■ Part 2. Current Principles of Repair
The craniofacial skeleton in terms of repair can be conceptualized as three functional and morphological units, created by division at the Le Fort levels I and III.27 The skeleton in this strategic depiction has a lower (“occlusal”) third, an upper (“cranial”) third, and a midfacial (“maxillary”) third.
The lower “occlusal” third contains the dental arches, palatal platform, and the bases of the seven buttresses as they begin their ascent to the upper face and cranium, and thus the dentition and upper digestive tract involved in mastication, swallowing, and speech ( Fig. 3.6A ).
The upper third of the craniofacial skeleton, composing the anterior and middle cranial vault, includes the roof of the orbit and affords protection and support for the brain and the cranial nerves as they make their outward egress to supply the bone and soft-tissue mask ( Fig. 3.6B ).
The middle third of the craniofacial skeleton contains a majority of the orbital frame, the walls and floor of the orbit, and the upper face, supporting and protecting the nasal conduits, sinuses, and orbital contents. Injury to the upper third is characterized by fractures that separate the face from the cranium; the level III Le Fort fault passes through the temporozygomatic and sphenozygomatic sutures, the frontomaxillary and nasofrontal sutures, the ethmoid and sphenoid sinuses, and the orbits.28 – 32
Accurate repair of the fractured craniofacial skeleton is based on relating the palatal platform, alveolus, and lower maxilla to the mandible. The lower “occlusal” third of the face is thus the first to be restored. The repair next reestablishes the frontal sinus and frontal boss; by doing so, the anterior cranial vault is restored and isolation of the dura and cranial content assured. Third and finally, the relationships of the central and lateral upper face to the cranial vault and cranial base are reestablished, the orbital frames are reassembled, and the orbits are returned to appropriate volume. The inferior and superior maxillary zones of the craniofacial skeleton may then appropriately relate to each other11 , 31 , 32 (see Chapter 9) ( Fig. 3.6C ).
Clinical Assessment and Indications for Repair
Immediate resuscitation and rapid retrieval of the injured dramatically improved after the early efforts of French Empire surgeon Dominique-Jean Barron Larrey and notably World War I veteran Antoine De Page.6 Certainly, the speed with which the injured are today whisked from the scene of injury to centers of advanced care is remarkable. Improved airway and anesthesia skills, the transient use of potent antibiotics, and rigid stabilization of comminuted bone have resulted in better outcomes.
These improvements have been reached despite a concomitant increase in the velocity of vehicles and missiles. Vehicular speeds exceeding 70 miles per hour are not uncommon. Also, rifle bullets traveling at 2500 feet per second have been supplanted by improvised explosive devices, delivering payloads at 25,000 feet per second, creating profound disruption of soft tissue and comminution of bone ( Fig. 3.7 ).
Sophistication in airway control and more logical strategies of fluid resuscitation and the development of trauma scores (see Chapter 6) warrant improved survival. Early intervention in cases of airway obstruction is now commonplace, beginning at the scene of injury. The development of sophisticated evacuation systems has made delivering quick-response teams by air or by surface to intervene at the scene of injury available. Airway management and protection of the spine have reached new levels of competence.
Greater emphasis has been placed today on early control of hemorrhage, attention to base deficit (acidosis), and the avoidance of persistent tissue hypoperfusion. Improved surface oxygen-monitoring technology and the infusion of thawed fresh-frozen plasma in lieu of packed red blood cells are now considered the more viable options in so-called damage-control resuscitation.32 – 44
Indiscriminate crystalloid fluid infusion, once dogma, has been discouraged since the millennium41 , 42 because of its harmful side effects, including induced hemodilution, hypothermia, coagulopathy, and postoperative immuno-logical suppression.41 The renewed, preferred use of blood products, notably fresh-frozen plasma in lieu of crystalloid, followed meta-analysis of data from several institutions.
Overlapping skill sets among specialties encourage a high level of corroborative care of the injured once a tertiary center is reached. “The initial consultation after high velocity-injury can be either the moment of truth or the moment of deception”45 (as in much reparative surgery).
The window of diagnosis is greatly aided today by high-resolution computerized tomography (HRCT) and three-dimensional reformatting (3-DR).46 – 49 The potential for survival despite widespread comminution of the entire craniofacial skeleton is now recognized, as revealed by computerized tomography, HRCT, and 3-DR. The detail of these studies is now such that a preliminary plan of operative care may be reasonably formulated before operative intervention occurs.11 , 48 , 49
Short delays in acquiring detailed radiographic assessment and careful preoperative planning cause little difference in intensive care or hospital length of stay and actuarially result in a negligible difference in rates of infection and complication.50 The brief delay in operative intervention affords the opportunity to reflectively review radiographs on numerous occasions before surgery and increases the yield of unrecognized injury.48
Intraoperative Radiographic Assessment
HRCT during surgery (using portable units) allows assessment of the repair of the craniofacial injury in an ongoing manner. This intraoperative modality has great promise as an adjunct to more precise reduction of fractures of the orbit and the orbitozygomatic complex. 3-DR will probably be optionally added.
General Patterns of Fracture
Patterns of injury, first identified at the turn of the preceding century when Le Fort exposed cadavers to various load forces, are now just a few of many patterns revealed by modern HRCT and 3-DR. Paradoxically, these radiographic studies also document the uniqueness of most patient injuries. So, while certain patterns of injury are apparent in each third of the craniofacial skeleton, the surgeon is aware that patients carry “an imprint specific to their individual injury.”51 , 52
Current radiographic studies provide considerable detail, such that an admix of simple patterns and extensive comminution may coexist in the same patient: one side or level may bear innocent, nondisplaced injuries, while the opposite side or a different level has been reduced to orts, with faults reaching distant, collateral areas. Anticipation of the myriad of patterns and the uniqueness of each injury improves preoperative assessment. Despite this foreknowledge, the final surgical formulation is deferred in several cases until broad exposure and manipulation of the fractured segments has been achieved to assess instability.52
Fractures of the palate tend to occur off the midline, in thin parasagittal bone, and often exit the anterior maxilla between the most mesial teeth of the anterior segment. The split palatal shelves splay outwardly with buccal version of the palatoalveolar segments, creating untoward instability of the lower third of the face. The instability of the palatal platform has the ability to profoundly influence the occlusion of the jaws ( Fig. 3.8 ).
Fractures of the mandible tend to be bilateral, with injury inflicted at the symphysis or body on one side and the angle or subcondylar neck on the other. The symphyseal fracture tends to be oblique, with telescopic overlapping of the mandibular fragments. When the angle is involved, the fault commonly begins at the inner (lingual) cortex, traverses the root socket of the third molar, and exits obliquely through the outer cortex ( Fig. 3.9 ).
Fractures of the fronto-orbital bar (frontal boss) frequently involve the anterior table of the frontal sinus. Fractures may be medial, lateral, or comminuted. Fracture may include both tables of the sinus and may extend to the nearby cribriform plate and/or the periorbit ( Fig. 3.10 ).
When the fracture passes medially through the floor, the outflow tract of the sinus, the cribriform plate, and the fovea (roof of the ethmoid sinus) are subject to comminution, dural tear, and, in time, chronic sinusitis. Alternately, when the fracture extends through the lateral frontal sinus floor, involvement of the underlying orbital roof is common. The fracture may traverse thick bone of the lower portion of the frontal boss and involve the nasofrontal suture, causing separation and downward displacement of the nasal complex.
Le Fort I maxillary fractures progress across the maxilla (superior to the apices of the teeth) and adjoining bones, traversing the anterior buttresses shortly after they ascend from the alveolus of the palate en route to the nasofrontal suture (frontal boss) and the cranial base. In their transverse propagation, the fracture lines pass through the antrum of the maxillary sinus and the nasal cavity, just above the nasal floor. By passing through the posterior wall of the maxillary sinus and the posterior buttresses, the faults create occlusal disjunction31 ( Fig. 3.11A–D ).
The Le Fort II fracture elects a more oblique pathway, leaving a greater portion of the lower maxilla and the pyriform aperature in the inferior occlusal fragment. The Le Fort II fracture separates the inferior maxilla and nose from the lateral midface and orbits by traversing the lateral midfacial buttress, the anterior face of the maxilla, and the medial midfacial buttress to reach the nasofrontal suture. Le Fort level III fractures are again relatively transverse, crossing the lateral and medial orbits and separating the cranium from the face. When the fracture lines cross the frontal boss and extend into the frontal sinus and the anterior fossa, they can be referred to as Le Fort IV fractures. The fault associated with pattern IV may pass through the sagittal maxillary (vomerine-sphenoidal) posterior buttress to reach the middle cranial fossa.28 , 31 , 53
Fractures may comminute the upper aspect of the anterior medial maxillary buttresses, profoundly affecting the transverse distance between the orbits and the position of the medial canthal tendon. Behind the medial buttresses are the lacrimal bones, the ethmoid sinuses, and the medial walls of the orbits. The medial orbital frame after nasomaxillary fractures may shift and assume a vertical position. The fracture fault may ascend to the frontal sinus and anterior fossa ( Fig. 3.12 ).
The fracture pattern of the zygoma and its arch on HRCT is one of the more important to understand and the most often underinterpreted. The disruption is too often referred to as a “tripod” or “quadripod” fracture, neither of which give the injury due justice.54 The fracture crosses the zygomatic arch, usually at or near the junction of the zygomatic process of the temporal bone and the temporal process of the zygomatic bone. The linearity of the zygomatic arch is disrupted, particularly when its span is comminuted. When the fracture cleaves the frontozygomatic suture, the lateral midfacial buttress, and inferior orbital rim, the zygoma is subject to rotation posteriorly, inferiorly, and medially; the zygomatic arch and the zygomatico-maxillary buttress are displaced (splayed) laterally ( Fig. 3.13 ).
The fracture may profoundly reduce the orbital volume as the orbital plate of the zygoma pivots inwardly after separating from the greater wing of the sphenoid. The anterior pole of the temporal lobe of the brain, in the floor of the middle fossa, may be injured when the fracture displaces the greater wing of the sphenoid.
Fracture patterns of the orbit reveal zones of vulnerability and disruption of the microbuttresses that gird the roof, floor, and walls from impact, thus relatively protecting the globe and other orbital contents from injury. When reviewing radiographs, the orbit may be conveniently perceived as being trisectional. Though arbitrary, each section (the orbital frame, a midsection, and an apex) can then be studied for distortion and displacement (see Chapter 8).
Some orbital fractures are isolated, and, in those circumstances, the fractures usually occur in one of three locations ( Fig. 3.14 ):
The anterior medial orbital floor
The (central aspect of the) medial orbital wall (below the level of the cribriform plate)
The posteromedial roof
The bone in these three “areas of orbital vulnerability” is thin and contoured, supported only by microbuttresses (see Chapter 8), and in a biomechanical sense (see Chapter 2), subject to “blow-in” or “blow-out” fracture.