McNamara Analysis
The McNamara analysis was introduced by Dr. James A. McNamara Jr. in a 1984 article in the American Journal of Orthodontics, "A method of cephalometric evaluation." Its defining feature is a preference for linear (millimeter) measurements over the angular measurements used by earlier analyses such as Steiner's — a choice that makes its output more directly usable when planning tooth and jaw movements in millimeters, and more sensitive to vertical (up-down) discrepancies that angular systems can miss.
The analysis is used both in conventional orthodontics and in orthognathic (jaw) surgery planning, since it separates the position of a jaw from its size — an important distinction, because a retruded but normally sized jaw calls for a very different treatment plan than a jaw that is genuinely underdeveloped.
What It Evaluates
McNamara's method divides the craniofacial skeleton into five functional groups: the maxilla relative to the cranial base, the maxilla relative to the mandible, the mandible relative to the cranial base, the dentition (tooth position within each arch and between arches), and the pharyngeal airway. Together these evaluate skeletal jaw position and size, dental compensation, vertical facial proportions, and airway space, giving a broad picture that spans skeletal, dental, and airway health.
Learn more: McNamara Analysis — Skeletal, Dental, and Airway Relationships
Key Measurements
- A point to Nasion perpendicular — how far forward or back the maxilla sits relative to a vertical reference line dropped from Nasion, perpendicular to the Frankfort Horizontal plane. Normal range: 0 to +1 mm.
- Pogonion to Nasion perpendicular — the position of the chin relative to the same vertical reference, used to detect mandibular retrusion or protrusion. Normal range: approximately -4 to 0 mm (males), -4 to -2 mm (females).
- Effective midfacial length (Co-A) — the linear distance from Condylion to point A, representing the true length of the maxilla. Normal range: approximately 95-100 mm (males), 91-96 mm (females).
- Effective mandibular length (Co-Gn) — the linear distance from Condylion to Gnathion, representing the true length of the mandible. Normal range: approximately 125-135 mm (males), 118-128 mm (females).
- Maxillomandibular differential — the difference between mandibular and midfacial length, used to judge whether jaw growth is proportionate.
- Lower anterior facial height (ANS-Me) — the vertical distance from the anterior nasal spine to Menton, describing the lower third of facial height. Normal range: approximately 65-75 mm (males), 60-70 mm (females).
- Upper and lower pharyngeal airway — linear measurements of the airway space behind the tongue and soft palate, used to flag airway constriction relevant to breathing and growth. Normal ranges: approximately 15-20 mm (upper) and 11-14 mm (lower).
Learn more: McNamara Analysis — Nasion Perpendicular and Airway Measurements
Clinical Interpretation
Because McNamara's measurements are linear, an orthodontist can read them almost directly in terms of "how many millimeters this jaw needs to move" rather than translating an angle into a clinical distance. A short Co-A or Co-Gn value indicates a jaw that is genuinely small (a size problem), while a normal length paired with an abnormal Nasion-perpendicular value indicates a jaw of normal size that is simply positioned too far back or forward (a position problem) — these two situations call for different treatment strategies, since growth guidance helps a small jaw but does little for a retruded one. A short lower anterior facial height combined with a low mandibular plane angle suggests a deep-bite, hypodivergent pattern, while the opposite suggests a hyperdivergent, open-bite tendency. A narrow pharyngeal airway measurement is often cross-checked against the patient's breathing history and may prompt referral for airway evaluation before or alongside orthodontic treatment.
Learn more: McNamara Analysis (Cephalometric Analysis) — Video Lecture