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Orthognathic Surgery Impact Calculator

Predict soft tissue changes and airway impact from planned jaw surgery movements (Le Fort I, BSSO, genioplasty).

About this calculator

This calculator translates planned hard-tissue (bony) movements from an orthognathic surgery plan into predicted soft-tissue changes, using the hard-to-soft-tissue prediction ratios cited in Proffit & Fields' Contemporary Orthodontics and Wolford's soft-tissue prediction work. Maxillary advancement or setback (Le Fort I) is entered separately from maxillary vertical impaction, mandibular advancement or setback (BSSO), and genioplasty movement in both the horizontal and vertical planes, because each bony movement follows a different soft-tissue response ratio -- the upper lip follows roughly 70% of maxillary anteroposterior movement, the lower lip and chin follow mandibular and genioplasty movement much more closely (90-100%), and posterior airway space is estimated to open by roughly 65% of a mandibular advancement. The pre-surgical ANB angle is a separate, informational input: it is combined with rough SNA/SNB shift estimates from the planned movements to project a post-surgical ANB angle, but it plays no role in any of the soft-tissue or airway predictions, which come entirely from the planned bony movements themselves.

These ratios are averages from published literature, not a patient-specific simulation -- individual soft-tissue thickness, scarring from prior surgery, and muscle tension can all shift the real outcome from the prediction. This tool is meant to support patient consultation and treatment-plan discussion alongside a proper VTO (visual treatment objective), not to replace one.

Inputs

mm
mm
mm
mm
mm
deg

Results

Upper Lip Change (mm)

0

Lower Lip Change (mm)0
Soft Tissue Chin Change (mm)0
Posterior Airway Change (mm)0
Predicted Post-Surgical ANB (deg)5
Total Lower Profile Change (mm)0
Expected Recovery (weeks)0
Nasal Base Change0
Nasal Tip Change0
Upper Lip Impaction0
Soft Tissue B Change0
Chin Vertical Change0
Surgery TypeNo surgical movement planned
How to Use This Calculator
  1. Enter planned Maxillary Advancement (mm, Le Fort I anteroposterior movement) and Maxillary Impaction (mm, vertical shortening or lengthening) if a maxillary osteotomy is planned.
  2. Enter planned Mandibular Advancement (mm, BSSO anteroposterior movement) if a mandibular osteotomy is planned.
  3. Enter Genioplasty AP Movement (mm) and Genioplasty Vertical Change (mm) if a chin procedure is planned.
  4. Enter the patient's Pre-Surgical ANB Angle (deg) — this feeds only the predicted post-surgical ANB output, not the soft-tissue or airway predictions.
  5. Read soft tissue response predictions using established hard-to-soft-tissue ratios, and review the estimated Surgery Type and Recovery period.
  6. Compare surgical prediction to VTO (visual treatment objective) for treatment plan verification.

What each input means

Maxillary Advancement (mm)
Positive = advancement, negative = setback. Le Fort I movement.
Maxillary Impaction (mm)
Positive = superior impaction (shortening), negative = inferior repositioning.
Mandibular Advancement (mm)
Positive = advancement, negative = setback. BSSO movement.
Genioplasty AP Movement (mm)
Positive = chin advancement, negative = setback.
Genioplasty Vertical Change (mm)
Positive = vertical reduction, negative = lengthening.
Pre-Surgical ANB Angle (deg)
Current ANB angle before surgery.

What each result means

Upper Lip Change (mm)
Predicted upper lip anteroposterior change.
Lower Lip Change (mm)
Predicted lower lip anteroposterior change.
Soft Tissue Chin Change (mm)
Predicted chin point soft tissue movement.
Posterior Airway Change (mm)
Estimated posterior airway space change.
Predicted Post-Surgical ANB (deg)
Estimated ANB angle after surgery.
Total Lower Profile Change (mm)
Combined lower lip and chin profile change.
Expected Recovery (weeks)
Estimated initial recovery period in weeks.

How this is calculated

Worked example, using the default values

  1. Identify Input Parameters
    4 parameters
    Maxillary Advancement (mm) = 0, Maxillary Impaction (mm) = 0, Mandibular Advancement (mm) = 0, Genioplasty AP Movement (mm) = 0 = 6 input(s) provided
  2. Calculate Upper Lip Change
    Upper Lip Change
    0 = 0
  3. Calculate Lower Lip Change
    Lower Lip Change
    0 = 0
  4. Calculate Soft Tissue Chin Change
    Soft Tissue Chin Change
    0 = 0

Engine last updated . Checked against 3 independently-derived tests — how we verify calculators. Built by Paul Gunder, a software engineer, not a licensed financial, medical, or legal professional.

Frequently Asked Questions

Does the pre-surgical ANB angle affect the predicted lip and chin movement?

No -- the pre-surgical ANB angle only feeds into the predicted post-surgical ANB angle output, which estimates the resulting skeletal classification after surgery. Every soft-tissue prediction (upper lip, lower lip, chin, nasal base, airway) is calculated purely from the planned bony movement amounts, independent of the patient's starting ANB angle.

Why does the upper lip move less than the maxilla itself during Le Fort I advancement?

The soft-tissue prediction ratio used here has the upper lip following about 70% of maxillary anteroposterior advancement, reflecting that lip tissue has some independent elasticity and does not translate 1:1 with the underlying bone. The lower lip and chin, by contrast, follow mandibular and genioplasty movements much more closely (90-100%) because there is less soft tissue draping over that bony segment.

How much does a mandibular advancement improve airway space?

This calculator estimates posterior airway space increases by about 65% of the planned mandibular advancement distance -- so a 10mm BSSO advancement predicts roughly 6.5mm of airway gain. This reflects why mandibular advancement is sometimes used as a surgical option for obstructive sleep apnea, though the actual airway response varies with individual soft-palate and tongue-base anatomy.

What counts as bimaxillary surgery in the results?

Bimaxillary surgery specifically requires both a maxillary (Le Fort I) and a mandibular (BSSO) osteotomy to be planned -- genioplasty does not count as a second jaw procedure toward that label, since it is a chin osteotomy, not a maxilla-or-mandible repositioning. So Le Fort I plus genioplasty alone (with no BSSO) is classified as single-jaw surgery with a genioplasty add-on, not bimaxillary surgery; only Le Fort I plus BSSO together (with or without an added genioplasty) qualify as bimaxillary. Adding more planned procedures -- whether a second jaw or a genioplasty add-on -- does increase the estimated initial recovery period.

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