Pseudosubluxation
From Radipedia
Cervical spine injuries are uncommon in children. Can have anterior displacement of C2 on C3 due to normal ligamentous laxity. Occurs in 25% of kids under 8 years at C2-3, normal up to 3 mm with the posterior line maintained (15% of kids at C3-4).
Pseudosubluxation only occurs with a straightening of normal cervical lordosis.
Subluxation with normal lordosis is pathologic until proven otherwise.