In the thoracic region, the thoracolumbar fascia attaches medially to the spinous processes of the thoracic vertebrae and laterally to the angles of all of the ribs.  

In the lumbar region, the posterior layer attaches to the spinous processes of the lumbar and sacral vertebrae and the supraspinous ligaments.  The middle layer attaches to the apex of the lumbar transverse processes, the intertransverse ligaments, the iliac crest and the lower border of the twelfth rib.  The anterior layer attaches to the vertical ridge on the anterior surface of the transverse processes of the lumbar vertebrae, the iliolumbar ligament and adjacent iliac crest.  Posterior and middle layers fuse at the lateral margin of the erector spinae.  The anterior layer fuses with the others at the lateral border of quadratus lumborum.