Chin Advancement, Augmentation, and Reduction as Adjuncts to Rhinoplasty

Chin deformities are commonly encountered defects in patients seeking rhinoplasty. Careful preoperative evaluation may identify patients who could benefit from concurrent augmentation or reduction mentoplasty. Alloplastic chin implants and sliding genioplasty represent the main accepted methods of chin augmentation. Although both procedures may be used for retrognathia or microgenia, the sliding genioplasty may also be used in chin asymmetry, prognathia, and vertical height discrepancies. This article outlines the methods to analyze the chin, and discusses the treatment options available for correction of chin deformities as an adjunct to rhinoplasty.

Key points

  • Chin retrusion is of importance for facial plastic surgeons because it is a commonly encountered defect in patients seeking rhinoplasty.

  • The chin should be evaluated as it relates to other adjacent structures, such as the lips, nose, and teeth. It is crucial to evaluate the chin in 3 dimensions: horizontal (anteroposterior), vertical, and transverse.

  • Horizontal chin deficiency may be camouflaged by an alloplast implant or filler injection.

  • Bony osteotomy of the mentum (genioplasty) can correct vertical and transverse chin deformities.

  • Injectable fillers, although often not permanent, give the advantage of three-dimensional chin augmentation, with the added benefit of allowing precise chin shaping.

Videos of chin augmentation and osseous genioplasty accompany this article at www.plasticsurgery.theclinics.com/

Introduction

Commonly recognized features of facial beauty include symmetry and harmonious proportions. Chin deformities may detract from an otherwise aesthetically pleasant facial profile. The chin projection and shape are generally regarded as important characteristics of facial attractiveness, especially in men. Some evidence suggests that men with broad chins are viewed as socially dominant across cultures. Broad-chinned men attain higher ranks in the military, are regarded as more masculine and attractive, and have greater reproductive success in some societies than do men with narrower and less projecting chins. Because cortical bone growth is stimulated by testosterone, and testosterone is immunosuppressive in high concentrations, the ability to have a broad chin and still be healthy is hypothesized to show high mate quality.

In studies analyzing female attractiveness, it is commonly reported that a small or narrow chin is associated with a more feminine appearance, which reinforces the notion that a broad chin is a signal of masculinity and suggests that chin size may have opposite effects in men versus women regarding selection. Recent studies have found significant geographic differences in male and female chin shapes. This finding is consistent with region-specific sexual selection and/or random genetic drift and thus challenges the universal sexual selection theory.

Retrusion of the chin is a condition that is commonly encountered in patients seeking rhinoplasty. Moreover, it is striking that most patients seeking rhinoplasty who have a retruded chin are often unaware of their microgenia, and the impact that their chin size has on their nasal and facial appearance. This lack of awareness is compounded by most patients seeing themselves in the mirror directly, rather than obliquely or laterally. Viewing only from a frontal perspective minimizes the impact that chin projection has on facial appearance. However, failure to address chin deformities is a common omission in patients having rhinoplasty. In patients with deficient projection of the chin (horizontal microgenia), the nose appears to project a large amount, even though nasal projection may be appropriate for the face. Several methods have been proposed for defining horizontal projection of the chin. None of these analyses is ideal. An appreciation of facial proportions, measurements, and relationships of the bony structures and soft tissues of the face assists surgeons in preoperative planning and establishing the goals of surgery.

When properly indicated and performed, a simultaneous rhinoplasty and chin augmentation, advancement or reduction, can produce a significant improvement in facial appearance. This article outlines the methods to analyze the chin, and discusses the treatment options available for correction of microgenia and macrogenia. These treatments can be important adjuncts to achieving a more harmonic profile in patients requesting rhinoplasty.

Introduction

Commonly recognized features of facial beauty include symmetry and harmonious proportions. Chin deformities may detract from an otherwise aesthetically pleasant facial profile. The chin projection and shape are generally regarded as important characteristics of facial attractiveness, especially in men. Some evidence suggests that men with broad chins are viewed as socially dominant across cultures. Broad-chinned men attain higher ranks in the military, are regarded as more masculine and attractive, and have greater reproductive success in some societies than do men with narrower and less projecting chins. Because cortical bone growth is stimulated by testosterone, and testosterone is immunosuppressive in high concentrations, the ability to have a broad chin and still be healthy is hypothesized to show high mate quality.

In studies analyzing female attractiveness, it is commonly reported that a small or narrow chin is associated with a more feminine appearance, which reinforces the notion that a broad chin is a signal of masculinity and suggests that chin size may have opposite effects in men versus women regarding selection. Recent studies have found significant geographic differences in male and female chin shapes. This finding is consistent with region-specific sexual selection and/or random genetic drift and thus challenges the universal sexual selection theory.

Retrusion of the chin is a condition that is commonly encountered in patients seeking rhinoplasty. Moreover, it is striking that most patients seeking rhinoplasty who have a retruded chin are often unaware of their microgenia, and the impact that their chin size has on their nasal and facial appearance. This lack of awareness is compounded by most patients seeing themselves in the mirror directly, rather than obliquely or laterally. Viewing only from a frontal perspective minimizes the impact that chin projection has on facial appearance. However, failure to address chin deformities is a common omission in patients having rhinoplasty. In patients with deficient projection of the chin (horizontal microgenia), the nose appears to project a large amount, even though nasal projection may be appropriate for the face. Several methods have been proposed for defining horizontal projection of the chin. None of these analyses is ideal. An appreciation of facial proportions, measurements, and relationships of the bony structures and soft tissues of the face assists surgeons in preoperative planning and establishing the goals of surgery.

When properly indicated and performed, a simultaneous rhinoplasty and chin augmentation, advancement or reduction, can produce a significant improvement in facial appearance. This article outlines the methods to analyze the chin, and discusses the treatment options available for correction of microgenia and macrogenia. These treatments can be important adjuncts to achieving a more harmonic profile in patients requesting rhinoplasty.

Preoperative planning and preparation

To precisely correct any chin deformity, careful preoperative analysis is essential. Specifically, the chin should be evaluated as it relates to other skeletal and soft tissue structures, including the lips, teeth, nose, and soft tissues of the neck. A detailed history of past trauma, orthodontic treatment, temporomandibular joint dysfunction, or prior oral surgery is important because many patients with dental malocclusion and underlying facial skeletal abnormalities are treated initially with orthodontics. This method of dental compensation may correct the malocclusion, but fails to improve the underlying skeletal deformity. It is therefore important to discuss prior therapy and the effects of chin shape and position on the facial profile with the patient.

Physical examination should include inspection and palpation of the chin, lips, nose, and teeth. The entire face should be observed at rest and during animation to evaluate the mentalis soft tissue mound and its support. With aging, patients may develop ptosis of the soft tissue pad of the chin. In patients with open bite deformities and lip incompetence, hyperactivity of the mentalis muscles (mentalis strain) can occur. For this reason, the dental occlusion should be carefully examined to determine whether orthodontics or orthognathic surgery is needed.

The evaluation of all patients for possible chin surgery should include consistent and reproducible clinical photographs in at least 3 views: anterior-posterior (AP; frontal), lateral (profile), and oblique. These photographs allow analysis of the contour and projection of the chin as it relates to other structures of the face and neck. If the physical evaluation and clinical photographs show a minor deformity requiring augmentation with an alloplast, radiographs of the chin are usually not necessary. However, if the deformity is more complex, (eg, vertical chin excess with horizontal deficiency or transverse bony asymmetry), radiographic analysis is usually obtained.

Radiographic evaluation of the chin routinely includes a panoramic radiograph (Panorex) and cephalometric radiographs in the AP and lateral views. The Panorex shows the cortical outline of the mandible and the vertical mandibular height. Also, this radiograph delineates the position of the tooth roots and the inferior alveolar or mandibular canals and mental foramina ( Fig. 1 ). This information aids in avoiding damage to the mental nerve during surgery. The inferior alveolar nerve, a branch of the third division of the fifth (V 3 ) cranial nerve, travels through the mandibular canal and exits the mental foramen as the mental nerve ( Fig. 2 ). The mental nerve supplies sensation to the skin and mucous membranes of the lower lip and chin. The mandibular canal is often located 2 to 3 mm below the level of the mental foramen. Bony osteotomies should therefore be performed at least 5 mm below the mental foramen.

Fig. 1
Panorex radiograph. The white arrow indicates the position of the mandibular canal.

Fig. 2
Cadaveric dissection showing the position of the left inferior alveolar nerve.

If bony genioplasty is considered, AP and lateral cephalometric radiographs should be obtained. AP radiographs allow detection and evaluation of transverse skeletal asymmetries of the chin. Chin asymmetries are common in patients with oculoauricular vertebral spectrum or hemifacial microsomia, but they are also commonly seen in nonsyndromic patients considering aesthetic surgery. When transverse bony or soft tissue asymmetries are overlooked preoperatively in patients with microgenia, augmentation of the chin with an alloplast can accentuate the deformity. Lateral cephalometric radiographs allow detailed analysis of both the facial soft tissues and the facial skeleton. The cephalogram should be obtained at a standard distance with the head positioned so that the Frankfurt horizontal line is parallel to the floor. From this standardized lateral radiograph, a series of soft tissue and skeletal points can be identified ( Fig. 3 ), which allows various analyses of the chin, as described by Ricketts, Steiner, Burstone, Gonzalez-Ulloa and Stevens, and others ( Figs. 4 and 5 ).

Fig. 3
Lateral cephalogram. A, anterior nasal spine; B, supramentale, N, nasion; P, soft tissue pogonion; S, sella; UL, upper lip.

Fig. 4
The method described by Gonzales-Ulloa and Stevens. Pg, pogonion.
( Data from Gonzales-Ulloa M, Stevens E. The role of chin correction in profileplasty. Plast Reconstr Surg 1966;41:477–86.)

Fig. 5
The horizontal relationships of the chin and upper and lower lips as they relate to the nasal perpendicular line.

The most frequently used evaluation of the chin drops a perpendicular line from the vermillion border of the lower lip and compares the AP position of this line with the soft tissue pogonion (the anteriormost projecting chin point). As a general guide, the pogonion in a male patient should ideally be at the level of this vertical line, whereas in women the pogonion should be positioned just posterior to this line. When class I occlusion is present and the position of the soft tissue pogonion is anterior to the proposed line, horizontal macrogenia is diagnosed, whereas microgenia is present if the chin is positioned posterior to the ideal line. Although this evaluation is effective for horizontal deformities (microgenia or macrogenia), it does not account for vertical or transverse discrepancies. Because many surgeons primarily use this evaluation method, vertical or transverse chin problems are often overlooked.

Analysis of vertical plane is also essential in determining the appropriate heights of the lower facial third and the chin. The simplest technique involves division of the face into 3 equal thirds ( Fig. 6 ). Because the frontal hairline can vary significantly between individuals, an alternate method described by Powell and Humphreys more accurately analyzes the vertical heights of the lower 2 thirds of the face. This method describes the middle portion of the face as the distance from the nasion to the subnasale and the lower portion as the distance from the subnasale to the menton. Other important analyses include inspection of the face in repose, when the maxillary incisor teeth should show 0 to 3 mm. If more than 3 mm of the maxillary incisors are visible at rest, excessive facial length, usually in the midface, may be present. Additional analysis of the lower face includes subdividing the lower third of the face. All of these analyses relate the height of the chin and lower face to the total facial height. In complex chin deformities, a vertical discrepancy, as well as a horizontal deficiency or excess, is often present.

Nov 21, 2017 | Posted by in Dental Materials | Comments Off on Chin Advancement, Augmentation, and Reduction as Adjuncts to Rhinoplasty
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