Thoracolumbar fascia

In the lumbar region, it is known as lumbar fascia and here consists of 3 layers (posterior, middle, and anterior) enclosing two muscular compartments. In the thoracic region, it consists of a single layer (an upward extension of the posterior layer of the lumbar fascia). The thoracolumbar fascia is most prominent at its lower end where its various layers fuse into a thick composite.

Anatomy

Thoracic region

In the thoracic region, the thoracolumbar fascia consists of a single layer - an upward extension of the posterior layer of the lumbar fascia, becoming progressively thinner before fading out above the 1st rib, replaced by the splenius muscle.

In the thoracic region, it forms a thin fibrous fascial covering for extensor muscles associated with the spine, separating them from muscles interconnecting the spine and upper extremity. Here it attaches to costal angles of all ribs, the spinous processes of all thoracic vertebrae, and the thoracic portion of the supraspinous ligament. It is situated deep to the serratus posterior superior muscle. Superiorly, it terminates by becoming continuous with the superficial layer of deep cervical fascia of the posterior neck.

Lumbar region

The thoracolumbar fascia is most prominent inferiorly - adjacent to the caudal lumbar spine, between the posterior superior iliac spines on either side - where its aponeurotic layers meld, forming a thickened sheet. The thickened, united inferior portion attaches firmly to the posterior superior iliac spine, and the sacrotuberous ligament. The thoracolumbar fascia extends as far inferiorly as the two ischial tuberotities.