9.3\ Genioplasty

9.3.1\ Discussion

Genioplasty consists of altering the projection of the genial tubercle of the mandible. It can be performed via an osteotomy through the genial tubercle and can generally be described as shortening or lengthening genioplasty. The genial tubercle can be repositioned in all three planes to correct the sagittal, vertical, and transverse components of the chin deformity by sliding the bone fragment (Fig. 9.4). The osteotomy is performed well below the dental roots and mental foramina in order to avoid complications. Prostheses can be used for lengthening genioplasty, such as those composed of silicone, either alone or in conjunction with advancement osteotomy (Figs. 9.5 and 9.6).

Fig. 9.4  Sliding genioplasty. 3D CT image shows anterior translation of the inferior portion of the mandibular body, producing a step-off (arrow)

Fig. 9.5  Chin augmentation with implant. Coronal CT images show a silicone prosthesis (arrow) positioned anterior to the genial tubercle

Fig. 9.6  Lengthening genioplasty with combined osteotomy and implant. The patient has a history of Nager’s syndrome with severe micrognathia. Sagittal CT image shows the low attenuation porous polyethylene implant (arrow) and the advanced genial tubercle with fixation hardware

9.4\ Mandibular Angle

Augmentation

9.4.1\ Discussion

Mandibular angle augmentation with alloplastic implants is an option for correcting hemifacial microsomia and other deformities (Fig. 9.7). The

a

most commonly used materials for augmentation include silicone and porous polyethylene. The goal is to improve facial contours while maintaining the pterygomasseteric sling. Cross-­ sectional imaging can be useful for evaluating the position of the implants and assessing for complications, such as foreign body granulomas and infection.

b

Fig. 9.7  Mandibular angle augmentation. The patient has a history of hypoplastic right mandible in a patient with hemifacial microsomia. The implant has a density intermediate between fat and fluid. The coronal T2-weighted

(a) and contrast-enhanced T1-weighted (b) MR images show that the implant material has intermediate T2 and low T1 signal (arrows)