3.2  Midface Fractures

Fig. 3.3  Classification of frontobasal fractures based on anatomical regions (1–5) (mod. a. Oberascher 1993)

•Region 1: Posterior wall of the frontal sinus

•Region 2: Anterior ethmoid–cribriform plate

•Region 3: Posterior ethmoid roof

•Region 4: Roof and lateral wall of sphenoid sinus and

adjacent petrous part of the temporal bone

• Region 5: Orbital roof

This classification is suggestive for the surgical approach, as it is not categorized according to fracture type but according to the topographical unilateral or bilaterally affected areas of the anterior skull base and so determines which region needs attention (Fig. 3.3).

•The classifications mentioned refer mainly to the course of frontobasal fractures; however, they do not include extensive cranio-maxillary fractures or serious panfacial fractures (PFs), which may not only present a midface avulsion from the skull base but also accompanying demolition of the upper, middle, and lower facial levels as well as the neurocranium with extensive basal and cerebral injuries.

3.2.1  Standard Classifications

Various classifications exist in midface fractures:

1.The widely used classification according to Le Fort (Le Fort 1901) is based on a combination of characteristic, mostly transverse fracture lines, which are defined by the traumatic impact on the center of the face in relation to anatomical structures on different levels of height:

•Le Fort I fractures (low-level fracture)

•Le Fort II fractures (pyramidal fracture)

•Le Fort III fractures (high-level fracture) (Fig. 3.4)

2.The topographic classification in central, centrolateral, and lateral midfacial fractures is internationally recognized (Mathog 1984; Rowe and Williams 1985; Bowerman 1985; Lew and Sinn 1991; Fonseca and Walker 1991; Prein et al. 1998; Schwenzer and Ehrenfeld 2002). The following fracture types are subsumed in these classifications:

•Central midface fractures

Le Fort I, II, sagittal midface fractures, Wassmund I, II, III fractures, naso-ethmoidal fractures, nasomaxillary fractures

•Centrolateral midface fractures

Le Fort III, Wassmund IV fractures

•Lateral midface fractures

Zygoma, zygomatic arch fractures, zygomaticorbital fractures

•Combined midface fractures

3.2  Midface Fractures

Midface fractures may be classified according to parameters as follows:

•Fracture level

•Topographic region and

•Extension of the fracture

Degree and direction of the applied traumatic force, as well as impact angle and the area struck, all influence the resulting injury to the midface and hence lead to varying types of fractures, varying in extent (Schwenzer and Pfeifer 1991).

Fig. 3.4  Fracture levels of Le Fort I–III transverse subcranial midface fractures (mod. a. Schwab 1995)

Orbito-maxillary fractures, maxillo-mandibular frac­ tures, zygomatic-mandibular fractures, zygomatic-orbital- maxillary fractures, zygomatic-orbito-cranial fractures, fronto-maxillary fractures, PFs.

3.2.2  Central Midface Fractures

Central midface fractures include fractures of the Le Fort I- and II-type. The central midface block is unhinged from the rest of the facial skeleton and dislocated ­posteriorly or maybe even wedged. The dislocation is partially determined by the direction of the applied force and partially by the muscular tension applied by the pterygoidal muscles. Both pterygoidal muscles pull the mobile midface section dorsally and caudally, so resulting in an occlusal disturbance.

With an additional sagittal fracture of the central midface complex, a diastema forms between the incisors and more severe dislocations can even result in a traumatic cleft palate (Lew and Sinn 1991; Fonseca

and Walker 1991; Ewers et al. 1995; Prein et al. 1998; Schwenzer and Ehrenfeld 2002).

Fracture course: Le Fort I/Wassmund I fracture

The line of fracture runs from the anterior bony aperture of the nose above the nasal spine through the facial wall of the maxillary sinus, the zygomatico-alveolar crest, the maxillary tuberosity, through the caudal apex of the pterygoid process, through the medial nasal wall of the maxillary sinus and then reaches the point of exit again at the anterior bony aperture of the nose.

As a general rule, the vomer is affected and the cartilaginousnasalseptumisoftendislocated.Occasionally the pterygoid does not fracture, instead the maxilla avulses at the pterygo-maxillary junction (Fig. 3.5).

In Le Fort II/Wassmund II and III fractures, the maxilla, nasal skeleton, ethmoid, and lacrimal bones are quarried out of the midface as a pyramid. Subcranial involvement is frequent (Ewers et al. 1998; Prein et al. 1998; Schwenzer and Ehrenfeld 2002).

Fracture course: Le Fort II/Wassmund II and III fracture

The line of fracture in Le Fort II/Wassmund II fractures runs above or within the nasal bones, the medial orbital wall, along the inferior orbital fissure, through the infra-orbital canal, infra-orbital foramen and facial wall of the maxillary sinus and usually splits the pterygoid process in the middle third.

In Wassmund III fractures, the nasal bone is not included in the fracture segment. The fracture runs from the orbital floor across the maxillary frontal process to the cranial border of the anterior aperture of the nose. The remaining fracture course is identical to that of the Le Fort II fracture.

Course variations are common in these fractures. Extensive dislocations and mid-facial impressions involving the ethmoid bone, the orbit and the nasolac­ rimal ducts, i.e., the naso-orbito-ethmoidal (NOE) complex, are not uncommon. Concurrently there are often comminuted fractures of the nasal framework or septum luxations as well as fractures of the osseous

components of the nasal septum, the vomer and the perpendicular plate of the ethmoid bone (Fig. 3.6).

3.2.3  Centrolateral Midface Fractures

Centrolateral midface fractures, i.e., subcranial Le Fort III fractures, result in a secession of the viscerocranium from the neurocranium (Ewers et al. 1995; Prein et al. 1998; Schwenzer and Ehrenfeld 2002).

Fracture course: Le Fort III/Wassmund IV fracture

Beginning at the fronto-nasal and fronto-maxillary sutures, by-passing the optical canal, the lacrimal bone and medial orbital wall are disrupted. The line of fracture continues through the inferior orbital fissure and bifurcates, on the one hand, dorso-medially through the pterygopalatine fossa to the base of the pterygoid process, and, on the other hand, antero-laterally to the

lateral orbital margin along the zygomaticosphenoidal suture as far as to the fronto-zygomatic suture. The frontal bone is herewith separated from the zygoma and the maxilla.

In addition, the connection between the zygomatic arch and the temporal bone is disrupted and the osseous nasal septum fractures directly under the skull base. In Wassmund IV fractures, the nasal compartment is omitted from the fracture course and the fracture continues along the naso-maxillary suture.

3.2.4  Skull Base and Fracture Levels in the Region of the Septum

Among the subcranial fractures, the Le Fort II and III fractures and the Wassmund III and IV fractures differ in distance to the anterior skull base (Becker and Austermann 1981; Joos et al. 2001).

In the Le Fort II fracture, the naso-septal fracture line runs closer to the base through the superior

perpendicular plate, vomer, and the cranial pterygoid process; likewise Wassmund III fractures, but these run more distant from the skull base at a considerable distance below the skull base through the inferior perpendicular plate and vomer and split the pterygoid process in the middle section.

In Wassmund IV fractures, the medio-sagittal fracture of the nasal septum runs slightly lower than in the

Le Fort III fractures, though close to the base in the osseous septal region.

However, the Le Fort III fracture runs immediately below the skull base. Both split the pterygoid process in its cranial portion (Rowe and Williams 1985; Schwenzer and Ehrenfeld 2002) (Fig. 3.7).

3.2.5  Lateral Midface Fractures

Lateral midface fractures dissever the connection between the zygomatic bone and the frontal bone cranially, the

Fig. 3.7  Relation between anterior cranial base and subcranial midface fractures in the region of the nasal septum (mod. a. Schwenzer and Ehrenfeld 2002). (a) Le Fort I, (b) Le Fort II, (c)

Wassmund III, (d) Le Fort III, (e) Wassmund IV, (f) combination: Wassmund IV and Le Fort I

greater wing of the sphenoid bone medially, the maxilla caudally and from the temporal bone dorsally (Lew and Sinn 1991; Fonseca and Walker 1991; Ewers et al. 1995; Prein et al. 1998; Schwenzer and Ehrenfeld 2002).

Fracture course: lateral midface fractures

In isolated zygomatic fractures, the line of fracture runs through the zygomaticofrontal suture, along the lateral orbital margin, and descends along the lateral and anterior orbital floor, to the infraorbital margin. From here, it proceeds across the facial wall of the maxillary sinus and frequently through the infraorbital foramen to the zygomaticoalveolar crest, then further across the dorso-lateral wall of the maxillary

sinus, back towards to the inferior orbital fissure. In addition, the zygomatic arch fractures. The orbital floor is regularly involved in zygomatic fractures, corresponding to the line of fracture (Figs. 3.8–3.10).

Depending on the applied forces, strong violence may lead to zygomatico-orbital comminuted fractures with polyfragmentation and dislocation of the central zygomatic complex. In the process, the zygomatic body is dislocated into the maxillary sinus, seldomly into the orbit. Collaterally the facial and dorsolateral wall of the maxillary sinus, as well as the orbital floor and the medial, more seldomly the lateral orbital walls, are demolished. Accompanying orbital injuries, further injuries such as ruptured bulbus and injuries to the optical nerve are possible (Lew and Sinn 1991; Raveh et al.1992).