Thoracic Biomechanical Responses of Small Female Postmortem Human Subjects in a Simplified Side-Impact Condition

Biomechanical response targets for the thorax have largely focused on the 50th percentile male, limiting their relevance for smaller females. Previous studies have provided side-impact female postmortem human subjects (PMHS) data from either oversimplified or realistic boundary conditions. This study aimed to generate thoracic biomechanical responses of small female PMHS in a simplified side-impact condition with realistic components and compare responses between two input energy levels. Twelve small female PMHS were seated on a simplified seat with FMVSS No. 213a seat foam and fabric and impacted once on the left thorax with either a 14.0 kg (low energy) or 23.7 kg (high energy) pneumatic impactor at 4.5 m/s. A rectangular impactor face (22.9 × 25.4 cm) covered with FMVSS No. 213a armrest foam simulated an intruding door panel. Thoracic deflection was measured using a chestband. Inertially compensated force was recorded via a load cell. Spinal kinematics were captured using six-degree-of-freedom motion blocks. Biomechanical responses were compared between groups using two-sample t-tests. The high-energy group exhibited significantly higher peak forces (2.5 vs. 1.9 kN, p = 0.0001), greater thoracic deflections (41.0 vs. 33.9 mm, p = 0.016), and increased deformation energy (91.6 vs. 61.0 J, p = 0.0001). Effective stiffness did not differ significantly between groups (p = 0.734). Energy loss increased with impact severity (66.2 vs. 56.7%, p = 0.020). Kinematic responses also increased with increased input energy. Peak y-accelerations were significantly greater at T4 in the high-energy group (p = 0.049). The sternum exhibited significantly greater peak z-angular velocity in the high-energy group (p = 0.038). Mean BioRank System Score (BRSS) of the force–deflection corridors between groups was 0.93. In summary, these findings provide essential biomechanical data and establish an important foundation for developing improved testing conditions and advancing the evaluation of female human body models (HBMs) and anthropomorphic test devices (ATDs) in side-impact scenarios.