F1 facet fracture
F1 is a non-displaced facet fracture (either superior or inferior cervical facets) from the AOSpine subaxial cervical spine injury classification system. Fracture fragments are smaller than 1 cm and comprise less than 40% of the lateral mass.
There was significant variability in diagnostic accuracy for F1 facet fracture through F3-type fractures, whereas almost universal agreement was achieved for F4-type injuries 1).
1)
Cabrera JP, Yurac R, Guiroy A, Joaquim AF, Carazzo CA, Zamorano JJ, White KP, Valacco M; and the AO Spine Latin America Trauma Study Group. Accuracy and reliability of the AOSpine subaxial cervical spine injury classification system grading subaxial cervical facet injury morphology. Eur Spine J. 2021 Apr 11. doi: 10.1007/s00586-021-06837-w. Epub ahead of print. PMID: 33842992.