A study of weight transmission through the cervical and upper thoracic regions of the vertebral column in man

Abstract

The role of the neural arch in weight transmission in the cervical and upper thoracic regions of the vertebral column has been investigated. Measurements at the levels of C₂, C₄, C₆, C₇, T₁ and T₅ vertebrae were made in 44 adult male vertebral columns. At each level, the area of the inferior surface of the body was compared with the area of the inferior articular facets, the pedicle index and the arch index; inclination of the pedicle in relation to the body was also measured. On the basis of these studies it was found that at C₂ level the compressive force acting on the superior articular surfaces was transmitted to the inferior surface of the body and to the two inferior articular facets. From C₂ to C₇, compressive force is transmitted through three parallel columns - one anterior, formed by the bodies and intervertebral discs, and two posterior, formed by the articulations of the articular processes on either side. Due to the posterior curvature in the cervical region, the posterior columns here sustain more of the compressive force. From C₇ level downwards, the compressive force is transmitted through two columns, i.e. one anterior formed by the bodies and intervertebral discs and one posterior formed by successive articulations of the laminae. Below C₇ level, compressive force from the posterior column is partly transferred to the anterior column through the pedicles at T₁ and T₂. In the upper thoracic region, due to the anterior curvature, the main part of the compressive force is transmitted through the anterior column, which sustains even greater compressive force than is suggested by body area, with resulting increased stress.