The safe zones for pin placement are located circumferentially around the whole continuity of the mandible along the lower and posterior borders and the condylar processes. There is one zone in the subcondylar neck that is crossed by the facial nerve trunk in an anterior-posterior direction which represents a high-risk zone for nerve injury. Therefore, this area should be avoided.
The condylar process itself can be used for K-wires outside the joint capsule. The posterior border of the ramus and the bone in the lower border of the outer angle region have the thinnest cross section of the whole safe zone but the intrabony nerve structures are running in a curvature located superiorly and medially.
The mandibular canal containing the inferior alveolar nerve limits the vertical height of the safe zone cranially in the mandibular body and angle.
The vicinity of the mental foramen should be avoided due to variances in the course of the mandibular canal next to the bony opening.
In the symphyseal area although there is a tiny continuation of the mandibular canal (incisal canal) the whole bone stock beneath the tooth apices is available for pin placement.
2. Bony cross sections and intraosseous structures
Mandibular canal/inferior alveolar nerve/no man’s land
See also: Heibel H, Alt KW, Wächter R, Bähr W. (2001) Cortical thickness of the mandible with special reference to miniplate osteosynthesis. Morphometric analysis of autopsy material Mund Kiefer Gesichtschir; 5(3):180-5.