The ethics, applications, and contributions of cadaver testing in injury prevention research.

OBJECTIVE: This study aims to establish best practices and guidelines to ensure that experimental research utilizing Postmortem Human Subjects (PMHS) for injury prevention adheres to relevant ethical principles, which are also commonly accepted in research involving human tissues and living subjects. Furthermore, it reviews existing literature to underscore the pivotal role of PMHS testing in evaluating the efficacy of safety systems, with a particular focus on airbag performance. METHODS: This paper conducts an examination of the primary ethical principles governing human subject research as outlined in the Declaration of Helsinki (1965) and traces their evolution up to the latest framework proposed by the Council for International Organizations of Medical Sciences (CIOMS) in 2002. Input was solicited from international experts and laboratories experienced in PMHS testing to understand how these ethical principles are implemented in practice. This is complemented by a comprehensive review of literature that assesses the contribution of PMHS testing to airbag performance enhancements in frontal impacts. RESULTS: The findings underscore the importance of informed consent from donors or their next-of-kin, as highlighted in CIOMS declarations, to ensure the ethical integrity of the donation process in line with international standards. The study also finds it customary for an independent review board to evaluate the research methodology and the necessity of employing PMHS tissue over alternative methods, such as computational models or crash test dummies. Despite various national regulations on human subject participation and living tissue research, no specific legal framework governing PMHS tissue use was identified. The systematic literature review revealed that PMHS testing has been crucial in identifying potential injury mechanisms not detected by Anthropomorphic Test Devices (ATD), significantly contributing to the enhancement of computer human body models and the biofidelity of crash test dummies. CONCLUSION: The International Council on the Biomechanics of Injury (IRCOBI) recognizes the need to provide guidance for research involving human cadaveric tissue to be conducted with the highest ethical standards. This study proposes five recommendations to ensure adherence to these ethical principles in PMHS testing, highlighting the paramount importance of obtaining informed consent and securing independent committee approval. Moreover, IRCOBI emphasizes that until a thorough understanding of tissue damage tolerance levels is achieved and human surrogates, such as ATDs or Human Body Models (HBM), reach full biofidelity, the use of human cadavers remains indispensable for developing effective injury prevention strategies and measures.

Accuracy of Instrumented Mouthguards During Direct Jaw Impacts Seen in Boxing.

PURPOSE: Measuring head kinematics data is important to understand and develop methods and standards to mitigate head injuries in contact sports. Instrumented mouthguards (iMGs) have been developed to address coupling issues with previous sensors. Although validated with anthropomorphic test devices (ATDs), there is limited post-mortem human subjects (PMHS) data which provides more accurate soft tissue responses. This study evaluated two iMGs (Prevent Biometrics (PRE) and Diversified Technical Systems (DTS) in response to direct jaw impacts. METHODS: Three unembalmed male cadaver heads were properly fitted with two different boil-and-bite iMGs and impacted with hook (4 m/s) and uppercut (3 m/s) punches. A reference sensor (REF) was rigidly attached to the base of the skull, impact kinematics were transformed to the head center of gravity and linear and angular kinematic data were compared to the iMGs including Peak Linear Acceleration, Peak Angular Acceleration, Peak Angular Velocity, Head Injury Criterion (HIC), HIC duration, and Brain Injury Criterion. RESULTS: Compared to the REF sensor, the PRE iMG underpredicted most of the kinematic data with slopes of the validation regression line between 0.72 and 1.04 and the DTS overpredicted all the kinematic data with slopes of the regression line between 1.4 and 8.7. CONCLUSION: While the PRE iMG was closer to the REF sensor compared to the DTS iMG, the results did not support the previous findings reported with use of ATDs. Hence, our study highlights the benefits of using PMHS for validating the accuracy of iMGs since they closely mimic the human body compared to any ATD's mandible.

Assessment of in situ chest deflection of post mortem human subjects (PMHS) and personalized human body models (HBM) in nearside oblique impacts.

OBJECTIVE: The present study has three objectives: First, to analyze the chest deflection measured in nearside oblique tests performed with three post mortem human subjects (PMHS). Second, to assess the capability of a HBM to predict the chest deflection sustained by the PMHS. Third to evaluate the influence on chest deflection prediction of subject-specific HBM. METHODS: Three dimensional chest deformation of five anterior chest landmarks was extracted from three PMHS (A-C) in three sled tests. The sled test configurations corresponded to a 30 degree nearside oblique impact at 35 km/h. Two different restraint system versions (RSv) were used. RSv1 was used for PMHS A and B while RSv2 was used for PMHS C. The capability of the SAFER HBM (called baseline model) to predict PMHS chest deflection was benchmarked by means of the PMHS test results. In a second step, the anthropometry, mass and pre-impact posture of the baseline HBM were modified to the PMHS-specific characteristics to develop a model to assess the influence of personalization techniques in the capability of the human body model to predict PMHS chest deflection. RESULTS: In the sled tests, the measured sternum compression relative to the eighth thoracic vertebra in the PMHS tests was 49, 54 and 55 millimeters respectively. The HBM baseline model predicted 48%, 43% and 34% of the deflections measured in the PMHS tests, while the personalized version predicted 38%, 34% and 28%. When chest deflection was analyzed in x-, y- and z-direction for the five chest landmarks it was found that neither the baseline HBM nor the personalized model predicted x, y and z axis deflections. CONCLUSIONS: The PMHS in situ chest deflection was found to be sensitive to the variation in restraint system and the three PMHS exhibited greater values of lower right chest deflection compared to what was found in available literature. The baseline HBM underpredicted peak chest deflection obtained in the PMHS test. The personalized model was not capable of predicting the chest deflection sustained by the PMHS. Hence, further biofidelity investigations have to be carried out on the human body thorax model for oblique loading.

Anatomically-based skeletal coordinate systems for use with impact biomechanics data intended for anthropomorphic test device development.

Post-mortem human subjects (PMHS) are frequently used to characterize biomechanical response and injury tolerance of humans to various types of loading by means of instrumentation installed directly on the skeleton. Data extracted from such tests are often used to develop and validate anthropomorphic test devices (ATDs), which function as human surrogates in tests for injury assessment. Given that the location and orientation of installed instrumentation differs between subjects, nominally similar measurements made on different PMHS must be transformed to standardized, skeletal-based local coordinate systems (LCS) before appropriate data comparisons can be made. Standardized PMHS LCS that correspond to ATD instrumentation locations and orientations have not previously been published. This paper introduces anatomically-defined PMHS LCS for body regions in which kinematic measurements are made using ATDs. These LCS include the head, sternum, single vertebrae, pelvis, femurs (distal and proximal), and tibiae (distal and proximal) based upon skeletal landmarks extracted from whole body CT scans. The proposed LCS provide a means to standardize the reporting of PMHS data, and facilitate both the comparison of PMHS impact data across institutions and the application of PMHS data to the development and validation of ATDs.

Normalizing and scaling of data to derive human response corridors from impact tests.

It is well known that variability is inherent in any biological experiment. Human cadavers (Post-Mortem Human Subjects, PMHS) are routinely used to determine responses to impact loading for crashworthiness applications including civilian (motor vehicle) and military environments. It is important to transform measured variables from PMHS tests (accelerations, forces and deflections) to a standard or reference population, termed normalization. The transformation process should account for inter-specimen variations with some underlying assumptions used during normalization. Scaling is a process by which normalized responses are converted from one standard to another (example, mid-size adult male to large-male and small-size female adults, and to pediatric populations). These responses are used to derive corridors to assess the biofidelity of anthropomorphic test devices (crash dummies) used to predict injury in impact environments and design injury mitigating devices. This survey examines the pros and cons of different approaches for obtaining normalized and scaled responses and corridors used in biomechanical studies for over four decades. Specifically, the equal-stress equal-velocity and impulse-momentum methods along with their variations are discussed in this review. Methods ranging from subjective to quasi-static loading to different approaches are discussed for deriving temporal mean and plus minus one standard deviation human corridors of time-varying fundamental responses and cross variables (e.g., force-deflection). The survey offers some insights into the potential efficacy of these approaches with examples from recent impact tests and concludes with recommendations for future studies. The importance of considering various parameters during the experimental design of human impact tests is stressed.