Trunk (thorax, abdomen, back)
Thoracolumbar Fascia, Posterior Layer
Fascia thoracolumbalis, lamina posterior
- Origin
- Arises from the spinous processes of the lumbar and lower thoracic vertebrae and the supraspinous ligament
- Insertion
- Attaches laterally and caudally to the iliac crest and the sacrum; fuses laterally with the middle layer to form the lateral raphe, the origin of the transversus abdominis muscle
- Function
- Serves as an origin aponeurosis for the latissimus dorsi and part of the gluteus maximus, and transmits force between the upper and lower extremities via this 'posterior oblique chain'
- Innervation
- No independent motor innervation (connective tissue structure, not contractile tissue)
- Movement & chain
- Crucial link in the posterior oblique sling (latissimus dorsi to contralateral gluteus maximus) for rotational gait stability.
- Palpation
- Directly palpable as a dense diamond-shaped aponeurotic sheet across the lumbar spine and sacrum.
- Clinical
- Cross-couples latissimus dorsi with the contralateral gluteus maximus in the posterior oblique sling; central to load transfer and lower back pain.
- Segmental innervation
- T7–L5 (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)