intramedullary

adjective

in·​tra·​med·​ul·​lary -ˈmed-ᵊl-ˌer-ē, -ˈmej-ə-ˌler-ē; -mə-ˈdəl-ə-rē 

: situated or occurring within a medulla

an intramedullary tumor of the spinal cord

especially : involving use of the marrow space of a bone for support

intramedullary pinning of a fracture of the thigh