Semispinalis Thoracis

Description

Running deep to the erector spinae in the posterior thorax, the semispinalis thoracis is isolated as a transversospinalis muscle spanning the midline-adjacent thoracic vertebrae. Muscle fascicles arise from the transverse processes of the lower thoracic vertebrae (classically T6 to T10) and ascend superomedially to insert on the spinous processes several segments above (often T1 to T4), crossing multiple intervertebral levels. Laterally, the ribs articulate with the thoracic vertebral bodies and transverse processes at the costovertebral and costotransverse joints, while superiorly the scapulae frame the upper posterior thorax as surface landmarks. Deep. Intervertebral. Semispinalis thoracis matters because it is one of the clearest examples of the transversospinalis architecture that produces extension and contralateral rotation of the vertebral column while providing segmental stabilization, a distinction that helps learners separate “global” extensors from deep stabilizers. Clinically, pain generators in the posterior thorax often involve thoracic facet joints and the medial branches of the dorsal rami, and targeted medial branch blocks or radiofrequency ablation are planned with an appreciation of the deep paraspinal layers that overlie the transverse processes. For posterior thoracic approaches, including exposure around the costotransverse junction or instrumentation planning, this anatomy explains why deep dissection rapidly enters a dense compartment hugging the laminae and spinous processes. Use this artwork for gross anatomy and kinesiology teaching on the thoracic spine, or as a figure in spine surgery, pain medicine, and rehabilitation publications discussing thoracic facet syndrome, dorsal ramus anatomy, and paraspinal muscle-sparing approaches. It also fits atlas plates that contrast semispinalis thoracis with multifidus and rotatores by level and fiber direction. Anatomical accuracy verified by SciePro's Medical Advisory Board.