Authors of section

Author

Boaz Arzi

Executive Editor

Amy Kapatkin

General Editor

Frank Verstraete

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Simple zygomatic arch fractures

Simple zygomactic arch fractures

Simple fractures of the zygomatic arch may occur due to blunt trauma to the side of the face. If no displacement is present, they may not be readily observed in physical exam. Clinical signs of pain and discomfort upon palpation should raise the suspicion for a zygomatic arch fracture.

Common fracture locations are:

  • The suture line of the zygomatic bone articulation with the maxilla.
  • The temporal process of the zygomatic bone articulation with the zygomatic process of the temporal bone.

These fractures can be nondisplaced or displaced (medially or laterally).

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Displacement of the eye occurs when there is medial displacement of the zygomatic arch. This can result in exophthalmos, endophthalmos, diplopia, or entrapment of ocular nerves or muscles.

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Prolapse of the eye can occur if the orbital ligament attachment is disrupted causing lateral displacement of the zygomatic arch.

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General information for all midfacial fractures

Human craniomaxillofacial surgeons use the Le Fort classification for midface fractures. Veterinary medicine lacks a classification system. Therefore, the authors have divided the midface arbitrarily based on a variety of cases that they have treated in the past 10 years.

From a biomechanical standpoint, the maxillofacial structures are relatively lightweight. Yet they have strong frames made of thin bones that also form the nasal cavity and paranasal sinuses. These maxillofacial frames are strengthened by the buttresses, which are thicker areas of the bones, designed to distribute the forces of mastication. The buttresses also help to maintain the position of the maxilla in the appropriate relationship with the base of the skull and the mandible. There are lateral, medial and caudal buttresses. The objective of reconstructing midfacial fractures is to restore these buttresses as well as the orbit and frontonasal vault. Fixation of bone fragments is done from the most unstable to more stable, in order to ‘simplify’ the fracture.

Midfacial fracture classification

  1. The frontonasal area: Frontal bone and part of nasal bone
  2. The zygomatic arch: Zygomatic process of the temporal bone and zygomatic bone
  3. Caudal midface: Maxilla and part of nasal bone
  4. Rostral midface: Maxilla, nasal and incisive bones
  5. Palatal: Incisive, maxilla, palatine
  6. Panfacial: When more than one region is involved

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The midface is unique because of its 3D complexity and the interaction of its hard and soft tissues. This area has a large number of blood vessels and cranial nerves.

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In the midface, form and function are interdependent; even minor disruption of the anatomy may be obvious, especially if it affects the occlusion of the teeth.

The degree of fracture comminution in the midface and the degree of injury to the soft tissue envelope contribute to the complexity of the repair.

Imaging

Modern imaging technologies allow analysis of fracture patterns and assessment of the fracture complexity. The gold standard for assessment of a fracture pattern is computed tomography (CT), that can produce thin section images with CT-based 3D data sets.

It is strongly advised to obtain postoperative CT scans to assess the surgical result.

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Cone beam CT technology is an evolving imaging modality in veterinary dental and craniomaxillofacial surgery. It gives a 3D view of all craniomaxillofacial structures in less time with less cost than a full CT. The resolution is not as good as the CT and its use for fracture planning is not well established.

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3D printing of the skull for surgical planning is very useful. The surgeon can visualize the trauma in 3D, perform the planned surgery on the model and evaluate the results before it is done on the patient.

DICOM voxel data set, 3D image analysis, and professional software are available for free on the internet.

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If visualization software for the DICOM datasets is not available, CT views of the midface (axial, coronal, and oblique parasagittal) are still recommended for simple fractures. 3D views are recommended for more complex fractures.

Plain X-rays alone are only adequate for structures such as dentition, and should only be used alone if CT is unavailable.

MRI or ultrasound can be helpful for soft tissue injuries but are not included in the standard diagnostic work up.

Special fracture consideration

If the entire upper jaw is fractured or dislocated, there will be a pronounced malocclusion at the frontonasal and frontomaxillary sutures. This is typically seen in young dogs.

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Clinical signs

Devitalization of bone fragments may occur with severe injury to the zygomatic arch.

Diplopia, paresis and paralysis of the eye and other facial structures can occur with medial displacement of the zygomatic arch. The eye becomes dislocated dorsally and rostrally. Bone fragments may be displaced caudal to the eye.

With lateral displacement of the zygomatic arch, the frontal process of the zygomatic bone either pulls or damages the orbital ligament, which may lead to displacement of the eye.

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The patient may exhibit pain, swelling, crepitus and bleeding from the side of the face. Dislocation of the eye may be obvious.

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