Spinalis Thoracis Muscle

Description

Positioned on the posterior thoracic wall, the spinalis thoracis appears as a narrow longitudinal column of the erector spinae running immediately adjacent to the thoracic spinous processes, medial to longissimus thoracis and deep to the more superficial posterior trunk musculature. Fibers course superiorly and slightly medially from lower thoracic and upper lumbar spinous processes to higher thoracic spinous processes, creating a segmented, tendinous profile along the midline. Lateral to this paraspinal track, the scapula and medial border region sit under the rhomboid major, which spans from the thoracic spinous processes to the medial margin of the scapula, with trapezius typically draping over it in an intact superficial layer. Relationships are clearest in posterior view. Understanding spinalis thoracis morphology helps when teaching the layered organization of the erector spinae and when planning posterior thoracic approaches that use the spinous processes as the primary midline landmark. In thoracic and lumbar spine surgery, paraspinal muscle stripping and retraction can denervate or devascularize these medial columns, a recognized contributor to postoperative paraspinal atrophy and persistent axial back pain. Rhomboid major matters here because its medial attachment shares the same spinous-process region, so scapulothoracic dissection and posterior shoulder approaches often cross teaching planes that confuse learners. Use this asset for anatomy lab atlases, orthopedic and neurosurgical education on posterior midline exposure, and rehabilitation texts that contrast scapular retractors (rhomboid major) with axial extensors (spinalis thoracis) during posture and thoracic kyphosis discussions. It also fits radiology primers that correlate surface midline landmarks with deeper paraspinal compartments. Anatomical accuracy verified by SciePro's Medical Advisory Board.