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The strength of spinal ligaments
Abstracts
876
PAlTERN
RECOGNITION
FEATURES FOR IDENTIFYING GAIT DISABILITY ON THE ANGLE-ANGLE DIAGRAM
BASED
JANE MACFARLANEand MAX DONATH (Department of Mechanical Engineering, University of Minnesota, Minneapolis, MN 55455, U.S.A.) Trauma and disease of the neuromuscular system often manifest themselves as abnormalities of walking function. There has been a long standing need for the development of objective quantitative measures which integrate the biomechanical data collected in the gait lab in a clinically useful manner, isolating out the factors contributing to the pathology, serving as a mechanism for tracking patients and also as a means for comparing the efficacies of various therapeutic procedures. Some interesting patterns have been observed in a proposed deviation from normal distance metric based on the angle-angle diagram as a model. By considering the trajectory of this ‘deviation from normal’ distance metric versus the percent of gait cycle, one can identify the critical times within the gait cycle when significant aberrant gait behavior appears. Furthermore, the area under the curve provides an integrative measure of gait deviation. IN YZVO MEASUREMENT
OF SPINAL
COLUMN
VIBRATIONS
M. PANJABI(Department of Surgery, Yale Medical School, New Haven, CT 06510, U.S.A.) G. ANDERSSON,L. JORNEUS.E. HULT and L. MA’ITSON (Department of Orthopaedics, Sahlgren Hospital, Gothenburg, Sweden)
Epidemiological studies suggest a relationship between low-back pain and vibrations. The experimental study presented here measures the actual in uiuo response of lumbar vertebrae when the body is subjected to vibrations. The material consisted of healthy volunteers. A specially-designed machine that produced pure sinusoidal vibrations was used. The input frequency ranged from 2 to 15 Hz (cycles per second) at accelerations of 1 and 3mse2. Vibrations were measured at two lumbar vertebrae and the sacrum with the help of specially-designed threeaccelerometer transducers (PATS) attached to the vertebral pins. Output from each PAT was transformed to its corresponding vertebral body accelerations. Three transmission functions were computed: axial, shear and rotatory accelerations of the vertebra1 body. Results. Axial acceleration peaked at about 5 Hz while the shear acceleration seemed to increase continuously from 2 to 15 Hz. The rotatory acceleration peaked at about 8 Hz. The results indicate that the vibration of a vertebra is complex even though the exciting acceleration is simple. We believe that studies of the type presented here will provide a better understanding of the dynamic behavior of the spinal column. EVALUATION
OF SPINAL DEFORMITY
BY MEANS OF INTRINSIC TORSION
CURVATURE
AND
J. DANSEREAU,P. ALLARD, P. S. THIRY, J. V. RASOand M. DUHAIME (Department of Mechanical Engineering, Ecole Polytechnique, Montreal; Pediatric Research Center, Sainte-Justine Hospital, Montreal; School of Physical and Occupational Therapy, McGill University, Montreal; Glenrose Hospital, Edmonton, Canada) The evolution of the spine deformity in Friedreich’s ataxia has been investigated by means of a tridimensional geometric reconstruction program using cubic spline functions and based on data collected on standardized biplanar radiographs. A previous study revealed that a significant ‘torsion’might be superimposed on the scoliosis. To appreciate more precisely this phenomenon, a new procedure using quintic spline functions was developed to obtain the classical Frent intrinsic curve parameters: curvature and torsion. The application of this new analysis tool to a typical case of Friedreich’s/ataxia over a twelve month period revealed that the maximum curvature of the spine is a good measure of the combined scoliosis and kyphosis. The most significant result of this investigation is that it provides a new diagnostic parameter: the maximum torsion difference in the scoliotic region. This parameter happens to describe very precisely the observed torsion phenomenon. This application should be extended in the assessment of other spinal deformities. THE STRENGTH
OF SPINAL
LIGAMENTS
J. B. MYKLEBUST,F. PINTAR, D. MAIMAN and A. SANCES.JR. (Department of Neurosurgery, Medical College of Wisconsin; Wood V. A. Medical Center, Milwaukee, WI 53226, U.S.A.) These studies were done to provide additional information for modeling the spinal column and to advance our understanding of the role of the spinal ligaments in trauma. Comparative studies were conducted in the macaque monkey and the human male cadaver to determine the strength in tension of individual spinal ligaments. Isolated ligamentous spines of 8-10 kg male macaque monkeys and fresh male human cadavers were studied. Each spine was mounted with 6 mm diameter Steinman pins fixed into vertebral bodies at two successive levels. Ablation of
Abstracts
877
all ligaments except the one under study was done. The ligaments were pulled in direct axial tension at rates from I-IOOcms-* with an MTS electrohydraulic system. The anterior and posterior longitudinal ligaments, joint capsules. ligamentum flavum, and interspinous ligaments were studied from the sacrum to the cervical level. The ligaments of upper cervical, and atlanto-occipital junction were also studied. The strongest ligaments were observed in the lower lumbar segments and in the atlanto-occipital regions. The anterior longitudinal ligament and joint capsules failed at loads of 30-300 N in the monkey and 50-500 N in the human cadavers. Supported in part by ONR Contract No. NC0014-77-C-0749
THE MECHANICS OF LUNG PARESCHY>IA THEODOREA. WILSON (Department of Aerospace Engineering and Mechanics. University of Minnesota. Minneapolis, MN 55455, U.S.A.) Lung parenchyma is a foam-like material with a large surface area, and surface tension significantly affects its mechanical behavior. Recent data show that surface area is smaller if surface tension is greater at the same lung volume. The tissue forces that are associated with the distortion caused by surface tension add to the recoil pressure of the lung. By invoking the principle that the sum of the tissue and surface energies is minimum at equilibrium, the separate contributions of tissue forces and surface tension to lung recoil can be sorted out. Further, different anatomical elements provide each contribution to total lung recoil. The peripheral tissue system provides the recoil of the saline-filled lung and the helical line elements that form the alveolar duct and are extended by the outward pull of surface tension provide the additional tissue component of the recoil of the airfilled lung. SHEARING
OF MUCUS
H.
G.
WINET*t,
BI’ CILIA AS INDICATED BY VELOCITY XIUCOCILIARY FLOh’S
PROFILES
I;u
T. YATES*,T. Y. WU* and J. HEADt (*California Institute of Technology and tuniversity of Southern California School of Medicine)
Flow velocity profiles within mucus ofa mucociliary system have been obtained in order to shed light on the need for ciliary penetration to move mucus. The profiles were obtained for mucus thicknesses ranging from about 400 to 700 Itm and bulk viscosity about 27 cp at I s- ’ shear rate. Fluorescent microspheres served as flow tracers and were mixed with the mucus which was deposited on an excised rectangle of frog palate ciliated epithelium. Profile layers-were determined by focusing with a microscope via a calibrated tine adjustment. Velocities were computed from tine and video recordings of the particle motions in each vertical mucus layer. Flow in the mucus blob was compared with a control Newtonian solution. Control data were compared with autologous mucus data. It was found that the two sets of profiles were indistinguishable for fluid depths above 60 jtrn from the mucosa. The near-mucosa profiles, in contrast, were unalike with mucus exhibiting the greater shear. We concluded that ciliary contact is not necessary for generation of mucus flow provided the ciliary shear is not negated by the observed mucus ‘Hake’ or ‘slab’ being in simultaneous contact with ciliostatic anchors. Supported by NIH grant HD-51442
STRAIN
ENERGY
and NSF grant CME 77-21236
CHARACTERISATION
OF HUhIAN TENSION
AORTIC
TISSUE
IN UNIAXIAL
K. B. SAHAYand DINESH MOHAN (Centre for Biomedical Engineering, Indian Institute of Technology, Delhi, India) Various forms of strain energy functions (or their derivatives) have been proposed to describe rubber like materials (RLMs) and soft biological tissues (SBTs), but there is little agreement on a suitable form. Four functions were selected and examined for SBT characterisation in this study. The purpose of this study was to see which of these four functions most adequately represent human thoracic aortic tissue behaviour at quasi-static strain rates in unaxial tension. Eight curves were selected from an earlier experimental study. Curve fitting was done for each one of them using an ICL 2960 computer. For tissues like human descending thoracic aorta, it appears that the Hart-Smith function and the Veronda and Westmann function are more appropriate than others. Details of the suitability of these functions are discussed in this paper. FINITE SAMUEL
DEFORMATION
OF THE LEFT
VENTRICLE
IN ISOVOLUMIC
RELAXATION
E. MOSKOWITZ(The Hebrew University, Division of Applied Mathematics, Bergmann Building, Givat Ram, Jerusalem 91904. Israel)
In isovolumic relaxation of the left ventricle, cavity pressure rapidly falls under biochemical control of the mechanical properties of the inhomogeneous and anisotropic myocardium.
876
PAlTERN
RECOGNITION
FEATURES FOR IDENTIFYING GAIT DISABILITY ON THE ANGLE-ANGLE DIAGRAM
BASED
JANE MACFARLANEand MAX DONATH (Department of Mechanical Engineering, University of Minnesota, Minneapolis, MN 55455, U.S.A.) Trauma and disease of the neuromuscular system often manifest themselves as abnormalities of walking function. There has been a long standing need for the development of objective quantitative measures which integrate the biomechanical data collected in the gait lab in a clinically useful manner, isolating out the factors contributing to the pathology, serving as a mechanism for tracking patients and also as a means for comparing the efficacies of various therapeutic procedures. Some interesting patterns have been observed in a proposed deviation from normal distance metric based on the angle-angle diagram as a model. By considering the trajectory of this ‘deviation from normal’ distance metric versus the percent of gait cycle, one can identify the critical times within the gait cycle when significant aberrant gait behavior appears. Furthermore, the area under the curve provides an integrative measure of gait deviation. IN YZVO MEASUREMENT
OF SPINAL
COLUMN
VIBRATIONS
M. PANJABI(Department of Surgery, Yale Medical School, New Haven, CT 06510, U.S.A.) G. ANDERSSON,L. JORNEUS.E. HULT and L. MA’ITSON (Department of Orthopaedics, Sahlgren Hospital, Gothenburg, Sweden)
Epidemiological studies suggest a relationship between low-back pain and vibrations. The experimental study presented here measures the actual in uiuo response of lumbar vertebrae when the body is subjected to vibrations. The material consisted of healthy volunteers. A specially-designed machine that produced pure sinusoidal vibrations was used. The input frequency ranged from 2 to 15 Hz (cycles per second) at accelerations of 1 and 3mse2. Vibrations were measured at two lumbar vertebrae and the sacrum with the help of specially-designed threeaccelerometer transducers (PATS) attached to the vertebral pins. Output from each PAT was transformed to its corresponding vertebral body accelerations. Three transmission functions were computed: axial, shear and rotatory accelerations of the vertebra1 body. Results. Axial acceleration peaked at about 5 Hz while the shear acceleration seemed to increase continuously from 2 to 15 Hz. The rotatory acceleration peaked at about 8 Hz. The results indicate that the vibration of a vertebra is complex even though the exciting acceleration is simple. We believe that studies of the type presented here will provide a better understanding of the dynamic behavior of the spinal column. EVALUATION
OF SPINAL DEFORMITY
BY MEANS OF INTRINSIC TORSION
CURVATURE
AND
J. DANSEREAU,P. ALLARD, P. S. THIRY, J. V. RASOand M. DUHAIME (Department of Mechanical Engineering, Ecole Polytechnique, Montreal; Pediatric Research Center, Sainte-Justine Hospital, Montreal; School of Physical and Occupational Therapy, McGill University, Montreal; Glenrose Hospital, Edmonton, Canada) The evolution of the spine deformity in Friedreich’s ataxia has been investigated by means of a tridimensional geometric reconstruction program using cubic spline functions and based on data collected on standardized biplanar radiographs. A previous study revealed that a significant ‘torsion’might be superimposed on the scoliosis. To appreciate more precisely this phenomenon, a new procedure using quintic spline functions was developed to obtain the classical Frent intrinsic curve parameters: curvature and torsion. The application of this new analysis tool to a typical case of Friedreich’s/ataxia over a twelve month period revealed that the maximum curvature of the spine is a good measure of the combined scoliosis and kyphosis. The most significant result of this investigation is that it provides a new diagnostic parameter: the maximum torsion difference in the scoliotic region. This parameter happens to describe very precisely the observed torsion phenomenon. This application should be extended in the assessment of other spinal deformities. THE STRENGTH
OF SPINAL
LIGAMENTS
J. B. MYKLEBUST,F. PINTAR, D. MAIMAN and A. SANCES.JR. (Department of Neurosurgery, Medical College of Wisconsin; Wood V. A. Medical Center, Milwaukee, WI 53226, U.S.A.) These studies were done to provide additional information for modeling the spinal column and to advance our understanding of the role of the spinal ligaments in trauma. Comparative studies were conducted in the macaque monkey and the human male cadaver to determine the strength in tension of individual spinal ligaments. Isolated ligamentous spines of 8-10 kg male macaque monkeys and fresh male human cadavers were studied. Each spine was mounted with 6 mm diameter Steinman pins fixed into vertebral bodies at two successive levels. Ablation of
Abstracts
877
all ligaments except the one under study was done. The ligaments were pulled in direct axial tension at rates from I-IOOcms-* with an MTS electrohydraulic system. The anterior and posterior longitudinal ligaments, joint capsules. ligamentum flavum, and interspinous ligaments were studied from the sacrum to the cervical level. The ligaments of upper cervical, and atlanto-occipital junction were also studied. The strongest ligaments were observed in the lower lumbar segments and in the atlanto-occipital regions. The anterior longitudinal ligament and joint capsules failed at loads of 30-300 N in the monkey and 50-500 N in the human cadavers. Supported in part by ONR Contract No. NC0014-77-C-0749
THE MECHANICS OF LUNG PARESCHY>IA THEODOREA. WILSON (Department of Aerospace Engineering and Mechanics. University of Minnesota. Minneapolis, MN 55455, U.S.A.) Lung parenchyma is a foam-like material with a large surface area, and surface tension significantly affects its mechanical behavior. Recent data show that surface area is smaller if surface tension is greater at the same lung volume. The tissue forces that are associated with the distortion caused by surface tension add to the recoil pressure of the lung. By invoking the principle that the sum of the tissue and surface energies is minimum at equilibrium, the separate contributions of tissue forces and surface tension to lung recoil can be sorted out. Further, different anatomical elements provide each contribution to total lung recoil. The peripheral tissue system provides the recoil of the saline-filled lung and the helical line elements that form the alveolar duct and are extended by the outward pull of surface tension provide the additional tissue component of the recoil of the airfilled lung. SHEARING
OF MUCUS
H.
G.
WINET*t,
BI’ CILIA AS INDICATED BY VELOCITY XIUCOCILIARY FLOh’S
PROFILES
I;u
T. YATES*,T. Y. WU* and J. HEADt (*California Institute of Technology and tuniversity of Southern California School of Medicine)
Flow velocity profiles within mucus ofa mucociliary system have been obtained in order to shed light on the need for ciliary penetration to move mucus. The profiles were obtained for mucus thicknesses ranging from about 400 to 700 Itm and bulk viscosity about 27 cp at I s- ’ shear rate. Fluorescent microspheres served as flow tracers and were mixed with the mucus which was deposited on an excised rectangle of frog palate ciliated epithelium. Profile layers-were determined by focusing with a microscope via a calibrated tine adjustment. Velocities were computed from tine and video recordings of the particle motions in each vertical mucus layer. Flow in the mucus blob was compared with a control Newtonian solution. Control data were compared with autologous mucus data. It was found that the two sets of profiles were indistinguishable for fluid depths above 60 jtrn from the mucosa. The near-mucosa profiles, in contrast, were unalike with mucus exhibiting the greater shear. We concluded that ciliary contact is not necessary for generation of mucus flow provided the ciliary shear is not negated by the observed mucus ‘Hake’ or ‘slab’ being in simultaneous contact with ciliostatic anchors. Supported by NIH grant HD-51442
STRAIN
ENERGY
and NSF grant CME 77-21236
CHARACTERISATION
OF HUhIAN TENSION
AORTIC
TISSUE
IN UNIAXIAL
K. B. SAHAYand DINESH MOHAN (Centre for Biomedical Engineering, Indian Institute of Technology, Delhi, India) Various forms of strain energy functions (or their derivatives) have been proposed to describe rubber like materials (RLMs) and soft biological tissues (SBTs), but there is little agreement on a suitable form. Four functions were selected and examined for SBT characterisation in this study. The purpose of this study was to see which of these four functions most adequately represent human thoracic aortic tissue behaviour at quasi-static strain rates in unaxial tension. Eight curves were selected from an earlier experimental study. Curve fitting was done for each one of them using an ICL 2960 computer. For tissues like human descending thoracic aorta, it appears that the Hart-Smith function and the Veronda and Westmann function are more appropriate than others. Details of the suitability of these functions are discussed in this paper. FINITE SAMUEL
DEFORMATION
OF THE LEFT
VENTRICLE
IN ISOVOLUMIC
RELAXATION
E. MOSKOWITZ(The Hebrew University, Division of Applied Mathematics, Bergmann Building, Givat Ram, Jerusalem 91904. Israel)
In isovolumic relaxation of the left ventricle, cavity pressure rapidly falls under biochemical control of the mechanical properties of the inhomogeneous and anisotropic myocardium.