Thoracic Variation Flashcards
What variations can be present in the thorax?
- Bony structures (ribs, sternum, vertebrae)
- Soft tissue structures (lungs, heart, vessels, thoracic duct, nerves)
What is a supernumerary rib?
An extra rib present
How is the axial skeleton formed?
Sclerotome component of somites that create vertebral bodies
How can costal processes form a variety of structures?
Depending on local Hox gene expression
What forms the foramen transversarium?
Fusion of cervical costal processes and transverse processes and vertebral body
Costal processes of what vertebrae become ribs?
Thoracic
What happens to the costal processes at lumbar level?
Fuse with transverse processes
What forms the pars lateralis?
Sacral costal processes (flat plates)
Supernumerary ribs from the 7th cervical vertebrae affects how much of the population?
0.5% - 2%
Is supernumerary rib more common in males or females?
Females (x2)
What can a supernumerary rib cause?
- Compression of brachial plexus
- Compression of subclavian vessels
- Thoracic outlet syndrome
Why are supernumerary ribs underreported on CT scans?
- Poor visibility on scan
- CTs create artefacts
How many cases of intrathoracic rib have been reported since 1947?
40
What causes intrathoracic ribs?
- Local depression of a rib
- Supernumerary rib
- Supernumerary variant of bifid rib
Symptoms of intrathoracic rib
Asymptomatic
Could cause pain if attached to diaphragmatic pleura
