The Prevalence and Clinical Implications of Atlantal Posterior Arch Defects: A CBCT Analysis of 500 Italian Patients

Atlas Posterior Arch Deficiency (APAD) is a rare anatomical variation of the atlas vertebra detected using cone-beam computed tomography (CBCT). This study assessed the prevalence, classification, and clinical implications of APAD in an Italian cohort. Methods: We analyzed CBCT images from 500 Italian patients (17–60 years) from the University “G. D’Annunzio” in Chieti. The sample was evenly split between genders. The sample was evenly split between genders. APAD classification was performed, identifying five morphological types. Imaging used a low-dose protocol with a Pax-Zenith 3D CBCT machine and Dolphin imaging software (12.0.9.58). Results: APAD was identified in thirteen patients—twelve with partial APAD and one with complete APAD. Two cases also had Ponticulus Posticus. Type A anomalies were most common; no cases of types B, C, D, or E were observed. None of the cases were symptomatic. Conclusions: APAD is rare in this cohort, with partial forms being the most frequent. CBCT is effective for diagnosing APAD, highlighting the importance of routine imaging in orthodontic assessments. Despite the absence of symptoms, awareness and monitoring for potential symptoms are important. Further research is needed to understand APAD’s clinical significance across different populations.