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Frontal view Ideal measurement Dysmorphology Indicated augmentation
Nose-chin
relationship
Maximal chin projection at or
3 mm posterior to vertical
nose-lip plane
Microgenia
Maximal projection
lies posterior to ideal
line
Macrogenia
Projection anterior to
ideal line
Microgenia generally
indicates implant
augmentation or bone
transplant
Macrogenia generally
indicates osseous
genioplasty
Lip-chin
relationship
Vertical line drawn between
maximal upper and lower lip
projection connects with
pogonion (Riedel line)
Microgenia
Pogonion lies
posterior to ideal line
Macrogenia
Pogonion anterior to
ideal line
See above
Cervicomental
angle
105–120 degrees Smaller cervicomental
angle
Cervical soft tissue
contouring (e.g.,
submental lipectomy) is
indicated with
genioplasty
Cephalometric analysis uses lateral and AP radiographs to assess the
underlying bony structures and soft tissues in greater detail when indicated,
although this is not commonly performed in the general population.
Generally, it is recommended to obtain cephalometric radiographs if
patients are indicated for osseous genioplasty [100] (Fig. 13).
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Fig. 13 Cephalogram is well utilized to identify discrepancies in patients with suspected underlying
orthognathic deformity [111]
These studies are essential for a better understanding of the relationship
between an individual patient’s skull base, maxilla, and mandible [112].
Identification and analysis of various soft tissue and skeletal landmarks
utilizes various analytical guidelines which are not detailed in this chapter.
Expanded discussion of lateral radiograph analysis using the methods of
Ricketts [113], Steiner [114], Burstone [115], and Gonzalez-Ulloa et al.
[116] is well described in the cited articles, as well as their application.
Additionally, the skin quality and texture should be examined prior to
surgery from both side and frontal views. Factors to note include thickness,
excess laxity, and irregularities/asymmetry of the soft tissue. Ptosis of
muscle and cutaneous tissues may be unaesthetically emphasized with chin
augmentation and may be better corrected with tissue repositioning, lifting,
and/or resection. The chin pad and adjacent soft tissues should be assessed
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at rest and with movement to determine the appropriate method of
reconstruction [117].
3.3 Surgical Techniques
3.3.1 Implant Augmentation
The implants used in genioplasty are composed of similar materials
discussed previously in cheek augmentation. Longer, laterally tapered
implants are well utilized in patients who would benefit from lateral
mandibular contour improvements. Button implants are rounder in shape,
placed medially to improve the projection of the central chin [97].
Currently, there are two well-defined techniques for the placement of
chin implants. The extraoral (submental) approach utilizes a 2–3 cm
incision in the submental crease into the subcutaneous fat. Some providers
favor the submental approach, as it reduces the risk of infection with
implant transfer through the oral cavity. There is greater visibility, allowing
for improved ease of implant placement, and additional surgeries may be
completed through this opening (neck lift, liposuction, platysmaplasty). The
intraoral approach allows for dissection through a gingivolabial incision,
eliminating the risk of resultant visible scarring [97, 118, 119] (Fig. 14).
Fig. 14 Incision location with the intraoral approach [120]
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With both approaches, the mentalis muscles are identified and divided
to expose the mandibular periosteum. Implants can be placed in a supra- or
subperiosteal plane, each with their own benefits and risks. If the
subperiosteal plane will be used, two vertical incisions are made bilaterally
about 2 mm from the midline into the mandibular periosteum. Use of a
periosteal elevator allows for creation of a 1 cm dissection plane beneath
the mandibular periosteum, extended to the length of the implant. Lateral
dissection along the mandible risks damage to the mental n. necessitating
identification and preservation during the procedure. The implants should
not be placed over this nerve, although lateral projection can be achieved
with narrower implants inserted below [97].
Supraperiosteal implants are shown to reduce anterior mandibular
erosion, although a more stable fixation is achieved in the subperiosteal
plane. Many surgeons prefer a biplanar implant placement, using
supraperiosteal dissection at the medial aspect and transitioning laterally to
the subperiosteal plane [98].
Alternatively, some surgeons prefer to fix the implant with a titanium
screw placed at the anterior mandible and advanced to a depth of 4 to 5
mm. This method helps to maintain implant placement and reduces risk of
migration. With all approaches, the implant should be secured to the
periosteum along the midline, prior to re-positioning of the mentalis muscle
[121].
Recently, the use of cancellous bone chips in lieu of silastic implants
has been documented in the literature. This approach can be performed
intraorally or sub-mentally, using similar incision and dissection techniques.
Tissue bank alloplastic cancellous bone chips are placed into the
subperiosteal pocket until the desired contour is achieved. Gentle
manipulation is used to mold the chin as discussed in the preoperative
consult, after which the periosteal incision is closed using figure of eight 4–
0 chromic sutures. This technique has the advantage of postoperative
manipulation, as the shape of the chin can be corrected as needed (for a
short time period) after the wound is closed [122].
Osteogenesis modulation is another technique that has been recently
developed to enhance the bony contour without subjecting the tissues to
invasive osteotomy augmentation. A battery-operated Modular implant is
surgically inserted using the techniques described above, which will
transmit electrical pulses directly against the mandible (Piezoelectric
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effect), stimulating bone formation. Cephalometric analysis of the four
patients before and after Modulator placement show improvements to
mandibular length (average 5.26mm) and vertical curvature (average
23.5mm). There were no significant complications, and results were
maintained at the 39-month follow-up. The Modulator is considered the
world’s first practical, reliable, long-term implant for intramembranous
bone remodeling, although its use in craniofacial malformations has not
been assessed [123] (Fig. 15).
Fig. 15 Results after placement of MedPor genious implant are shown in the left image [124]
3.3.2 Osseous Genioplasty
Osseous genioplasty usually uses general anesthesia with nasal intubation
preferred to endotracheal intubation for the improved oral visibility.
Tumescent anesthesia is injected inferior to the mucogingival sulcus in the
oral cavity and continued to the second premolar bilaterally. An incision is
made (either with a scalpel or electrocautery device) into the mucosa of the
labial lip. Additional caution should be taken to spare the frenulum, keeping
above the gingival attachment.
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Deeper, perpendicular incisions are used to dissect the mentalis muscle
and gain access to the periosteum. Dissection within the subperiosteal plane
exposes the mandibular border at the inferior aspect, taking care to avoid
the mental foramen (located in the vicinity of the second premolar
bilaterally). Once the mental foramen and neurovascular bundle have been
identified and protected, exposure continues posteriorly to allow for optimal
visibility [125] (Fig. 16).
Fig. 16 The use of robotic surgery such as with the Craniofacial Plastic Surgery Robot theoretically
allows for improved identification of neurovascular structures and pre-planned drill paths based upon
an individual’s specific anatomy [126]
After adequate exposure has been achieved, an oscillating bone saw is
used to complete a full-thickness osteotomy at a pre-marked point on the
anterior mandible. To avoid damage to the neurovascular structures, the cut
should be made 6 mm below the mental foramen and 5 mm below the
canine root [127, 128]. The angle at which osteotomy is performed should
be precalculated to allow for optimal sliding of the mandibular segments.
After the anterior portion is removed, a periosteal elevator is placed
between the anterior detachment and the remaining mandible to fully
separate both pieces. The genioglossus and geniohyoid muscles should
remain intact, and they are stretched at this point if chin advancement is
indicated [121].
Individuals with microgenia or inadequate chin projection are indicated
for chin advancement, in which the anterior detached fragment will be
advanced to the desired location and fixed in place with custom plates and
screws. When vertical shortening of the chin is indicated, two osteotomies
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are performed, allowing for improved vertical modification and/or removal
of a bone segment. The lower osteotomy should be performed first to allow
for stable bone removal. Any rough edges will be refined with a rasp after
adequate fixation, and the tissues are closed in multiple layers [121, 129].
There are additional variations to this technique, including wedge
genioplasty (removal of a bony segment) or interpositional genioplasty
(insertion of a graft for added vertical length) [130, 131]. Customized
modifications can be applied in the centering genioplasty, with a unilateral
wedge removed from one side and augmentation of the bony structure upon
reattachment. Telescopic genioplasty has been recently published, in which
the width of the removed bone is no wider than the medial intercanthal
width. This allows for improved chin projection while avoiding excessive
widening or narrowing of the anterior mandible [121, 132].
3.4 Complications and Outcomes
Chin augmentation with implants incurs a relatively low rate of
complications, and patients are often highly satisfied (>90%) with the
surgical results [133]. There have been reports of possible implant-related
complications, including infections, implant displacement, and
dissatisfaction with surgical outcomes [134, 135].
Resorption of the anterior mandible bone is a commonly encountered
adverse effect of silastic implant placement, due to the dynamic movements
of the chin with expression and speech [107, 136]. Placement of implants in
the supraperiosteal plane reduces the extent and occurrence of erosion.
Many patients assessed with lateral radiographs after implant placement
showed mild degrees of bone loss despite asymptomatic presentation,
indicating a need for additional research regarding the true impact of this
complication [134, 137].
Osseous genioplasty is a relatively more invasive and complex
procedure, and as such incurs additional risk to patients. The rate at which
complications occur has not been clearly established, with their frequency
ranging from 3% to 30%. Documented adverse events resultant from
osseous genioplasty include infection, hematoma formation, chin ptosis,
dental/periodontal lesions, and irregular jaw contour [138, 139]. Of these
complications, transient neurosensory disturbances had the most negative
impact on patient satisfaction (Fig. 17).
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Fig. 17 Postoperative results of computer-assisted osseous genioplasty for correction of deviated
chin are shown in the right images, with a comparison to the preoperative appearance (left images)
[140]
4 Rhytidectomy
The removal of wrinkles, or rhytidectomy, involves removal of excess skin
and surgical lifting of skin tissues. This procedure is commonly referred to
as facelift, as it is performed in deeper (sub-SMAS) and/or superficial
planes through various incision sites along the side of the face to lift and
restabilize the tissues. To date, a variety of techniques have been described,
trending in recent years toward minimally invasive approaches such as
endoscopic facelift or MACS-Lift [141].
4.1 Review of Relevant Anatomy
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The impact of skin aging of the upper face is discussed in greater detail
with nonsurgical facial augmentation. With aging, weakening of ligaments
and increased skin laxity can deepen facial folds (notably the nasolabial
fold) and increased severity of jowls. The periorbital area is targeted by
these changes as well, lending to the appearance of sagging eyelids and
rhytids [142].
Extensive knowledge of the fascial layers is necessary when performing
rhytidectomy, as many of the surgical maneuvers involve dissection within
fascial planes. The superficial musculoaponeurotic system, or SMAS, is
superficial to the parotid gland and significant for its facial muscle
investments. Superficial temporal fascia (above the zygomatic arch) and
temporoparietal fascia merge superiorly with SMAS tissues, and deeper
investing fascial layers of the platysma muscle (neck) are integrated
inferiorly [143] (Figs. 18 and 19).
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Fig. 18 The arrangement of ligamental attachments within the platysmal muscle and their
connections to facial tissue [144]
Fig. 19 Illustration of the weakening of platysmal muscles and resultant separation in the lower pane
(b), compared with a stronger muscle not yet impacted by aging in the upper pane (a) [145]
The facial nerve emerges through the parotid gland and bifurcates at the
pes anserinus, dividing into upper temporofacial and lower cervicofacial
branches. The upper temporofacial branches include temporal, zygomatic,
and buccal nerves, providing innervation to muscles in the upper face and
cheeks. The mandibular and cervical nerves originate from the lower
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