Human Head-Neck Kinetics Under Whiplash Loading

Abstract

Abstract The objective of the study was to determine the biomechanics of the human head-neck complex secondary to whiplash loading. Intact human cadaver head-neck complexes were prepared by maintaining the integrity of the skin and musculature around the ligamentous column. Retroreflective targets were inserted into the bony articulations of the cervical spine at all levels. The specimens were rigidly fixed to a six-axis load cell at the distal end. Instrumentation consisted of triaxial angular velocity sensors and accelerometers on the cranium. A linear accelerometer was attached to the distal end of the preparation. The specimens were subjected to dynamic loading at speeds ranging from 1.6 to 4.2 m/s. They were placed on the slider of the mini-sled pendulum which applied the whiplash loading pulse from the posterior to the anterior direction. The input pulse was measured in terms of acceleration-time histories. Principles of continuous motion analysis were used to determine the kinematics of the head-neck complex as a function of time. The specimens were radiographed pre- and post-test. Results indicated that the structure undergoes continuous change in the head-neck curvature. Initially, the cranium lags the cervical spine resulting in a reverse curvature, the upper cervical spine undergoes flexion with a concomitant extension of the lower cervical spine, and finally, the head catches-up with the lower cervical spine resulting in a single curvature. Increasing velocities/accelerations produced nonlinear increases in extension moment, axial and shear forces, and head-neck kinematics. These strength and kinematic information add to our knowledge of the understanding of the biomechanics of the human head-neck under whiplash.