Ricketts Analysis
The Ricketts analysis was developed by Dr. Robert M. Ricketts through the Rocky Mountain Data Systems project, which processed large numbers of cephalograms to identify measurements that reliably predicted facial growth and treatment outcomes. First outlined in his 1960 paper "A foundation for cephalometric communication," it grew into one of the most extensive cephalometric systems in orthodontics, with a full form spanning more than 30 measurements covering skeletal pattern, dental relationships, soft-tissue profile, and facial aesthetics.
What sets Ricketts apart from earlier analyses is its emphasis on growth prediction: many of its measurements were chosen specifically because they remain stable as a patient grows, and Ricketts was among the first to publish age-adjusted norms rather than a single fixed target for all patients.
What It Evaluates
The analysis assesses the direction and amount of facial growth (via the facial axis and related vertical measurements), the anteroposterior relationship between the jaws (via convexity), the position and angulation of the incisors relative to the chin, and the soft-tissue lip profile. Because several of its landmarks are chosen for long-term stability, it is used not only to diagnose the current relationship of the jaws and teeth but also to forecast how a patient's face is likely to grow, which is central to planning the timing and type of orthodontic or orthopedic treatment.
Learn more: Ricketts Cephalometric Analysis — Diagnostic Framework Overview
Key Measurements
- Facial Axis — the angle between the Basion-Nasion (Ba-N) cranial base line and the line from PT (pterygomaxillary point) to Gnathion, describing the direction of mandibular growth. Normal value: 90° ± 3.5°. Values above 90° indicate a forward (anterior, hypodivergent) growth rotation; values below 90° indicate a backward (posterior, hyperdivergent) growth rotation.
- Convexity — the linear distance from point A to the Nasion-Pogonion (facial plane) line, describing the anteroposterior relationship between the maxilla and mandible. Normal value: +2 mm ± 2 mm (age 9).
- Mandibular Plane Angle — the angle between the mandibular plane and the Frankfort Horizontal, describing vertical facial divergence. Normal value: 26° ± 4° (age 9).
- Lower Facial Height — the angle formed by ANS-Xi-Pm, assessing the proportion of the lower face. Normal value: 47° ± 4°.
- Lower incisor protrusion (L1 to A-Pog) — the linear distance from the lower incisor edge to the A-Pogonion line, measuring how far forward the lower incisor sits over its bony base. Normal value: +1 mm ± 2 mm.
- Lower incisor inclination — the angulation of the lower incisor relative to the A-Pog line. Normal value: 22° ± 4°.
- Upper incisor to Frankfort Horizontal (U1-FH) — the angulation of the upper incisor relative to the Frankfort plane. Normal value: 111° ± 6°.
- Interincisal angle (U1-L1) — the angle between the long axes of the upper and lower incisors. Normal value: 130° ± 10°.
Learn more: Ricketts Analysis — 11-Factor Measurement Breakdown with Norms
Clinical Interpretation
The facial axis is often the first number an orthodontist checks, because unlike many measurements it changes very little with growth: a value near 90° suggests a balanced growth pattern, while a value well below 90° warns of a hyperdivergent (vertical grower) pattern that tends to resist correction and can complicate bite closure, and a value well above 90° suggests a hypodivergent (horizontal grower) pattern often associated with deep bites. Convexity is then used much like Steiner's ANB to judge the sagittal jaw relationship — a strongly positive value points toward skeletal Class II, a negative value toward skeletal Class III. Because Ricketts separates incisor position into protrusion (a linear distance) and inclination (an angle), an orthodontist can distinguish a tooth that is bodily too far forward from one that is simply tipped forward, which changes whether treatment should move the crown, the root, or both.
Learn more: Diagnostic Performance of Cephalometric Parameters for Vertical Growth Pattern Assessment