Where is the fascia located and what are its boundaries?
The fascia is located in the back and lumbar region, encloses the deep back muscles, and lies adjacent to the erector spinae muscle (m. erector spinae). At the level of the upper thoracic vertebrae, it appears as a thin plate, gradually thickens toward the lumbar region, and appears as a dense aponeurosis at the level of the lower thoracic vertebrae.
Medially, the superficial layer attaches to the spinous processes of the thoracic and lumbar vertebrae, the sacrum, and the iliac crest, and laterally to the angles of the ribs. Posteriorly, the axillary fascia (fascia axillaris) continues into the thoracolumbar fascia.
What is the internal structure and what are the layers of the fascia?
The fascia consists of two layers that participate in forming the sheath for the deep back muscles:
- Superficial (posterior) layer — attaches medially to the spinous processes of the thoracic and lumbar vertebrae, the sacrum, and the iliac crest, and laterally to the angles of the ribs. At the lateral edge of the erector spinae muscle, it fuses with the deep layer.
- Deep (anterior) layer — extends from the transverse processes of the lumbar vertebrae to the 12th rib and further superiorly. In the lumbar region, it forms a fibrous sheath for the deep muscles; laterally, it fuses with the quadratus lumborum muscle and the intertransverse muscles.
At the lateral edge of m. erector spinae, both layers unite to form the fibrous sheath of the muscle. Anteriorly from their fusion site, the aponeurosis of the transversus abdominis muscle originates.
What are the functions and muscular connections of the structure?
The thoracolumbar fascia strengthens the posterior trunk wall and participates in the transmission of muscular forces.
The fascia is connected with:
- deep back muscles, which are located beneath the fascia thoracolumbalis;
- erector spinae muscle (m. erector spinae), enclosed in an aponeurotic sheath formed by the fascial layers;
- gluteus maximus muscle (m. gluteus maximus), which originates from the thoracolumbar fascia;
- latissimus dorsi muscle (m. latissimus dorsi): the fascia fuses with the fascia of the latissimus dorsi and forms a sheath for it in the lumbar region;
- internal oblique muscle of the abdomen (m. obliquus internus abdominis), originating from the fascia thoracolumbalis at the site of fusion of its layers;
- transversus abdominis muscle (m. transversus abdominis), originating from the deep layer of the fascia thoracolumbalis.
What is the clinical significance in surgery?
The fascia is significant during surgical interventions in the retroperitoneal space, such as Fedorov's incision (lumbotomy). During this approach, tissues are dissected layer by layer, including the fascia thoracolumbalis and m. quadratus lumborum. Afterward, the parietal peritoneum with adipose tissue is bluntly dissected medially and superiorly, then the kidney is palpated through the fascia, the fascia is incised, the adipose capsule is bluntly dissected, and the kidney is luxated into the wound.
The thoracolumbar fascia resembles a sheath for the deep back muscles: its superficial and deep layers enclose the erector spinae muscle and form a fibrous sheath.
Class and exam questions
What layers does the thoracolumbar fascia consist of?
It consists of two layers: superficial (posterior) and deep (anterior), which enclose the deep back muscles.
Where is the thoracolumbar fascia thickest?
The fascia has its greatest thickness in the lumbar region, whereas it thins out in the upper thoracic sections.
Which muscles are connected with the fascia in the lumbar region?
It is connected with the deep back muscles, erector spinae muscle, quadratus lumborum muscle, latissimus dorsi muscle, internal oblique, and transversus abdominis muscles.
What else to study on this topic
- Erector spinae muscle (m. erector spinae)
- Quadratus lumborum muscle (m. quadratus lumborum)
- Transversus abdominis muscle (m. transversus abdominis)
- Retroperitoneal space and lumbotomy
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