Preoperative analysis of facial contours

Due to the countless variations in facial shape, most analytical measurements used to determine aesthetic standards are unreliable. Modern analysis and determination of angles are the first step in contour determination. However, facial correction is a three-dimensional procedure, which exponentially increases the variability of the structure and the final treatment results. A good understanding of skeletal anatomy and the ability to determine individual topographic features help the surgeon select the optimal implant and method of its placement.

Augmentation of the skeletal components of the face with allografts alters the deepest, skeletal level of the face in three dimensions. Facial evaluation prior to contouring surgery begins with an understanding of the individual skeletal anatomy and the identification of signs of aesthetic deficiencies. Determining the relationship between structural and topographic features is important to achieve the best results by selecting the optimal shape, size, and position of the implant.

Evaluation of mandibular contour defects

Defining the zonal principles of anatomy in the premandibular space allows the surgeon to create an individualized contour of the chin and lower cheeks. Chin implants have traditionally been placed in the area between the mental foramina. This well-known location constitutes the only segment or zone of the mandible that can be successfully reshaped. Implants placed only in the central segment, without extending laterally, often create an unnatural protrusion that is unattractive. The mid-lateral zone of the premandibular space can be defined as the area extending from the mental foramina to the oblique line of the horizontal part of the body of the mandible. When this zone is enlarged, in addition to the central part of the chin, there is an expansion of the contour of the anterior line of the mandible. This is the basis for the development of extended anatomical and anterior cheek chin implants. The posterolateral zone, the third zone of the premandibular space, includes the posterior half of the horizontal part of the body of the mandible, the angle of the mandible and the first 2-4 cm of the ascending ramus. This area can be enhanced with a mandibular angle implant, which will widen or lengthen the back of the mandibular angle, creating a stronger back jaw line.

The zonal principle of skeletal anatomy is useful for dividing the midface area into distinct anatomical zones. Zone 1, the largest area, includes most of the zygomatic bone and the first third of the zygomatic arch. Enlargement of this zone brings out the zygomatic eminence. This creates a pointed, angular appearance. Zone 2 covers the middle third of the zygomatic arch. Correction of this zone, together with zone 1, accentuates the zygomatic bone from the side, widening the upper third of the face. Zone 3, the paranasal area, lies between the infraorbital foramen and the nasal bone. A vertical line dropped from the infraorbital foramen marks the lateral edge of zone 3, limiting the area of medial dissection during zygomatic augmentation. Increasing the volume of zone 3 adds fullness beneath the orbit. Zone 4 includes the posterior third of the zygomatic arch. Enlargement in this area produces an unnatural appearance and is not indicated in most cases. The tissues covering this area are attached to the bone, and separation here must be done carefully, since the temporozygomatic branch of the facial nerve passes superficially here, behind the temporoparietal fascia, over the zygomatic arch, and can be damaged. Zone 5 is the subzygomatic triangle.

Defects of the contour of the middle part of the face

The topographic classification of midface contour defects is very useful as a reference guide for matching the anatomical characteristics of the deformity to specific implants. Type I deformity occurs in patients who have good fullness of the midface but inadequate development of the skeletal component of the malar region. In this case, a shell implant on the malar bone would be preferable, augmenting the malar bone and creating a higher zygomatic arch. The larger surface area of the implant provides better stability and helps reduce rotation and displacement. Extension of the implant downward into the subzygomatic space creates a more natural transition from the area of maximum augmentation to adjacent areas of relative depression. Type II deformity is observed in patients with atrophy and drooping of the soft tissues of the midface in the subzygomatic region, with adequate malar development. In this case, subzygomatic implants are used to augment or fill these defects or to create forward protrusion. Type II deformity is the most common, found in the majority of aging individuals, for whom a subzygomatic implant can be effectively used in combination with facelift surgery. Type III deformity occurs in patients with thin skin and prominent malar eminences. This combination causes an abrupt transition from the malar bone at the top to an area of pronounced depression below the malar bone, giving the appearance of a severely emaciated, skeletal face. Type IV deformity, which is described as a "volume-deficient" face, is the result of malar underdevelopment and a deficiency of soft tissue in the subzygomatic area. In this situation, a combined zygomatic/subzygomatic implant must serve two purposes: it must proportionally augment the deficient skeletal structure in the malar area and it must fill the void created by the lack of soft tissue in the subzygomatic area. Since this condition is also associated with premature aging of the skin in the form of excess wrinkles and deep folds in the midface, patients are often considered optimal candidates for rhytidectomy. Full midface reconstruction and lateral mandibular augmentation using a combined zygomatic/subzygomatic and anterior cheek implant provided the structural foundation for the subsequent rhytidectomy to be successful in correcting the deep folds that were present medially in the midface. The groove-type (type V) deformity is defined by a deep groove that often occurs at the junction of the thin eyelid skin and the thicker cheek skin. In this deformity, a pronounced fold extends downward and laterally from the inner canthus across the inferior orbital rim and the infraorbital portion of the malar bone. Silicone elastomer, ePTFE, and fat implants are used to correct this deformity.

The only approach to correct submandibular and nasozygomatic depressions is to lift the soft tissues of the infraorbital area and midface, combined with a superficial cheek lift. This affects the vector of tissue displacement during aging. A superficial lift involves lifting the thicker cheek skin and subcutaneous tissues to cover the lower orbital rim. It also reduces the heaviness of the upper nasolabial fold. It is most effective in the lateral areas, up to the level of the midline of the pupil. In more severe medial trench deformities, if additional augmentation is required, infraorbital fat located in the area of the marginal arch or a special implant can be used simultaneously. A superficial plane separation is superior to a deep periosteal separation due to its ease of execution, direct access to the elastic malar pad, and a low incidence of complications. Of course, caution and knowledge of the anatomy of the midface are required to perform a midface lift. If there is excessive midface lift (or overcorrection of weak-looking suborbital skin), the downward pull created by the oral muscles can cause the lower eyelid to shift. Cheek lift techniques are still new and are undergoing modification as they are increasingly used in midface rejuvenation.

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