Where is the Costal Groove Located?
The costal groove is an anatomical landmark on the rib body (corpus costae). A rib consists of a head (caput costae) directed toward the vertebral column, a neck (collum costae), and its longest part, the body. The body features the costal angle (angulus costae), and the costal groove runs along the inferior border of its internal surface.
- Location — the groove runs along the inferior border of the internal surface of the rib body.
- Termination — the groove terminates at the costal crest (crista costae).
- Features of the 1st and 2nd Ribs — the 1st rib (costa prima), which is small and lies almost horizontally, has no groove on its inferior surface; the inferior surface is smooth. The costal groove is also absent on the 2nd rib (costa secunda).
- Features of Floating Ribs (11th–12th) — these ribs (costae fluctuantes) have a simpler structure: they lack a rib tubercle, the costal angle is not prominent, and the head lacks a crest. The costal groove may only be faintly visible on the 11th rib; it is generally absent on the 12th rib.
What is Associated with the Costal Groove?
The costal groove (sulcus costae) helps form the osseomuscular space of the lateral chest wall. This space is bounded by the costal groove itself, along with the internal and innermost intercostal muscles.
Deep to the sulcus costae on the internal surface of the chest wall lie the innermost intercostal muscles (mm. intercostales intimi); together with the vessels and nerve, they form the neurovascular bundle.
Topography of the intercostal neurovascular bundle from superior to inferior:
- Vein.
- Artery.
- Nerve.
Topographic Features: The intercostal nerve often extends beyond the edge of the costal groove into the intermuscular tissue. Anterior to the midaxillary line, the vessels and nerves are not protected by the ribs.
Clinical Significance in Trauma
The unique anatomy of the intercostal vessels explains the bleeding patterns seen in chest wall injuries:
- Difficult Hemostasis — the fascial sheath of the vessels is fused with the periosteum. Consequently, vessel walls cannot collapse when injured.
- Bleeding from Both Ends — anastomoses exist between the anterior and posterior intercostal arteries, forming an arterial ring.