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Analysis of the geometric properties of human long bones using computer axial tomography
868
Abstracts
asymmetrical biomechanics, the best example is a structural or functional short leg, most often lose the battle against gravitational forces sooner than those who are musculoskeletally symmetrical. The role of the clinician is to be aware of such biomechanical changes, diagnose the total condition properly, assist the individual in normalizing his antigravity biomechanics (posture) and maintaining the dynamic stabilizing qualities of the musculature that unfortunately diminish with age. FATIGUE
BEHAVIOR
OF IIMMATURE PRIMATE
CORTICAL
BONE*
T. S. KELLER, J. D. LOVIN, D. M. SPENGLERand D. R. CARTER (Orthopaedic Research Laboratory, SVAMC, Seattle. WA 98108, U.S.A.) Strain controlled uniaxial fatigue and monotonic tensile failure tests were conducted on turned cortical bone specimens obtained from immature primate femora, comparing bone obtained from anatomically different regions within the same bone. A strain range of 0.006 and strain rate of 0.02 s-’ resulted in increased hysteresis and loss of bone stiffness similar lo that reported for mature bone femora. Results showed that bone fatigue resistance decreased with increasing age in the range 50,000 cycles to I lo0 cycles. The ultimate stress and strain of the proximal femoral sections were greater than the distal femoral sections. The fatigue resistance and moduli of the anterior > posterior > lateral > medial sections, indicating that bone fatigue damage accumulates more rapidly in anatomical regions of bone with few or no muscle insertion sites. * Research funded by the Veterans Administration. A THEORETICAL
MODEL
FOR MECHANICALLY
INDUCED
BONE REMODELING
p. T. DAVY and R. T. HART (Case Western Reserve University, Cleveland, OH, U.S.A. and Tulane
University, New Orleans, LA, U.S.A.) A unilied model is proposed for relating the remodeling response of bone to the local strain history. The relationship between strain history and remodeling history is regarded as a feedback-modulated process with external load history as an input. The local strain history is assumed to elicit a strain remodeling signal which is modulated by metabolic and genetic factors. The resulting remodeling potential determines rate of recruitment and activation ofosteoblasts and osteoclasts. The sum of osteoblastic and osteoclastic activity determines the rate at which geometric properties and material properties change thereby producing the feedback to the strain history. The various relationships in the loop are assumed to be time dependent. Representing these relations as dilferential equations leads to specific model forms which allow for strain rate effects on remodeling which have been reported experimentally. SURFACE STRAIN STUDIES OF THE HUMAN
PATELLA
S. A. GOLDSTEIN,
A.-P. C. WEISS, R. KASMAN and L. S. MATTHEWS (The Biomechanics, Trauma and Sports Medicine Laboratory, University of Michigan Medical Centre, Ann Arbor, MI 48109. U.S.A.)
middle and distal poles of the anterior surface of fresh human cadaver patellas in seventeen intact knee joints. Using a custom loading apparatus, strain recordings were made with the knees flexed from 0 to 90’ in 15’ increments, at quadriceps loads of 0-I8OON. After testing, all knees were removed from the loading fixture and a total knee arthroplasty with patellar replacement was performed using either a domed or bifaceted patellar prosthesis. The experiment was then repeated. All strain recordings were documented as a function of load, flexion angle, location and prosthetic replacement.
Three strain gages were cemented on proximal,
ANALYSIS
OF THE GEOMETRIC PROPERTIES OF HUMAN USING COMPUTER AXIAL TOMOGRAPHY
LONG BONES
D. L. DICKIE and S. A. GOLDSTEIN (The Biomechanics, Trauma and Sports Medicine Laboratory, Section of Orthopaedic Surgery) M. J. FLYNN (Department of Radiology, University of Michigan Medical Center) P. BRIDGES(Department of Anthropology, University of Michigan Medical Center) The study of the strength of bone as the human form has evolved has been of interest in the field of biomechanics for decades. The spatial distribution of bone material can provide much information regarding bone function. Due lo the value of many fossils, some bones cannot be physically altered (i.e. sectioned) in order to examine material distribution characteristics. The application of computed tomography provides a nondestructive modality with sufficient resolution to accurately determine the geometric properties of bone. Samples of two ancient Indian populations have been analyzed to compare the effects of pre and post agricultural lifestyles of bone’s geometric properties. These properties have been computed directly from the digital CT output data following an interactive question/response session for each cross section.
Abstracts
asymmetrical biomechanics, the best example is a structural or functional short leg, most often lose the battle against gravitational forces sooner than those who are musculoskeletally symmetrical. The role of the clinician is to be aware of such biomechanical changes, diagnose the total condition properly, assist the individual in normalizing his antigravity biomechanics (posture) and maintaining the dynamic stabilizing qualities of the musculature that unfortunately diminish with age. FATIGUE
BEHAVIOR
OF IIMMATURE PRIMATE
CORTICAL
BONE*
T. S. KELLER, J. D. LOVIN, D. M. SPENGLERand D. R. CARTER (Orthopaedic Research Laboratory, SVAMC, Seattle. WA 98108, U.S.A.) Strain controlled uniaxial fatigue and monotonic tensile failure tests were conducted on turned cortical bone specimens obtained from immature primate femora, comparing bone obtained from anatomically different regions within the same bone. A strain range of 0.006 and strain rate of 0.02 s-’ resulted in increased hysteresis and loss of bone stiffness similar lo that reported for mature bone femora. Results showed that bone fatigue resistance decreased with increasing age in the range 50,000 cycles to I lo0 cycles. The ultimate stress and strain of the proximal femoral sections were greater than the distal femoral sections. The fatigue resistance and moduli of the anterior > posterior > lateral > medial sections, indicating that bone fatigue damage accumulates more rapidly in anatomical regions of bone with few or no muscle insertion sites. * Research funded by the Veterans Administration. A THEORETICAL
MODEL
FOR MECHANICALLY
INDUCED
BONE REMODELING
p. T. DAVY and R. T. HART (Case Western Reserve University, Cleveland, OH, U.S.A. and Tulane
University, New Orleans, LA, U.S.A.) A unilied model is proposed for relating the remodeling response of bone to the local strain history. The relationship between strain history and remodeling history is regarded as a feedback-modulated process with external load history as an input. The local strain history is assumed to elicit a strain remodeling signal which is modulated by metabolic and genetic factors. The resulting remodeling potential determines rate of recruitment and activation ofosteoblasts and osteoclasts. The sum of osteoblastic and osteoclastic activity determines the rate at which geometric properties and material properties change thereby producing the feedback to the strain history. The various relationships in the loop are assumed to be time dependent. Representing these relations as dilferential equations leads to specific model forms which allow for strain rate effects on remodeling which have been reported experimentally. SURFACE STRAIN STUDIES OF THE HUMAN
PATELLA
S. A. GOLDSTEIN,
A.-P. C. WEISS, R. KASMAN and L. S. MATTHEWS (The Biomechanics, Trauma and Sports Medicine Laboratory, University of Michigan Medical Centre, Ann Arbor, MI 48109. U.S.A.)
middle and distal poles of the anterior surface of fresh human cadaver patellas in seventeen intact knee joints. Using a custom loading apparatus, strain recordings were made with the knees flexed from 0 to 90’ in 15’ increments, at quadriceps loads of 0-I8OON. After testing, all knees were removed from the loading fixture and a total knee arthroplasty with patellar replacement was performed using either a domed or bifaceted patellar prosthesis. The experiment was then repeated. All strain recordings were documented as a function of load, flexion angle, location and prosthetic replacement.
Three strain gages were cemented on proximal,
ANALYSIS
OF THE GEOMETRIC PROPERTIES OF HUMAN USING COMPUTER AXIAL TOMOGRAPHY
LONG BONES
D. L. DICKIE and S. A. GOLDSTEIN (The Biomechanics, Trauma and Sports Medicine Laboratory, Section of Orthopaedic Surgery) M. J. FLYNN (Department of Radiology, University of Michigan Medical Center) P. BRIDGES(Department of Anthropology, University of Michigan Medical Center) The study of the strength of bone as the human form has evolved has been of interest in the field of biomechanics for decades. The spatial distribution of bone material can provide much information regarding bone function. Due lo the value of many fossils, some bones cannot be physically altered (i.e. sectioned) in order to examine material distribution characteristics. The application of computed tomography provides a nondestructive modality with sufficient resolution to accurately determine the geometric properties of bone. Samples of two ancient Indian populations have been analyzed to compare the effects of pre and post agricultural lifestyles of bone’s geometric properties. These properties have been computed directly from the digital CT output data following an interactive question/response session for each cross section.