The longissimus is the intermediate and longest column of the erector spinae, running from the common tendon at the pelvis to the mastoid process. It is the main dorsal spine extensor in the thoracic and cervical regions. The longissimus thoracis is the primary muscle split during posterior spinal approaches — minimally invasive TLIF uses a muscle-splitting approach through the longissimus-iliocostalis intermuscular plane.
| Origin | Thoracis: common tendon (thoracolumbar fascia and iliac crest). Cervicis: T1-T5 transverse processes. Capitis: C4-T5 articular and transverse processes |
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| Insertion | Thoracis: transverse processes T1-T12 and rib angles. Cervicis: C2-C6 transverse processes. Capitis: mastoid process |
| Nerve Supply | Dorsal rami of spinal nerves |
| Blood Supply | Intercostal, lumbar, and cervical arteries |
| Actions | Bilateral: spinal extension (the intermediate erector column); Unilateral: ipsilateral lateral flexion; Longissimus capitis: extends and rotates the head ipsilaterally |
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Minimally invasive lumbar spine surgery uses the Wiltse approach — the natural intermuscular plane between the longissimus and iliocostalis — to access the lateral facets and transverse processes for pedicle screw placement without stripping the medial multifidus from the spinous processes.
The longissimus forms the prominent middle paraspinal mass from the sacrum to the cervical spine, palpable as the intermediate column between the spinous processes and the more lateral iliocostalis.
Longissimus haematoma from penetrating trauma or anticoagulation producing paraspinal swelling and local back pain managed with imaging and conservative treatment.
