Trunk (thorax, abdomen, back)
Thoracolumbar Fascia, Middle Layer
Fascia thoracolumbalis, lamina media
- Origin
- Arises from the transverse processes of the lumbar vertebrae and the inferior border of the 12th rib
- Insertion
- Attaches caudally to the iliac crest and the iliolumbar ligament; fuses laterally with the anterior and posterior layers to form the lateral raphe
- Function
- Together with the anterior and posterior layers, forms the osteofibrous canal housing the erector spinae and quadratus lumborum muscles, and transmits force to the transversus abdominis muscle via the lateral raphe
- Innervation
- No independent motor innervation (connective tissue structure, not contractile tissue)
- Movement & chain
- Acts as a biomechanical tension band between spine and lateral abdominals stabilizing lumbar lordosis.
- Palpation
- Lies between erector spinae and quadratus lumborum attached to lumbar transverse processes; not directly palpable.
- Clinical
- Origin for transversus abdominis and internal oblique; critical hydraulic amplifier mechanism stabilizing the lumbar spine under load.
- Segmental innervation
- L1–L4 (posterior rami of spinal nerves)
- In clinical practice
- Ergonomic patient repositioning (log-roll technique in spinal trauma) and pressure offloading; maintain neutral spinal alignment in bedridden patients.
- Region in the model
- Trunk (thorax, abdomen, back)