spiral ligament spiral ligament the spiral ligament is a fibrous cushion located between the stria vascularis and the bony otic capsule. spiral ligamentfloor of ductus cochlearis.detailsidentifierslatinligamentum spirale ductus cochlearismeshd055493ta98a15.3.03.099ta27030fma77834anatomical terminology the periosteum, forming the outer wall of the cochlear duct (latin: ductus cochlearis), is greatly thickened and altered in character. additional images transverse section of the cochlear duct of a fetal cat. diagrammatic longitudinal section of the cochlea.