Genioplasty
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Direct answer
Genioplasty is surgical reshaping of the chin by an osteotomy through the mandibular symphysis, performed entirely through an intraoral vestibular incision. The classic advancement genioplasty cuts a horizontal sliding osteotomy at least 4-5 mm below the root apices and the mental foramina, and moves the chin segment forward (commonly 6-10 mm), fixing it with plates or wires; the same access allows reduction, setback, centre-shift or vertical changes with wedge grafts and steps. Because the segment carries only the genial musculature and the skin pedicle, its blood supply is robust, but the mental nerves must be protected and lower incisor apices avoided. Altered chin sensation is the commonest complication, and detached genial muscles reattach to hold the new position.
What you must remember
- The safe osteotomy: horizontal cut placed at least 4-5 mm below the root apices of the lower incisors (commonly around 10-12 mm below the incisal edge... measured on a lateral cephalogram pre-operatively) and below the level of the mental foramina laterally, stepped down to protect the nerve as it exits.
- Types by movement: advancement, reduction (inferior border resection or down-fracture with bony reduction), setback, centre-shift for asymmetry, vertical lengthening with interpositional graft, and vertical shortening with a wedge osteotomy.
- Fixation: titanium miniplates (often prebent genioplasty plates), lag screws, or historical wire fixation; rigid fixation permits earlier mobilisation.
- Blood supply logic: the segment survives on the lingual soft-tissue pedicle (genioglossus, geniohyoid) after buccal periosteum is stripped — a textbook demonstration that jaw segments live on their lingual or muscular pedicle.
- Muscle matters: the genial tubercles with genioglossus attachment travel with the fragment in an advancement, cited in sleep-surgery discussions (genioglossus advancement); mentalis muscle resuspension during closure prevents chin ptosis and witch's chin.
- Complications list: altered sensation of the lower lip and chin (commonest, usually transient), tooth devitalisation, asymmetry, ptosis of the chin pad, plate exposure, and relapse without fixation.
- Soft tissue response: chin soft tissue follows hard tissue advancement by roughly a similar order (commonly quoted about 1:1 in the midrange for genioplasty), less predictable at large movements.
Advancing a receded chin step by step
A 22-year-old with a Class I occlusion but a deficient chin requests profile improvement; orthodontics alone will not help, and bimaxillary surgery is disproportionate to the deformity. Cephalometric planning marks the osteotomy on a tracing: a horizontal line from canine to canine at least 5 mm below the incisor apices, dropping bilaterally below the mental foramina. Under nasally administered hypotensive anaesthesia, a vestibular incision is made 10-15 mm labial to the depth of the sulcus, leaving free gingiva intact; the mentalis muscle is incised obliquely and the symphysis exposed subperiosteally only far enough — the buccal periosteum is stripped, but the segment's lingual muscle pedicle is never disturbed. A fissure bur scores the outer cortex and the osteotomy is completed with copious irrigation, avoiding apices and nerves; the segment is down-fractured and mobilised with the pedicle intact, advanced 8 mm, and fixed with a prebent plate. The edges can be smoothed, and if the patient needed vertical shortening, a second horizontal cut would remove a wedge. The mentalis is carefully resuspended to prevent pad ptosis, and a pressure dressing limits oedema and haematoma. Sensation is documented at review: transient hypoaesthesia for weeks is usual, and the patient was told so before surgery.
Where the viva digs
The examiner's first dig is the number: "how far below the apices?" — 4-5 mm minimum, and the mental nerve is protected by dropping the lateral end of the cut inferiorly, since the nerve exits the foramen and runs forward. The second dig is blood supply: candidates who strip both buccal and lingual soft tissue in their description have devascularised the chin segment in front of the examiner. The third is the differential question — genioplasty versus implant augmentation versus orthognathic advancement — where genioplasty suits isolated chin deficiency with normal occlusion, and implants suit smaller augmentations in patients declining osteotomy. Indian boards often close with the witch's chin: mentalis resuspension and layered closure are the operative answers, and the phrase "ptosis of the chin pad" earns the mark.
Frequently asked questions
Where is the osteotomy placed in genioplasty?
In a horizontal line at least 4-5 mm below the lower incisor apices, sloping below the mental foramina laterally to guard the nerve.
What movements can a genioplasty achieve?
Advancement, setback, reduction, vertical lengthening or shortening, and centre-shift for asymmetry — all through the same intraoral access.
Why does the osteotomised chin segment survive?
Its lingual muscular pedicle (genioglossus, geniohyoid) supplies it after buccal periosteal stripping, a robust intraosseous-free blood supply.
What is the commonest complication of genioplasty?
Altered sensation of the lower lip and chin from neuropraxia or injury near the mental nerves, usually transient but discussed in consent.
How is chin pad ptosis prevented?
By careful resuspension of the mentalis muscle and a two-layer vestibular closure, avoiding an incision placed too close to the free gingiva.