Improvement of Human Body Model Rib Fracture Risk Prediction: Creation of injury risk curves and rib cortical bone regression models for age adjusted risk prediction
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Typ
Examensarbete för masterexamen
Program
Biomedical engineering (MPBME), MSc
Publicerad
2020
Författare
Blennow, Amanda
Modellbyggare
Tidskriftstitel
ISSN
Volymtitel
Utgivare
Sammanfattning
In motor vehicle collision, one of the most commonly injured body regions is the
thorax and these injuries are in many cases the cause of death among belted, adult
drivers. Rib fractures are particularly dangerous among elderly and to enable injury
prevention, proper risk assessment is of great importance. In a recent study, the
effect of age, sex and strain rate on the rib cortical bone material was investigated,
enabling creation of new injury risk curves and rib cortical bone material models.The
aim of this thesis was thus to improve the human body model rib fracture risk
prediction by creating new rib fracture risk curves and material models of human
rib cortical bone for individually adapted rib fracture risk prediction.
Using the methods of parametric survival modelling, injury risk curves for rib fracture
risk prediction were developed for prediction using both ultimate strain and
total strain energy density. It was found that the new strain based risk curve corresponds
to a decrease in ultimate strain of 12 % per decade of life, compared to
the 5 % per decade of life in the currently used risk curve. Regression models of the
mechanical properties elastic modulus, plastic hardening modulus and yield stress,
of human rib cortical bone were created and thus, construction of age dependent
stress-strain curves was enabled. The stress-strain curves also model the individual
variability, suggesting mechanical parameter values for weak, average and strong
individuals of any given age.
The material models were implemented in the SAFER HBM and four post mortem
human subject sled tests were reproduced and outputs were evaluated with both the
newly created injury risk curves and the injury risk curves that have been used up
until now. It was found that both the new injury risk curves and the material models
affected the predicted injury risks and particularly among elderly. Due to the large
set of data used for the development of injury risk curves, the new strain-based risk
curve possesses a higher statistical validity, compared to the old strain-based risk
curve, and can therefore be considered as a better alternative. The energy-based
risk prediction proved to be less sensitive to the material model used compared to
the strain-based risk prediction . This is promising in terms of predicting risks that
are less sensitive to individual variability.
Beskrivning
Ämne/nyckelord
Injury Risk Curve , Rib Fracture Risk , Risk Prediction , Regression , Rib Cortical Bone , Material Model , Survival Analysis , Human Body Model