In short. The two sides are measured and planned separately, before and after the operation. Why swelling reads as asymmetry, and what a genuine difference means.
Key points
- The swelling after an angle reduction does not resolve at the same rate on the two sides, so one side of the face usually reads wider than the other for months.
- That is expected and it is not a result.
- A difference that is still present once the swelling has gone, judged from comparable photographs at around six to twelve months, is the only kind worth acting on.
Nobody has two identical sides of the jaw, and an angle reduction is planned on both of them. The operation is therefore not one decision applied twice. Each side is measured, each side has its own limit set by where the canal runs, and each side is reduced by an amount chosen for it. A plan that removes the same amount from both is the commonest way a difference that was never noticed becomes visible.
Before the operation
Facial asymmetry is normal and mostly goes unnoticed until it is measured. Imaging shows differences between the two sides that an examination cannot, and clinical photographs taken from the front, at rest and on movement, record what the eye reads. Both are used to decide whether the two sides are treated the same way or differently, and that decision is written into the plan rather than left to the operating theatre. The purpose of measuring is not to find a fault but to avoid creating one, because this operation removes bone and cannot add it.
Swelling is uneven, and that is not asymmetry
The swelling after an angle reduction does not resolve at the same rate on the two sides, so one side of the face usually reads wider than the other for months. That is expected and it is not a result. A difference that is still present once the swelling has gone, judged from comparable photographs at around six to twelve months, is the only kind worth acting on.
After the operation
The assessment of the two sides is repeated afterwards with the same tools: photographs taken at the same distance in the same light, at rest and on movement. Comparing them with the pre-operative set is what separates a difference that was always there from one the operation produced. Judging the two sides in a mirror, at different times of day, is not a comparison at all.
What can be done about a real difference
Where a genuine difference persists, the easier correction is usually a small further reduction on the wider side. Adding to the narrower side is the more difficult direction, because material placed on bone does not behave like the bone that was reduced, and it cannot reproduce a contour that was removed. It is planned from the same measurements as the first operation, and only after the shape has settled.
What is worth raising with the team
- A difference that is still present after the swelling has settled, rather than one that changes week to week.
- A difference that was not present before the operation, confirmed against your own earlier photographs.
- A difference with pain, a new click, or a change in how the teeth meet, which are assessed rather than watched.
Symmetry in the mathematical sense is not achievable and is not the aim. The aim is a difference small enough not to be read in ordinary life, which is a different and more honest target.
Frequently asked questions
Should I ask for both sides of my jaw to be reduced by the same amount?
No, and a plan that proposes it without measuring both sides separately is built on an assumption. Most faces differ slightly from left to right to begin with, and reducing both by an identical amount can make a difference that was never noticed more visible. Each side has its own measurement and its own limit set by where the canal runs.
How long after surgery can asymmetry be judged rather than guessed at?
Until the swelling has settled, which is around six months, and honestly at a year. Swelling resolves at different rates on the two sides of the same face, so one side can read wider for months in a face that is not asymmetrical at all. A difference assessed before that point is being assessed through swelling.
Can the narrower side be built up instead of reducing the wider one?
It can be attempted and it is the more difficult direction. Material placed on bone does not behave like the mandible it replaces and cannot reproduce a contour that was removed, whereas taking a little more bone from the wider side is a smaller operation on a shape that is already known. That imbalance is the reason this operation is planned conservatively in the first place.
Risks & Limitations
- The change is permanent and the amount removed is treated as fixed. Bone that has been taken away cannot be put back, and material added later does not behave like the mandible it replaces.
- The canal carrying the nerve to the chin runs inside the bone being cut. Numbness of the chin and lower lip is expected rather than rare, usually improves over months, and may not return fully.
- The nerve that moves the lower lip runs near the outer surface of the bone. Weakness after surgery is usually temporary and usually resolves; a lasting weakness is uncommon but possible.
- The vessels supplying the face run close to the surface of the angle. Bleeding afterwards is the complication this operation most wants to avoid, because a collection of blood in the floor of the mouth can compromise the airway.
- The masseter is detached from the bone it was attached to and reattaches. Width can partly return if the muscle thickens again, which is not the bone growing back.
- Swelling hides the result for months. The face reads wider than expected at two weeks, unevenly at three months, and the result is judged honestly at around a year.
When to Seek Care
- Difficulty breathing, a feeling of pressure or swelling in the floor of the mouth, or difficulty swallowing. Seek emergency care at once.
- Swelling that is increasing rather than settling after the first week, or that is much greater on one side. Contact the team.
- Weakness of the lower lip that appears after the first week, or that is worsening rather than improving.
- Numbness that is spreading rather than staying stable, or a wound in the mouth that is opening or discharging.
- Fever, or feeling generally unwell with a swollen and tender jaw. Calf pain or swelling in one leg, or chest pain and shortness of breath, need emergency care at once.
References & Further Reading
- American Society of Plastic Surgeons (ASPS) — procedure and safety guidance
- National Institute for Health and Care Excellence (NICE, UK) — relevant guidance
- Cochrane Library — systematic reviews
- 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.