Biomechanical tolerance of whole lumbar spines in straightened posture subjected to axial acceleration

Abstract

Quantification of biomechanical tolerance is necessary for injury prediction and protection of vehicular occupants. This study experimentally quantified lumbar spine axial tolerance during accelerative environments simulating a variety of military and civilian scenarios. Intact human lumbar spines (T12-L5) were dynamically loaded using a custom-built drop tower. Twenty-three specimens were tested at sub-failure and failure levels consisting of peak axial forces between 2.6 and 7.9 kN and corresponding peak accelerations between 7 and 57 g. Military aircraft ejection and helicopter crashes fall within these high axial acceleration ranges. Testing was stopped following injury detection. Both peak force and acceleration were significant (p < 0.0001) injury predictors. Injury probability curves using parametric survival analysis were created for peak acceleration and peak force. Fifty-percent probability of injury (95%CI) for force and acceleration were 4.5 (3.9-5.2 kN), and 16 (13-19 g). A majority of injuries affected the L1 spinal level. Peak axial forces and accelerations were greater for specimens that sustained multiple injuries or injuries at L2-L5 spinal levels. In general, force-based tolerance was consistent with previous shorter-segment lumbar spine testing (3-5 vertebrae), although studies incorporating isolated vertebral bodies reported higher tolerance attributable to a different injury mechanism involving structural failure of the cortical shell. This study identified novel outcomes with regard to injury patterns, wherein more violent exposures produced more injuries in the caudal lumbar spine. This caudal migration was likely attributable to increased injury tolerance at lower lumbar spinal levels and a faster inertial mass recruitment process for high rate load application. Published 2017. This article is a U.S. Government work and is in the public domain in the USA. J Orthop Res 36:1747-1756, 2018.

Failure tolerance of the human lumbar spine in dynamic combined compression and flexion loading

“…Alternatively, the IRF can be used in pure compression cases (with the absence of flexion moment) since the experiments included six specimens that failed in pure compression before flexion moment could be applied. Likewise, injury risk prediction using only compression force in the IRF from this study were similar to those predicted using an existing IRF with compression force as the input predictor 27 . Both studies had similar average donor age of 49 years old with a wide range of ages, included both males and females, and produced similar fracture types.…”

Association between Preseason/Regular Season Head Impact Exposure and Concussion Incidence in NCAA Football

“…Injury tolerance refers to the body's capacity to resist specific loads before sustaining injury and is often characterized using injury risk curves that relate increasing biomechanical loads to greater injury risk. For example, studies have proposed injury tolerance relationships for concussion (4), lumbar spine fracture (37), cervical spine fracture (38), blunt thoracic injury (39), and a variety of other body components. However, characterization of concussion tolerance is more complicated than many other injuries for various reasons that include significant variability in the severity and type of concussive symptoms (40) and varying athlete attitudes toward concussion reporting (41)(42)(43) that may contribute to underreporting or overreporting of concussions.…”

Reducing Lumbar Spine Vertebra Fracture Risk With an Adaptive Seat Track Load Limiter

“…Alternative risk functions addressing lumbar vertebra fractures have been proposed by Stemper et al (2018) and Ortiz-Paparoni et al (2021). The former's was based on compression forces at the lumbar spine measured in drop tower tests, from 23 PMHS lumbar specimens.…”