Basic Biomechanics of the Thoracic Spine and Rib Cage

The thoracic spine is the middle section of the spinal complex. Connecting the cervical and lumbar spinal sections, the thoracic spine has to ensure a high stability regarding the muscle-controlled sagittal balance of the spine by the erector spinae and the abdominal muscles, an optimum force transmission from the upper body to the lower spinal sections, as well as an adequate flexibility in performing three-dimensional motions. While the intersegmental stability of the cervical and lumbar spine is mainly determined by the adjacent musculature, the thoracic spinal segments are mostly stabilized by the additional bony and ligamentous structures of the rib cage. In addition to its functions as protector of the inner organs, supporter of the trunk muscle activity by providing a strong framework, and enhancer of the respiration by expanding and contracting, the rib cage can therefore be seen as a fourth spinal column in the thoracic section.