Radiological study of foramen arcuale: implications for screw insertion via posterior arch for fixation of C1 vertebrae in atlantoaxial instability using plain radiograph

Abstract

Introduction: Foramen arcuale is an osseous structure forming a bridge from the superior articular process of the atlas that completely or partially encircles the vertebral artery. We retrospectively reviewed plain cervical radiographs as suggested by neurosurgeons, neurologists and orthopaedic surgeons for evaluation of cervical spine problems. When foramen arcuale is present, it creates a false impression of a broad posterior arch and can pose a risk during neurosurgery. The aim of this study is to investigate the prevalence of foramen arcuale in the Jalgaon & Baramati population. Materials and Methods: 1255 lateral cervical spine radiographs were obtained from the radiology department, GMC, Jalgaon & GMC Baramati. The patient of which 655 (59.04%) were males and 600(31.42%) were females. Cases were classified as an incomplete and complete bony ridge. Results: Overall prevalence of Foramen arcuale was 8.36%, with complete lesions in 3.50% and incomplete lesions in 4.86%. We noted an increasing percentage of patients with Foramen arcuale from the younger to the adolescent age group, with significantly greater prevalence in patients aged 15-30 years compared with the younger groups. Lesions were more common in males (59.04%) compared with females (31.42%), but no statistically significant difference between genders was detected for complete as well as incomplete foramen arcuale (p=0.95). Conclusion: The foramen arcuale is a relatively common osseous structural variant therefore; surgeons should consider the risk of the presence of an FA prior to procedures on the atlas in each patient. So we suggest the identification of this variant by preoperative lateral radiograph as a starting point for C1 lateral mass for screw fixation via the posterior arch for atlantoaxial instability. If foramen arcuale is suspected or confirmed on a radiograph, 3D CT scanning should be considered for variations in size and shape of foramen arcuale and the possibility of injury to the vertebral artery.

Keywords

• foramen arcuale (fa)
• vertebral artery
• atlas
• atlantoaxial instability
• lateral cervical radiograph
• lateral mass screw