David Fyhrie | University of California, Davis (original) (raw)

Papers by David Fyhrie

Journal of Biomechanics, 1993

A model of the human foot was developed for use in a dynamic simulation of full body locomotiob. ... more A model of the human foot was developed for use in a dynamic simulation of full body locomotiob. The model consisted of a rigid frame upon which nonlinear, viscxxlasstic balls were placed to represent the foot sole. In addition, rigid toes were connected to the foot fnme via rcvolutc joints having viscoclastic behavior. The sphere material property equations were determined with optimization methods using experimental human heel impact force/deformation data from the literature. Several model geometries were tested using both kinematically and dynamically driven simulation procedures and compared with experimentally measured normal gait foot kinematic and ground reaction loads. The model was found to approximate the measured data we11 though some implementation difficulties were encountered due to the simulation techniques.

Transforming growth factor β (TGF-β), abundant in bone matrix, is believed to be an important loc... more Transforming growth factor β (TGF-β), abundant in bone matrix, is believed to be an important local regulator of osteoblast and osteoclast activity during bone growth and remodeling. Understanding how TGF-β controls bone remodeling is important to determine the underlying causes of the universal age-related loss of bone mass that can cause osteoporosis, debilitating fracture and death.

The compliance technique has been used to monitor crack length during fracture and fatigue testin... more The compliance technique has been used to monitor crack length during fracture and fatigue testing of materials. Difficulties arise when this technique is applied to anisotropic biological materials such as bone. In this tutorial, two different methods of analyzing compliance calibration data are described: the standard ASTM method and a new approach developed by the authors specifically for anisotropic materials. An example is given showing how data from equine cortical bone can be analyzed.

Articular cartilage is the load bearing soft tissue that covers the contacting surfaces of long b... more Articular cartilage is the load bearing soft tissue that covers the contacting surfaces of long bones in articulating joints. Healthy cartilage allows for smooth joint motion, while damaged cartilage prohibits normal function in debilitating joint diseases such as osteoarthritis.

OBJECTIVE: Understanding the mechanical functions of specific cartilage molecules such as aggreca... more OBJECTIVE: Understanding the mechanical functions of specific cartilage molecules such as aggrecan is important for understanding both healthy cartilage and disease progression. Cartilage is primarily composed of chondrocytes and an extracellular matrix consisting of multiple biopolymers, ions, and water. Aggrecan is one matrix biopolymer which consists of a core protein and multiple anionic glycosaminoglycans.

Abstract Mutations in sclerostin function or expression cause sclerosing bone dysplasias, involvi... more Abstract Mutations in sclerostin function or expression cause sclerosing bone dysplasias, involving decreased antagonism of Wnt/Lrp5 signaling. Conversely, deletion of the VHL tumor suppressor in osteoblasts, which stabilize HIF-α isoforms and thereby enables HIF-α/β-driven gene transcription, increases bone mineral content and cross-sectional area compared to wild-type controls. We examined the influence of cellular hypoxia (1% oxygen) upon sclerostin expression and canonical Wnt signaling.

Our understanding of mechanical controls on bone remodeling comes from studies of animals with su... more Our understanding of mechanical controls on bone remodeling comes from studies of animals with surgically implanted strain gages, but in vivo strain measurements have been made in a single human only once. That study showed that strains in the human tibia during walking and running are well below the fracture threshold. However, strains have never been monitored in vivo during vigorous activity in people, even though prolonged strenuous activity may be responsible for the occurrence of stress fractures.

Articular cartilage lines synovial joints and functions as a low-friction deformable tissue to en... more Articular cartilage lines synovial joints and functions as a low-friction deformable tissue to enable smooth and stable joint articulation. The objective of this study was to determine the relationships between cartilage stress-relaxation properties and the collagen and GAG NMR transverse relaxation times (T2) toward understanding mechanisms of cartilage viscoelasticity.

Dr. Fyhrie or an immediate family member has received research or institutional support from Airc... more Dr. Fyhrie or an immediate family member has received research or institutional support from Aircast, DePuy, Medtronic, Musculoskeletal Transplant Foundation, National Institutes of Health (NIAMS and NICHD), Stryker, and Zimmer. Dr. Nelson or an immediate family member has received research or institutional support from Stryker and IVIVI Technologies. Dr. Gibson or an immediate family member has received royalties from BioMarin and has received research or institutional support from Smith & Nephew DonJoy.

The level of structural detail that can be acquired and incorporated in a finite element (FE) ana... more The level of structural detail that can be acquired and incorporated in a finite element (FE) analysis might greatly influence the results of microcomputed tomography (CT)-based FE simulations, especially when relatively large bones, such as whole vertebrae, are of concern. We evaluated the effect of scanning and reconstruction voxel size on the CT-based FE analyses of human cancellous tissue samples for fixed-and free-end boundary conditions using different combinations of scan/reconstruction voxel size.

Abstract The sexual dimorphism in age-related loss of human vertebral cancellous bone is not full... more Abstract The sexual dimorphism in age-related loss of human vertebral cancellous bone is not fully understood and could be related to dimorphism in the bone cell populations. The objective of this study was to investigate age-and gender-related differences in the osteocyte population and its relationship with bone volume fraction for human vertebral cancellous bone.

It has become common to study the mechanical properties of whole bones using finite element model... more It has become common to study the mechanical properties of whole bones using finite element models (FEM) created from high resolution computed tomography and magnetic resonance images taken at a resolution compatible with in vivo scanning [1–10].

Abstract Transforming and insulin-like growth factors are important in regulating bone mass. Thus... more Abstract Transforming and insulin-like growth factors are important in regulating bone mass. Thus, one would anticipate correlations between matrix concentrations of growth factors and functional properties of bone. We therefore investigated the relationships of (1) TGF-β2 and (2) IGF-I matrix concentrations with the trabecular microstructure, stress distribution, and mechanical properties of tibial cancellous bone from six male human cadavers.

ABSTRACT Understanding compositional changes that occur when bone fails may help predict fracture... more ABSTRACT Understanding compositional changes that occur when bone fails may help predict fracture risk. Compositional differences that arise among failed, strained, and undamaged regions of bone can be determined using Raman spectroscopy and double-notch specimens. A double-notch specimen is a rectangular bone beam that has identical, rounded notches milled equidistant from each end.

RESULTS Initial moduli of all three specimen groups were alike (Table 1, p= 0.768). Stress-strain... more RESULTS Initial moduli of all three specimen groups were alike (Table 1, p= 0.768). Stress-strain curves (fig. 1) from specimens loaded to 20% strain increase were qualitatively similar to non-fatigued specimens from comparable regions, albeit with somewhat reduced material properties. By contrast, 40% strain increase specimens had a radically different stress-strain relationship, characterized by an elastic region that deviates early from linearity, poorly-defined yield and a truncated post-yield region.

Nanoindentation has been widely used to study bone tissue mechanical properties. The common metho... more Nanoindentation has been widely used to study bone tissue mechanical properties. The common method and equations for analyzing nanoindentation, developed by Oliver and Pharr, are based on the assumption that the material is linearly elastic.

Materials, including bone, often fail due to loading in the presence of critical flaws. The relat... more Materials, including bone, often fail due to loading in the presence of critical flaws. The relative amount, location, and interaction of these flaws within a stressed volume of material play a role in determining the failure properties of the structure. As materials are generally imperfect, larger volumes of material have higher probabilities of containing a flaw of critical size than do smaller volumes. Thus, larger volumes tend to fail at fewer cycles compared with smaller volumes when fatigue loaded to similar stress levels.

BACKGROUND: Pedicle screw fixation to stabilize lumbar spinal fusion has become the gold standard... more BACKGROUND: Pedicle screw fixation to stabilize lumbar spinal fusion has become the gold standard for posterior stabilization. A significant percentage of surgical candidates are classified as obese or morbidly obese. For these patients, the depth of the incisions and soft tissue makes it extremely difficult to insert pedicle screws along the pedicle axis. As such, the pedicle screws can only be inserted in a much more sagittal axis. However, biomechanical stability of the angled screw insertion has been controversial.

Abstract Stress fractures are overuse injuries of bone that affect elite athletes and military re... more Abstract Stress fractures are overuse injuries of bone that affect elite athletes and military recruits. One response of cortical bone to stress fracture is to lay down periosteal callus. The objectives of this study were to determine if material properties are different among bones with different stages of stress fracture callus, at both a callus site and at a distal site. Cortical specimens were mechanically tested to determine their stress–strain response. Material property differences were examined using nonparametric and regression analyses.

Abstract The hypothesis that the human sodium–iodide symporter, NIS, can be used to detect NIS ex... more Abstract The hypothesis that the human sodium–iodide symporter, NIS, can be used to detect NIS expression using standard radiological techniques was tested using adenoviral transduced NIS expression in human tumor xenografts grown in mice and in a naive dog prostate. Nonradioactive iodide was administered systemically to animals that 1–3 days previously had received a local injection of a replication-competent adenovirus expressing NIS under the control of the CMV promoter.

Journal of Biomechanics, 1993

A model of the human foot was developed for use in a dynamic simulation of full body locomotiob. ... more A model of the human foot was developed for use in a dynamic simulation of full body locomotiob. The model consisted of a rigid frame upon which nonlinear, viscxxlasstic balls were placed to represent the foot sole. In addition, rigid toes were connected to the foot fnme via rcvolutc joints having viscoclastic behavior. The sphere material property equations were determined with optimization methods using experimental human heel impact force/deformation data from the literature. Several model geometries were tested using both kinematically and dynamically driven simulation procedures and compared with experimentally measured normal gait foot kinematic and ground reaction loads. The model was found to approximate the measured data we11 though some implementation difficulties were encountered due to the simulation techniques.

Transforming growth factor β (TGF-β), abundant in bone matrix, is believed to be an important loc... more Transforming growth factor β (TGF-β), abundant in bone matrix, is believed to be an important local regulator of osteoblast and osteoclast activity during bone growth and remodeling. Understanding how TGF-β controls bone remodeling is important to determine the underlying causes of the universal age-related loss of bone mass that can cause osteoporosis, debilitating fracture and death.

The compliance technique has been used to monitor crack length during fracture and fatigue testin... more The compliance technique has been used to monitor crack length during fracture and fatigue testing of materials. Difficulties arise when this technique is applied to anisotropic biological materials such as bone. In this tutorial, two different methods of analyzing compliance calibration data are described: the standard ASTM method and a new approach developed by the authors specifically for anisotropic materials. An example is given showing how data from equine cortical bone can be analyzed.

Articular cartilage is the load bearing soft tissue that covers the contacting surfaces of long b... more Articular cartilage is the load bearing soft tissue that covers the contacting surfaces of long bones in articulating joints. Healthy cartilage allows for smooth joint motion, while damaged cartilage prohibits normal function in debilitating joint diseases such as osteoarthritis.

OBJECTIVE: Understanding the mechanical functions of specific cartilage molecules such as aggreca... more OBJECTIVE: Understanding the mechanical functions of specific cartilage molecules such as aggrecan is important for understanding both healthy cartilage and disease progression. Cartilage is primarily composed of chondrocytes and an extracellular matrix consisting of multiple biopolymers, ions, and water. Aggrecan is one matrix biopolymer which consists of a core protein and multiple anionic glycosaminoglycans.

Abstract Mutations in sclerostin function or expression cause sclerosing bone dysplasias, involvi... more Abstract Mutations in sclerostin function or expression cause sclerosing bone dysplasias, involving decreased antagonism of Wnt/Lrp5 signaling. Conversely, deletion of the VHL tumor suppressor in osteoblasts, which stabilize HIF-α isoforms and thereby enables HIF-α/β-driven gene transcription, increases bone mineral content and cross-sectional area compared to wild-type controls. We examined the influence of cellular hypoxia (1% oxygen) upon sclerostin expression and canonical Wnt signaling.

Our understanding of mechanical controls on bone remodeling comes from studies of animals with su... more Our understanding of mechanical controls on bone remodeling comes from studies of animals with surgically implanted strain gages, but in vivo strain measurements have been made in a single human only once. That study showed that strains in the human tibia during walking and running are well below the fracture threshold. However, strains have never been monitored in vivo during vigorous activity in people, even though prolonged strenuous activity may be responsible for the occurrence of stress fractures.

Articular cartilage lines synovial joints and functions as a low-friction deformable tissue to en... more Articular cartilage lines synovial joints and functions as a low-friction deformable tissue to enable smooth and stable joint articulation. The objective of this study was to determine the relationships between cartilage stress-relaxation properties and the collagen and GAG NMR transverse relaxation times (T2) toward understanding mechanisms of cartilage viscoelasticity.

Dr. Fyhrie or an immediate family member has received research or institutional support from Airc... more Dr. Fyhrie or an immediate family member has received research or institutional support from Aircast, DePuy, Medtronic, Musculoskeletal Transplant Foundation, National Institutes of Health (NIAMS and NICHD), Stryker, and Zimmer. Dr. Nelson or an immediate family member has received research or institutional support from Stryker and IVIVI Technologies. Dr. Gibson or an immediate family member has received royalties from BioMarin and has received research or institutional support from Smith & Nephew DonJoy.

The level of structural detail that can be acquired and incorporated in a finite element (FE) ana... more The level of structural detail that can be acquired and incorporated in a finite element (FE) analysis might greatly influence the results of microcomputed tomography (CT)-based FE simulations, especially when relatively large bones, such as whole vertebrae, are of concern. We evaluated the effect of scanning and reconstruction voxel size on the CT-based FE analyses of human cancellous tissue samples for fixed-and free-end boundary conditions using different combinations of scan/reconstruction voxel size.

Abstract The sexual dimorphism in age-related loss of human vertebral cancellous bone is not full... more Abstract The sexual dimorphism in age-related loss of human vertebral cancellous bone is not fully understood and could be related to dimorphism in the bone cell populations. The objective of this study was to investigate age-and gender-related differences in the osteocyte population and its relationship with bone volume fraction for human vertebral cancellous bone.

It has become common to study the mechanical properties of whole bones using finite element model... more It has become common to study the mechanical properties of whole bones using finite element models (FEM) created from high resolution computed tomography and magnetic resonance images taken at a resolution compatible with in vivo scanning [1–10].

Abstract Transforming and insulin-like growth factors are important in regulating bone mass. Thus... more Abstract Transforming and insulin-like growth factors are important in regulating bone mass. Thus, one would anticipate correlations between matrix concentrations of growth factors and functional properties of bone. We therefore investigated the relationships of (1) TGF-β2 and (2) IGF-I matrix concentrations with the trabecular microstructure, stress distribution, and mechanical properties of tibial cancellous bone from six male human cadavers.

ABSTRACT Understanding compositional changes that occur when bone fails may help predict fracture... more ABSTRACT Understanding compositional changes that occur when bone fails may help predict fracture risk. Compositional differences that arise among failed, strained, and undamaged regions of bone can be determined using Raman spectroscopy and double-notch specimens. A double-notch specimen is a rectangular bone beam that has identical, rounded notches milled equidistant from each end.

RESULTS Initial moduli of all three specimen groups were alike (Table 1, p= 0.768). Stress-strain... more RESULTS Initial moduli of all three specimen groups were alike (Table 1, p= 0.768). Stress-strain curves (fig. 1) from specimens loaded to 20% strain increase were qualitatively similar to non-fatigued specimens from comparable regions, albeit with somewhat reduced material properties. By contrast, 40% strain increase specimens had a radically different stress-strain relationship, characterized by an elastic region that deviates early from linearity, poorly-defined yield and a truncated post-yield region.

Nanoindentation has been widely used to study bone tissue mechanical properties. The common metho... more Nanoindentation has been widely used to study bone tissue mechanical properties. The common method and equations for analyzing nanoindentation, developed by Oliver and Pharr, are based on the assumption that the material is linearly elastic.

Materials, including bone, often fail due to loading in the presence of critical flaws. The relat... more Materials, including bone, often fail due to loading in the presence of critical flaws. The relative amount, location, and interaction of these flaws within a stressed volume of material play a role in determining the failure properties of the structure. As materials are generally imperfect, larger volumes of material have higher probabilities of containing a flaw of critical size than do smaller volumes. Thus, larger volumes tend to fail at fewer cycles compared with smaller volumes when fatigue loaded to similar stress levels.

BACKGROUND: Pedicle screw fixation to stabilize lumbar spinal fusion has become the gold standard... more BACKGROUND: Pedicle screw fixation to stabilize lumbar spinal fusion has become the gold standard for posterior stabilization. A significant percentage of surgical candidates are classified as obese or morbidly obese. For these patients, the depth of the incisions and soft tissue makes it extremely difficult to insert pedicle screws along the pedicle axis. As such, the pedicle screws can only be inserted in a much more sagittal axis. However, biomechanical stability of the angled screw insertion has been controversial.

Abstract Stress fractures are overuse injuries of bone that affect elite athletes and military re... more Abstract Stress fractures are overuse injuries of bone that affect elite athletes and military recruits. One response of cortical bone to stress fracture is to lay down periosteal callus. The objectives of this study were to determine if material properties are different among bones with different stages of stress fracture callus, at both a callus site and at a distal site. Cortical specimens were mechanically tested to determine their stress–strain response. Material property differences were examined using nonparametric and regression analyses.

Abstract The hypothesis that the human sodium–iodide symporter, NIS, can be used to detect NIS ex... more Abstract The hypothesis that the human sodium–iodide symporter, NIS, can be used to detect NIS expression using standard radiological techniques was tested using adenoviral transduced NIS expression in human tumor xenografts grown in mice and in a naive dog prostate. Nonradioactive iodide was administered systemically to animals that 1–3 days previously had received a local injection of a replication-competent adenovirus expressing NIS under the control of the CMV promoter.