  We analyze the effect of the phonon dynamics on a recently proposed model for
the uniform-incommensurate transition seen in TiOX compounds. The study is
based on a recently developed formalism for nonadiabatic spin-Peierls systems
based on bosonization and a mean field RPA approximation for the interchain
coupling. To reproduce the measured low temperature spin gap, a spin-phonon
coupling quite bigger than the one predicted from an adiabatic approach is
required. This high value is compatible with the renormalization of the phonons
in the high temperature phase seen in inelastic x-ray experiments. Our theory
accounts for the temperature of the incommensurate transition and the value of
the incommensurate wave vector at the transition point.
