Segner-Hasund Analysis

The Segner-Hasund Analysis (also known as the Hasund Analysis, part of the "Bergen Technique" or "Individualized Cephalometrics") is a European cephalometric method developed by Prof. Asbjørn Hasund at the University of Bergen, first presented in 1974, and later refined together with Dietmar Segner. Unlike analyses that compare a patient to a single fixed set of "normal" values, its core innovation is the harmony box: a graphical tool that evaluates whether a patient's measurements are internally consistent with one another, even if each individual value falls outside the textbook average.

Its clinical purpose is to classify the sagittal (prognathic/orthognathic/retrognathic) and vertical facial pattern of a patient while accounting for the natural correlations between skeletal measurements — so a patient with a slightly large SNA is not penalized as "abnormal" if their other values shift proportionally in the expected direction.

What It Evaluates

The analysis traces bony and soft-tissue reference points on the lateral cephalogram and derives a set of angular measurements describing the sagittal position of the maxilla and mandible relative to the cranial base, and the vertical inclination of the jaw and palatal planes. Instead of judging each angle in isolation against a population average, Segner and Hasund built statistical regression relationships between the measurements: given a patient's SNA, the "expected" (harmonious) values for the other angles can be predicted, and the patient's actual values are then compared to that individualized prediction rather than to a fixed population mean.

Learn more: Floating norms for individualising the ANB angle and the WITS appraisal in orthodontic cephalometric analysis based on guiding variables (PMC)

Key Measurements

  • SNA — Angle from Sella to Nasion to Point A; anteroposterior position of the maxilla relative to the cranial base. Typical range approximately 80.5°–84°.
  • SNB — Angle from Sella to Nasion to Point B; anteroposterior position of the mandible relative to the cranial base. Typical range approximately 79°–82.5°.
  • NSBa — Angle describing the cranial base flexure (Nasion-Sella-Basion); used as a correction factor since a steep or flat cranial base can shift SNA/SNB readings independent of true jaw position.
  • NL-NSL — Angle between the palatal plane (NL) and the anterior cranial base (NSL); describes maxillary vertical inclination.
  • ML-NSL — Angle between the mandibular plane (ML) and the anterior cranial base (NSL); describes mandibular vertical inclination (a steep-mandibular-plane indicator). Typical range approximately 24°–33°.
  • Harmony Box — Not a single angle but a graphical construct plotting SNB, NL-NSL, ML-NSL, and NSBa as functions of SNA (used as the independent reference variable), with shaded bands showing the statistically expected ("harmonious") range for each dependent measurement.

Learn more: Craniofacial Cephalometric Morphology in Polish Adolescents with Cleft Palate Only (PMC) — applies the Segner and Hasund cephalometric variables (SNA, SNB, NSBa, NL-NSL, ML-NSL)

Clinical Interpretation

An orthodontist plots the patient's SNA value first, then checks whether SNB, NL-NSL, ML-NSL, and NSBa fall inside their corresponding harmony bands for that SNA. If all measurements fall within their bands, the facial pattern is considered internally harmonious even if some individual values are outside the population average — meaning the patient's skeletal proportions are self-consistent and growth or treatment mechanics can generally proceed with standard expectations. If one or more measurements fall outside their band, that signals a true disharmony (for example, a mandible that is disproportionately retrognathic even after accounting for a naturally large SNA), which flags a case as more skeletally complex and may prompt consideration of growth modification, camouflage, or surgical planning. This approach is especially valued in orthognathic surgery planning and in evaluating post-surgical stability, since it isolates genuine skeletal imbalance from normal individual variation.

Learn more: Floating norms as a means to describe individual skeletal patterns — D. Segner, European Journal of Orthodontics (PubMed)

References