1) Accessory Ribs
These ribs result from the development of the costal processes of
the cervical or lumbar vertebrae. Such ribs are usually rudimentary. An accessory lumbar rib is more common but is clinically in-significant because it pro-duces no symptoms. The accessory cervical rib has an incidence of 0.5 to 1% in the population. It is attached to the 7th cervical vertebra and may be unilateral or bilateral. Pressure of a cervical rib on the brachial plexus or sub clavian vessels often produces symptoms. Surgical removal of the accessory rib relieves the symptoms.