Head rotational kinematics and tissue deformation metrics obtained from finite element models (FE... more Head rotational kinematics and tissue deformation metrics obtained from finite element models (FEM) have the potential to be used as traumatic axonal injury (TAI) assessment criteria and headgear evaluation standards. These metrics have been used to predict the likelihood of TAI occurrence; however, their ability in the assessment of the extent of TAI has not been explored. In this study, a pig model of TAI was used to examine a wide range of head loading conditions in two directions. The extent of TAI was quantified through histopathology and correlated to the FEM-derived tissue deformations and the head rotational kinematics. Peak angular acceleration and maximum strain rate of axo-nal fiber and brain tissue showed relatively good correlation to the volume of axonal injury, with similar correlation trends for both directions separately or combined. These rotational kinematics and tissue deformations can estimate the extent of acute TAI. The relationships between the head kinematics and the tissue strain, strain rate, and strain times strain rate were determined over the experimental range examined herein, and beyond that through parametric simulations. These relationships demonstrate that peak angular velocity and acceleration affect the underlying tissue deformations and the knowledge of both help to predict TAI risk. These relationships were combined with the injury thresholds, extracted from the TAI risk curves, and the kinematic-based risk curves representing overall axonal and brain tissue strain and strain rate were determined for predicting TAI. After scaling to humans, these curves can be used for real-time TAI assessment.
Journal of the Mechanical Behavior of Biomedical Materials, 2020
When the head is rotated rapidly, the movement of the brain lags that of the skull. Intracranial ... more When the head is rotated rapidly, the movement of the brain lags that of the skull. Intracranial contents between the brain and skull include meninges, cerebrospinal fluid (CSF), and cerebral vasculature. Among the cerebral vasculature in this space are the parasagittal bridging veins (BVs), which drain blood from the brain into the superior sagittal sinus (SSS), which is housed within the falx cerebri, adhered to the inner surface of the skull. Differential motion between the brain and skull that may occur during a traumatic event is thought to stretch BVs, causing damage and producing extra-axial hemorrhage (EAH). Finite element (FE) modeling is a technique often used to aid in the understanding and prediction of traumatic brain injury (TBI), and estimation of tissue deformation during traumatic events provides insight into kinematic injury thresholds. Using a FE model of the newborn porcine head with neonatal porcine brain and BV properties, single and cyclic rapid head rotations without impact were simulated. Measured BV failure properties were used to predict BV rupture. By comparing simulation outputs to observations of EAH in a development group of in vivo studies of rapid non-impact head rotations in the piglet, it was determined that failure of 16.7% of BV elements was associated with a 50% risk of EAH, and showed in a separate validation group that this threshold predicted the occurrence of EAH with 100% sensitivity and 100% specificity for single rapid non-impact rotations. This threshold for failed BV elements performed with 90% overall correct prediction in simulations of cyclic rotational head injuries. A 50% risk of EAH was associated with head angular velocities of 94.74 rad/s and angular accelerations of 29.60 krad/s 2 in the newborn piglet. Future studies may build on these findings for BV failure in the piglet to develop predictive models for BV failure in human infants.
A B S T R A C T Traumatic brain injury is a leading cause of cognitive and behavioral deficits in... more A B S T R A C T Traumatic brain injury is a leading cause of cognitive and behavioral deficits in children in the US each year. There is an increasing interest in both clinical and pre-clinical studies to discover biomarkers to accurately diagnose traumatic brain injury (TBI), predict its outcomes, and monitor its progression especially in the developing brain. In humans, the heterogeneity of TBI in terms of clinical presentation, injury causation, and mechanism has contributed to the many challenges associated with finding unifying diagnosis, treatment, and management practices. In addition, findings from adult human research may have little application to pediatric TBI, as age and maturation levels affect the injury biomechanics and neurophysiological consequences of injury. Animal models of TBI are vital to address the variability and heterogeneity of TBI seen in human by isolating the causation and mechanism of injury in reproducible manner. However, a gap between the pre-clinical findings and clinical applications remains in TBI research today. To take a step toward bridging this gap, we reviewed several potential TBI tools such as biofluid biomarkers, electroencephalography (EEG), actigraphy, eye responses, and balance that have been explored in both clinical and pre-clinical studies and have shown potential diagnostic, prognostic, or monitoring utility for TBI. Each of these tools measures specific deficits following TBI, is easily accessible, non/minimally invasive, and is potentially highly translatable between animals and human outcomes because they involve effort-independent and non-verbal tasks. Especially conspicuous is the fact that these biomarkers and techniques can be tailored for infants and toddlers. However, translation of preclinical outcomes to clinical applications of these tools necessitates addressing several challenges. Among the challenges are the heterogeneity of clinical TBI, age dependency of some of the biomarkers, different brain structure, life span, and possible variation between temporal profiles of biomarkers in human and animals. Conducting parallel clinical and pre-clinical research, in addition to the integration of findings across species from several preclinical models to generate a spectrum of TBI mechanisms and severities is a path toward overcoming some of these challenges. This effort is possible through large scale collaborative research and data sharing across multiple centers. In addition, TBI causes dynamic deficits in multiple domains, and thus, a panel of biomarkers combining these measures to consider different deficits is more promising than a single biomarker for TBI. In this review, each of these tools are presented along with the clinical and pre-clinical findings, advantages, challenges and prospects of translating the pre-clinical knowledge into the human clinical setting.
The objective of this study is to determine the effective mass of a head impact during a standing... more The objective of this study is to determine the effective mass of a head impact during a standing fall using a Humanetics TM HYBRID III 5th percentile female and a 50th percentile male anthropomorphic test dummy (ATD). The ATDs were instrumented with an array of tri-axial accelerometers and dropped from different initial positions onto a force plate. Five scenarios of falls were conducted to study the effect of fall direction/type on the effective mass of the head impact. The effective mass for forward and backward standing falls can be estimated as the mass of the head plus 49% and 47% of the neck mass for the female and male ATDs. The lateral fall showed different response where less of the neck mass is involved resulting in an effective mass, which includes the mass of the head plus 6% and 22% of the neck mass for the female and male ATDs, respectively.
Volume 3A: Biomedical and Biotechnology Engineering, 2013
ABSTRACT Traumatic Brain Injury (TBI) contributes to a major number of deaths and cases of perman... more ABSTRACT Traumatic Brain Injury (TBI) contributes to a major number of deaths and cases of permanent disability each year. Falls are the leading cause of TBI with the highest rates for children 0–4 years old and for adults age 75 and older. Accordingly, there is a significant interest in fall-related injury mechanism and head impact. Since the dynamics of human fall and head injury mechanisms are highly variable due to the inherent and complex nature of human falling, the aim of the present study is to describe the dynamics of backward falls and risk of injury due to head impact. In order to have a better understanding of head impact, A HYBRID III 5th Percentile Female test (Denton ATD, Inc.) instrumented with a tri-axial accelerometer with measuring range of ±500g at the center of gravity of the head was dropped from standing posture by using a controlled release mechanism. The dynamic model of fall was captured using a T-series Vicon motion capture system synchronized with a force plate to measure the impact force and a tri-axial accelerometer to measure the impact acceleration of the head. The acceleration impact data measured at 20 KHz and the motion capture system was capable to retrieve 500 samples per second. The primary objective of this study was to determine the equivalent mass involved during head impact due to a backward fall. This effective mass is a key quantity to design the head impact experimental setups, protection devices and computer simulations of head impact. Based on the force and acceleration measurements in several tests, the head impact effective mass is approximately found to be the mass of head itself plus 48% the neck mass. Two scenarios of backward fall were studied and discussed. First, falling while the hip joints are involved and the trunk moves forward and second, falling while the hip joints act like a fixed joint. For the first scenario the impact forces and accelerations peak measured using the HYBRID III were found to be 10±1.8KN and 255±42g, respectively, and for the second scenario the larger impact forces, 14.5±0.9KN, and acceleration peaks, 364±27g, were measured in all tests.
2008 5th International Symposium on Mechatronics and Its Applications, 2008
In this paper a control approach for a flexible robotic manipulator using a Model-Based Fuzzy tec... more In this paper a control approach for a flexible robotic manipulator using a Model-Based Fuzzy technique is investigated. The developed controller is based on Takagi-Sugeno fuzzy modelling and LMI (Linear Matrix Inequality) analysis. By utilizing the concept of parallel distributed compensation (PDC) by considering decay rate and constraints on control input, the design of fuzzy controller is presented. The effectiveness of the proposed method is demonstrated through comparison with other existing methods.
... Published by Elsevier Ltd. Permissions & Reprints. Performance-oriented parallel distribu... more ... Published by Elsevier Ltd. Permissions & Reprints. Performance-oriented parallel distributed compensation. Morteza Seidi a , E-mail The Corresponding Author and Amir HD Markazi Corresponding Author Contact Information , a , E-mail The Corresponding Author. ...
The purpose of this case report was to study effects of X-Stop implant surgery on the continuous ... more The purpose of this case report was to study effects of X-Stop implant surgery on the continuous spinal movement kinematics using 3D motion analysis. A proposed 3D kinematic spinal model was used to assess lumbar continuous active range of motion (AROM) during a standardized lumbar extension/flexion preoperatively and at 2 months postoperatively of a patient who underwent the X-Stop procedure. To investigate levels of muscle activities, electromyography recordings were made from right and left rectus abdominis, erector spinae and biceps femoris muscles. Also, functional mobility and patient quality of life were evaluated using the 6-minute walk test and the Swiss spinal stenosis and PROMIS-29 questionnaire. At 2 months postoperative, lumbar AROM increased by 18.5 and 14° for flexion and extension respectively and less muscle activation level was observed, despite the increase in lumbar AROM. Unlike positional magnetic resonance imaging (MRI) that is a common approach to assess spinal posture in static positions, the proposed continuous-motion analysis approach is able to analyze the lumbar AROM dynamically during flexion and extension. In this case report, the results indicate that the lumbar AROM, functional mobility and quality of life have been improved following X-Stop surgical intervention.
Falls in the elderly population is an important concern to individuals, family, friends, and in ... more Falls in the elderly population is an important concern to individuals, family, friends, and in the healthcare industry. When the head is left unprotected, head impact levels can reach upwards of 500 g (gravitational acceleration), which is a level that can cause serious injury or death. A protective system for a fall injury needs to be designed with specific criteria in mind including energy protection level, thickness, stiffness, weight, and cost among others. The current study quantifies the performance of a protective head gear design for persons prone to falls. The main objective of this paper is to evaluate the injury mitigation of head protection gear made from a patented system of polyurethane honeycomb and dilatant materials. To that end, a twin wire fall system equipped with a drop arm that includes a Hybrid-III head/neck assembly was used. The head was instrumented with a 9 accelerometer array so that angular acceleration is calculated directly from the linear acceleration signals. The test apparatus captures impact velocity, linear and angular acceleration components simultaneously. Tests were performed on two different material systems for frontal, side and rear impact cases. The honeycomb-dilatant system for each design consists of a cast 6mm thick, polyurethane honeycomb in the front section and a 6mm thick, honeycomb in the rear, that are nominally 55 Shore A and 40 Shore A durometer, respectively and the outer shell was a dilatant material. The peak linear acceleration, peak angular acceleration and the Head Injury Criterion (HIC) were captured to evaluate the performance of two material systems. A significant reduction of the peak linear and angular acceleration and HIC during impact was observed. Dropping the head/neck assembly equipped with the protection system from 45cm height (rear impact) resulted in linear acceleration, angular acceleration and HIC reduction from 308g to 82g, 14,127rad s-2 to 4,126rad s-2 and 879 to 136, respectively for the thicker material system.
The kinematics and kinetics of head impact due to a standing fall onto a hard surface are summari... more The kinematics and kinetics of head impact due to a standing fall onto a hard surface are summarized. Head injury due to impact from falls represents a significant problem, especially for older individuals. When the head is left unprotected during a fall, the impact severity can be high enough to cause significant injury or even death. To ascertain the range of head impact parameters, the dynamic response was captured for the pedestrian version of the 5th percentile female and 50th percentile male Hybrid III anthropomorphic test dummies as they were dropped from a standing position with different initial postures. Five scenarios of falls were considered including backward falls with/without hip flexion, forward falls with/without knee flexion and lateral falls. The results show that the head impact parameters are dependent on the fall scenario. A wide range of impact parameters was observed in 107 trials. The 95% prediction interval for the peak translational acceleration, peak angular acceleration, peak force, impact translational velocity and peak angular velocity are 146-502 g, 8.8-43.3 krad/s(2), 3.9-24.5 kN, 2.02-7.41 m/s, and 12.9-70.3 rad/s, respectively.
The objective of this study is to determine the effective mass of a head impact during a standing... more The objective of this study is to determine the effective mass of a head impact during a standing fall using a HumaneticsTM HYBRID III 5th percentile female and a 50th percentile male anthropomorphic test dummy (ATD). The ATDs were instrumented with an array of tri-axial accelerometers and dropped from different initial positions onto a force plate. Five scenarios of falls were conducted to study the effect of fall direction/type on the effective mass of the head impact. The effective mass for forward and backward standing falls can be estimated as the mass of the head plus 49% and 47% of the neck mass for the female and male ATDs. The lateral fall showed different response where less of the neck mass is involved resulting in an effective mass, which includes the mass of the head plus 6% and 22% of the neck mass for the female and male ATDs, respectively.
A test method based upon a Hybrid-III head and neck assembly that includes measurement of both li... more A test method based upon a Hybrid-III head and neck assembly that includes measurement of both linear and angular acceleration is investigated for potential use in impact testing of protective headgear. The test apparatus is based upon a twin wire drop test system modified with the head/neck assembly and associated flyarm components. This study represents a preliminary assessment of the test apparatus for use in the development of protective headgear designed to prevent injury due to falls. By including angular acceleration in the test protocol it becomes possible to assess and intentionally reduce this component of acceleration. Comparisons of standard and reduced durometer necks, various anvils, front, rear, and side drop orientations, and response data on performance of the apparatus are provided. Injury measures summarized for an unprotected drop include maximum linear and angular acceleration, head injury criteria (HIC), rotational injury criteria (RIC), and power rotational head injury criteria (PRHIC). Coefficient of variation for multiple drops ranged from 0.4 to 6.7% for linear acceleration. Angular acceleration recorded in a side drop orientation resulted in highest coefficient of variation of 16.3%. The drop test apparatus results in a reasonably repeatable test method that has potential to be used in studies of headgear designed to reduce head impact injury.
The main idea of the original parallel distributed compensation (PDC) method is to partition the ... more The main idea of the original parallel distributed compensation (PDC) method is to partition the dynamics of a nonlinear system into a number of linear subsystems, design a number of state feedback gains for each linear subsystem, and finally generate the overall state feedback gain by fuzzy blending of such gains. A new modification to the original PDC method is proposed here, so that, besides the stability issue, the closed-loop performance of the system can be considered at the design stage. For this purpose, the state feedback gains are not considered constant through the linearized subsystems, rather, based on some prescribed performance criteria, several feedback gains are associated to every subsystem, and the final gain for every subsystem is obtained by fuzzy blending of such gains. The advantage is that, for example, a faster response can be obtained, for a given bound on the control input. Asymptotic stability of the closed loop system is also guaranteed by using the Lyapunov method. To illustrate the effectiveness of the new method, control of a flexible joint robot (FJR) is investigated and superiority of the designed controller over other existing methods is demonstrated.
In this paper a control approach for a flexible robotic manipulator using a model-based fuzzy tec... more In this paper a control approach for a flexible robotic manipulator using a model-based fuzzy technique is investigated. The developed controller is based on Takagi-Sugeno fuzzy modelling and LMI (linear matrix inequality) analysis. By utilizing the concept of parallel distributed compensation (PDC) by considering decay rate and constraints on control input, the design of fuzzy controller is presented. The effectiveness of the proposed method is demonstrated through comparison with other existing methods.
Head rotational kinematics and tissue deformation metrics obtained from finite element models (FE... more Head rotational kinematics and tissue deformation metrics obtained from finite element models (FEM) have the potential to be used as traumatic axonal injury (TAI) assessment criteria and headgear evaluation standards. These metrics have been used to predict the likelihood of TAI occurrence; however, their ability in the assessment of the extent of TAI has not been explored. In this study, a pig model of TAI was used to examine a wide range of head loading conditions in two directions. The extent of TAI was quantified through histopathology and correlated to the FEM-derived tissue deformations and the head rotational kinematics. Peak angular acceleration and maximum strain rate of axo-nal fiber and brain tissue showed relatively good correlation to the volume of axonal injury, with similar correlation trends for both directions separately or combined. These rotational kinematics and tissue deformations can estimate the extent of acute TAI. The relationships between the head kinematics and the tissue strain, strain rate, and strain times strain rate were determined over the experimental range examined herein, and beyond that through parametric simulations. These relationships demonstrate that peak angular velocity and acceleration affect the underlying tissue deformations and the knowledge of both help to predict TAI risk. These relationships were combined with the injury thresholds, extracted from the TAI risk curves, and the kinematic-based risk curves representing overall axonal and brain tissue strain and strain rate were determined for predicting TAI. After scaling to humans, these curves can be used for real-time TAI assessment.
Journal of the Mechanical Behavior of Biomedical Materials, 2020
When the head is rotated rapidly, the movement of the brain lags that of the skull. Intracranial ... more When the head is rotated rapidly, the movement of the brain lags that of the skull. Intracranial contents between the brain and skull include meninges, cerebrospinal fluid (CSF), and cerebral vasculature. Among the cerebral vasculature in this space are the parasagittal bridging veins (BVs), which drain blood from the brain into the superior sagittal sinus (SSS), which is housed within the falx cerebri, adhered to the inner surface of the skull. Differential motion between the brain and skull that may occur during a traumatic event is thought to stretch BVs, causing damage and producing extra-axial hemorrhage (EAH). Finite element (FE) modeling is a technique often used to aid in the understanding and prediction of traumatic brain injury (TBI), and estimation of tissue deformation during traumatic events provides insight into kinematic injury thresholds. Using a FE model of the newborn porcine head with neonatal porcine brain and BV properties, single and cyclic rapid head rotations without impact were simulated. Measured BV failure properties were used to predict BV rupture. By comparing simulation outputs to observations of EAH in a development group of in vivo studies of rapid non-impact head rotations in the piglet, it was determined that failure of 16.7% of BV elements was associated with a 50% risk of EAH, and showed in a separate validation group that this threshold predicted the occurrence of EAH with 100% sensitivity and 100% specificity for single rapid non-impact rotations. This threshold for failed BV elements performed with 90% overall correct prediction in simulations of cyclic rotational head injuries. A 50% risk of EAH was associated with head angular velocities of 94.74 rad/s and angular accelerations of 29.60 krad/s 2 in the newborn piglet. Future studies may build on these findings for BV failure in the piglet to develop predictive models for BV failure in human infants.
A B S T R A C T Traumatic brain injury is a leading cause of cognitive and behavioral deficits in... more A B S T R A C T Traumatic brain injury is a leading cause of cognitive and behavioral deficits in children in the US each year. There is an increasing interest in both clinical and pre-clinical studies to discover biomarkers to accurately diagnose traumatic brain injury (TBI), predict its outcomes, and monitor its progression especially in the developing brain. In humans, the heterogeneity of TBI in terms of clinical presentation, injury causation, and mechanism has contributed to the many challenges associated with finding unifying diagnosis, treatment, and management practices. In addition, findings from adult human research may have little application to pediatric TBI, as age and maturation levels affect the injury biomechanics and neurophysiological consequences of injury. Animal models of TBI are vital to address the variability and heterogeneity of TBI seen in human by isolating the causation and mechanism of injury in reproducible manner. However, a gap between the pre-clinical findings and clinical applications remains in TBI research today. To take a step toward bridging this gap, we reviewed several potential TBI tools such as biofluid biomarkers, electroencephalography (EEG), actigraphy, eye responses, and balance that have been explored in both clinical and pre-clinical studies and have shown potential diagnostic, prognostic, or monitoring utility for TBI. Each of these tools measures specific deficits following TBI, is easily accessible, non/minimally invasive, and is potentially highly translatable between animals and human outcomes because they involve effort-independent and non-verbal tasks. Especially conspicuous is the fact that these biomarkers and techniques can be tailored for infants and toddlers. However, translation of preclinical outcomes to clinical applications of these tools necessitates addressing several challenges. Among the challenges are the heterogeneity of clinical TBI, age dependency of some of the biomarkers, different brain structure, life span, and possible variation between temporal profiles of biomarkers in human and animals. Conducting parallel clinical and pre-clinical research, in addition to the integration of findings across species from several preclinical models to generate a spectrum of TBI mechanisms and severities is a path toward overcoming some of these challenges. This effort is possible through large scale collaborative research and data sharing across multiple centers. In addition, TBI causes dynamic deficits in multiple domains, and thus, a panel of biomarkers combining these measures to consider different deficits is more promising than a single biomarker for TBI. In this review, each of these tools are presented along with the clinical and pre-clinical findings, advantages, challenges and prospects of translating the pre-clinical knowledge into the human clinical setting.
The objective of this study is to determine the effective mass of a head impact during a standing... more The objective of this study is to determine the effective mass of a head impact during a standing fall using a Humanetics TM HYBRID III 5th percentile female and a 50th percentile male anthropomorphic test dummy (ATD). The ATDs were instrumented with an array of tri-axial accelerometers and dropped from different initial positions onto a force plate. Five scenarios of falls were conducted to study the effect of fall direction/type on the effective mass of the head impact. The effective mass for forward and backward standing falls can be estimated as the mass of the head plus 49% and 47% of the neck mass for the female and male ATDs. The lateral fall showed different response where less of the neck mass is involved resulting in an effective mass, which includes the mass of the head plus 6% and 22% of the neck mass for the female and male ATDs, respectively.
Volume 3A: Biomedical and Biotechnology Engineering, 2013
ABSTRACT Traumatic Brain Injury (TBI) contributes to a major number of deaths and cases of perman... more ABSTRACT Traumatic Brain Injury (TBI) contributes to a major number of deaths and cases of permanent disability each year. Falls are the leading cause of TBI with the highest rates for children 0–4 years old and for adults age 75 and older. Accordingly, there is a significant interest in fall-related injury mechanism and head impact. Since the dynamics of human fall and head injury mechanisms are highly variable due to the inherent and complex nature of human falling, the aim of the present study is to describe the dynamics of backward falls and risk of injury due to head impact. In order to have a better understanding of head impact, A HYBRID III 5th Percentile Female test (Denton ATD, Inc.) instrumented with a tri-axial accelerometer with measuring range of ±500g at the center of gravity of the head was dropped from standing posture by using a controlled release mechanism. The dynamic model of fall was captured using a T-series Vicon motion capture system synchronized with a force plate to measure the impact force and a tri-axial accelerometer to measure the impact acceleration of the head. The acceleration impact data measured at 20 KHz and the motion capture system was capable to retrieve 500 samples per second. The primary objective of this study was to determine the equivalent mass involved during head impact due to a backward fall. This effective mass is a key quantity to design the head impact experimental setups, protection devices and computer simulations of head impact. Based on the force and acceleration measurements in several tests, the head impact effective mass is approximately found to be the mass of head itself plus 48% the neck mass. Two scenarios of backward fall were studied and discussed. First, falling while the hip joints are involved and the trunk moves forward and second, falling while the hip joints act like a fixed joint. For the first scenario the impact forces and accelerations peak measured using the HYBRID III were found to be 10±1.8KN and 255±42g, respectively, and for the second scenario the larger impact forces, 14.5±0.9KN, and acceleration peaks, 364±27g, were measured in all tests.
2008 5th International Symposium on Mechatronics and Its Applications, 2008
In this paper a control approach for a flexible robotic manipulator using a Model-Based Fuzzy tec... more In this paper a control approach for a flexible robotic manipulator using a Model-Based Fuzzy technique is investigated. The developed controller is based on Takagi-Sugeno fuzzy modelling and LMI (Linear Matrix Inequality) analysis. By utilizing the concept of parallel distributed compensation (PDC) by considering decay rate and constraints on control input, the design of fuzzy controller is presented. The effectiveness of the proposed method is demonstrated through comparison with other existing methods.
... Published by Elsevier Ltd. Permissions & Reprints. Performance-oriented parallel distribu... more ... Published by Elsevier Ltd. Permissions & Reprints. Performance-oriented parallel distributed compensation. Morteza Seidi a , E-mail The Corresponding Author and Amir HD Markazi Corresponding Author Contact Information , a , E-mail The Corresponding Author. ...
The purpose of this case report was to study effects of X-Stop implant surgery on the continuous ... more The purpose of this case report was to study effects of X-Stop implant surgery on the continuous spinal movement kinematics using 3D motion analysis. A proposed 3D kinematic spinal model was used to assess lumbar continuous active range of motion (AROM) during a standardized lumbar extension/flexion preoperatively and at 2 months postoperatively of a patient who underwent the X-Stop procedure. To investigate levels of muscle activities, electromyography recordings were made from right and left rectus abdominis, erector spinae and biceps femoris muscles. Also, functional mobility and patient quality of life were evaluated using the 6-minute walk test and the Swiss spinal stenosis and PROMIS-29 questionnaire. At 2 months postoperative, lumbar AROM increased by 18.5 and 14° for flexion and extension respectively and less muscle activation level was observed, despite the increase in lumbar AROM. Unlike positional magnetic resonance imaging (MRI) that is a common approach to assess spinal posture in static positions, the proposed continuous-motion analysis approach is able to analyze the lumbar AROM dynamically during flexion and extension. In this case report, the results indicate that the lumbar AROM, functional mobility and quality of life have been improved following X-Stop surgical intervention.
Falls in the elderly population is an important concern to individuals, family, friends, and in ... more Falls in the elderly population is an important concern to individuals, family, friends, and in the healthcare industry. When the head is left unprotected, head impact levels can reach upwards of 500 g (gravitational acceleration), which is a level that can cause serious injury or death. A protective system for a fall injury needs to be designed with specific criteria in mind including energy protection level, thickness, stiffness, weight, and cost among others. The current study quantifies the performance of a protective head gear design for persons prone to falls. The main objective of this paper is to evaluate the injury mitigation of head protection gear made from a patented system of polyurethane honeycomb and dilatant materials. To that end, a twin wire fall system equipped with a drop arm that includes a Hybrid-III head/neck assembly was used. The head was instrumented with a 9 accelerometer array so that angular acceleration is calculated directly from the linear acceleration signals. The test apparatus captures impact velocity, linear and angular acceleration components simultaneously. Tests were performed on two different material systems for frontal, side and rear impact cases. The honeycomb-dilatant system for each design consists of a cast 6mm thick, polyurethane honeycomb in the front section and a 6mm thick, honeycomb in the rear, that are nominally 55 Shore A and 40 Shore A durometer, respectively and the outer shell was a dilatant material. The peak linear acceleration, peak angular acceleration and the Head Injury Criterion (HIC) were captured to evaluate the performance of two material systems. A significant reduction of the peak linear and angular acceleration and HIC during impact was observed. Dropping the head/neck assembly equipped with the protection system from 45cm height (rear impact) resulted in linear acceleration, angular acceleration and HIC reduction from 308g to 82g, 14,127rad s-2 to 4,126rad s-2 and 879 to 136, respectively for the thicker material system.
The kinematics and kinetics of head impact due to a standing fall onto a hard surface are summari... more The kinematics and kinetics of head impact due to a standing fall onto a hard surface are summarized. Head injury due to impact from falls represents a significant problem, especially for older individuals. When the head is left unprotected during a fall, the impact severity can be high enough to cause significant injury or even death. To ascertain the range of head impact parameters, the dynamic response was captured for the pedestrian version of the 5th percentile female and 50th percentile male Hybrid III anthropomorphic test dummies as they were dropped from a standing position with different initial postures. Five scenarios of falls were considered including backward falls with/without hip flexion, forward falls with/without knee flexion and lateral falls. The results show that the head impact parameters are dependent on the fall scenario. A wide range of impact parameters was observed in 107 trials. The 95% prediction interval for the peak translational acceleration, peak angular acceleration, peak force, impact translational velocity and peak angular velocity are 146-502 g, 8.8-43.3 krad/s(2), 3.9-24.5 kN, 2.02-7.41 m/s, and 12.9-70.3 rad/s, respectively.
The objective of this study is to determine the effective mass of a head impact during a standing... more The objective of this study is to determine the effective mass of a head impact during a standing fall using a HumaneticsTM HYBRID III 5th percentile female and a 50th percentile male anthropomorphic test dummy (ATD). The ATDs were instrumented with an array of tri-axial accelerometers and dropped from different initial positions onto a force plate. Five scenarios of falls were conducted to study the effect of fall direction/type on the effective mass of the head impact. The effective mass for forward and backward standing falls can be estimated as the mass of the head plus 49% and 47% of the neck mass for the female and male ATDs. The lateral fall showed different response where less of the neck mass is involved resulting in an effective mass, which includes the mass of the head plus 6% and 22% of the neck mass for the female and male ATDs, respectively.
A test method based upon a Hybrid-III head and neck assembly that includes measurement of both li... more A test method based upon a Hybrid-III head and neck assembly that includes measurement of both linear and angular acceleration is investigated for potential use in impact testing of protective headgear. The test apparatus is based upon a twin wire drop test system modified with the head/neck assembly and associated flyarm components. This study represents a preliminary assessment of the test apparatus for use in the development of protective headgear designed to prevent injury due to falls. By including angular acceleration in the test protocol it becomes possible to assess and intentionally reduce this component of acceleration. Comparisons of standard and reduced durometer necks, various anvils, front, rear, and side drop orientations, and response data on performance of the apparatus are provided. Injury measures summarized for an unprotected drop include maximum linear and angular acceleration, head injury criteria (HIC), rotational injury criteria (RIC), and power rotational head injury criteria (PRHIC). Coefficient of variation for multiple drops ranged from 0.4 to 6.7% for linear acceleration. Angular acceleration recorded in a side drop orientation resulted in highest coefficient of variation of 16.3%. The drop test apparatus results in a reasonably repeatable test method that has potential to be used in studies of headgear designed to reduce head impact injury.
The main idea of the original parallel distributed compensation (PDC) method is to partition the ... more The main idea of the original parallel distributed compensation (PDC) method is to partition the dynamics of a nonlinear system into a number of linear subsystems, design a number of state feedback gains for each linear subsystem, and finally generate the overall state feedback gain by fuzzy blending of such gains. A new modification to the original PDC method is proposed here, so that, besides the stability issue, the closed-loop performance of the system can be considered at the design stage. For this purpose, the state feedback gains are not considered constant through the linearized subsystems, rather, based on some prescribed performance criteria, several feedback gains are associated to every subsystem, and the final gain for every subsystem is obtained by fuzzy blending of such gains. The advantage is that, for example, a faster response can be obtained, for a given bound on the control input. Asymptotic stability of the closed loop system is also guaranteed by using the Lyapunov method. To illustrate the effectiveness of the new method, control of a flexible joint robot (FJR) is investigated and superiority of the designed controller over other existing methods is demonstrated.
In this paper a control approach for a flexible robotic manipulator using a model-based fuzzy tec... more In this paper a control approach for a flexible robotic manipulator using a model-based fuzzy technique is investigated. The developed controller is based on Takagi-Sugeno fuzzy modelling and LMI (linear matrix inequality) analysis. By utilizing the concept of parallel distributed compensation (PDC) by considering decay rate and constraints on control input, the design of fuzzy controller is presented. The effectiveness of the proposed method is demonstrated through comparison with other existing methods.
Uploads
Papers by Morteza Seidi