Shimizu T, et al. - Authors evaluated the incidence of anterior arch fracture (AAF) of the atlas following C1 (first cervical vertebra) laminectomy without fusion, and its risk factors. As per the data, following C1 laminectomy without fusion, the incidence of AAF was not uncommon. The patients at high risk of AAF could be identified by the preoperative assessment using CT. For AAF, the independent risk factors were a large inferior facet angle (IFA, defined as the coronal inclination angle of the C1/2 facet as measured on CT) and the presence of subaxial ankylosis (bony ankylosis below C2 on CT). No significant differences were seen in the subaxial cervical balance as measured on x-ray between the AAF and non-AAF groups.