An uncinate process of a vertebra is a hook-shaped process on the lateral borders (side edges) of the superior (top) surface of the vertebral bodies of the third to the seventh cervical vertebrae

Cervical vertebrae

In vertebrates, cervical vertebrae are those vertebrae immediately inferior to the skull.Thoracic vertebrae in all mammalian species are defined as those vertebrae that also carry a pair of ribs, and lie caudal to the cervical vertebrae. Further caudally follow the lumbar vertebrae, which also...

 and first thoracic vertebra. This bony part prevents a vertebra from sliding backwards off the vertebra below it (i.e. it prevents posterior linear translation movements of the vertebral bodies) and limits lateral flexion. Luschka's joints

Luschka's joints

In anatomy, Luschka's joints are formed between uncinate processes above, and uncus below; see synovial. They are located in the cervical region of the vertebral column between C3 and C6. Two lips project upward from the superior surface of the vertebral body below, and one projects downward from...

involve the vertebral uncinate processes.