Spinalis Thoracis

musculus spinalis thoracis

Spinalis thoracis is the medial column of the thoracic erector spinae, connecting lower thoracic and upper lumbar spinous processes to the upper thoracic spinous processes. It is the thinnest of the three erector spinae columns in the thoracic region.

Nerve: Dorsal rami of thoracic spinal nerves Blood Supply: Posterior intercostal arteries Region: Chest

Anatomical Data

Origin, Insertion & Supply

Origin	Spinous processes of T11-L2
Insertion	Spinous processes of T1-T4 (upper thoracic)
Nerve Supply	Dorsal rami of thoracic spinal nerves
Blood Supply	Posterior intercostal arteries

Biomechanics

Function & Actions

Actions	Extends the thoracic spine; Ipsilateral lateral thoracic flexion

Clinical Relevance

Clinical Notes

Spinalis thoracis is identified in posterior thoracic approaches as the most medial paraspinal muscle layer. Its spinous process attachments serve as the medial reference for pedicle screw placement in thoracic instrumented fusion.

Palpation

Palpated as the central thoracic paraspinal mass during resisted trunk extension.

Pathology

Common Injuries & Conditions

Spinalis Thoracis Disruption in Posterior Approach

Division of spinalis thoracis fibres during posterior thoracic instrumented fusion contributing to post-operative trunk extensor weakness and back pain.