Middle Layer of Thoracolumbar Fascia

Anatomical Relations

The thoracolumbar fascia is continuous with the deep cervical fascia of the neck superiorly. Medially, it is attached to the spinous processes of the vertebrae and the supraspinous ligament. It extends laterally to fuse with the aponeurosis of the transversus abdominis muscle and the transversalis fascia.

In the lumbar region, the thoracolumbar fascia is composed of three layers including anterior, middle, and posterior.

The anterior layer covers the anterior surface of quadratus lumborum muscle. Medially, it is attached to the transverse processes of lumbar vertebrae, and laterally, it is continuous with the aponeurosis of the origin of transversus abdominis muscle and transversalis fascia. Inferiorly, it is attached to the iliolumbar ligament and the adjoining iliac crest; while, superiorly, it is continuous with the deep cervical fascia at the back of the neck. It forms the lateral arcuate ligament of the diaphragm and passes anterior to serratus posterior inferior muscle (Standring, 2016).

The middle layer of thoracolumbar fascia is attached to the lower border of the twelfth rib and lumbocostal ligament superiorly, while attaching to the iliac crest inferiorly. Medially, it is attached to the transverse processes and intertransverse ligaments of the lumbar vertebrae (Standring, 2016).

The posterior layer of thoracolumbar fascia is attached to the spines and associated supraspinous ligaments of the lumbar and sacral vertebrae. It has two laminae, the superficial and deep. The posterior and middle layers merge to form a lateral raphe at the lateral margin of the paraspinal and quadratus lumborum muscles. This fuses with the anterior layer of the thoracolumbar fascia to form the aponeurotic origin of transversus abdominis muscle (Standring, 2016).

Function

The thoracolumbar fascia forms a thin covering and osteofascial compartment for the intrinsic back muscles. Together with collagenous tissues of the back muscles, it plays a vital role in the mechanical stability of the lower back, by transferring load between the trunk and the lower limbs (Willard et al., 2012).

List of Clinical Correlates

- Back pain through nociceptive nerve endings in the thoracolumbar fascia

References

Standring, S. (2016) Gray's Anatomy: The Anatomical Basis of Clinical Practice. Gray's Anatomy Series 41st edn.: Elsevier Limited.Willard, F. H., Vleeming, A., Schuenke, M. D., Danneels, L. and Schleip, R. (2012) 'The thoracolumbar fascia: anatomy, function and clinical considerations', J Anat, 221(6), pp. 507-36.