Nigel Shrive | University of Calgary (original) (raw)
Papers by Nigel Shrive
The menisci are anisotropic hydrated connective tissues, situated in the tibiofemoral joint. The ... more The menisci are anisotropic hydrated connective tissues, situated in the tibiofemoral joint. The menisci transmit approximately 50% of the load across this joint [1, 2]. In this tissue, compression would only be experienced in the axial (vertical) direction, and as such, many studies have tested samples in the axial direction to determine the compressive properties [3–5]. The material behaviour of the menisci has been described as biphasic, meaning the response of the tissue to applied load is time dependent and determined by both the solid constituents and their interaction with the fluid component [3]. Due to the low permeability of the tissue, deformation results in relative movement of the solid matrix and the fluid it contains, resulting in the creation of drag forces between the two phases. Fluid exudation from the matrix governs the viscoelastic behaviour of the tissue, including stress relaxation and creep [6]. The swelling behaviour of meniscal samples in varying osmotic en...
American journal of orthopedics (Belle Mead, N.J.), 2010
The optimal plating configuration for open reduction and internal fixation of complex distal hume... more The optimal plating configuration for open reduction and internal fixation of complex distal humerus fractures is controversial. We evaluated cyclic fatigue performance and biomechanical stiffness in a cadaveric model of distal humerus fractures: precontoured nonlocking parallel plates versus a 90° nonlocking construct. A paired design was used, and 8 matched pairs of cadaveric arms were evaluated for bone density and plated. An osteotomy gap was created to simulate comminution, and constructs were randomized to anteroposterior, mediolateral, and torsional stiffness testing. Finally, 350 N was applied cyclically until deformation was permanent, Although there was a trend toward more stiffness of the parallel construct in anteroposterior, mediolateral, and torsional testing, it was not significant (P>.05). Likewise, there was no significant difference in number of cycles to failure (P>.05). Given these results, we suggest that it is reasonable to use a 90° construct or a parall...
Proceedings of the ICE - Engineering History and Heritage, 2015
The Hudson Bay Trading Company constructed the Prince of Wales Fort in the early eighteenth centu... more The Hudson Bay Trading Company constructed the Prince of Wales Fort in the early eighteenth century with the goal of securing the fur trade in northern Canada. As a result of the fort's northern latitude the walls remained partially frozen throughout much of each year until recently. Warming in the climate has raised the average yearly temperature so freeze–thaw cycles have caused a breakdown of the mortar within the stone masonry, enabling washout from melting snow and rain. This has led to lateral deformation in some sections of the walls and collapse in others. Two-dimensional finite-element models have been formulated to represent the in situ conditions of a damaged wall section with varying strength mortar and bond conditions. The models were created in Abaqus and focus on the case of self-weight. Micro-modelling techniques were employed to model the stones and grout individually. Results indicate a significant reduction in either the strength or bonding capacity of the mor...
This article describes the development of a new anchor for post-tensioning applications involving... more This article describes the development of a new anchor for post-tensioning applications involving carbon fiber-reinforced polymer tendons. A mechanical gripping, split-wedge anchor method was chosen. The anchor was developed using ultra-high-performance concrete (UHPC) with very high compressive strength, enhanced durability and fracture toughness. Twelve tests, incorporating 14 anchors, examined both static and dynamic performances of the anchor. Static tests resulted in an average anchor capacity of 99.7 kN, with a coefficient of variation of 2%. Dynamic load testing exhibited excellent fatigue performance for the UHPC anchor. The UHPC anchor will first be used in post-tensioned masonry diaphragm walls.
Journal of Biomechanical Engineering, 2011
Reproduction of the in vivo motions of joints has become possible with improvements in robot tech... more Reproduction of the in vivo motions of joints has become possible with improvements in robot technology and in vivo measuring techniques. A motion analysis system has been used to measure the motions of the tibia and femur of the ovine stifle joint during normal gait. These in vivo motions are then reproduced with a parallel robot. To ensure that the motion of the joint is accurately reproduced and that the resulting data are reliable, the testing frame, the data acquisition system, and the effects of limitations of the testing platform need to be considered. Of the latter, the stiffness of the robot and the ability of the control system to process sequential points on the path of motion in a timely fashion for repeatable path accuracy are of particular importance. Use of the system developed will lead to a better understanding of the mechanical environment of joints and ligaments in vivo.
Connective Tissue Research, 2014
Abstract Clinical evidence suggests that synovium can add to adjacent articular cartilage damage,... more Abstract Clinical evidence suggests that synovium can add to adjacent articular cartilage damage, potentially contributing to the development of osteoarthritis (OA). Inflammation of the synovium (synovitis) is dependent on the type of injury sustained, the time after injury and concomitant changes in other joint tissues. To define the role of synovitis in OA development, there is a need for baseline measures that can reliably distinguish synovial inflammation from normal synovium both within and between joints. This study tested the hypothesis that normal synovium from distinct anatomical locations in young and adult sheep is homogeneous with respect to consistently low molecular expression of the inflammatory mediators - tumour necrosis factor alpha (TNF-α) and interleukins (IL) such as IL-1β, IL-1Ra, IL-6 and IL-8. Additionally, maturation will not influence the expression of these select inflammatory biomarkers. Samples of synovium from four anatomic locations (medial and lateral margins, suprapatellar pouch (patella region), posterior to the posterior cruciate ligament, from each joint of 5 adult and 4 immature animals were graded histologically or analyzed for mRNA expression of inflammatory cytokines. Histologically, no evidence of synovitis was noted although some variance in sub-intimal fibrosis was observed between sample locations in mature sheep. Molecular expression of all inflammatory mediators was low and homogeneously expressed at constitutive levels in all sample locations. These findings confirm the hypothesis that the normal sheep synovium is a homogeneous tissue throughout the joint and establishes the baseline expression levels for several pro-inflammatory mediators in both immature and mature sheep.
Canadian Journal of Civil Engineering, 2000
Masonry is cost competitive on a life cycle basis with other forms of construction, and should th... more Masonry is cost competitive on a life cycle basis with other forms of construction, and should therefore be considered as a structural material more frequently by both architects and engineers. Post-tensioned geometric sections of masonry are structurally efficient wall systems. Post-tensioning with carbon fibre reinforced polymer (CFRP) is an attractive solution to potential corrosion problems with unbonded tendons. Tests on CFRP post-tensioned diaphragm walls have revealed that shear strength in prestressed masonry is an area deserving more study and improvement. The tests also showed that the bonding pattern of the masonry at the web-flange junction can have a substantial effect on the resulting strength of that connection. A test series to evaluate the effects of prestress force and bed reinforcement on shear strength has been carried out and a summary of the results is presented here. Tests to determine the effect of bonding pattern on the strength of the web-flange connection have also been conducted.
Bed joint reinforcement is used in concrete masonry walls to improve resistance against both inan... more Bed joint reinforcement is used in concrete masonry walls to improve resistance against both inand out-of-plane lateral loading. There is no doubt that the use of joint reinforcement enhances the post-cracking performance of masonry walls, but there are divergent results in the literature as to whether the use of joint reinforcement increases or decreases the overall shear resistance of masonry walls. It could be that the method of construction is the cause of the discrepancy in results, so an experimental program was executed to study the effect of two different ways of placing the bed joint reinforcement in the walls. The first method was to lay the bed joint reinforcement on the dry blocks with the mortar subsequently being placed on top, whereas the second method was to place the mortar on the face-shells and then embed the joint reinforcement in the mortar. The first method is the method used on site in Canada, while the second method would supposedly give better results as the...
Journal of orthopaedic research : official publication of the Orthopaedic Research Society, Mar 3, 2016
Post-traumatic osteoarthritis (PTOA) development is often observed following traumatic knee injur... more Post-traumatic osteoarthritis (PTOA) development is often observed following traumatic knee injuries involving key stabilising structures such as the cruciate ligaments or the menisci. Both biomechanical and biological alterations that follow knee injuries have been implicated in PTOA development, although it has not been possible to differentiate clearly between the two causal factors. This review critically examines the outcomes from pre-clinical lapine and ovine injury models arising in the authors' laboratories and differing in severity of PTOA development and progression. Specifically, we focus on how varying severity of knee injuries influence the subsequent alterations in kinematics, kinetics, and biological outcomes. The immediate impact of injury on the lubrication capacity of the joint is examined in the context of its influence on biomechanical alterations, thus linking the biological changes to abnormal kinematics, leading to a focus on the potential areas for interv...
Advanced Materials Research, 2010
Gestão & Tecnologia de Projetos, 2012
Canada is a young country with respect to its built heritage. The need to conserve examples of it... more Canada is a young country with respect to its built heritage. The need to conserve examples of its structures as a record of the history of settlement and growth has been recognized for some time by the somewhat small conservation community. The heritage conservation sector is growing compared to new construction. Unfortunately, there is a distinct lack of professional expertise (architects and engineers) familiar with the older traditional construction materials and methods, leading to some recommendations with respect to heritage structures being inconsistent with conservation principles. There is even less knowledge with respect to understanding how modern interventions will affect the construction supposedly being conserved. There is therefore a need for education in conservation principles and methodology. Two new programs are described, one at the undergraduate level at Carleton University, and the other at the graduate level at the University of Calgary. Both of these programs are being developed with advice from the Heritage Conservation Directorate of Public Works and Government Services Canada. The potentially negative consequences of the current lack of expertise for heritage structures are compounded by the current system for deciding whether or not a structure has heritage value. The system is inconsistent across the country, depending on how the guidelines interpreted and enforced. The federal and provincial and some municipal governments have collaborated in establishing guidelines for their areas of responsibility, but there is no overarching regulation for the protection of heritage across the country.
Journal of orthopaedic science : official journal of the Japanese Orthopaedic Association, 2006
Previous clinical studies have reported that conservatively managed medial collateral ligament (M... more Previous clinical studies have reported that conservatively managed medial collateral ligament (MCL) injuries remained unstable 9 years post injury with subjective complaints of muscle weakness, reinjuries, and post-traumatic osteoarthritis. Animal studies have also reported that healing MCLs were weaker and more lax than controls. Therefore, our purpose was to study the early effects of ligament repair on scar laxity, creep, and creep recovery in a rabbit model of bilateral medial collateral ligament (MCL) injury. Each rabbit had one MCL cut in midsubstance which was not repaired, while the other MCL had a sagittal Z-plasty repair. Six weeks after surgery, isolated bone-MCL-bone complexes were biomechanically tested for MCL laxity, cyclic creep, creep recovery, and then loaded to ultimate failure. Nonrepaired scars were significantly more lax than both repaired Z-plasty scars and normal controls. In contrast, there was no significant difference in MCL laxity between repaired scars ...
Journal of orthopaedic science : official journal of the Japanese Orthopaedic Association, 2000
To test the hypothesis that loading conditions can be used to "engineer" ligament autog... more To test the hypothesis that loading conditions can be used to "engineer" ligament autograft behaviors, the effect of cyclic tension on the mRNA levels of matrix molecules and collagenase in in-vivo immobilized and mobilized 6-week rabbit medial collateral ligament (MCL) autografts was examined using an in-vitro system. Femur-[autograft MCL]-tibia complexes were subjected to a tensile stress of 4 MPa at 0.5 Hz for 1 min, followed by 14 min of rest. This 15-min testing cycle was repeated for 4 h. Semi-quantitative reverse transcrip-tase polymerase chain reaction (RT-PCR) was performed on RNA from mechanically treated MCL autografts, using rabbit-specific primer sets for types I and III collagen, biglycan, decorin, fibromodulin, lumican, versican, matrix metalloproteinase-1 (MMP-1, collagenase-1), MMP-13 (collagenase-3), and a housekeeping gene, glyceraldehyde-3-phosphate dehydrogenase (GAPDH). Interestingly, 4 h of culture of normal control MCLs led to increased mRNA levels ...
American journal of physiology. Heart and circulatory physiology, 2001
The interventricular septum, which flattens and inverts in conditions such as pulmonary hypertens... more The interventricular septum, which flattens and inverts in conditions such as pulmonary hypertension, is considered by many to be an unstressed membrane, in that its position is assumed to be determined solely by the transseptal pressure gradient. A two-dimensional finite element model was developed to investigate whether compression and bending moments (behavior incompatible with a membrane) exist in the septum during diastole under abnormal loading, i.e., pulmonary artery (PA) constriction. Hemodynamic and echocardiographic data were obtained in six open-chest anesthetized dogs. For both control and PA constriction, the measured left ventricular and right ventricular pressures were applied to a residually stressed mesh. Adjustments were made to the stiffness and end-bending moments until the deformed and loaded residually stressed mesh matched the observed configuration of the septum. During PA constriction, end-bending moments were required to obtain satisfactory matches but not ...
Artery Research, 2015
ABSTRACT
The Knee, 2015
Meniscal injury has been well documented as a frequent consequence of both acute and chronic ACL ... more Meniscal injury has been well documented as a frequent consequence of both acute and chronic ACL deficiency. The purpose of this study was to evaluate the effect of ACL deficiency on meniscal loads in vivo and determine how these loads would change over time after ACL injury. The in vivo kinematics of the stifle joint of five sheep were measured during normal gait, as well as 4 and 20 weeks after ACL transection. A unique robotic testing platform was then programmed to reproduce all the previously recorded kinematics and the loads carried by medial and lateral menisci during gait were estimated. The results demonstrated a significant increase in both medial and lateral meniscal loads 20 weeks following ACL transection, mainly during mid-stance phase of gait (p = 0.007 and p = 0.003, respectively), with interesting inter-subject variability. A moderate correlation (R(2) ≥ 0.5) between in situ meniscal loads and anterior tibial translations was also detected over time after injury, increased translations post injury generally corresponded to larger meniscal loads. The dramatic increase in meniscal loads long term post ACL transection probably explains the meniscal changes or injuries reported clinically in many chronic ACL-deficient knees.
Current Opinion in Orthopaedics, 1993
Nontraditional Methods of Sensing Stress, Strain, and Damage in Materials and Structures, 1997
The criteria for the design of a device for measuring strain in flexible materials, particularly ... more The criteria for the design of a device for measuring strain in flexible materials, particularly soft tissues, are described. An extensometer is described which meets the design criteria. The resolution of the extensometer depends on its gage length. With a gage length of 5 mm, a resolution ...
The menisci are anisotropic hydrated connective tissues, situated in the tibiofemoral joint. The ... more The menisci are anisotropic hydrated connective tissues, situated in the tibiofemoral joint. The menisci transmit approximately 50% of the load across this joint [1, 2]. In this tissue, compression would only be experienced in the axial (vertical) direction, and as such, many studies have tested samples in the axial direction to determine the compressive properties [3–5]. The material behaviour of the menisci has been described as biphasic, meaning the response of the tissue to applied load is time dependent and determined by both the solid constituents and their interaction with the fluid component [3]. Due to the low permeability of the tissue, deformation results in relative movement of the solid matrix and the fluid it contains, resulting in the creation of drag forces between the two phases. Fluid exudation from the matrix governs the viscoelastic behaviour of the tissue, including stress relaxation and creep [6]. The swelling behaviour of meniscal samples in varying osmotic en...
American journal of orthopedics (Belle Mead, N.J.), 2010
The optimal plating configuration for open reduction and internal fixation of complex distal hume... more The optimal plating configuration for open reduction and internal fixation of complex distal humerus fractures is controversial. We evaluated cyclic fatigue performance and biomechanical stiffness in a cadaveric model of distal humerus fractures: precontoured nonlocking parallel plates versus a 90° nonlocking construct. A paired design was used, and 8 matched pairs of cadaveric arms were evaluated for bone density and plated. An osteotomy gap was created to simulate comminution, and constructs were randomized to anteroposterior, mediolateral, and torsional stiffness testing. Finally, 350 N was applied cyclically until deformation was permanent, Although there was a trend toward more stiffness of the parallel construct in anteroposterior, mediolateral, and torsional testing, it was not significant (P>.05). Likewise, there was no significant difference in number of cycles to failure (P>.05). Given these results, we suggest that it is reasonable to use a 90° construct or a parall...
Proceedings of the ICE - Engineering History and Heritage, 2015
The Hudson Bay Trading Company constructed the Prince of Wales Fort in the early eighteenth centu... more The Hudson Bay Trading Company constructed the Prince of Wales Fort in the early eighteenth century with the goal of securing the fur trade in northern Canada. As a result of the fort's northern latitude the walls remained partially frozen throughout much of each year until recently. Warming in the climate has raised the average yearly temperature so freeze–thaw cycles have caused a breakdown of the mortar within the stone masonry, enabling washout from melting snow and rain. This has led to lateral deformation in some sections of the walls and collapse in others. Two-dimensional finite-element models have been formulated to represent the in situ conditions of a damaged wall section with varying strength mortar and bond conditions. The models were created in Abaqus and focus on the case of self-weight. Micro-modelling techniques were employed to model the stones and grout individually. Results indicate a significant reduction in either the strength or bonding capacity of the mor...
This article describes the development of a new anchor for post-tensioning applications involving... more This article describes the development of a new anchor for post-tensioning applications involving carbon fiber-reinforced polymer tendons. A mechanical gripping, split-wedge anchor method was chosen. The anchor was developed using ultra-high-performance concrete (UHPC) with very high compressive strength, enhanced durability and fracture toughness. Twelve tests, incorporating 14 anchors, examined both static and dynamic performances of the anchor. Static tests resulted in an average anchor capacity of 99.7 kN, with a coefficient of variation of 2%. Dynamic load testing exhibited excellent fatigue performance for the UHPC anchor. The UHPC anchor will first be used in post-tensioned masonry diaphragm walls.
Journal of Biomechanical Engineering, 2011
Reproduction of the in vivo motions of joints has become possible with improvements in robot tech... more Reproduction of the in vivo motions of joints has become possible with improvements in robot technology and in vivo measuring techniques. A motion analysis system has been used to measure the motions of the tibia and femur of the ovine stifle joint during normal gait. These in vivo motions are then reproduced with a parallel robot. To ensure that the motion of the joint is accurately reproduced and that the resulting data are reliable, the testing frame, the data acquisition system, and the effects of limitations of the testing platform need to be considered. Of the latter, the stiffness of the robot and the ability of the control system to process sequential points on the path of motion in a timely fashion for repeatable path accuracy are of particular importance. Use of the system developed will lead to a better understanding of the mechanical environment of joints and ligaments in vivo.
Connective Tissue Research, 2014
Abstract Clinical evidence suggests that synovium can add to adjacent articular cartilage damage,... more Abstract Clinical evidence suggests that synovium can add to adjacent articular cartilage damage, potentially contributing to the development of osteoarthritis (OA). Inflammation of the synovium (synovitis) is dependent on the type of injury sustained, the time after injury and concomitant changes in other joint tissues. To define the role of synovitis in OA development, there is a need for baseline measures that can reliably distinguish synovial inflammation from normal synovium both within and between joints. This study tested the hypothesis that normal synovium from distinct anatomical locations in young and adult sheep is homogeneous with respect to consistently low molecular expression of the inflammatory mediators - tumour necrosis factor alpha (TNF-α) and interleukins (IL) such as IL-1β, IL-1Ra, IL-6 and IL-8. Additionally, maturation will not influence the expression of these select inflammatory biomarkers. Samples of synovium from four anatomic locations (medial and lateral margins, suprapatellar pouch (patella region), posterior to the posterior cruciate ligament, from each joint of 5 adult and 4 immature animals were graded histologically or analyzed for mRNA expression of inflammatory cytokines. Histologically, no evidence of synovitis was noted although some variance in sub-intimal fibrosis was observed between sample locations in mature sheep. Molecular expression of all inflammatory mediators was low and homogeneously expressed at constitutive levels in all sample locations. These findings confirm the hypothesis that the normal sheep synovium is a homogeneous tissue throughout the joint and establishes the baseline expression levels for several pro-inflammatory mediators in both immature and mature sheep.
Canadian Journal of Civil Engineering, 2000
Masonry is cost competitive on a life cycle basis with other forms of construction, and should th... more Masonry is cost competitive on a life cycle basis with other forms of construction, and should therefore be considered as a structural material more frequently by both architects and engineers. Post-tensioned geometric sections of masonry are structurally efficient wall systems. Post-tensioning with carbon fibre reinforced polymer (CFRP) is an attractive solution to potential corrosion problems with unbonded tendons. Tests on CFRP post-tensioned diaphragm walls have revealed that shear strength in prestressed masonry is an area deserving more study and improvement. The tests also showed that the bonding pattern of the masonry at the web-flange junction can have a substantial effect on the resulting strength of that connection. A test series to evaluate the effects of prestress force and bed reinforcement on shear strength has been carried out and a summary of the results is presented here. Tests to determine the effect of bonding pattern on the strength of the web-flange connection have also been conducted.
Bed joint reinforcement is used in concrete masonry walls to improve resistance against both inan... more Bed joint reinforcement is used in concrete masonry walls to improve resistance against both inand out-of-plane lateral loading. There is no doubt that the use of joint reinforcement enhances the post-cracking performance of masonry walls, but there are divergent results in the literature as to whether the use of joint reinforcement increases or decreases the overall shear resistance of masonry walls. It could be that the method of construction is the cause of the discrepancy in results, so an experimental program was executed to study the effect of two different ways of placing the bed joint reinforcement in the walls. The first method was to lay the bed joint reinforcement on the dry blocks with the mortar subsequently being placed on top, whereas the second method was to place the mortar on the face-shells and then embed the joint reinforcement in the mortar. The first method is the method used on site in Canada, while the second method would supposedly give better results as the...
Journal of orthopaedic research : official publication of the Orthopaedic Research Society, Mar 3, 2016
Post-traumatic osteoarthritis (PTOA) development is often observed following traumatic knee injur... more Post-traumatic osteoarthritis (PTOA) development is often observed following traumatic knee injuries involving key stabilising structures such as the cruciate ligaments or the menisci. Both biomechanical and biological alterations that follow knee injuries have been implicated in PTOA development, although it has not been possible to differentiate clearly between the two causal factors. This review critically examines the outcomes from pre-clinical lapine and ovine injury models arising in the authors' laboratories and differing in severity of PTOA development and progression. Specifically, we focus on how varying severity of knee injuries influence the subsequent alterations in kinematics, kinetics, and biological outcomes. The immediate impact of injury on the lubrication capacity of the joint is examined in the context of its influence on biomechanical alterations, thus linking the biological changes to abnormal kinematics, leading to a focus on the potential areas for interv...
Advanced Materials Research, 2010
Gestão & Tecnologia de Projetos, 2012
Canada is a young country with respect to its built heritage. The need to conserve examples of it... more Canada is a young country with respect to its built heritage. The need to conserve examples of its structures as a record of the history of settlement and growth has been recognized for some time by the somewhat small conservation community. The heritage conservation sector is growing compared to new construction. Unfortunately, there is a distinct lack of professional expertise (architects and engineers) familiar with the older traditional construction materials and methods, leading to some recommendations with respect to heritage structures being inconsistent with conservation principles. There is even less knowledge with respect to understanding how modern interventions will affect the construction supposedly being conserved. There is therefore a need for education in conservation principles and methodology. Two new programs are described, one at the undergraduate level at Carleton University, and the other at the graduate level at the University of Calgary. Both of these programs are being developed with advice from the Heritage Conservation Directorate of Public Works and Government Services Canada. The potentially negative consequences of the current lack of expertise for heritage structures are compounded by the current system for deciding whether or not a structure has heritage value. The system is inconsistent across the country, depending on how the guidelines interpreted and enforced. The federal and provincial and some municipal governments have collaborated in establishing guidelines for their areas of responsibility, but there is no overarching regulation for the protection of heritage across the country.
Journal of orthopaedic science : official journal of the Japanese Orthopaedic Association, 2006
Previous clinical studies have reported that conservatively managed medial collateral ligament (M... more Previous clinical studies have reported that conservatively managed medial collateral ligament (MCL) injuries remained unstable 9 years post injury with subjective complaints of muscle weakness, reinjuries, and post-traumatic osteoarthritis. Animal studies have also reported that healing MCLs were weaker and more lax than controls. Therefore, our purpose was to study the early effects of ligament repair on scar laxity, creep, and creep recovery in a rabbit model of bilateral medial collateral ligament (MCL) injury. Each rabbit had one MCL cut in midsubstance which was not repaired, while the other MCL had a sagittal Z-plasty repair. Six weeks after surgery, isolated bone-MCL-bone complexes were biomechanically tested for MCL laxity, cyclic creep, creep recovery, and then loaded to ultimate failure. Nonrepaired scars were significantly more lax than both repaired Z-plasty scars and normal controls. In contrast, there was no significant difference in MCL laxity between repaired scars ...
Journal of orthopaedic science : official journal of the Japanese Orthopaedic Association, 2000
To test the hypothesis that loading conditions can be used to "engineer" ligament autog... more To test the hypothesis that loading conditions can be used to "engineer" ligament autograft behaviors, the effect of cyclic tension on the mRNA levels of matrix molecules and collagenase in in-vivo immobilized and mobilized 6-week rabbit medial collateral ligament (MCL) autografts was examined using an in-vitro system. Femur-[autograft MCL]-tibia complexes were subjected to a tensile stress of 4 MPa at 0.5 Hz for 1 min, followed by 14 min of rest. This 15-min testing cycle was repeated for 4 h. Semi-quantitative reverse transcrip-tase polymerase chain reaction (RT-PCR) was performed on RNA from mechanically treated MCL autografts, using rabbit-specific primer sets for types I and III collagen, biglycan, decorin, fibromodulin, lumican, versican, matrix metalloproteinase-1 (MMP-1, collagenase-1), MMP-13 (collagenase-3), and a housekeeping gene, glyceraldehyde-3-phosphate dehydrogenase (GAPDH). Interestingly, 4 h of culture of normal control MCLs led to increased mRNA levels ...
American journal of physiology. Heart and circulatory physiology, 2001
The interventricular septum, which flattens and inverts in conditions such as pulmonary hypertens... more The interventricular septum, which flattens and inverts in conditions such as pulmonary hypertension, is considered by many to be an unstressed membrane, in that its position is assumed to be determined solely by the transseptal pressure gradient. A two-dimensional finite element model was developed to investigate whether compression and bending moments (behavior incompatible with a membrane) exist in the septum during diastole under abnormal loading, i.e., pulmonary artery (PA) constriction. Hemodynamic and echocardiographic data were obtained in six open-chest anesthetized dogs. For both control and PA constriction, the measured left ventricular and right ventricular pressures were applied to a residually stressed mesh. Adjustments were made to the stiffness and end-bending moments until the deformed and loaded residually stressed mesh matched the observed configuration of the septum. During PA constriction, end-bending moments were required to obtain satisfactory matches but not ...
Artery Research, 2015
ABSTRACT
The Knee, 2015
Meniscal injury has been well documented as a frequent consequence of both acute and chronic ACL ... more Meniscal injury has been well documented as a frequent consequence of both acute and chronic ACL deficiency. The purpose of this study was to evaluate the effect of ACL deficiency on meniscal loads in vivo and determine how these loads would change over time after ACL injury. The in vivo kinematics of the stifle joint of five sheep were measured during normal gait, as well as 4 and 20 weeks after ACL transection. A unique robotic testing platform was then programmed to reproduce all the previously recorded kinematics and the loads carried by medial and lateral menisci during gait were estimated. The results demonstrated a significant increase in both medial and lateral meniscal loads 20 weeks following ACL transection, mainly during mid-stance phase of gait (p = 0.007 and p = 0.003, respectively), with interesting inter-subject variability. A moderate correlation (R(2) ≥ 0.5) between in situ meniscal loads and anterior tibial translations was also detected over time after injury, increased translations post injury generally corresponded to larger meniscal loads. The dramatic increase in meniscal loads long term post ACL transection probably explains the meniscal changes or injuries reported clinically in many chronic ACL-deficient knees.
Current Opinion in Orthopaedics, 1993
Nontraditional Methods of Sensing Stress, Strain, and Damage in Materials and Structures, 1997
The criteria for the design of a device for measuring strain in flexible materials, particularly ... more The criteria for the design of a device for measuring strain in flexible materials, particularly soft tissues, are described. An extensometer is described which meets the design criteria. The resolution of the extensometer depends on its gage length. With a gage length of 5 mm, a resolution ...