Session: 06-01-01: Injury and Damage Biomechanics I - Organ and Tissue Injury Biomechanics 1

Paper Number: 145850

145850 - Elderly Occupant Human Body Model: Comprehensive Development and Validation for Frontal Impact Scenarios 

Introduction
As the elderly population grows, their increased injury risk in vehicle accidents, due to altered body structures and materials, becomes a pressing concern. This study addresses the urgent need to understand these injury mechanisms and develop specific safety measures. We aim to create a detailed human body model representing an elderly individual, specifically a 75-year-old, by modifying the baseline 50th percentile model from the Global Human Body Models Consortium (GHBMC). This model's development is a crucial step towards designing effective countermeasures to enhance the safety of elderly vehicle occupants.

Methods
In this study, we develop and validate a biomechanical model of an elderly individual, tailored to reflect the anthropometry and tissue material characteristics of the 75-year-old population. Utilizing the Centers for Disease Control and Prevention (CDC) data, we morphed a baseline model, representative of a 26-year-old, to emulate the elderly, incorporating posture data from the University of Michigan Transportation Research Institute (UMTRI). This model was then rigorously validated against experimental data from post-mortem human surrogate (PMHS) impact tests. This involved modifying the model's geometry and material properties to reflect elderly characteristics, with changes to the elastic modulus, yield stress, and failure strains based on literature. The model underwent validation through three types of impact tests, Thorax Impact: We used pendulum impact data with impactors weighing 10.4 kg and 23.6 kg at a speed of 7m/s to validate the model's thoracic response. Abdomen Impact: The model's abdominal response was validated using data from impacts with a 25 mm diameter, 48 kg bar at speeds of 6 m/s and 9 m/s. Frontal Sled Tests: We conducted tests at 6.7 m/s using a setup that included various safety features to validate the model's overall frontal impact response.

Results
In our results, the elderly occupant model, after undergoing specific morphing processes to match elderly anthropometry, revealed key numerical outcomes in various impact scenarios. The model's mass adjustment resulted in 88 kg to reflect the elderly's physique. During the thorax impact validation, the model exhibited chest stiffness of 78 N/mm up to 30 mm of deformation and 6 N/mm between 30 mm and 90 mm deformation for the 10 kg impactor, and 80 N/mm up to 30 mm deformation and 22.5 N/mm between 30 mm and 90 mm for the 23 kg impactor. These responses highlight the model's ability to mimic elderly thoracic biomechanics accurately. In abdomen impact scenarios, stiffness values were recorded at 49.2 kN/m and 29.8 kN/m for impact velocities of 9 m/s and 6 m/s, respectively. These responses are consistent with existing literature values, reinforcing the model's validity. For the frontal sled tests, the CORA analysis yielded values of 0.62, 0.72, and 0.63 for head, T1, and pelvis accelerations, respectively, averaging a CORA value of 0.65, indicating a good fit with experimental data. Head excursions were noted at 155 mm and 297 mm in the x and z directions, aligning closely with experimental measurements, thus further validating the model's efficacy in replicating elderly occupant dynamics during vehicular impacts.

Discussion

In this study, we developed a model representing a 75-year-old male, using a morphing technique to tailor the model's body regions to elderly specifications. Our goal was to create a tool that aids in designing safety measures for elderly vehicle occupants. By morphing the GHBMC model to reflect the anatomy of an elderly individual and adjusting the material properties of tissues based on literature, we crafted a model that accurately responds to impact scenarios like thorax, abdomen, and frontal sled tests. This model's ability to replicate elderly thoracic injuries demonstrates its value in developing protective strategies, highlighting its potential to enhance vehicle safety for the elderly demographic.

Presenting Author: Karthik Somasundaram Medical college of Wisconsin

Presenting Author Biography: Dr. Karthik Somasundaram is an assistant professor in the joint department of biomedical engineering. His research interest includes biomechanics of the spine, pelvis and thorax with focus on examining the mechanics of the orthopedic regions pertinent to different crash environments using experimental and computational techniques.

Authors:

Karthik Somasundaram Medical college of Wisconsin
Balaji Harinathan Medical College of Wisconsin
Narayan Yoganandan Medical College of Wisconsin