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Vertebrae, together with intervertebral discs, compose the vertebral column, also referred to as the "spine." The vertebral column extends from the skull to the coccyx and is divided into cervical, thoracic, lumbar, and sacral regions (see Image. Vertebral Column). The spine serves multiple vital roles, including protection of the spinal cord and branching spinal nerves, structural support for the thorax and abdomen, and facilitation of flexibility and mobility. Intervertebral discs permit mobility while preserving the supportive strength of the vertebral column. The thoracic region contains 12 vertebrae, designated T1 to T12. Intervertebral discs, in conjunction with the laminae, pedicles, and articular processes of adjacent vertebrae, form spaces through which spinal nerves exit. The thoracic vertebrae collectively contribute to a kyphotic curvature of the vertebral column. Thoracic vertebrae are distinguished by an additional function of providing articulation sites for the ribs.[1][2][3] Typical vertebrae consist of a vertebral body, a vertebral arch, and 7 processes (see Image. Typical Thoracic Vertebra Anatomy). The vertebral body bears the majority of the axial load transmitted through the vertebral column. Vertebral bodies increase in size from superior to inferior. The vertebral body is composed of trabecular bone containing red marrow, surrounded by a thin external layer of compact bone. The vertebral arch, together with the posterior aspect of the vertebral body, forms the vertebral (spinal) canal, which contains the spinal cord. The arch consists of bilateral pedicles, which are cylindrical segments of bone connecting the arch to the vertebral body. The arch also includes bilateral laminae, which form most of the arch and connect the transverse and spinous processes. A typical vertebra contains 4 articular processes, including 2 superior and 2 inferior processes. These processes articulate with the inferior and superior articular processes of adjacent vertebrae, respectively. The articulation between opposing articular facets forms a facet, or zygapophyseal, joint. Facet joints maintain vertebral alignment, limit excessive motion, and bear load in certain positions.

A typical vertebra contains 4 articular processes, including 2 superior and 2 inferior processes. These processes articulate with the inferior and superior articular processes of adjacent vertebrae, respectively. The articulation between opposing articular facets forms a facet, or zygapophyseal, joint. Facet joints maintain vertebral alignment, limit excessive motion, and bear load in certain positions. The spinous process projects posteriorly and inferiorly from the vertebral arch and may overlap inferior vertebrae to varying degrees, depending on the spinal region. Two transverse processes project laterally from the vertebral arch in a symmetric configuration. Typical thoracic vertebrae exhibit several features that distinguish this region from the cervical and lumbar vertebrae. Vertebrae T5 to T8 are often considered the most representative, as these levels demonstrate features present across the thoracic region. The defining characteristic of thoracic vertebrae is the presence of costal facets. Each thoracic vertebra contains 6 costal facets, including 2 facets on the transverse processes and 4 demifacets. Facets on the transverse processes articulate with the tubercle of the corresponding rib. The demifacets are bilaterally paired and located on the superior and inferior posterolateral aspects of the vertebral body. This arrangement permits articulation such that the superior demifacet of the inferior vertebra and the inferior demifacet of the superior vertebra both articulate with the head of the same rib. For example, the inferior demifacet of T4 and the superior demifacet of T5 articulate with the head of rib 5. The length of the transverse processes progressively decreases from superior to inferior levels. The orientation of the ribs and the morphology of the spinous processes substantially limit flexion and extension within the thoracic spine. Vertebrae T5 to T8 demonstrate the greatest rotational capacity within the thoracic region. Thoracic vertebrae possess superior articular facets oriented in a posterolateral direction. The spinous processes are elongated relative to other spinal regions and project posteroinferiorly. This angulation increases progressively through the midthoracic levels before decreasing rapidly from T9 to T12. Intervertebral disc height in the thoracic region is, on average, the smallest among the vertebral regions.

Thoracic vertebrae possess superior articular facets oriented in a posterolateral direction. The spinous processes are elongated relative to other spinal regions and project posteroinferiorly. This angulation increases progressively through the midthoracic levels before decreasing rapidly from T9 to T12. Intervertebral disc height in the thoracic region is, on average, the smallest among the vertebral regions. Three atypical vertebrae are present within the thoracic region (see Image. Atypical Thoracic Vertebrae). These vertebrae differ in costal facet configuration and articular morphology from typical thoracic vertebrae. The superior costal facets of T1 are complete, or “whole,” costal facets. These facets articulate exclusively with the 1st rib. C7 lacks costal facets. T1 also contains typical inferior demifacets that articulate with the 2nd rib. The spinous process of T1 is elongated and resembles that of a cervical vertebra. In some individuals, the length approaches that of the vertebra prominens at C7. Vertebrae T11 and T12 are atypical in that each contains a single pair of complete costal facets. These facets articulate with the 11th and 12th ribs, respectively. Facets on the transverse processes are absent at these levels. Anatomic variation may result in T10 exhibiting similar atypical characteristics. When this variation is present, T9 lacks an inferior demifacet, as articulation with the 10th rib is unnecessary. Vertebra T12 is further distinguished by its transitional anatomy between the thoracic and lumbar regions. Thoracic characteristics include the presence of costal facets and superior articular facets that permit rotation and flexion. Lumbar characteristics include inferior articular processes oriented to restrict rotation while allowing flexion and extension. T12 also contains mammillary processes. These small tubercles are located on the posterior surface of the superior articular processes and serve as attachment sites for the intertransversarii and multifidus muscles.