The (absent) pedicle sign, also called the winking owl sign, occurs on plain x ray film when a pedicle is absent.

The term, winking owl sign, where the missing pedicle corresponds to the closed eye, the contralateral pedicle to the other open eye, and the spinous process to the beak of the animal AP views of the thoracic or lumbar spine

destroyed pedicle

spinal epidural metastases

intraspinal malignancies

tuberculosis and other infections

uncommon: primary bone lesion; lymphoma

congenital absence/hypoplasia of a pedicle

neurofibromatosis

poorly visualised

radiation therapy