Posterior and lateral ponticles of atlas: An osteological study at Fatima Jinnah Medical University, Lahore

Background: Among the cervical vertebrae, atlas is known to have many variations, posterior ponticle being the commonest. It may completely or incompletely covers the groove of vertebral artery leading to ischemia of posterior circulation. Therefore, vertebral artery is at greater risk of injury during neurological and spinal surgeries. Prevalence of posterior ponticles varies widely among different populations, for instance in Turkish population it was 10.8%, in American 22.1%, Kenyan 14.7%, Brazilian and Indian 16.7%. The prevalence of lateral ponticle in Kenyan population was reported to be 3.9% and in Indians it was 2%. However, the data regarding the prevalence of these ponticles is largely lacking in Pakistan. Therefore, this research was designed to determine the prevalence of posterior and lateral ponticle in atlas vertebrae of Pakistani population. Materials and methods: A total of 47 human atlas vertebrae of unknown age and gender from bone bank of Department of Anatomy Fatima Jinnah Medical University, Lahore were studied for the presence of complete and incomplete posterior and lateral ponticles. The bones studied were completely intact and did not have any pathology. Results: Total incidence of ponticles was 38 % in this study, of which 36% were posterior ponticles and 2% were lateral ponticles. Bilateral incomplete posterior ponticles/were found in 8 (17%) atlas vertebrae whereas bilateral complete posterior ponticles/foramen arcuale were found in only 1 (2%) atlas vertebrae. Unilateral incomplete posterior ponticle was identified on right side in 5 (11%) and left side in 2 (4%) atlas vertebrae. Unilateral complete posterior ponticle was found in only 1 (2%) atlas on the left side whereas no such finding was identified on right side in any vertebra. Unilateral complete lateral ponticle was found in only 1 (2%) atlas on the right side but not on left side. No bilateral complete lateral ponticle and incomplete unilateral or bilateral lateral ponticles were identified in this study. Conclusion: Presence of posterior and lateral ponticles pose a risk of vertebrobasilar vascular insufficiency and may cause variety of symptoms. Vertebral artery may be at risk during neurosurgical procedures when having a foramen arculae and may give a false impression of much wider posterior arch of atlas. Knowing the prevalence of this can help neurosurgeons, general surgeons, radiologists, and chiropractors in management of the patients.