In short. Chin projection and jaw width are two measurements of the same mandible that need two different operations. Projection is an anteroposterior change judged in profile against the lips and the nose; width is a transverse change judged from the front between the jaw angles. They are independent findings, and a plan can address one, the other, or both.
Key points
- Projection is judged in profile; width is judged from the front.
- Projection changes the front of the mandible; width changes the posterior part at the jaw angle.
- The two findings are independent and can occur in either combination.
- The wrong operation changes a face the patient was content with and leaves the complaint untouched.
- Where both are complaints, both are planned rather than substituted.
What are chin projection and jaw width measuring?
Projection is the distance the chin sits forwards relative to the rest of the face, and it is judged in profile against the lips and the nose. Width is the distance across the lower face between the angles of the jaw, and it is judged from the front. A face can be narrow in profile and wide from the front, or the reverse. The two findings are not related to one another.
The table sets the two dimensions side by side.
| Dimension | Chin projection | Jaw width |
|---|---|---|
| View used | Profile | Front view |
| Anatomical target | Front of the mandible | Posterior mandible at the jaw angle |
| What is measured | How far the chin sits forwards, against the lips and nose | Distance across the lower face between the two angles |
| What the operation changes | The profile | The width of the lower face |
| What it leaves unchanged | Width between the angles | How far the chin projects |
| Independence | A narrow profile can sit on a wide front view, or the reverse | The same finding, read from the other view |
| Effect of the wrong choice | Profile changes, width complaint untouched | Width changes, profile complaint untouched |
Where does the confusion come from?
Because both are described with the same words. A patient who says her jaw looks heavy may mean that the chin is weak in profile, which makes the lower face look long, or that the jaw angle is wide from the front, which makes the lower face look broad. The two produce different impressions and completely different operations. The examination exists to establish which finding is present, not to decide which operation to perform. Treating them as one subject is the most common planning error in this area.
Each operation changes one dimension
Chin projection is changed by operating on the front of the mandible. Jaw width is changed by operating on the posterior mandible at the jaw angle, which is a different part of the same bone. Each operation does what it was designed to do, and neither substitutes for the other, because each changes one dimension and leaves the other as it was. Reducing the jaw can make the lower face read as narrower, which sometimes changes how the chin appears, but it does not change how far the chin projects.
The wrong operation is not neutral
Narrowing a jaw that was not the complaint changes a face the patient was content with from the front, and does nothing about the profile she was unhappy with. Adding projection to a chin that was not the complaint changes the profile without touching the width. In both cases the operation does what it was designed to do and the patient's actual concern is untouched. Treating the other area also adds operating time and healing for a change the patient did not ask for.
Can one operation change both?
It can, and that is a plan rather than a single operation. The chin and the posterior mandible are different parts of the same bone, they are measured differently, and one can be treated without the other. Where both are complaints, both are addressed. Where only one is, treating the other adds operating time and healing for a change the patient did not ask for. The planning order follows the assessment: establish which view bothers the patient and what about it, then treat the parts that correspond to the findings.
How do you tell which one is your complaint?
Take a profile photograph and a front photograph at the same distance in the same light. Look at the profile and ask whether the chin itself is what you would change. Then look at the front and ask whether the width between the jaw angles is what you would change. Patients who do this frequently find that only one of the two is actually their complaint, and that is the decision the operation depends on. Patients also frequently arrive complaining of one and caring about the other, which is worth establishing before an operation rather than after it. The useful thing to carry into an assessment is which view bothers you and what about it. A patient who can say that gets a plan built from two measurements rather than from an impression of the whole lower face.
When should the plan be questioned?
- An operation is proposed without the profile and the front view being assessed separately.
- Narrowing the jaw is offered as the answer to a chin that looks weak in profile.
- A single measurement is used to describe a face that reads differently in the two views.
Any of these suggests that the two have been confused. The assessment should separate the views before it proposes an operation.
Sources
- NICE — guidance on cosmetic surgery
- British Association of Plastic, Reconstructive and Aesthetic Surgeons (BAPRAS) — patient information on facial surgery
- Chinese Medical Association Plastic Surgery Branch — clinical guidance on mandibular contouring
Internal links
Frequently asked questions
Can one operation change both the profile and the width?
It can, and that is a plan rather than a single operation. The chin and the posterior mandible are different parts of the same bone, they are measured differently, and one can be treated without the other. Where both are complaints, both are addressed; where only one is, treating the other adds operating time and healing for a change the patient did not ask for.
How do I tell which one is my complaint?
Look at two views rather than one. In profile, the question is how far the chin projects relative to the lips and the nose. From the front, the question is how wide the lower face reads between the two angles of the jaw. Patients frequently arrive complaining of one and caring about the other, which is worth establishing before an operation rather than after it.
Does reducing the jaw make the chin look smaller?
It can make the lower face read as narrower, which sometimes changes how the chin appears, and it does not change how far the chin projects. Where the complaint is that the chin looks weak in profile, narrowing the jaw does not address it. The two measurements are independent, and the plan is built from both of them rather than from the impression of the whole.
Risks & Limitations
- Removing bone is easier than restoring it. Over-reduction is difficult and sometimes impossible to correct, so the amount removed is decided from imaging and treated as fixed.
- The marginal mandibular nerve, which moves the lower lip, runs through the operative field. Weakness after surgery is usually temporary and usually resolves over weeks to months; a lasting weakness is uncommon but possible.
- Swelling hides the result for months. The face reads unevenly at two weeks, is not close to final until around six months, and is judged honestly at around a year.
- Numbness of the chin and the lower lip is expected, is watched rather than treated in the early weeks, and may not return fully in some areas.
- The two sides of a jaw are rarely identical, and reducing both by the same amount can make a pre-existing difference more visible.
- The operation changes width and the border between the jaw angle and the chin. It does not lengthen the face, correct a bite, or change the soft tissue over the new contour.
When to Seek Care
- Swelling that is increasing rather than settling after the first week, or that is much greater on one side — contact the team.
- A wound that is opening, or discharge, spreading redness or warmth around an incision.
- A weakness of the lower lip that is worsening rather than improving, or difficulty breathing or swallowing &mdash — seek emergency care at once.
- Fever, or feeling generally very unwell with a wound or a swollen area.
- Calf pain, swelling or tenderness in one leg, or shortness of breath or chest pain &mdash — seek emergency care at once.
References & Further Reading
- American Society of Plastic Surgeons (ASPS) - facial bone contouring and patient safety guidance
- National Institute for Health and Care Excellence (NICE, UK) - guidance on facial surgery and on venous thromboembolism prevention
- Cochrane Library - systematic reviews in oral and maxillofacial surgery
- British Association of Plastic, Reconstructive and Aesthetic Surgeons (BAPRAS) - patient information on facial surgery
- Chinese Medical Association Plastic Surgery Branch - clinical guidance
This page is patient education, not medical advice, and it does not cite individual studies. Discuss your own case with a qualified clinician. To arrange an assessment at Chongqing West District Hospital, see Contact & Consultation.