Surgical and Radiologic Anatomy

, Volume 40, Issue 6, pp 653–665 | Cite as

The variable position of the inferior alveolar nerve (IAN) in the mandibular ramus: a computed tomography (CT) study

  • Andrew Y.E. Yeh
  • Brian P. Finn
  • Robert H. B. Jones
  • Alastair N. Goss
Original Article



This study was designed to quantify the important anatomical landmarks and the path of the inferior alveolar nerve (IAN) within the human mandibular body and ramus, in particular with reference to the bilateral sagittal split osteotomy (BSSO).

Materials and methods

Four hundred and eleven CT scans were studied, 299 of these were involved in determining the position of lingula; and 230 were involved in determining the course of IAN in the mandibular molar region, namely from the mesial of the mandibular first molar to the distal of the mandibular second molar; 118 were involved with both measurements.


On average, the lingula was located 17.0 ± 2.2 mm from the external oblique ridge; 11.6 ± 2.0 mm from the internal oblique ridge; 17.2 ± 2.7 mm from the sigmoid notch; and 15.6 ± 1.9 mm from the posterior border of the mandible. The course of the IAN in the mandibular molar region was found to descend vertically from the distal of the mandibular second molar (7) to reach its lowest point between the first and second molars (6 and 7), and then ascend towards the mesial of the first molar (6). Horizontally, the IAN was found to traverse medially between the distal of the 7 and the middle of the 7, and then changes its path laterally towards the mesial of the 6.


Precise knowledge of the individual’s position of the IAN will help surgical planning.


Inferior alveolar nerve (IAN) Lingula Mandibular molars Bilateral sagittal split osteotomy (BSSO) 





Deepest point of sigmoid/mandibular notch


External oblique ridge (anterior border of mandibular ramus)


Internal oblique ridge (anterior border of mandibular ramus)


Posterior border of mandibular ramus


Distance between SN and Ln


Distance between EOR and Ln


Distance between IOR and Ln


Distance between PBMR and Ln

(EOR–Ln) − (IOR–Ln)

Distance difference between EOR–Ln and IOR–Ln

Lingula ratio


Mes 6

Mesial surface of the mandibular first molar

Mid 6

Midpoint between the mesial and distal surfaces of the mandibular first molar

Int 6/7

Interproximal area between the mandibular first and second molars

Mid 7

Midpoint between the mesial and distal surfaces of the mandibular second molar

Dis 7

Distal surface of the mandibular second molar


Inferior alveolar nerve/neurovascular bundle


Inferior border of mandible


Thickness of inferior border cortex


Buccal border of mandible


Thickness of buccal cortex


Distance between IAN and IBM


Distance between IAN and BB

(IAN-IBM)-TIBC ≤ 1mm

Difference between (IAN-IBM) and TIBC ≤ 1 mm


(IAN-IBM) is equal to TIBC

(IAN-BB)-TBC ≤ 1mm

Difference between (IAN-BB) and TBC ≤ 1 mm


(IAN-BB) is equal to TBC


Author contributions

All authors provided input for the manuscript writing and discussion. Yeh: Protocol development; Data collection and management; Data analysis; Manuscript writing and editing. Finn: Protocol development; Data collection; Manuscript editing. Jones: Manuscript editing. Goss: Manuscript editing.

Compliance with ethical standards

Ethical approval

This study has ethics approval by the Human Research Ethics Committee with reference number: HREC/17/QCH/13-1114LR.

Conflict of interest

The authors declare that they have no conflict of interest.


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Copyright information

© Springer-Verlag France SAS, part of Springer Nature 2018

Authors and Affiliations

  1. 1.Woolloongabba Oral Health Centre, Metro South Oral Health ServicesQueensland HealthWoolloongabbaAustralia
  2. 2.Private Practice Oral and Maxillofacial SurgeryCairnsAustralia
  3. 3.Oral and Maxillofacial Surgery UnitThe University of AdelaideAdelaideAustralia

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