A spinal rod having first and second end members. The end members may be flexible or rigid. An expandable intermediate section is positioned between the first and second end members. The intermediate section may be axially expandable upon the introduction of a substance into a port that may be located in either of the first and second end members or the intermediate section. The intermediate section may be expandable between a first size, where the first and second end members are spaced a first distance apart, and a second enlarged size, where the first and second end members are spaced a second greater distance apart.