A 34-year-old man requires a chest drain for a traumatic haemothorax. The registrar explains that the drain should be passed just over the upper border of the rib below to avoid the intercostal neurovascular bundle. Between which two layers does this bundle run in the costal groove?
- A. Endothoracic fascia and parietal pleura
- B. External intercostal and internal intercostal
- C. Innermost intercostal and endothoracic fascia
- D. Internal intercostal and innermost intercostal
- E. Serratus anterior and external intercostal
Show the answer and explanation
Answer: D. Internal intercostal and innermost intercostal
The intercostal vein, artery and nerve (VAN, superior to inferior) lie in the costal groove on the inferior border of each rib, in the neurovascular plane between the internal and innermost intercostal muscles. This plane is continuous with the plane between internal oblique and transversus abdominis in the abdominal wall. Instruments should therefore pass over the upper border of the rib below; posteriorly, medial to the rib angle, the vessels may cross the middle of the space, which is another reason for lateral insertion.
Why the other options are wrong
- A. This plane lies deep to all the intercostal muscles and does not contain the main bundle.
- B. The main bundle lies deep to the internal intercostal, not superficial to it.
- C. The endothoracic fascia lies deep to the innermost layer, separating it from the pleura; the bundle is superficial to the innermost layer.
- E. This plane is outside the thoracic cage and carries only cutaneous branches.