9.12\ Coronoidectomy

9.12.1\ Discussion

Excessively elongated coronoid processes of the mandible can result in trismus. Treatment consists of coronoidectomy, which can be performed endoscopically, and involves performing osteoto-

a

mies across the base of the coronoid process but often leaving at least some portion of the coronoid process behind (Fig. 9.23). Alternatively, transzygomatic coronoidectomy performed for zygomaticocoronoid ankyloses or pseudoarthrosis typically involves resection of the abnormal section of the zygomatic arch and coronoid process (Fig 9.24).

b

Fig. 9.23  Endoscopic coronoidectomy. The patient had a history of Hecht syndrome (trismus-­pseudocamptodactyly syndrome). Preoperative sagittal CT image (a) shows an

abnormally elongated coronoid process. Postoperative sagittal CT image (b) shows interval fragmentation of the coronoid process

Fig. 9.24  Transzygomatic coronoidectomy. The patient has a history of arthrogryposis multiplex congenita. The preoperative axial (a) and 3D (b) CT images show left

zygomaticocoronoid ankylosis (arrow). The postoperative axial (c) and 3D (d) CT images show interval resection of the fused zygomaticocoronoid segment

9.13\ Mandibulectomy

and Mandibular

Reconstruction

9.13.1\ Discussion

Various types of mandibulectomy can be performed for treating both developmental and neoplastic conditions. Marginal mandibulectomy consists of excising part of the surface of the mandible, usually the inner surface, and is mainly performed to minimal tumor extension into the mandible (Fig. 9.25). Segmental mandibulectomy consists of resecting the full thickness of a portion of the mandible, leaving a gap between segments of the mandible (Fig. 9.26). The mandible is often reconstructed using a variety of grafts, such as a free fibula osteocutaneous flap. Plates and screws are also incorporated for securing the

bone segments. Condylectomy consists of resecting the mandibular condyle, often along with the disc and joint capsule (Figs. 9.27 and 9.28). This procedure may be performed for resection of lesions that affect the ­temporomandibular joint such as pigmented villonodular synovitis or neoplasm of the mandible that extends to the condyle. Occasionally, transport distractors for osteogenesis are used in the reconstruction. Complications related to mandibulectomy and condylectomy include infection (Fig. 9.29), devascularization/osteonecrosis (Fig. 9.30), hardware failure (Fig. 9.31), dislocation/malocclusion that is often accompanied by accelerated degenerative disease of the temporomandibular joints secondary to the altered biomechanical stresses (Fig. 9.32), and tumor recurrence, which is often best depicted on MRI (Fig. 9.33).

Fig. 9.27  Condylectomy. The 3D CT image demonstrates the absence of the right mandibular condyle leaving a gap between the healed mandibular ramus osteotomy and glenoid (encircled)

Fig. 9.28  Partial mandibulectomy and condylectomy with condylar prosthesis. 3D CT shows a left mandibular body and condyle prosthesis. There is also a custom bipolar transport distractor (arrow)

Fig. 9.29  Graft infection. Sagittal CT image shows gas and fluid collections (arrows) in the surgical bed

Fig. 9.30  Devitalized fibular graft. Coronal CT image shows demineralization of the right mandibular fibular bone graft (arrow)

Fig. 9.31  Hardware fracture. Axial CT image (a) obtained after partial mandibulectomy and sideplate and screw reconstruction shows a displaced fracture of a screw

Fig. 9.32  Temporomandibular joint dislocation and accelerated arthritis. Axial CT image obtained after right partial mandibulectomy shows anterior dislocation of the right condyle due to the unopposed forces of the pterygoid muscles after surgery. There is also secondary degenerative change affecting the left temporomandibular joint related to the altered biomechanics

(encircled). Axial CT image in a different patient (b) shows overlap of the fractured mandibular reconstruction plate

Fig. 9.33  Tumor recurrence. The patient has a history of ameloblastoma treated via left hemimandibulectomy. Coronal fat-suppressed post-contrast T1-weighted MRI shows a heterogeneous mass in the region of the left glenoid fossa with intracranial extension