Acceleration-induced strains in the intact vertebral column

¹ Department of Anatomy, The University of Michigan, Ann Arbor; and Department of Engineering Mechanics, Wayne State University, Detroit, Michigan

Results of more than 170 tests with the embalmed bodies of a 69-year-old white male and two Negro males 56 and 82 years of age which were subjected to a maximum acceleration of 20 g revealed an approximately linear relation between acceleration and strain in the sacral ala and lumbar vertebrae. This relationship was less linear for the thoracic and cervical vertebrae. The magnitude of compressive strain in the anterior aspect of the body of C₃ and L₃ is a function of the degree of freedom of movement of the head and thorax. The strain in C₃ is progressively increased by increasing freedom of movement of the head and thorax but the opposite effect occurs in L₃. The anterior aspect of the body of C₃ is subjected to compressive strain in the normal position of the head but extension of the head changes the strain to tension. Seating the cadaver on a polyurethan cushion 4 in. thick increased the peak strain in the vertebral column. No vertebral fractures or dislocations demonstrable by X rays have been produced by maximum accelerations of 20 g. End-plate fractures of 28 fresh vertebrae were produced by an average load of 672 lb (435–900 lb) statically applied in a materials-testing machine.