Topics

Topic

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First rib

The first rib is the shortest, broadest, and most curved of the twelve ribs, situated at the apex of the thoracic cage. It articulates posteriorly with the T1 vertebra at the costovertebral and costotransverse joints, and anteriorly with the manubrium of the sternum via its costal cartilage. Its superior surface features grooves for the subclavian artery and vein, and the scalene tubercle, which serves as an attachment for the anterior scalene muscle, is located on its superior medial aspect. The first rib plays a crucial role in supporting the thoracic inlet, stabilizing the upper thorax, and serving as a site for muscular and neurovascular attachments.

Synonyms

  • Rib I

  • Superior rib

  • First thoracic rib

Function

  • Forms the superior boundary of the thoracic cage

  • Provides attachment for scalene muscles and ligamentous structures

  • Supports the thoracic inlet and upper limb neurovascular structures

  • Protects vital structures such as the subclavian artery, vein, and brachial plexus

MRI Appearance
T1-weighted images:

  • Appears as a hypointense linear structure relative to surrounding soft tissues

  • Cortical bone is very low signal, while the bone marrow shows intermediate signal

  • Surrounding muscles appear intermediate signal, and subcutaneous fat is hyperintense, providing natural contrast

  • Fractures or marrow lesions may appear as disruption of low-signal cortex or abnormal marrow signal

T2-weighted images:

  • Cortical bone remains hypointense, marrow is intermediate to hyperintense depending on fat content

  • Edema, infection, or neoplastic infiltration in marrow appears bright hyperintense, making pathology conspicuous

  • Adjacent soft tissues and vessels are distinguishable by contrast with bone

STIR (Short Tau Inversion Recovery):

  • Fat suppression highlights bone marrow edema or soft tissue pathology

  • Normal bone cortex remains hypointense, while marrow edema or fracture-associated hemorrhage is bright hyperintense

  • Soft tissue inflammation in adjacent muscles or pleura is also well visualized

CT Appearance

  • Cortical bone of the first rib is hyperdense, clearly outlining its curvature and articulations

  • Medullary cavity shows soft tissue density, distinguishable from the hyperdense cortex

  • Surrounding air in the lungs appears hypodense, providing natural contrast to the rib

  • CT is ideal for assessing fractures, congenital anomalies, bony lesions, and thoracic inlet morphology

  • Superior surface grooves for subclavian vessels and the scalene tubercle can be visualized on high-resolution scans

MRI images

First rib mri axial image -img-00000-00000