Understanding whiplash injury and prevention mechanisms using a human model of the neck.

OBJECTIVES

Various models for rear crash simulation exist and each has unique advantages and limitations. Our goals were to: determine the neck load and motion responses of a human model of the neck (HUMON) during simulated rear crashes; evaluate HUMON's biofidelity via comparisons with in vivo data; and investigate mechanisms of whiplash injury and prevention.

METHODS

HUMON, consisting of a neck specimen (n=6) mounted to the torso of BioRID II and carrying a surrogate head and stabilized with muscle force replication, was subjected to simulated rear crashes in an energy-absorbing seat with fixed head restraint (HR) at peak sled accelerations of 9.9g (ΔV 9.2kph), 12.0g (ΔV 11.4kph), and 13.3g (ΔV 13.4kph). Physiologic spinal rotation ranges were determined from intact flexibility tests. Average time-history response corridors (±1 standard deviation) were computed for spinal motions, loads, and injury criteria.

RESULTS

Neck loads generally increased caudally and consisted of shear, compression, and flexion moment caused by straightening of the kyphotic thoracic and lordotic lumbar curvatures, upward torso ramping, and head inertial and head/HR contact loads. Nonphysiologic rotation occurred in flexion at C7/T1 prior to head/HR contact and in extension at C6/7 and C7/T1 during head/HR contact.

CONCLUSIONS

HUMON's neck load and motion responses compared favorably with in vivo data. Lower cervical spine flexion-compression injuries prior to head/HR contact and extension-compression injuries during head/HR contact may be reduced by refinement of existing seatback, lapbelt, and HR designs and/or development of new injury prevention systems.