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Anatomy of The Lumbar Back Muscles-Thoracolumbar Fascia

The thoracolumbar fascia has three layers—anterior, middle, and posterior—creating an envelope for the muscles of the lumbar spine. The anterior layer originates from the anterior surfaces of the transverse processes of the lumbar spine and intertransverse ligaments, and it covers the anterior surface of the quadratus lumborum.

The middle layer is attached to the tips of the lumbar transverse processes and intertransverse ligaments before it passes behind the quadratus lumborum. The posterior layer “arises from the lumbar spinous processes in the middle posteriorly and wraps around the back muscles to blend with the outer layers of the thoracolumbar fascia”.

The posterior layer consists of two laminae: superficial which are oriented in a caudomedial direction and deep layer which are oriented in a caudolateral direction. The three layers, particularly the middle and posterior layers, blend laterally to the quadratus lumborum to form the lateral raphe.

The posterior layer provides indirect attachment for the TrA to the lumbar spine through the lateral raphe. The thoracolumbar fascia gives attachment to the middle fibers of the TrA, the posterior fibers of the internal oblique, the latissimus dorsi, the gluteus maximus, the lower trapezius, and the hamstrings.

When the TrA contracts, tension of the thoracolumbar fascia increases via the lateral raphe. Pressure in the abdominal cavity also increases

Richardson et al. It have suggested that the TrA contributes to support the abdominal contents. They also have suggested that it provides contributions to respiration and to movements in the lumbar spine of extension and rotation.

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