Head rotation during vertical impact predicted using initial head angle and anthropometry.

Abstract

INTRODUCTION: Dynamic inertial loading to the head and neck complex, similar to what is experienced during the rocket boost phase of pilot ejection, results in diverse kinematic responses when observed in live human volunteers. The purpose of this study was to develop a predictive model of head rotation during the compressive phase of pilot ejection. METHODS: Post hoc analyses were conducted on data from two previous experimental studies. This analysis included observing 138 tests involving 27 human volunteers (both men and women) where the various kinematic responses were categorized into five modes based on the location of primary rotation and the direction of head rotation. Several statistical methods (logistic regression, linear regression, and Fisher's Exact test) were employed to evaluate the influence of independent variables, body anthropometry, and initial head angle on dependent variables head acceleration and direction of head rotation. RESULTS: Statistical results of this data indicated that initial head position and body anthropometry are significant factors with respect to head response during the compressive phase of an ejection. Two statistical tools were developed; one to assist in predicting the location of primary head rotation, and the other to predict the direction of head rotation. DISCUSSION: By using the two statistical tools together, a simplified method was developed for predicting the modes of head response to vertical impact based on initial position and anthropometry. The results of this study show the importance of initial position prior to an ejection and may assist in identifying individuals at greater risk of injury during an ejection.