BIOMECHANICS OF SKULL FRACTURE

This study was conducted to determine the biomechanics of the human he ad under quasistatic and dynamic loads. Twelve unembalmed intact human cadaver heads were tested to failure using an electrohydraulic testin g device. Quasistatic loading was done at a rate of 2.5 mm/s. Impact l oading tests were conducted at a rate of 7.1 to 8.0 mis. Vertex, parie tal, temporal, frontal, and occipital regions were selected as the loa ding sites. Pathological alterations were determined by pretest and po sttest radiography, close-up computed tomography (CT) images, macrosco pic evaluation, and defleshing techniques. Biomechanical force-deflect ion response, stiffness, and energy-absorbing characteristics were obt ained. Results indicated the skull to have nonlinear structural respon se. The failure loads, deflections, stiffness, and energies ranged fro m 4.5 to 14.1 kN, 3.4 to 16.6 mm, 467 to 5867 N/mm, and 14.1 to 68.5 J , respectively. The overall mean values of these parameters for quasis tatic and dynamic loads were 6.4 kN (+/-1.1), 12.0 mn (+/-1.6), 812 N/ mm (+/-139), 33.5 J (+/-8.5), and 11.9 kN (+/-0.9), 5.8 mm (+/-1.0), 4 023 N/mm (+/-541), 28.0 J (+/-5.1), respectively. It should be emphasi zed that these values do not account for the individual variations in the anatomical locations on the craniun of the specimens. While the X- rays and CT scans identified the fracture, the precise direction and l ocation of the impact on the skull were not apparent in these images. Fracture widths were consistently wider at sites remote from the loadi ng region. Consequently, based on retrospective images, it may not be appropriate to extrapolate the anatomical region that sustained the im pact forces. The quantified biomechanical response parameters will ass ist in the development and validation of finite element models of head injury.