title: On the nature of facetal distraction spacers.
authors.affiliation: Department of Neurosurgery, University of Siena, Policlinico Santa Maria alle Scotte, 53100 Siena, Italy E-mail: francesco.cacciola@gmail.com.
authors.forename: Francesco
authors.initials: F
authors.lastname: Cacciola
authors.affiliation: Department of Neurosurgery, University of Siena, Policlinico Santa Maria alle Scotte, 53100 Siena, Italy E-mail: francesco.cacciola@gmail.com.
authors.forename: Laura
authors.initials: L
authors.lastname: Lippa