What The Thoracolumbar Fascia Is:
From a back view, the thoracolumbar fascia makes a diamond shape. Because of its shape, and its fairly central location on the back, the thoracolumbar fascia is in a position to help unify the movements of the upper body with that of the lower.
Why the Thoracolumbar Fascia Is Unique:
The Three Layers of the Thoracolumbar Fascia:
Muscles and Their Relation to The Thoracolumbar Fascia:
Many back muscles attach to the thoracolumbar fascia. For example, the erector spinae, a muscle group also known as the paraspinals, run longitudinally down the spine. The paraspinals are attached to the thoracolumbar fascia, as well as to the bony spine.
The lumbar part of the posterior layer of the thoracolumbar fascia extends from the 12th (lowest) rib down to the top of your hip bone (called the iliac crest). Along the way, it connects with the internal oblique abdominal muscle and the transverse abdominal muscle. Because of these connections, the thoracolumbar fascia helps bridge the muscles of the back to the muscles of the abdominal wall.
The latissimus dorsi, a large, superficially located back muscle that plays a major role in bearing and moving the weight of the body with the arms and shoulders, originates from the thoracolumbar fascia. (The fibers of the lats, as this muscle is often called, extend outward from the fascia.)
The front part of the thoracolumbar fascia (the anterior layer) covers a muscle called the quadratus lumborum. The quadratus lumborum bends the trunk to the side and helps maintain a healthy upright posture. The quadratus, as it is sometimes called for short, is often implicated in muscle-related low back pain.
The Strength of the Thoracolumbar Fascia:
The thoracolumbar fascia is particularly strong in the lumbar area of the back. That strength is reinforced by the fact that it attaches to the spinal bones.
Loukas M, Shoja MM, Thurston T, Jones VL, Linganna S, Tubbs RS. "Anatomy and biomechanics of the vertebral aponeurosis part of the posterior layer of the thoracolumbar fascia." Surg Radiol Anat. 2008 Mar;30(2):125-9. Epub 2007 Dec 18. http://www.ncbi.nlm.nih.gov/pubmed/18087664
Moore, K., Dalley, A. Clinically Oriented Anatomy. Fifth. Edition. Lippincott, Williams & Wilkins. 2006. Baltimore.