Reassessing Combat Helmet Protection Against Blunt and Blast Threats: A Structured Scoping Review

Traumatic brain injury (TBI) remains a leading cause of morbidity among military personnel, despite improved personal protective equipment. Although modern combat helmets effectively prevent penetration and skull fractures, their ability to mitigate behind-helmet blunt trauma (BHBT) and primary blast-induced TBI (bTBI) is less clear. This review evaluates combat helmet protection considering biomechanical, medical, and operational evidence.

A structured scoping literature review was conducted according to the SANRA framework. Searches were performed in PubMed, Scopus, and SciFinder using combinations of terms related to "combat helmet," "blunt trauma," "ballistic impact," "blast exposure," and "traumatic brain injury." Peer-reviewed studies, experimental reports, and regulatory standards (NIJ, NATO STANAG) were included. Data were synthesized thematically by injury mechanism, protection metric, and helmet design characteristics.

Ballistic helmets significantly reduce skull fractures and contusions but provide limited protection against diffuse axonal injury and blast overpressure. Rotational acceleration correlates strongly with predicted strain and mild TBI, yet is not incorporated into current standards. Pad stiffness, fit, and coverage strongly influence both ballistic and blast protection, creating trade-offs between impact absorption and blast under wash. Finite element models and biomarker studies show complementary value but require in vivo validation.

Current helmet standards insufficiently address complex threat biomechanics. Future developments should integrate multidimensional metrics, linear and rotational kinematics, strain thresholds, and sensor-derived field data, while balancing tactical functionality with neurobiological protection.