Atlanto-occipital gap in Nigerians: Its relationship to difficult intubation

Abstract

Background: The vertical distance between the occiput of the skull and the superior surface of the posterior tubercle of the atlas is referred to as the Atlanto-Occipital Gap (AOG). The AOG is one of the major factors that limit extension of the head on the neck and it varies widely in the population at large. The mean Atlanto-Occipital Gap (AOG) is not known yet a short AOG may be the sole or part of the cause of difficult or failed intubation.
Aim: To determine the normal values of the Atlanto-Occipital Gap (AOG) in Nigerians and determine its relationship to difficult intubation.
Methods: The atlanto-occipital gap (AOG) was investigated radiographically in 2 patients in whom intubation was unsuccessful and in 40 control patients (27 males, 13 females) who underwent successful intubation during surgery.
Results: The mean AOG in the control group was found to be 9.96 mm ± 3.10 for males and 6.20 mm ± 3.10 for females. In the two female patients in whom intubation was impossible, the mean AOG was found to be 5 mm ± 2.00. When A O G is calculated without reference to sexes, the AOG for Nigerians is 8.75 mm ± 3.90. The difference between the A O G of males and females was found to be significant (p< 0.05). Similarly, the difference between the AOG of the control group and those who could not be intubated was significant (p< 0.05). The AOG was also significantly higher in the female control group than in the female patients that could not be intubated (p< 0.05).
Conclusion: Our investigation has revealed that AOG varied widely in the Nigerian population and this variation is more marked in males than in females. Secondly, from our findings a short AOG is strongly linked to difficult intubation and Nigerian females with shorter AOG will be prone to difficult intubation than their male counterparts. We conclude that AOG is a predictive variable in difficult intubation and its pre-operative assessment will be of immense use to the anaesthesiologist and the surgeon.


Port Harcourt Medical Journal Vol. 1(1) September 2006: 48-51