Mark Taylor | Flinders University of South Australia (original) (raw)

Papers by Mark Taylor

Clinical Biomechanics, 2013

"Abstract BACKGROUND: Studies have highlighted asymmetries in knee joint moments in individuals ... more "Abstract
BACKGROUND: Studies have highlighted asymmetries in knee joint moments in individuals with osteoarthritis and joint replacements. However, there is a need to investigate the forces at the knee joints to establish the extent of loading asymmetries.
METHODS: Twenty healthy (mean age, 62; range, 55-79years) and 34 pre- to post-knee arthroplasty (mean age, 64; range, 39-79years) participants performed gait and sit-stand activities in a motion capture laboratory. Knee joint forces and moments were predicted using inverse dynamics and used to calculate peak loading and impulse data which were normalized to body weight. Comparisons were made between affected and contralateral limbs, and changes from pre- to post-knee arthroplasty.
FINDINGS: Pre-knee arthroplasty peak vertical knee forces were greater in the contralateral limb compared to the affected limb during both gait 3.5 vs. 3.2∗body weight and sit-stand 1.8 vs. 1.5∗body weight. During gait, peak knee adduction moment asymmetries significantly changed from pre- to post-knee arthroplasty (-0.3 to 0.8∗% body weight∗m∗height), although differences in vertical knee forces remained. There were no significant changes in loading during sit-stand from pre- to post-knee arthroplasty. The healthy participants showed no noteworthy asymmetries.
INTERPRETATION: This study showed loading asymmetries in knee forces between affected and contralateral limbs both pre- and post-knee arthroplasty. Continued over reliance of the contralateral limb could lead to pathology.

"

"Knowledge of joint forces and moments is essential for comparisons between healthy people and th... more "Knowledge of joint forces and moments is essential for comparisons between healthy people and those with pathological conditions, with observed changes at joints providing basis for a particular intervention. Currently the literature analysing both kinematics and kinetics at the knee has been limited to small samples, typically of young subjects or those who have undergone joint arthroplasty. In this study, we examined tibiofemoral joint (TFJ) kinematics and kinetics during gait, sit-stand-sit, and step-descent in 20 healthy older subjects (aged 53-79 years) using motion capture data and inverse dynamic musculoskeletal models.
Mean peak distal-proximal force in the TFJ were 3.1, 1.6, and 3.5 times body weight (N/BW) for gait, sit-stand, and step-descent respectively. There were also significant posterior-anterior forces, with sit-stand activity peaking at 1.6N/BW. Moments about the TFJ peaked at a mean of 0.07Nm/BW during the sit-stand activity. One of the most important findings of this study was variability found across the subjects, who spanned a wide age range, showing large standard deviations in all of the activities for both kinematics and kinetics. These data have provided an initial prediction for assessing kinematics and kinetics in the older population. Larger studies are needed to refine the database, in particular to reduce the variability in the results by studying sub-populations, to enable more robust comparisons between healthy and pathological TFJ kinematics and kinetics."

Journal of Biomechanics, 2012

ABSTRACT Pre-clinical computational testing of total knee replacements (TKRs) often only conside... more ABSTRACT
Pre-clinical computational testing of total knee replacements (TKRs) often only considers a single patient model with simplified applied loads. In studies of multiple patients, most only take into account geometric differences, especially in studies on the knee. Limited availability of kinetic data means that it is difficult to account for inter-patient variability. Principal component analysis (PCA) based statistical models have been used to capture the variation of a set of data and generate new instances of the data. This study presents a method to create a statistical model of kinetic waveform data. A PCA based statistical model was created of the tibiofemoral joint loads for level gait of preoperative TKR patients using data predicted from a musculoskeletal model. A reconstruction test showed that, using principal components (PCs) representing 95% variance, the median root-mean-squared (RMS) error was <0.1 body weight (BW) for the forces and <0.001 BWm for the moments. Leave-one-out tests were also performed and although the median RMS error increased for each load in comparison to the reconstruction error (maximum was 0.2 BW for the axial force and 0.012 BWm for the varus–valgus moment) these were considered within an acceptable limit. The purpose of creating a statistical model is to be able to sample a large set of data representing a population from a small set of clinical data. Such models can potentially be used in population based studies of TKRs incorporating inter-patient variability.

Muscle dimension changes on ultrasound imaging (USI) indicate contractile activity. Quadriceps fo... more Muscle dimension changes on ultrasound imaging (USI) indicate contractile activity. Quadriceps force and rectus femoris (RF) dimensions were examined to assess USI for stimating contraction level. In 15 healthy males, mean age 24.8 years, isometric quadriceps force was measured in 90 degrees knee flexion during submaximal and maximal voluntary contractions (MVCs) and at MVC in extension. Mid-thigh cross-sectional area (CSA), depth and width, and surface electromyography (EMG) of RF were recorded. Muscle width decreased curvilinearly as both force and EMG increased. At MVC, width was 3.2 +/- 0.5 cm, 25% smaller than at rest (4.4 +/- 0.7 cm), and similar to MVC in extension (-23%). CSA decreased linearly to -18% at MVC. RF thickness increased by only 10% (at 30% to MVC). Similar width changes at MVC in flexion and extension indicate the clinical potential of USI for assessing quadriceps contractility. Sensitivity is limited to assessing strength to within 25% of MVC in young males.

For a better understanding of traumatic bone fractures, knowledge of the mechanical behavior of b... more For a better understanding of traumatic bone fractures, knowledge of the mechanical behavior of bone at high strain rates is required. Importantly, it needs to be clarified how quasistatic mechanical testing experiments relate to real bone fracture. This merits investigating the mechanical behavior of bone with an increase in strain rate. Various studies examined how cortical and trabecular bone behave at varying strain rates, but no one has yet looked at this question using individual trabeculae.

This research describes a general theoretical framework for the constitutive modeling of biologic... more This research describes a general theoretical framework for the constitutive modeling of biological soft connective tissues. The approach is based on the theory of continuum fiber-reinforced composites at finite strain. Explicit expressions of the stress tensors in the material and spatial configurations are first established in the general case, without precluding any assumption regarding possible kinematic constraints or any particular mechanical symmetry of the material.

Abstract Failure of the resurfaced femoral head may occur in the short term owing to femoral neck... more Abstract Failure of the resurfaced femoral head may occur in the short term owing to femoral neck fracture or in the long term owing to aseptic loosening as a result of strain shielding. Resurfacing arthroplasties are not all the same. In particular, there is considerable debate regarding the role of the metaphyseal stem and cementing technique.

An early intervention prosthesis which minimizes the extent of resected healthy bone would be adv... more An early intervention prosthesis which minimizes the extent of resected healthy bone would be advantageous to patients for whom a total or unicompartmental replacement would sacrifice extensive healthy tissue. In this study the use of a device to treat osteoarthritis localized upon a single condyle of the femur with an associated irreparable meniscal tear is considered. The effects of implant alignment are considered from the standpoint of kinematics and potential for cartilage damage.

The incidence of aseptic loosening can be predicted from migration measurements for proximal femo... more The incidence of aseptic loosening can be predicted from migration measurements for proximal femoral, 1-4 proximal tibial 5,6 and acetabular components. 7 A common pattern of migration has an initial rapid phase while the implant is settling into a layer of necrotic bone. 8 This is followed by a slower continuous phase, the rate of which has been linked to later failure, but the cause of this is uncertain. The rate of medium-term migration depends on the method of fixation; press-fit prostheses migrate significantly more than cemented and osseo-integrated devices. The nature of both phases of migration suggests that it is a mechanical phenomenon, or at least mechanically triggered, rather than a biological process. Current theories of aseptic loosening cannot account for this pattern of migration. In cemented replacements, the debonding of either of the cement interfaces may initiate aseptic loosening, 9 but this theory assumes that loosening begins some years after surgery. Migration measurements indicate that loosening often begins very soon after implantation. Bone resorption, perhaps due to stress shielding, has been suggested as the primary mode of failure of cementless femoral prostheses.

BACKGROUND: Interpositional arthroplasty is considered by many surgeons for the treatment of isol... more BACKGROUND: Interpositional arthroplasty is considered by many surgeons for the treatment of isolated medial compartment osteoarthritis of the knee. In this procedure, an interpositional spacer is inserted into the medial compartment of the joint with no bone resection and no mechanical fixation. Major problems such as implant dislocation, severe pain or need for revision have been reported post-operatively.

Abstract The difficulty of achieving good distal contact between a cementless hip endoprosthesis ... more Abstract The difficulty of achieving good distal contact between a cementless hip endoprosthesis and the femur is well established. This finite element study investigates the effect on the stress distribution within the femur due to varying lengths of distal gap. Three-dimensional anatomical models of two different sized femurs were generated, based upon computer tomograph scans of two cadaveric specimens. A further six models were derived from each original model, with distal gaps varying from 10 to 60 mm in length.

Previous studies have suggested that a controlled stiffness prosthesis is required to address the... more Previous studies have suggested that a controlled stiffness prosthesis is required to address the conflicting requirements of minimizing stress shielding and micromotion. The design for a controlled stiffness prosthesis is proposed and a preliminary analytical investigation performed to assess its predicted performance before fabrication of a prototype component. The novel prosthesis consisted of a cobalt-chrome core and a flexible composite outer layer.

One possible loosening mechanism of the femoral component in total hip replacement is fatigue cra... more One possible loosening mechanism of the femoral component in total hip replacement is fatigue cracking of the cement mantle. A computational method capable of simulating this process may therefore be a useful tool in the preclinical evaluation of prospective implants. In this study, we investigated the ability of a computational method to predict fatigue cracking in experimental models of the implanted femur construct. Experimental specimens were fabricated such that cement mantle visualisation was possible throughout the test.

In previous finite element studies of cementless hip stems reported in the literature, the effect... more In previous finite element studies of cementless hip stems reported in the literature, the effect of bone quality on the initial micromotion and interface bone strain has been rarely reported. In this study, the effect of varying cortical and cancellous bone modulus on initial stem micromotion and interface bone strain was examined and the potential consequence of these changes on bone ingrowth and implant migration was reported.

The fatigue failure of bone has been implicated in a number of pathologies. Both implant design a... more The fatigue failure of bone has been implicated in a number of pathologies. Both implant design and clinical assessment would be enhanced by the ability to simulate fatigue failure. Like most materials, bone exhibits a decreasing fatigue life with increasing stress. During fatigue, bone also creeps and loses stiffness. The adequate characterization of all of these effects is necessary for finite element simulations of fatigue failure.

Fatigue failure of bone has been implicated in a number of clinical failure scenarios. At the mat... more Fatigue failure of bone has been implicated in a number of clinical failure scenarios. At the material level, the fatigue behaviour of cancellous bone is poorly understood. At the continuum level, the fatigue behaviour of cortical and cancellous bone are similar, exhibiting material degradation during a fatigue test.

Abstract We have compared the survival and radiological outcome at ten years after total hip repl... more Abstract We have compared the survival and radiological outcome at ten years after total hip replacement using two techniques for preparing the femoral canal. The same prosthesis was used throughout and all operations were performed by the same surgical team. In technique 1 the canal was over-reamed by 2 mm and in technique 2 it was reamed to the same size as the prosthesis. Technique 1 was performed on 92 patients and technique 2 on 97 patients.

Explicit finite element (FE) and multi-body dynamics (MBD) models have been developed to evaluate... more Explicit finite element (FE) and multi-body dynamics (MBD) models have been developed to evaluate total knee replacement (TKR) mechanics as a complement to experimental methods. In conjunction with these models, probabilistic methods have been implemented to predict performance bounds and identify important parameters, subject to uncertainty in component alignment and experimental conditions.

The aim of this study was to analyse the influence of muscle action and a horizontally constraine... more The aim of this study was to analyse the influence of muscle action and a horizontally constrained femoral head on the strain distribution within the intact femur. The strain distribution was measured for three loading configurations: joint reaction force only, joint reaction force plus abductors, and joint reaction force plus the abductors, vastus lateralis and iliopsoas. In each case the strains were recorded from 20 uniaxial strain gauges placed on the medial, lateral, anterior and posterior aspects of the proximal femur.

Computational tools are emerging as design tools for the development of total joint replacement w... more Computational tools are emerging as design tools for the development of total joint replacement with improved wear performance. The current wear models of polyethylene assume that wear is linearly proportional to sliding distance; however, it is hypothesized that the wear rate varies and is higher near a change in direction, but diminishes with continued unidirectional sliding, which eventually exhibits negligible wear.

Clinical Biomechanics, 2013

"Abstract BACKGROUND: Studies have highlighted asymmetries in knee joint moments in individuals ... more "Abstract
BACKGROUND: Studies have highlighted asymmetries in knee joint moments in individuals with osteoarthritis and joint replacements. However, there is a need to investigate the forces at the knee joints to establish the extent of loading asymmetries.
METHODS: Twenty healthy (mean age, 62; range, 55-79years) and 34 pre- to post-knee arthroplasty (mean age, 64; range, 39-79years) participants performed gait and sit-stand activities in a motion capture laboratory. Knee joint forces and moments were predicted using inverse dynamics and used to calculate peak loading and impulse data which were normalized to body weight. Comparisons were made between affected and contralateral limbs, and changes from pre- to post-knee arthroplasty.
FINDINGS: Pre-knee arthroplasty peak vertical knee forces were greater in the contralateral limb compared to the affected limb during both gait 3.5 vs. 3.2∗body weight and sit-stand 1.8 vs. 1.5∗body weight. During gait, peak knee adduction moment asymmetries significantly changed from pre- to post-knee arthroplasty (-0.3 to 0.8∗% body weight∗m∗height), although differences in vertical knee forces remained. There were no significant changes in loading during sit-stand from pre- to post-knee arthroplasty. The healthy participants showed no noteworthy asymmetries.
INTERPRETATION: This study showed loading asymmetries in knee forces between affected and contralateral limbs both pre- and post-knee arthroplasty. Continued over reliance of the contralateral limb could lead to pathology.

"

"Knowledge of joint forces and moments is essential for comparisons between healthy people and th... more "Knowledge of joint forces and moments is essential for comparisons between healthy people and those with pathological conditions, with observed changes at joints providing basis for a particular intervention. Currently the literature analysing both kinematics and kinetics at the knee has been limited to small samples, typically of young subjects or those who have undergone joint arthroplasty. In this study, we examined tibiofemoral joint (TFJ) kinematics and kinetics during gait, sit-stand-sit, and step-descent in 20 healthy older subjects (aged 53-79 years) using motion capture data and inverse dynamic musculoskeletal models.
Mean peak distal-proximal force in the TFJ were 3.1, 1.6, and 3.5 times body weight (N/BW) for gait, sit-stand, and step-descent respectively. There were also significant posterior-anterior forces, with sit-stand activity peaking at 1.6N/BW. Moments about the TFJ peaked at a mean of 0.07Nm/BW during the sit-stand activity. One of the most important findings of this study was variability found across the subjects, who spanned a wide age range, showing large standard deviations in all of the activities for both kinematics and kinetics. These data have provided an initial prediction for assessing kinematics and kinetics in the older population. Larger studies are needed to refine the database, in particular to reduce the variability in the results by studying sub-populations, to enable more robust comparisons between healthy and pathological TFJ kinematics and kinetics."

Journal of Biomechanics, 2012

ABSTRACT Pre-clinical computational testing of total knee replacements (TKRs) often only conside... more ABSTRACT
Pre-clinical computational testing of total knee replacements (TKRs) often only considers a single patient model with simplified applied loads. In studies of multiple patients, most only take into account geometric differences, especially in studies on the knee. Limited availability of kinetic data means that it is difficult to account for inter-patient variability. Principal component analysis (PCA) based statistical models have been used to capture the variation of a set of data and generate new instances of the data. This study presents a method to create a statistical model of kinetic waveform data. A PCA based statistical model was created of the tibiofemoral joint loads for level gait of preoperative TKR patients using data predicted from a musculoskeletal model. A reconstruction test showed that, using principal components (PCs) representing 95% variance, the median root-mean-squared (RMS) error was <0.1 body weight (BW) for the forces and <0.001 BWm for the moments. Leave-one-out tests were also performed and although the median RMS error increased for each load in comparison to the reconstruction error (maximum was 0.2 BW for the axial force and 0.012 BWm for the varus–valgus moment) these were considered within an acceptable limit. The purpose of creating a statistical model is to be able to sample a large set of data representing a population from a small set of clinical data. Such models can potentially be used in population based studies of TKRs incorporating inter-patient variability.

Muscle dimension changes on ultrasound imaging (USI) indicate contractile activity. Quadriceps fo... more Muscle dimension changes on ultrasound imaging (USI) indicate contractile activity. Quadriceps force and rectus femoris (RF) dimensions were examined to assess USI for stimating contraction level. In 15 healthy males, mean age 24.8 years, isometric quadriceps force was measured in 90 degrees knee flexion during submaximal and maximal voluntary contractions (MVCs) and at MVC in extension. Mid-thigh cross-sectional area (CSA), depth and width, and surface electromyography (EMG) of RF were recorded. Muscle width decreased curvilinearly as both force and EMG increased. At MVC, width was 3.2 +/- 0.5 cm, 25% smaller than at rest (4.4 +/- 0.7 cm), and similar to MVC in extension (-23%). CSA decreased linearly to -18% at MVC. RF thickness increased by only 10% (at 30% to MVC). Similar width changes at MVC in flexion and extension indicate the clinical potential of USI for assessing quadriceps contractility. Sensitivity is limited to assessing strength to within 25% of MVC in young males.

For a better understanding of traumatic bone fractures, knowledge of the mechanical behavior of b... more For a better understanding of traumatic bone fractures, knowledge of the mechanical behavior of bone at high strain rates is required. Importantly, it needs to be clarified how quasistatic mechanical testing experiments relate to real bone fracture. This merits investigating the mechanical behavior of bone with an increase in strain rate. Various studies examined how cortical and trabecular bone behave at varying strain rates, but no one has yet looked at this question using individual trabeculae.

This research describes a general theoretical framework for the constitutive modeling of biologic... more This research describes a general theoretical framework for the constitutive modeling of biological soft connective tissues. The approach is based on the theory of continuum fiber-reinforced composites at finite strain. Explicit expressions of the stress tensors in the material and spatial configurations are first established in the general case, without precluding any assumption regarding possible kinematic constraints or any particular mechanical symmetry of the material.

Abstract Failure of the resurfaced femoral head may occur in the short term owing to femoral neck... more Abstract Failure of the resurfaced femoral head may occur in the short term owing to femoral neck fracture or in the long term owing to aseptic loosening as a result of strain shielding. Resurfacing arthroplasties are not all the same. In particular, there is considerable debate regarding the role of the metaphyseal stem and cementing technique.

An early intervention prosthesis which minimizes the extent of resected healthy bone would be adv... more An early intervention prosthesis which minimizes the extent of resected healthy bone would be advantageous to patients for whom a total or unicompartmental replacement would sacrifice extensive healthy tissue. In this study the use of a device to treat osteoarthritis localized upon a single condyle of the femur with an associated irreparable meniscal tear is considered. The effects of implant alignment are considered from the standpoint of kinematics and potential for cartilage damage.

The incidence of aseptic loosening can be predicted from migration measurements for proximal femo... more The incidence of aseptic loosening can be predicted from migration measurements for proximal femoral, 1-4 proximal tibial 5,6 and acetabular components. 7 A common pattern of migration has an initial rapid phase while the implant is settling into a layer of necrotic bone. 8 This is followed by a slower continuous phase, the rate of which has been linked to later failure, but the cause of this is uncertain. The rate of medium-term migration depends on the method of fixation; press-fit prostheses migrate significantly more than cemented and osseo-integrated devices. The nature of both phases of migration suggests that it is a mechanical phenomenon, or at least mechanically triggered, rather than a biological process. Current theories of aseptic loosening cannot account for this pattern of migration. In cemented replacements, the debonding of either of the cement interfaces may initiate aseptic loosening, 9 but this theory assumes that loosening begins some years after surgery. Migration measurements indicate that loosening often begins very soon after implantation. Bone resorption, perhaps due to stress shielding, has been suggested as the primary mode of failure of cementless femoral prostheses.

BACKGROUND: Interpositional arthroplasty is considered by many surgeons for the treatment of isol... more BACKGROUND: Interpositional arthroplasty is considered by many surgeons for the treatment of isolated medial compartment osteoarthritis of the knee. In this procedure, an interpositional spacer is inserted into the medial compartment of the joint with no bone resection and no mechanical fixation. Major problems such as implant dislocation, severe pain or need for revision have been reported post-operatively.

Abstract The difficulty of achieving good distal contact between a cementless hip endoprosthesis ... more Abstract The difficulty of achieving good distal contact between a cementless hip endoprosthesis and the femur is well established. This finite element study investigates the effect on the stress distribution within the femur due to varying lengths of distal gap. Three-dimensional anatomical models of two different sized femurs were generated, based upon computer tomograph scans of two cadaveric specimens. A further six models were derived from each original model, with distal gaps varying from 10 to 60 mm in length.

Previous studies have suggested that a controlled stiffness prosthesis is required to address the... more Previous studies have suggested that a controlled stiffness prosthesis is required to address the conflicting requirements of minimizing stress shielding and micromotion. The design for a controlled stiffness prosthesis is proposed and a preliminary analytical investigation performed to assess its predicted performance before fabrication of a prototype component. The novel prosthesis consisted of a cobalt-chrome core and a flexible composite outer layer.

One possible loosening mechanism of the femoral component in total hip replacement is fatigue cra... more One possible loosening mechanism of the femoral component in total hip replacement is fatigue cracking of the cement mantle. A computational method capable of simulating this process may therefore be a useful tool in the preclinical evaluation of prospective implants. In this study, we investigated the ability of a computational method to predict fatigue cracking in experimental models of the implanted femur construct. Experimental specimens were fabricated such that cement mantle visualisation was possible throughout the test.

In previous finite element studies of cementless hip stems reported in the literature, the effect... more In previous finite element studies of cementless hip stems reported in the literature, the effect of bone quality on the initial micromotion and interface bone strain has been rarely reported. In this study, the effect of varying cortical and cancellous bone modulus on initial stem micromotion and interface bone strain was examined and the potential consequence of these changes on bone ingrowth and implant migration was reported.

The fatigue failure of bone has been implicated in a number of pathologies. Both implant design a... more The fatigue failure of bone has been implicated in a number of pathologies. Both implant design and clinical assessment would be enhanced by the ability to simulate fatigue failure. Like most materials, bone exhibits a decreasing fatigue life with increasing stress. During fatigue, bone also creeps and loses stiffness. The adequate characterization of all of these effects is necessary for finite element simulations of fatigue failure.

Fatigue failure of bone has been implicated in a number of clinical failure scenarios. At the mat... more Fatigue failure of bone has been implicated in a number of clinical failure scenarios. At the material level, the fatigue behaviour of cancellous bone is poorly understood. At the continuum level, the fatigue behaviour of cortical and cancellous bone are similar, exhibiting material degradation during a fatigue test.

Abstract We have compared the survival and radiological outcome at ten years after total hip repl... more Abstract We have compared the survival and radiological outcome at ten years after total hip replacement using two techniques for preparing the femoral canal. The same prosthesis was used throughout and all operations were performed by the same surgical team. In technique 1 the canal was over-reamed by 2 mm and in technique 2 it was reamed to the same size as the prosthesis. Technique 1 was performed on 92 patients and technique 2 on 97 patients.

Explicit finite element (FE) and multi-body dynamics (MBD) models have been developed to evaluate... more Explicit finite element (FE) and multi-body dynamics (MBD) models have been developed to evaluate total knee replacement (TKR) mechanics as a complement to experimental methods. In conjunction with these models, probabilistic methods have been implemented to predict performance bounds and identify important parameters, subject to uncertainty in component alignment and experimental conditions.

The aim of this study was to analyse the influence of muscle action and a horizontally constraine... more The aim of this study was to analyse the influence of muscle action and a horizontally constrained femoral head on the strain distribution within the intact femur. The strain distribution was measured for three loading configurations: joint reaction force only, joint reaction force plus abductors, and joint reaction force plus the abductors, vastus lateralis and iliopsoas. In each case the strains were recorded from 20 uniaxial strain gauges placed on the medial, lateral, anterior and posterior aspects of the proximal femur.

Computational tools are emerging as design tools for the development of total joint replacement w... more Computational tools are emerging as design tools for the development of total joint replacement with improved wear performance. The current wear models of polyethylene assume that wear is linearly proportional to sliding distance; however, it is hypothesized that the wear rate varies and is higher near a change in direction, but diminishes with continued unidirectional sliding, which eventually exhibits negligible wear.