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Topic

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Intercostal space

The intercostal space is the anatomical interval between two adjacent ribs. It contains muscles, nerves, and vessels that are essential for respiration and chest wall integrity. Each intercostal space is numbered according to the rib forming its upper boundary and extends from the vertebral column posteriorly to the sternum anteriorly.

Intercostal spaces are important landmarks in thoracic anatomy, imaging interpretation, surgical access, and procedures such as thoracentesis and chest tube placement.

Synonyms

  • Intercostal interval

  • Intercostal gap

Location

  • Situated between adjacent ribs

  • Extends from the thoracic vertebrae posteriorly to the sternum anteriorly

  • Present throughout the thoracic cage

  • Numbered according to the superior rib

  • Lies superficial to the pleura and lungs

Anatomical components

  • Intercostal muscles:

    • External intercostal muscles

    • Internal intercostal muscles

    • Innermost intercostal muscles

  • Neurovascular bundle:

    • Intercostal vein

    • Intercostal artery

    • Intercostal nerve

    • Arranged in the costal groove of the upper rib (V–A–N from superior to inferior)

  • Endothoracic fascia

  • Parietal pleura (deep boundary)

Relations

Superiorly:

  • Inferior border of the upper rib

  • Costal groove containing intercostal vessels and nerve

Inferiorly:

  • Superior border of the lower rib

Superficially:

  • Skin and subcutaneous tissue

  • Superficial fascia

Deep:

  • Endothoracic fascia

  • Parietal pleura

  • Lung (during inspiration)

Anteriorly:

  • Costal cartilages and sternum

Posteriorly:

  • Thoracic vertebrae

X-ray appearance

Chest radiograph:

  • Intercostal spaces: Radiolucent gaps between ribs

  • Width: Varies with lung volume and respiratory phase

  • Soft tissues: Not individually distinguished

  • Clinical utility: Used to assess lung inflation and chest wall symmetry

CT appearance

Non-contrast CT (soft-tissue window):

  • Muscles: Soft-tissue density layers between ribs

  • Neurovascular bundle: Usually not individually resolved

  • Pleura: Thin soft-tissue interface deep to the space

CT lung window:

  • Intercostal space: Appears as a boundary between lung parenchyma and chest wall

  • Lung parenchyma: Air-filled, low attenuation

  • Pleural surface: Sharp interface with chest wall

  • Utility: Helpful for assessing pleural contact, lung expansion, and chest wall–lung relationships

MRI appearance

T1-weighted images:

  • Intercostal muscles: Intermediate signal intensity

  • Fat in neurovascular plane: High signal

  • Ribs: Low signal cortical bone

T2-weighted images:

  • Muscles: Intermediate signal

  • Neurovascular fat plane: High signal

  • Pleura: Thin low-signal line

STIR:

  • Muscles: Intermediate signal with fat suppression

  • Fat planes: Suppressed signal

  • Useful for evaluating intercostal soft-tissue anatomy and muscle planes

X ray image

Intercostal space X ray Anatomy, Location and Imaging Appearance -img-00000-00000

CT image

Intercostal space CT Anatomy, Location and Imaging Appearance -img-00000-00000

CT image

Intercostal space CT Anatomy, Location and Imaging Appearance -img-00000-00000_00001