Lumbar Intervertebral Foramina 
The boundaries of the lumbar intervertebral foramina are:

Inferior body of the vertebra above
Intervertebral disc
Superior edge of the pedicle below
Anterior surface of the facet joint and adjacent lamina of vertebra above
Inferior edge of the pedicle above

Disease in the region of the intervertebral foramen can cause compression on the emerging nerve root.  The root can also be compressed at different sites along its path.  Presentation of cauda equina or nerve root entrapment will therefore depend on which root is compressed and where it is compressed.