Understanding Injury Mechanisms of Blast-Induced Neurotrauma: Validation of Human Injury Surrogates

Principal Investigator: MERKLE, ANDREW
Institution Receiving Award: JOHNS HOPKINS UNIVERSITY
Program: DRMRP
Proposal Number: DR080764
Award Number: W81XWH-09-2-0168
Funding Mechanism: Advanced Technology/Therapeutic Development Award
Partnering Awards:
Award Amount: $12,171,344.00


Rationale: Increased terrorist use of explosive munitions and other improvised explosive devices (IEDs) that generate blast present a substantial continuing threat to both military and civilian personnel. We believe blast-induced injury, referred to as the signature wound of the war in Iraq, to be the most significant health issue facing our Warfighters today. In both civilian and military environments, exposure to blast can cause acute injuries that may be prevented with effective injury mitigation strategies. To develop protective measures against blast injury, it is critical that the manner in which the injury occurs to the human body is well understood. This interaction between the blast conditions and the response of the human body can be investigated using computational models. However, the development and validity of these models is dependent upon the inclusion of mechanically important anatomical structures, rate-specific material property characterization of biological tissues, and accurate replication of environmental loading conditions. While past models have lacked one or more of these features, we believe that all are critical in the development of validated blast models. Upon validation, the human computational models will become valuable tools used to predict blast threat injury type and severity, evaluate the efficacy of existing injury mitigation strategies, and assist in the design and testing of proposed personal and vehicle protection systems.

Objective: Our objective is to develop biomedically validated human computational models capable of simulating and predicting blast-induced injury due to multiple blast threat scenarios. The proposed models differ from past efforts in four critical areas: Anatomic fidelity, high strain-rate material properties, blast-specific applicability, and human-based validation. While past models have lacked one or more of these features, we believe that all are critical in the development of validated blast injury models. To achieve these goals, we must identify the decisive mechanisms through which a blast generated by explosion interacts with the human body and causes injury. Having properly identified these conditions, we will develop computational models to simulate the blast environment representative of open-field, enclosed, and vehicle-mounted scenarios. Human body models consisting of the head, neck, and thoracic structures will be exposed to these simulated blast conditions and the biomechanical response will be obtained. This response, used to predict injury, will be validated based on a combination of real-world data and experimental testing. The human models will be used to allow developers to design, test, and evaluate personal and vehicle protection systems with the intent of reducing the frequency and severity of injuries.

Research Applications and Advancement: The Team's efforts in human model development and validation will contribute to a reduction in blast-induced injuries. A fundamental step in the model development effort will require the characterization of human tissue material response at blast loading rates within the first 2 years of the program. Due to a paucity of data in the literature, these findings alone will address a critical gap and provide sought-after data to all researchers using human models to investigate impact injuries. A hierarchical model-validation approach rooted in tissue testing will create fully validated human computational models capable of predicting the type, location, and severity of injury sustained due to blast loading at the conclusion of 5 years. These models will be capable of evaluating injury mitigation systems and assessing the direct implication of design changes on the risk of human injury. Designers of personal protective equipment and vehicle safety systems will be able to use these models when considering the efficacy of their system in preventing injuries. The Defense Acquisition Community will be able to integrate the use of human models when investigating the performance of potential safety technologies prior to acquisition. Other industries, including the automotive industry, will benefit from the advancements generated during this effort. The tissue-level injury criteria will replace the system level criteria widely used currently and allow direct prediction of injury risk in automotive impacts. These improved injury criteria will lead to a better understanding of specific injury mechanisms and ultimately result in the design of improved, advanced safety systems.