Introduction

The McNamara cephalometric analysis is one of the most widely recognized approaches to orthodontic diagnosis and treatment planning. Developed by James A. McNamara Jr., the analysis combines traditional cephalometric concepts with measurements designed to evaluate the actual position and size of the maxilla and mandible.

One of the main strengths of the McNamara analysis is its emphasis on linear measurements. Rather than relying primarily on angular relationships, the analysis evaluates the position and dimensions of the jaws relative to cranial and facial reference structures.

This approach can be particularly useful when assessing patients with sagittal discrepancies, vertical abnormalities, mandibular deficiency, maxillary excess, or dentofacial disharmony.

The McNamara analysis also includes measurements related to the upper airway, making it especially interesting when skeletal morphology and airway dimensions need to be considered together.

Historical Background

The McNamara analysis was developed as an alternative and complementary approach to conventional cephalometric analyses. Traditional analyses such as Steiner, Downs, and Tweed rely heavily on angular measurements and relationships between skeletal landmarks.

McNamara recognized that angular measurements can sometimes be influenced by variations in craniofacial morphology. His analysis therefore placed considerable emphasis on linear measurements and anatomical relationships.

The objective was not to replace existing cephalometric systems, but rather to provide clinicians with additional information that could improve the diagnosis of skeletal discrepancies and treatment planning.

What Does the McNamara Analysis Evaluate?

The McNamara analysis evaluates several major components of the craniofacial complex:

• Maxillary position
• Mandibular position
• Maxillary skeletal length
• Mandibular effective length
• Vertical facial relationships
• Mandibular plane orientation
• Dental relationships
• Upper airway dimensions

These measurements allow the orthodontist to determine whether a malocclusion is primarily related to skeletal position, skeletal size, dental compensation, or a combination of these factors.

The McNamara Reference System

The McNamara analysis uses several anatomical landmarks and reference lines to evaluate the sagittal and vertical relationships of the maxilla and mandible.

Important landmarks include:

• Nasion (N)
• Point A
• Point B
• Anterior Nasal Spine (ANS)
• Posterior Nasal Spine (PNS)
• Menton (Me)
• Gonion (Go)
• Condylion (Co)
• Porion (Po)
• Orbitale (Or)

The analysis is particularly dependent on accurate identification of the anatomical landmarks used to determine jaw position and effective jaw length.

Maxillary Position

One of the key measurements in the McNamara analysis is the relationship between the maxilla and the nasion perpendicular.

The horizontal position of Point A is assessed relative to a vertical reference line constructed through Nasion. This provides a linear assessment of the anteroposterior position of the maxilla.

Unlike the ANB angle, which describes the relative relationship between the maxilla and mandible, this measurement focuses more directly on the absolute position of the maxilla.

Mandibular Position

The sagittal position of the mandible is also assessed relative to the Nasion perpendicular.

The horizontal position of Point B can provide information about mandibular retrusion or protrusion. This is particularly useful when evaluating patients with Class II or Class III skeletal patterns.

A mandibular deficiency may be caused by a combination of positional and dimensional factors. McNamara therefore emphasizes not only mandibular position but also effective mandibular length.

Effective Maxillary Length

The McNamara analysis evaluates the effective length of the maxilla using a linear measurement between Condylion and Point A.

This measurement provides an estimate of the effective sagittal dimension of the maxillary component of the facial skeleton.

It is particularly useful when comparing the maxillary size with mandibular effective length. A patient may have a normal mandibular position but a relatively short mandible, or conversely, a relatively large mandible with a normal sagittal position.

Effective Mandibular Length

One of the most clinically useful aspects of the McNamara analysis is the evaluation of effective mandibular length.

This is generally measured from Condylion (Co) to Gnathion (Gn).

This measurement helps distinguish between a mandible that is short and one that is primarily positionally retruded.

This distinction can be clinically important. Two patients may have similar Class II relationships, but one may have a normally sized mandible positioned posteriorly while the other has a genuinely short mandible.

The treatment implications can be different depending on the underlying skeletal diagnosis.

Maxillomandibular Differential

McNamara also considers the relationship between effective maxillary and mandibular lengths.

The difference between Co–Gn and Co–A provides information about the relative sagittal size of the mandible and maxilla.

This is one reason the McNamara analysis can provide information that complements angular analyses such as ANB.

Vertical Assessment

The McNamara analysis also evaluates the vertical position of the anterior portion of the maxilla and the mandibular plane.

The vertical position of the maxilla can be evaluated using the relationship between Anterior Nasal Spine and the Frankfort horizontal plane.

This provides information about whether the maxilla is positioned vertically in a relatively normal position or whether there is evidence of vertical maxillary excess or deficiency.

The mandibular plane angle is also considered when assessing the vertical skeletal pattern.

Mandibular Plane Angle

The mandibular plane is commonly evaluated relative to the Frankfort horizontal plane.

This measurement provides information about the vertical facial pattern and mandibular rotation.

As with all cephalometric measurements, these values should be interpreted in relation to the patient's overall facial morphology rather than as isolated diagnostic thresholds.

Dental Measurements

The McNamara analysis does not focus exclusively on skeletal structures. Dental relationships are also evaluated to determine the degree of dentoalveolar compensation.

Important measurements include the position of the maxillary and mandibular incisors relative to their respective skeletal bases.

These measurements can help answer an important diagnostic question:

For example, a patient with a skeletal Class II relationship may have proclined mandibular incisors that partially compensate for the skeletal discrepancy. Recognizing this compensation is important before deciding on orthodontic mechanics or surgical correction.

Maxillary Incisor Position

The position of the maxillary incisors is evaluated relative to the maxillary skeletal base and the vertical reference structures.

Excessive proclination or retroclination may indicate dental compensation or contribute to the appearance of a sagittal discrepancy.

Evaluating incisor position is particularly important before treatment because orthodontic tooth movement can modify the apparent facial and skeletal relationships.

Mandibular Incisor Position

Mandibular incisor position is another important component of the analysis.

The inclination and position of the mandibular incisors can provide information about dentoalveolar compensation and the available limits for orthodontic tooth movement.

This is particularly relevant in patients with significant skeletal discrepancies, where excessive incisor compensation may limit the amount of dental camouflage that can be safely achieved.

Airway Assessment

A distinctive feature of the McNamara approach is the inclusion of measurements of the upper airway.

Two commonly evaluated regions are the nasopharyngeal and oropharyngeal airway spaces.

The airway measurements are generally taken from the posterior pharyngeal wall to the relevant anatomical structures in the sagittal plane.

McNamara Analysis and Class II Malocclusion

The McNamara analysis is particularly useful in the evaluation of Class II malocclusion.

A Class II skeletal relationship can result from several different combinations:

• Maxillary prognathism
• Mandibular retrognathia
• Short mandibular length
• A combination of maxillary and mandibular abnormalities
• Dental compensation

Traditional angular measurements may identify a Class II relationship but do not always explain its underlying anatomical cause.

By combining maxillary position, mandibular position, and effective jaw lengths, McNamara analysis can help identify which skeletal component contributes most strongly to the discrepancy.

McNamara Analysis and Class III Malocclusion

The same principle applies to Class III malocclusion.

A Class III skeletal relationship may result from maxillary deficiency, mandibular excess, or a combination of both.

Assessing effective maxillary and mandibular lengths can help differentiate between these patterns.

This distinction can be particularly important when evaluating patients for orthopedic treatment, orthodontic camouflage, or orthognathic surgery.

McNamara Analysis in Growing Patients

Linear measurements are particularly useful in growing patients because craniofacial dimensions change substantially with age.

McNamara emphasized the importance of comparing measurements with appropriate age- and sex-related reference standards.

In a growing patient, the clinician should not simply ask whether a measurement is currently outside a reference range. It is also important to consider the patient's growth potential and expected changes over time.

Serial cephalometric records can therefore provide additional information about changes in effective maxillary and mandibular lengths.

McNamara Analysis and Functional Appliances

In patients with mandibular deficiency, McNamara measurements can be useful when evaluating treatment involving functional or orthopedic appliances.

By documenting effective mandibular length and mandibular position before treatment, the orthodontist can compare subsequent records and evaluate skeletal and dental changes.

This distinction is important because treatment changes can include both skeletal adaptation and dentoalveolar compensation.

McNamara Analysis and Orthognathic Surgery

The analysis can also contribute to the assessment of patients being considered for orthognathic surgery.

Effective jaw lengths and sagittal jaw positions can help characterize the skeletal discrepancy before treatment.

In a surgical patient, the analysis should be integrated with clinical facial analysis, photographs, dental occlusion, three-dimensional imaging when appropriate, and the patient's functional and aesthetic objectives.

Cephalometric values alone should never determine the surgical plan.

Main Measurements of the McNamara Analysis

Step-by-Step Clinical Interpretation

A practical way to interpret the McNamara analysis is to follow a structured sequence.

1. Evaluate maxillary position. Determine whether the maxilla is appropriately positioned relative to the Nasion perpendicular.
2. Evaluate mandibular position. Assess the sagittal position of the mandible.
3. Evaluate maxillary length. Examine Co–A to determine the effective maxillary dimension.
4. Evaluate mandibular length. Examine Co–Gn to determine whether mandibular deficiency is positional, dimensional, or both.
5. Compare the jaw lengths. Evaluate the maxillomandibular differential.
6. Assess the vertical pattern. Examine maxillary vertical position and mandibular plane orientation.
7. Evaluate the incisors. Determine whether dental compensation is present.
8. Assess the airway when clinically indicated. Use airway measurements as complementary information rather than as an isolated diagnosis.

Advantages of the McNamara Analysis

• Strong emphasis on linear skeletal measurements
• Useful assessment of effective jaw length
• Helps differentiate skeletal size from skeletal position
• Useful for growing patients
• Provides information about vertical facial relationships
• Includes complementary airway measurements
• Can be combined with other cephalometric analyses
• Useful for orthodontic and orthognathic treatment planning

Limitations of the McNamara Analysis

Like all cephalometric systems, the McNamara analysis has limitations.

• Cephalometric radiographs provide a two-dimensional representation of three-dimensional anatomy.
• Landmark identification can introduce measurement error.
• Reference values vary with age, sex, ethnicity, and population.
• Linear measurements are affected by the magnification and imaging characteristics of the radiograph.
• Airway measurements on lateral cephalograms provide only a limited two-dimensional assessment of a complex three-dimensional structure.
• The analysis cannot replace clinical examination and comprehensive facial analysis.

For these reasons, McNamara measurements should be interpreted as part of a broader diagnostic process rather than as absolute treatment thresholds.

McNamara Analysis in Digital Orthodontics

Digital orthodontic software can significantly simplify the process of performing a McNamara analysis.

Once the relevant landmarks have been identified, software can automatically calculate linear measurements, angular measurements, jaw-length differentials, and airway dimensions.

AI-assisted landmark detection can further reduce the time required for manual tracing.

McNamara Compared with Other Cephalometric Analyses

McNamara is particularly useful when combined with other classical cephalometric systems.

Rather than choosing a single analysis, clinicians can use complementary measurements from several systems to obtain a more complete understanding of the patient's craniofacial morphology.

Clinical Example: A Class II Patient

Consider a growing patient presenting with a Class II molar and canine relationship and increased overjet.

A conventional analysis may demonstrate an increased ANB angle. However, this finding alone does not determine the underlying cause of the Class II relationship.

The McNamara analysis can then be used to evaluate:

• The sagittal position of the maxilla
• The sagittal position of the mandible
• Effective maxillary length
• Effective mandibular length
• The maxillomandibular differential
• Vertical facial relationships
• Incisor compensation

The resulting diagnosis may show that the patient has a relatively normal maxilla but a short and retruded mandible. Alternatively, the primary discrepancy may be maxillary, or the patient may have a combination of both.

This additional information can improve treatment planning and help determine whether orthopedic, orthodontic, or surgical approaches should be considered.

Why Effective Jaw Length Matters

One of the most important concepts in the McNamara analysis is the distinction between position and size.

A mandible can be located posteriorly because it is short, because it is positioned posteriorly despite having an adequate length, or because both conditions are present.

These different anatomical situations can produce a similar clinical Class II appearance.

Effective jaw-length measurements therefore provide a valuable additional perspective on the diagnosis.

This distinction is central to the clinical value of the McNamara approach.

Key Clinical Takeaways

Conclusion

The McNamara cephalometric analysis provides a comprehensive framework for evaluating skeletal and dental relationships in orthodontic patients.

Its major strength is the use of linear measurements to assess both the position and effective size of the maxilla and mandible. This allows clinicians to distinguish between positional discrepancies and dimensional discrepancies that may appear similar clinically.

The analysis is particularly valuable in Class II and Class III malocclusions, growing patients, vertical skeletal discrepancies, and cases where treatment planning requires a detailed understanding of jaw dimensions.

The inclusion of airway measurements adds another useful dimension to the analysis, although these measurements should be interpreted cautiously and should not be considered a substitute for a dedicated airway assessment when clinically indicated.

In modern orthodontics, McNamara analysis can be integrated with other cephalometric systems such as Steiner, Tweed, Downs, and Jarabak to create a more complete diagnostic picture.

Ultimately, the value of cephalometric analysis does not come from a single number. It comes from understanding how multiple measurements interact to explain the patient's individual craniofacial morphology and guide treatment planning.

References

1. McNamara JA Jr. A method of cephalometric evaluation. American Journal of Orthodontics. 1984;86(6):449–469.
2. McNamara JA Jr. Components of Class II malocclusion in children 8–10 years of age. Angle Orthodontist.
3. McNamara JA Jr, Brudon WL. Orthodontic and Orthopedic Treatment in the Mixed Dentition. Needham Press.
4. Proffit WR, Fields HW, Larson B, Sarver DM. Contemporary Orthodontics. Elsevier.
5. Jacobson A. Radiographic Cephalometry: From Basics to 3-D Imaging. Quintessence Publishing.