NCCT-based percentile mapping yielded reproducible thresholds for drill depth relative to the facial canal. Limiting depth to ≤15 mm at the incus, ≤11 mm at the midpoint, and ≤10 mm at the stylomastoid level provides an anatomically grounded reference that may support operative depth awareness and safer mastoid drilling, particularly when conventional landmarks are unreliable.
Jungberg et al. (Mon,) studied this question.