CLINICIAN EDUCATION:  Thoracolumbar Fascia

There is much discussion as of late regarding the importance of the thoracolumbar fascia. Yet, few realize the importance of its role in both pain and movement dysfunctions.

ANATOMY
The thoracolumbar fascia (TLF) is a dense area of connective tissue and is the largest aponeurosis in the body. It spans from the sacrum, coccys and posterior spine of the ilium inferiorly to the iliac crest laterally. Its expanse has connections to each spinous process before ending superiorly as the nuchal fascia of the cervical spine.

It is comprised of 3 layers: anterior (thinnest), middle and posterior (thickest). The quadratus lumborum (QL) is located between the anterior and middle portions while the erector spinae are encapsulated between the middle and posterior sheets. The TLF continues to cover the paraspinal muscles in the thoracic region where it serves to separate them from the muscles that attach to and move the shoulder girdle complex.

The TLF is highly innervated with free nerve endings (nociceptors for pain transmission). These fibers are known to give sensory input and are highly responsive to both mechanical and noxious chemical stimulation. The TLF fibers also appear to be an extension of the dorsal horn neurons for innervation of the posterior trunk.

LUMBO-PELVIC FUNCTION – Protection
The TLF serves as an aponeurosis to protect the abdominal organs. While the bony thorax protects the organs of the thoracic cavity, the abdominal aponeurosis combines with the TLF to protect the small and large intestines. The TLF specifically serves to protect the lower portions of the kidney as well as the ureters in the retroperotineal space.

LUMBO-PELVIC FUNCTION – Mobility
The primary role of the TLF is to transmit forces between the upper and lower extremities. The transverse abdominis (TrA) is under somatic control and is designed to create trunk stability by tensioning the TLF. The tension of the TLF creates stable proximal attachments for the latissimus dorsi to create forceful shoulder extension and the gluteus maximus for hip extension. During ambulation, the TLF transfers force from the gluteus maximus to the contralateral latissimus dorsi (superficial posterior fascial line of Anatomy Trains) while the opposite limbs move into flexion (cross-crawl patterning).

As the TLF tensions, it pulls on the spinous process at each level and stiffens the spine. Once the lumbar spine is stable, the psoas has a firm proximal attachment to contract against to create a forceful hip flexion. Tensioning of the thoracic spine and rib cage creates stable proximal attachments for the rectus abominis and pectoralis major to contract against.

LUMBAR PAIN
Samples taken from individuals undergoing back surgery demonstrate numerous encapsulations of the free nerve endings that may be responsible for some of their pain. These encapsulations can occur from healing micro- or macro-traumas to the fascia that heals improperly.

Areas of adhesions in the TLF can create abnormal shearing forces on the spine itself. This can create a variety of tilts and rotations of the spinal vertebrae as they are pulled towards the areas of adhesion in the fascia. The TLF can create so much shearing force that it can actually fracture the spinous processes of the lumbar spine.

Other sources of lumbar pain are related to dysfunction of the TrA. If the TrA is not contracting or undergoes delayed contraction, the spine loses its stability. Furthermore, the extensors lose their proximal stability and are unable to appropriately contract leading to abnormal hip extension and arm swing during ambulation.

REHABILITATION
Appropriate medical care is needed to appropriate diagnose the source of low back pain. While low back pain can be an indicator a disease state (cancer, kidney stones, etc), it is primarily a musculoskeletal condition. Treatment should consist of manual therapy techniques to restore normal mobility to the TLF and the overlying skin to decrease shear on the spine and compression of nociceptors. Neuromuscular re-education techniques should be utilized to restore appropriate timing of TrA contraction.

REFERENCES
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