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Genioplasty overview
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GENIOPLASTY
DR MOHAMMED HANEEF
Introduction and History Pre-operative evaluation and facial
analysis Implant materials and sizing Implantation technique Complications
IntroductionMultiple factors contribute to the
aesthetically pleasing face○ Skin
TextureColorThickness
○ Soft tissueComposition, location
○ Bony contoursSize, shape, location, and symmetry
○ Cultural norms
CLASSIFICATION OF CHIN DEFORMITIES
Class I macrogenia a. Horizontal b. Vertical c. Combination of both Class II microgenia a. Horizontal b. Vertical c. Combination of both Class III combined a. horizontal macrogenia with vertical microgenia b. horizontal microgenia with vertical macrogenia
Class IV assymmetric chin a. Short anterior facial height b. Normal anterior facial height c. Long anterior facial height Class V Witch’s chin(soft tissue
ptosis) Class VI pseudomacrogenia Class VII pseudomicrogenia
PREOPERATIVE EVALUATION
Lip position, shape Depth of labio mental fold Soft tissue around chin Mentalis muscle activity Cephalometric evaluation downs analysis steiners analysis tweeds analysis
SOFT TISSUE EVALUATION Gonzalez – Uloa & Steven’s
analysis A line is dropped from the soft
tissue Nasion perpendicular to frankfort horizontal plane
This line is called zero meridean Ideally Soft tissue pogonian of the
chin should be at or just posterior to the zero meridean
HISTORY OF GENIAL PROCEDURES
Hofer in 1942 described horizontal sliding osteotomy
Trauner & Obwegesser in 1957 horizontal sliding osteotomy with intraoral incision
Reichenbach in 1965 wedge osteotomy & vertical shortening of chin
Advanced sliding genioplasty
Chin Augmentation Often an adjunct
to rhinoplasty Particularly
important in creating an aesthetic profile
Horizontal osteotomy with advancement Incision half way the depth of vestibule
and extended to canine region bilaterally.
Periosteum left intact on the inferior border
Line of osteotomy should be 5 mm below canine root & 10 to 15 mm above the inferior border & 5 mm below the lowest mental foramen
Fragment stabilized by unicortical or bicortical wires bone plates prebent chin plates lag screws
HORIZONTAL OSTEOTOMY WITH REDUCTION
Prefabricated chin fixation plate or H shaped plate is used
When the chin is set back postero lingual area has a palpable step defect.
To prevent this postero lingual area is contoured
Labio mental fold is enhanced by contouring the anterior superior edge.
Vertical increase of the chin
Vertical decrease of the chin
DOUBLE SLIDING HORIZONTAL OSTEOTOMY
In very deficient chin Creation of a stepped intermediate
wafer of bone between the inferior fragment and mandible
This segment is advanced to produce bony contact between upper and lower fragments
Correction of assymmetry of chin Done in unilateral condylar hyper
or hypoplasia where the chin is deviated.
Done for the lateral movement of the chin
Also known as propeller osteotomy First osteotomy is performed
parallel to the inter pupillary line Second osteotomy is performed
parallel to the lower border of the chin
Altering the width of the chin
Altering the posterior dimension Before the chin is mobilised fix a 4
hole straight plate at the labial cortex of the chin
Midline osteotomy is performed both buccal and lingual cortex
Chin widened using bone plate as a hinge
To narrow the chin triangular midline ostectomy is performed.
Altering the anterior dimension
For narrowing the anterior dimension of chin a midline ostectomy is performed at the centre and this part is removed
Lateral segments are moved medially
For widening the anterior dimension of chin osteotomy is performed in the centre of the chin fragment
After increasing the width bone graft is placed between the segments
Augmentation using implants Autologous
Calvarial bone Metals
CorrosiveHigh rate of bone erosion
Polymers – most commonly used
Polymers – carbon chain based molecules with crosslinking Dimethylsiloxanes
○ Silicone based○ Silastic
Polyamide ○ Supramid
Polyethylene (polyester fiber)○ Mersilene (Polyethylene
terephthalate) ○ Dacron○ Medpor (porous polyethylene)
Expanded polytetrafluoroethylene (PTFE)○ Gore-Tex○ Avanta
PTFE○ Teflon○ Proplast I and II
Polymethylmethacrylate (PMMA)
Silicone chin implants
Composite polymer implantsHard Tissue Replacement (HTR)○ PMMA + polyhydroxyethylmethacrylate
and calcium hydroxideHydrophilic outer layer for osseointegration
Silastic implant with Dacron backing○ Increase interface soft tissue ingrowth
Complications Wound dehiscenseProlonged neurosensory disturbancesAvascular necrosis of mobilised segmentsHemorrhage causing lingual hematomaChin ptosisBony resorption under alloplastsDevitalisation of teethMandibular fracture Mucogingival problems
References
Fonseca vol2 orthognathic surgery Johan P Reyneke – Essentials of
orthognathic surgery
