on the anatomical region time after operation working in the favor of increase. Hysteresis loop of "loading-unloading" cycle corresponds energy absorption capacity. Results were obtained during relaxation tests. This research showed that tibia is superior comparing with the other two, whereas fibula is the weakest in terms of mechanical strength. Although it needs more detailed structural analysis to make a judgement, it is clear that according to our study, the density of Haversian channels is operative primarily. 4407 Mo-Tu, no. 40 (P55) Bone quality after osteonecrosis of the rat femoral head G. Yamako 1, R. Takano 2, K. Tokunaga 2, N. Endo 2, T. Hara 3. 1Graduate
School of Science and Technology, Niigata University, Niigata, Japan, 2Division of Orthopaedic Surgery, Niigata University, Niigata, Japan, 3Faculty of Engineering, Niigata University, Niigata, Japan The morbidity of osteonecorsis of the femoral head (ION) has grown rapidly. The death of osteocytes for ION could lead to the structural failure and the hip joint distruction. An essential ION treatment is to prevent collapse of a degeneration site in the femoral head with necrosis. Therefore, it is crucial to demonstrate the mechanism of the femoral head collapse. The biomechanical and structural degeneration of the cancellous bone after ION has been few documented, while regenerating processes of the bone tissue have been shown to lead the structural degeneration. The purpose of this study is to evaluate the trabecular architecture, the mineralization of bone and the mechanical property in the regenerating cancellous bone region after ION. ION was surgically induced in the left femoral head of a young wister rat. After 7, 21 and 42 days postoperation, the metaphysis cancellous bone was scanned on micro CT system. To measure bone mineral density (BMD) using micro CT, we developed a phantom containing K2HPO4 solutions of known concentrations. Histomorphometry analysis was performed using the parallel plate model to measure bone volume (BVF), trabecular thickness (Tb. Th), trabecular number (Tb. N), and trabecular space (Tb. Sp). The apparent modulus of the cancellous bone structure was calculated by voxel based FE model simulating an uniaxial loading condition. The analyzed data showed that significant decreasing in BMD, BVF, Tb. Th and apparent modulus on day 7 after induction of traumatic ischemia. These findings quantitatively revealed that the trabecular bone of regeneration site after ION could transiently decrease in the structural and mechanical strength. This suggests that bone tissues after ION regenerates by pathological bone repair that could lead to collapse of the femoral head even in human ION. 4132 Mo-Tu, no. 41 (P55) Effect of chemical sterilization on mechanical properties of human cortical bone and patellar tendon allografts M.E. Zobitz, P.M. Huddleston, D.B. Jones. Orthopedic Biemechanics
Laboratory, Mayo Clinic, Rochester, MN, USA Although musculoskeletal allografts are increasingly being utilized in a variety of orthopedic procedures, they pose the serious risk of disease transmission as highlighted by the death of a young patient after receiving a contaminated allograft [1]. Gamma irradiation has been widely used to minimize this risk, but it weakens musculoskeletal allografts [2]. The BioCleanse ® (Regeneration Technologies Inc., Alachua, FL) tissue sterilization process is a fully-automated, low-temperature chemical sterilization process that has been validated to consistently eliminate bacteria, bacterial spores, fungi, and viruses and renders allograft tissue sterile. The purpose of this study was to determine if the BioCleanse ® process alters the mechanical properties of cortical bone and patellar tendon allografts, compared to untreated control. Cortical bone specimens (n=178, age range 29-62) were machined into cylindrical geometries. Destructive testing was performed in axial compression, diametral compression, shear, and three-point bending. Bi-lateral bone-patellar tendon-bone specimens (n = 40, age range 19-88) were harvested and tested in a linear manner. Creep testing was performed by applying 1000 cycles of loading (50-250 N) followed by a test to failure. For each testing method, the effect of treatment on the ultimate strength and tendon creep was statistically analyzed. For the cortical bone specimens, among the four testing modes there were no significant differences between the Control and BioCleanse ® treated specimens. In the patellar tendon allografts there was, similarly, no significant differ-
Poster Presentations
ence in tendon creep or ultimate strength between Control and BioCleanse ® treated groups. The clinical significance of these findings is that the chemical sterilization process does not have an adverse effect on the biomechanical properties of cortical bone or patellar tendon allografts. References [1] Kainer MA, et al. N Engl J Med. 2004; 25: 2564-7. [2] Pelker RR, et al. Clin Orthop. 1983; 174: 54-7.
4641 Mo-Tu, no. 42 (P55) Behavior of cortical bone under loading in micro level; an experimental and FEM study A.R. Heidari 1, M.R. Eslami 2, A.R. Arshi 3, E. Mallakin 3. 1Fracture Lab,
Biomedical Engineering Faculty, Amir Kabir University, Tehran, Iran, 2ASME Mem., Mechanical Engineering Faculty, Amir Kabir University, Tehran, Iran, 3Biomedical Engineering Faculty, Amir Kabir University, Tehran, Iran Behavior of cortical bone in micro level has great effects on micromechanics of this tissue so bone researchers are focusing on smaller and smaller size scales. The objective of this research was to develop a detailed Finite Element Composite micromechanical model for haversian cortical bone. This model has made as an n-layered cylinder with internal stresses by real dimensions. Cement line, Osteon Layers, Interstitial Bone, Volkmann Canals and other porosities are included. In this study, the simultaneous effect of static and dynamic loading on stress distribution has taken into account. Solutions obtained by applying uniform macroscopic stresses to the boundaries of model. The results showed a maximum value of stress near haversian canal. In the next step, several samples obtained from bovine bone according to standards by machinery. Fracture tests done by INSTRON machine, and SEM pictures obtained from fracture surfaces. The figures showed cracks are in same orientation and same spots that software had marked as maximum stress spots. References [1] Braidotti P., Branca F. P., Sciubba E., Stagni L. An elastic compound tube model for single osteon. J Biomechanics 1995; 28(4): 439-444. [2] Guo X. R., Liang L. C., Goldestein S. A. Micromechanics of osteonal cortical bone fracture. J Biomechanics engineering 1998; 120:112-117. [3] Hogan H. A. Micromechanics modeling of haversian cortical bone properties. J Biomechanics, 1992; 25(5): 549-556. [4] Lakes R. S., Nakamura S., Behiri T. C., Bonfield W. Fracture mechanics of bone with short cracks. J Biomechanics 1990; 23(10): 967-975. [5] Melvin J. W. Fracture mechanics of bone. J Biomechanical Engineering 1993; 115: 549-554. [6] Fergal J., Taylor D., T. Clive Lee. The effect of bone microstructure on the initiation and growth of microcracks, Bone 2001; 28(2): 215-219.
5547 Mo-Tu, no. 43 (P55) High hydrostatic pressure as an alternatve sterilization method to irradiation or autoclaving of tumor-afflicted bone? P. Diehl 1, E. Steinhauser 1, J. Schauwecker 1, M. Schmitt 2, U. Magdolen 1, R. Gradinger 1, W. Mittelmeier 3 . 1Orthopedic Surgery, Technical University ef
Munich, Munich, Germany, 2Obstetrics and Gynecology, Technical University of Munich, Munich, Germany, 3 Orthopedic Surgery, University of Restock, Restock, Germany Introduction: In orthopedic surgery, sterilization of bone used for reconstruction of osteoarticular defects caused by malignant tumors is carried out in different ways. At present, to devitalize tumor-bearing osteochondral segments, extracorporal irradiation or autoclaving is used. Both methods have substantial disadvantages, e.g. loss of biomechanical and biological integrity of the bone. As an alternative approach, high hydrostatic pressure (HHP) treatment of bone is a new technology, now being used in preclinical testing to inactivate tumor afflicted bone without alteration of biological properties of bone. The aim of this study was to investigate the influence of HHP on bone, tendons, and cartilage. Method: Freshly resected human cortical bone chips and trabecular bone cylinder from femoral bones, 19 paired Achilles tendons harvested from both limbs of pigs and cylindric osteochondral segments of 20 bovine femoral condyles were subjected to HHP of 0, 300 and 600MPa (10min, RT). The biomechanical properties of the trabecular and cortical bone specimens were tested by a load-to-failure compression and a four-point-bending test. Tendons were exposed to a uniaxial tensile test until failure and cartilage was evaluated by a repetitive ball indention test. Testing parameters were Young's modulus (N/mm 2) and strength (N/mm2). For morphological investigations samples of tendons were labelled immunhistologically with HE, collagen I and versican, samples of cartilage with aggrecan and link-protein. Results: No significant difference was observed between the bone, tendons and cartilage treated at HHP of 300 to 600 MPa and the controls, regarding strength and Young's modulus. The biomechanical results were confirmed by