Inion Not a Reliable Landmark of the Torcula in Posterior Fossa Craniotomies

Elisha Harry Otieno, Philip Mwachaka, Paul Odula, Isaac Cheruiyot, Jeremiah Munguti
Department of Human Anatomy, University of Nairobi, Kenya.
Correspondence to: Elisha Harry Otieno; email:


Background: Sub-occipital craniotomies are used in surgical approaches into the posterior cranial fossa. The inion is used as an extracranial landmark of the torcula in burr hole placement. However, inadvertent damage to the torcula and the related sinuses due to variant intracranial location of the torcula has been reported. This study aimed at determining the position of the torcula in relation to the inion. Method: 40 adult open skulls were obtained and the positional relationship between the inion and the torcula assessed. Results: The torcula was at the same level with the inion in half of the cases (50%), below it in 12 cases (30%), and above in 8 cases (20%). The position above the inion ranged from 0.38 to 2.40 cm and below it from 0.75 to 2.45 cm. Conclusion: The torcula lies either at the level of the inion in only half of the cases. The surgeon should augment this physical landmark with radiographs to avoid iatrogenic injuries.


Keywords: Inion, Posterior fossa, Craniotomies

Ann Afr Surg. 2020;17(3):103–105


Conflicts of Interest: None

Funding: None

© 2020 Author. This work is licensed under the Creative Commons Attribution 4.0 International License

Submitted: 11 November 2019

Revised: 12 February 2020

Accepted: 6 March 2020

Online first: 29 May 2020


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