  We revisit the mechanism of vortex unpinning caused by the neutron-vortex
scattering \cite{prad1} in the inner crust of a pulsar. The strain energy
released by the crustquake is assumed to be absorbed in some part of the inner
crust and causes pair-breaking quasi-neutron excitations from the existing free
neutron superfluid in the bulk of the inner crust. The scattering of these
quasi-neutrons with the vortex core normal neutrons unpins a large number of
vortices from the thermally affected regions and results in pulsar glitches. We
consider the geometry of a cylindrical shell of the affected pinning region to
study the implications of the vortex unpinning in the context of pulsar
glitches. We find that a pulsar can release about $\sim 10^{11} - 10^{13}$
vortices by this mechanism. These numbers are equivalent to the glitch size of
orders $\sim 10^{-11} - 10^{-9}$ for Vela-like pulsars with the characteristic
age $\tau \simeq 10^4$ years. We also suggest a possibility of a vortex
avalanche triggered by the movement of the unpinned vortices. A rough estimate
of the glitch size caused by an avalanche shows an encouraging result.
