The longissimus thoracis is the largest component of the erector spinae and the primary extensor of the thoracic and lumbar spine, forming the prominent muscle column on either side of the thoracic spinous processes. Its massive cross-sectional area in the mid-thoracic region provides the sustained extensor force that prevents thoracic kyphosis progression during ageing. The thoracolumbar fascia encases the erector spinae group including the longissimus thoracis.
| Origin | Common erector spinae aponeurosis from the sacrum, ilium, and lower lumbar spinous processes |
|---|---|
| Insertion | Transverse processes of all thoracic vertebrae and posterior surfaces of ribs 3 through 12 |
| Nerve Supply | Posterior rami of thoracic and lumbar spinal nerves |
| Blood Supply | Posterior intercostal and lumbar arteries |
| Actions | Extension of the thoracic and lumbar spine; Ipsilateral lateral flexion of the spine; Assists forced expiration via costal attachments |
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During lifting it acts eccentrically during the lowering phase as the primary spinal extensor, storing elastic energy in the thoracolumbar fascia that assists the concentric return to upright. This stretch-shortening cycle reduces the metabolic cost of repetitive lifting.
The erector spinae including the longissimus thoracis are assessed for asymmetry in scoliosis, where the convex-side muscles are more prominent in structural curves and the asymmetry reflects rotational deformity. Erector spinae plane (ESP) block injections lateral to the thoracic transverse processes target the longissimus thoracis region to provide multilevel thoracic analgesia as an alternative to epidural anaesthesia.
The longissimus thoracis is the prominent muscle column palpable 2 to 4 cm lateral to the thoracic spinous processes on either side, clearly visible in lean individuals.
Acute or cumulative injury producing thoracolumbar back pain with extension restriction, one of the most common presentations in manual workers and athletes.
