Surgical Management of Maxillofacial Fractures
Library of Congress Cataloging-in-Publication Data
Names: Sawatari, Yoh, author.
Title: Surgical management of maxillofacial fractures / Yoh Sawatari.
Description: Batavia, IL : Quintessence Publishing Co, Inc., [2019] | Includes bibliographical references and index.
Identifiers: LCCN 2018056134 | ISBN 9780867157949 (hardcover) | ISBN 9780867158427 (ebook)
Subjects: | MESH: Maxillary Fractures--surgery | Oral Surgical Procedures--methods | Face--surgery
Classification: LCC RD523 | NLM WU 610 | DDC 617.5/2059--dc23
LC record available at https://lccn.loc.gov/2018056134
©2019 Quintessence Publishing Co, Inc
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Editor: Leah Huffman
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Printed in China
Contents
Foreword
Preface
1Introduction to Facial Architecture
2Frontal Sinus Fractures
3NOE Fractures
4ZMC Fractures
5Orbital Fractures
6Le Fort Fractures
7Approaches to the Midface
8Mandibular Fractures
9Concomitant Fractures and the Panfacial Fracture
Index
Foreword
Facial trauma is the foundation of oral and maxillofacial surgery. Historically, it proved to be the conduit for the exodontists of the past to move from their offices and clinics into the operating room and hospital to become oral surgeons. It was these innovative and forward-thinking oral surgeons who refined and advanced the management of facial trauma to an expanded scope as they became oral and maxillofacial surgeons. Today, it is the profession of oral and maxillofacial surgery that has answered the call and accepted the intricacies and the demanding precision required in treating the hard and soft tissues of facial trauma to become its leader and most reliable responder.
It is this attention to detail, precision of surgery, and comprehensive modern-day trauma management that Surgical Management of Maxillofacial Fractures by Dr Yoh Sawatari so aptly presents in a clear, logical, and understandable manner. This book is supported by clear clinical photographs and pre- and postoperative CT scans, and it is beautifully illustrated. In a unique blend of descriptive text and images, Dr Sawatari directs the reader through a detailed assessment phase, surgical approach and technique phase, as well as a critical postoperative assessment phase born from his own extensive experience as Director of Facial Trauma at one of the world’s busiest Level I Trauma Centers. This book is a required learning tool for interns, residents, and fellows as well as a reference and refresher for the established practitioner.
Preface
While the basic concepts behind facial fracture management—the application of force, the geometry and objective measurements, and the biology of tissue healing—have remained unchanged throughout history, significant advances in fixation techniques and imaging have improved the outcome. Within the past 20 years, imaging and its accessibility have dramatically improved the manner in which facial fractures are managed. The combination of data that can be gathered, the efficiency with which it can be gathered, and the accessibility allows for preoperative, intraoperative, and postoperative assessment of facial trauma surgery. By obtaining high-resolution, detailed maxillofacial CT scans with 3D reconstruction, the surgeon is capable of assessing the facial fracture in great detail prior to intervention. If necessary, virtual surgical planning and custom plating can then be utilized to improve efficiency of the surgery and accuracy of the reduction. The surgeon can now be familiar with the exact fracture pattern and its relationship to adjacent stable structures. Intraoperative imaging can then be obtained during the surgical procedure, which allows for assessment and confirmation of adequate reduction during the surgery. Finally, postoperative imaging allows the surgeon to scrutinize the results, correlate the imaging with the clinical outcome, and modify techniques to obtain an improved outcome. The management of facial fractures is never straightforward or easy. However, with the advancements in imaging, the understanding of the injury and objectives has increased, and the resultant surgical outcomes have improved.
This textbook was written for the novice surgeon who undertakes the difficult task of managing facial fractures. It is a concise overview of the management of the different categories of facial fractures written based on knowledge and strategy gained over the past 18 years. The book was not designed to introduce new concepts or go into exhaustive detail but rather to streamline thoughts and strategies and to focus solely on the management of facial fractures. Each chapter describes one type of fracture and includes preoperative clinical/radiographic assessment, treatment planning, surgical execution, and an overview of potential complications and pitfalls. While the book can certainly be read from start to finish, it was designed to be a quick reference for any surgeon who faces the management of facial fractures and asks the question: How do I manage a [insert fracture type here] fracture?
Acknowledgments
I would like to thank my mentors who have guided me and provided me with the tools that allowed me to create this textbook. These individuals include Ken Moran, Eric Carlson, Mark Stevens, Marco Morales, and Eustorgio Lopez, with special thanks to Michael Peleg and Robert Marx. Each of these individuals has given me opportunities and provided me with knowledge, guidance, and friendship to allow me to mature as an oral and maxillofacial surgeon and as a human being.
I would also like to thank Leah Huffman for her editorial expertise and patience. Thanks are also due to my surgical colleagues, who throughout the years have provided me with the intellect, creativity, support, and contributions to make this book possible.
Finally, I would like to thank my parents and brothers for their support and encouragement, and of course my son and daughter, and especially my wife, for their inspiration, love, and support.
Introduction to Facial Architecture
The face is defined by the contours and projection of the facial skeleton. All soft tissue structures including muscle, skin, ligaments, and tendons are supported by the facial skeleton and provide animation to the face. Critical structures including the optic nerve and sensory nerves are encased within deep architecture of the facial skeleton, and the facial nerves are intimately associated with these bones. In addition, the facial skeleton provides direct functional support, including the movement of the mandible, and fractures of the periorbital area can have a significant effect on vision and the ability to direct vision.
Besides the projection and contours of the face, the primary defining feature that affects both the appearance and functionality of the face is symmetry. Facial symmetry is based on the reflection of the bilateral face along the midsagittal plane. Although subtle facial asymmetry is a norm regarding facial features, displaced facial bone fractures and resultant deformities along with functional deficits associated with nonreduced malpositioned facial bones are the primary indications necessitating surgical management of the facial skeleton.
When attempting to understand facial fractures and the effect on appearance and function, the surgeon must begin by compartmentalizing the face and defining the character of the bones. The facial skeleton may be divided into three different regions: the frontal region, the midface, and the mandible. The projection and contours of these three regions have the greatest effect to define facial features. From the most superior aspect of the face, the frontal region defines the forehead extending from the trichion to the supraorbital bar. This region is responsible for brow projection and forehead contour. The frontal bone is not considered one of the facial bones but is part of the skull base. The second region is the midface area. The midface is what encompasses and defines the facial skeleton, as it is comprised of six pairs of facial bones—the zygomatic, maxilla, nasal, lacrimal, palatine, and inferior nasal concha—and the vomer. This midface area is the most critical region of the face in regard to facial projection, symmetry, and function. The periorbital area draws the majority of attention, and its projection is defined by the periorbital rims, nasal projection, intercanthal distance, zygomatic projection, zygomatic width, maxillary projection, and maxillary dental position. In addition, the midface bony structures define globe position (both depth and vertical level) and affect globe motility and occlusion as well as masticatory function. The last region that defines the face is the mandible. The mandible is critical for occlusion, masticatory function, chin projection, and transverse lower third width. In addition to facial projection and function as described above for each individual region, each region also has its own sensory branch of the trigeminal nerve. Thus, any fractures in these regions can compromise sensation on top of defects of form and function.
The facial bones can now be further conceptualized and defined into two different types of structures: dense rigid buttresses and laminar sheets. The buttresses are traditionally dense cortical pillars that provide stability and structure to the face. They are responsible for the contours and dimensions of the face as well as the support for the laminar bone and the entire soft tissue component of the face enveloping the facial skeleton. The buttresses are further divided into horizontal and vertical buttresses (Fig 1-1). Horizontal buttresses are characterized by dense bone and have an arcuate shape. The first horizontal buttress is the supraorbital bar. This section is comprised of the frontal bone and extends from the zygomaticofrontal (ZF) suture across the midline to the contralateral ZF suture. This bar provides supraorbital projection and shape to the brows and is the major prominence of the forehead. Progressing inferiorly, the next horizontal bar is at the infraorbital rims and zygomatic arches. This bar extends from the zygomatic arch on one side, across the infraorbital rims to the contralateral arch. The third horizontal buttress is the arc comprising the cortex from the pterygoid plate extending to the floor of the nose through the anterior nasal spine across to the contralateral pterygoid plate. The fourth horizontal buttress is the inferior aspect of the mandible (Fig 1-2). The vertical buttresses are also dense cortical pillars, but they exist in more of an upright columnar orientation. The first vertical buttress of the face includes the bilateral paired nasofrontal section extending along the piriform rim. The second vertical buttress is the ZF junction. The third paired buttress is at the pterygoid plates, and the last is the ramus of the mandible (see Fig 1-2). Finally, there are areas of the face where the vertical and horizontal buttresses intersect with each other. This is at the maxillary buttress, the base of the piriform aperture, the nasofrontal junction, and the angle of the mandible.
Fig 1-1 (a to c) Facial buttresses (red, vertical; blue, horizontal).
Fig 1-2 (a and b) Facial architecture: Vertical buttresses are struts, and horizontal buttresses are arcs.
To understand fracture patterns, it is important to understand the concept of vertical and horizontal buttresses and the intersections they create. Based on the distribution of forces, the horizontal and vertical buttresses fracture in different ways. Because the majority of facial fractures develop from the application of force from an anterior-to-posterior vector, the way in which the facial bones fracture is somewhat predictable. When force is applied to the horizontal buttresses, due to the arcuate shape, the bone fractures with displacement of the anterior segment posteriorly (losing projection), and the posterior segments splay in a lateral dimension (Fig 1-3). On the other hand, when vertical buttresses fracture, the central section of the buttress also displaces in a posterior vector, and the vertical height is shortened (Fig 1-4). Understanding the differences between how these buttresses fracture allows the surgeon to understand the resultant deformities that are created from these facial fractures. The loss of projection of a naso-orbitoethmoidal (NOE), Le Fort, or zygomaticomaxillary complex (ZMC) fracture is due to fracture of a vertical buttress. On the other hand, the development of telecanthus, the widening of the zygomatic arch, and the widening of the posterior mandible from a symphysis fracture are due to fractures of a horizontal buttress.
Fig 1-3 (a) All horizontal buttresses are arcs. (b) Force application to a horizontal buttress leads to decreased anterior projection and increased posterior transverse width.
Fig 1-4 (a) All vertical buttresses are struts. (b) Force application to a vertical buttress leads to decreased anterior projection and decreased vertical height.
In order to effectively manage facial fractures, the objective is to reverse the damage that the buttresses sustained and restore appropriate facial dimensions. This translates to the uprighting of the vertical buttresses, the reduction of the posterior horizontal buttresses, and the restoration of anterior projection for both vertical and horizontal buttresses. Thus, generally all fractures of the face will require restoration of the anterior projection, restoration of the vertical height, and closure of the widened posterior dimensions of the face (Fig 1-5). The management of each fracture type is ultimately dependent on the location of the fracture (Fig 1-6), and the concept of fracture management is always the same: Use adjacent stable bone as a reference and bring unstable fractured segments to the stable references; this is reduction. Once the fractured segments are aligned and the preinjury position is established, fixation is used to (1) stabilize the fracture to prevent collapse of the segments and (2) allow for appropriate bony apposition for immobility and adequate healing. The stable references are invariably the vertical and horizontal buttresses of the face, and the fixation points for all facial fractures are traditionally the intersection of the vertical and horizontal buttresses.
Fig 1-5 (a) Force application from anterior to posterior. (b) Force application to horizontal and vertical buttresses. (c) Increase in transverse dimension of the zygomatic arches and mandible. (d) Increase in transverse dimension of the maxilla.
Fig 1-6 (a and b) Frontal and lateral views showing the delineation of facial fractures. (c and d) Frontal bone, (e and f) ZMC. (g and h) NOE. (i and j) Le Fort 1. (k and i) Le Fort 2. (m and n) Le Fort 3.
Once the concept of facial buttresses is understood, the next step is to understand the different patterns of facial fractures. Essentially all facial fractures are a combination of vertical and horizontal buttress fractures. However, there are multiple factors that influence the incidence of each type. The first factor that determines the incidence of fractures is the location on the face. Any area of the face that projects more tends to be more susceptible to fracture. The nose is first, followed by the ZMC, and then the mandible. The second factor that dictates the incidence of fractures is the mechanism. The most common cause of facial fractures is assault, followed by falling and motor vehicle crashes. The third factor that influences fracture type is the amount of force applied to the face. The classic physics laws are always at work when analyzing facial fractures:
F = ma [force equals mass times acceleration]
KE = ½mv2 [kinetic energy is directly proportional to the mass of an object and the square of its velocity]
An assault by a fist is far different from an assault with a solid object, which is again very different from the force of a high-velocity motor vehicle crash to the face. The greater the force, the greater the damage inflicted, and the more fractures, the more comminution that the patient will likely develop from the injury.
Clinical Examination
The clinical examination should be thorough and systematic, efficient and effective. A routine should be established with sequencing and techniques so as not to miss any relevant findings. It is critical to utilize the clinical examination to gather as much information as possible regarding the visible injuries that were sustained and the deformities that provide clues to the fractures that lie within (Fig 1-7).
Fig 1-7 (a) Clinical view of a panfacial fracture. (b) Clinical view of a severely displaced ZMC. (c) Clinical view of a severely displaced NOE.
The clinical examination involves a sequence of steps. Beginning at the vertex of the skull and proceeding with the examination in a top-down fashion is generally the most logical and thorough method (Fig 1-8). The points of origin and end are not as important as being thorough to comprehensively cover all aspects of the facial skeleton. For an examination to be effective, the provider must visualize and palpate all facial components. With visualization, positive findings including deformities, edema, erythema, ecchymosis, lacerations, exposed bone, foreign bodies, malocclusion, bleeding, and asymmetry should be noted. In addition, with visualization, any reactive movement is also documented. This includes assessment of facial nerve function, ocular motility, and temporomandibular joint function. With palpation, steps, mobility, exposed bony edges, edema, and crepitus should all be noted. Reaction to the palpation also offers information on the status of the injury and information on underlying fractures.
Fig 1-8 Clinical examination sequence. (a) Superior view. (b) Inspection and palpation of the frontal region. (c) Inspection and palpation of the supraorbital rim. (d) Inspection and palpation of the infraorbital rim. (e) Inspection and palpation of the nasofrontal region. (f) Inspection and palpation of the zygomatic arches. (g) Inspection and palpation for a Le Fort 2 fracture. (h) Inspection and palpation for a Le Fort 3 fracture. (i) Inspection and palpation of the mandible.
Factors that can affect the examination
Due to the nature and degree of the traumatic injury and the time that has elapsed since the injury, the degree of edema will vary. If the patient has sustained a high-velocity, high-force injury, he or she will likely present with significant edema. This can affect the examination in multiple ways. First, it makes the determination of skeletal deformities and symmetry more difficult. Second, it affects the ability to palpate for steps and mobility. If the fracture segments are significantly displaced or grossly mobile, these features will be detectable in any amount of edema. However, if there are minimally displaced fractures with little mobility, it would be far more difficult to assess for these subtle changes in the facial skeleton. Edema is less of an issue when more time has elapsed since the injury, and any resulting deformities and asymmetry will be much more visible with time.
The second factor that affects the examination is the patient’s consciousness. If the facial fracture is due to a low-velocity impact, the patient will most likely be lucid and should be able to communicate with the surgeon for assessment of the face. When performing the examination, the patient will follow commands for the ocular examination, can describe any malocclusion, and can describe any neural deficits. In addition, when palpating for bony irregularities and fracture displacement, any mobility of fracture segments of bone can cause pain for the patient. During the examination, the palpation can elicit a reaction from the patient, oftentimes providing additional information or confirmation of an injury in a specific area.
Radiographic Examination
Like the clinical examination, a thorough systematic method should be established for the radiographic examination. With the exception of the orthopantomogram (panoramic radiograph) for mandibular fractures, all patients who are suspected of having facial trauma should have a noncontrast computed tomogram completed with a minimum of a reconstructed coronal and sagittal perspective. In addition, a 3D reconstruction is very useful for understanding the 3D relationship between stable and unstable bone, the relationship between concomitant fractures, and assessment of symmetry (Fig 1-9). Specific computed tomography (CT) findings of the individual facial fractures are described in each chapter of this book.
Fig 1-9 Radiographic evaluation. (a) Frontal 3D reconstruction. (b) Lateral 3D reconstruction. (c) Maxilla lateral 3D reconstruction. (d) 3D reconstruction showing the zygoma and maxilla. (e) 3D reconstruction showing the mandible.
Treatment Plan
One of the most important aspects of the management of facial fractures is the development of a treatment plan. The treatment plan allows the surgeon to approach and manage the facial fractures in an efficient manner. Unfortunately, the management of facial fracture is not always straightforward, and even with all the time spent on evaluation and planning, the plan may not always be executed in the manner it was established. However, each plan is established based on accumulated data and knowledge and application of surgical principles, and following a plan will minimize the incidence of errors and increase the likelihood of achieving an expected outcome.
Data collection
The first step in establishing the plan is to gather all data. As described above, this includes the collection of clinical data. Once the clinical evaluation is complete, a thorough radiographic evaluation needs to be completed. It is at this stage that the surgeon must assess not only the extent but also the complexity of the procedure to be performed, including a determination of which structures adjacent to the fractures are involved, such as soft tissues, globe, and nerves. In addition, functional issues including entrapment, trismus, and malocclusion are also assessed. At this point, the fractures are assessed as to the level of comminution, the presence of concomitant fractures, and the favorability of fractures.
Problem list
The data is then processed, and all the fractures are identified and defined. A list of all injuries and fractures is compiled.
Surgical plan
Treatment planning is based on the injury, the resultant functional and cosmetic deformities associated with the injury, the benefit of repair to the patient, and the stability of the patient. At this point, the surgeon then makes a decision as to which facial fractures require management from the compiled problem list (Fig 1-10). The decision to surgically intervene is very objective. The two classic assessment criteria are functional limitations and cosmetic deformities. Both of these criteria are a result of fractured facial bones, and the ultimate questions remain: (1) If intervention is performed, will facial form and function be restored? (2) When the intervention is performed, will there be a significant risk of iatrogenic injury? In addition, if intervention is not performed, will there be any long-term sequelae for the patient? With these factors placed into consideration for each fracture type, the surgeon can make a rational decision to proceed with facial fracture repair. Once the surgeon has elected to intervene, a determination is then made as to which components of the fracture will be reduced and fixated. This will in turn determine which access will be utilized to manage the select facial fractures. Once access has been determined, the sequencing of access and sequencing of reduction and fixation can be finalized. The various access types and the sequencing of reduction and fixation are reviewed in subsequent fracture-specific chapters.
Fig 1-10 (a) Surgical treatment plan. (b) Execution of the treatment plan.
One additional aspect of planning is the airway. Generally, any fracture of the mandible or maxilla requires a nasal intubation so that intermaxillary fixation (IMF) can be placed to assist with the establishment of occlusion and stabilization of the fractures. For any frontal region and midface fractures, aside from the Le Fort type fracture, oral intubation is required to keep the airway out of the surgical field. When there is a combination of both midface and mandibular fractures, the surgeon can pass an oral tube posterior to the dentition (space dependent), perform a planned tracheostomy (Fig 1-11a), or complete a submental intubation (Fig 1-11b). Any patient that has an oral intubation should have the endotracheal tube secured with a circumdental wire around the first molar or second premolar. This will keep the face clear of any tape and provides confidence that the endotracheal tube will not be dislodged during manipulation of the facial fractures.
Fig 1-11 Airway management. (a) Tracheostomy. (b) Submental intubation.
The final aspect of planning is the timing of intervention. In general, for facial fractures, with the exception of isolated orbital floor fractures, there is no significant benefit to delaying the intervention. Depending on the presence of other concomitant injuries, the patient may not be stable from a neurologic (brain and spine), hemodynamic, pulmonary, infectious, or ocular standpoint to undergo general anesthesia and facial fracture intervention. Because facial fractures are never considered an emergency, even in the presence of open fractures of the face, all surgical interventions for open reduction and internal fixation (ORIF) will be deferred until all clearances are obtained to intervene. At times, weeks to months may elapse between the injury and the surgical intervention to allow sufficient recovery time or to achieve the physiologic stability necessary for the patient to undergo facial fracture management. With each week, the facial edema will subside, but the bones will start to form fibrous unions. While the speed and degree to which a patient’s bones will begin to fuse varies, generally the younger the patient, the quicker the bones will fuse. The bony fusion of a teen is significantly different from a patient in her 70s. Therefore, the key is to intervene as soon as possible because the ability to mobilize fractured segments becomes significantly more difficult after approximately 3 weeks.
If intervention is delayed, two strategies must be considered. The first option to consider is if there is a conservative treatment modality that can be implemented to assist in preventing significant deformities or malocclusion for the patient. For the frontal and periorbital areas, the management options are limited. However, for any fractures of the maxilla or mandible, the application of IMF will assist greatly in establishing occlusion and restoring some aspects of facial projection. There is a significant difference between managing healed fractures for cosmetics alone versus cosmetics and function. As long as there is no unstable cervical injury, a patient can have arch bars, IMF screws, or IMF bars applied with minimal morbidity and invasiveness.
If the patient is still not cleared 4 weeks postinjury, the ability to mobilize the bony segments becomes significantly more difficult. At this point the fractures are no longer mobile, there is definite fibrous union between segments, and considerable effort is required to mobilize these fractures. If the surgeon elects to intervene at this point, fortunately, the fracture lines can still be identified and chisels and possibly rotary instruments can likely be used to separate the segments. If more time elapses, it will be more difficult to identify the fractures and form a cleavage point and propagate fractures. In general, when performing delayed intervention, the type and location of the fracture will affect how easy it is to osteotomize and separate the segments.
Frontal sinus
Generally, anterior table segments can be easily separated, manipulated, and fixated. This is due to the presence of the sinus deep to the anterior table, so it is safe to use force to fulcrum off the stable adjacent calvarium to aid in the separation of the segments. However, if the surgeon is dealing with the posterior table, if anterior table segments are attached to the posterior table, or if fractures propagate along the skull, then treatment should be deferred. It is practically impossible to mobilize fused skull segments, and if excessive force is used, there is a high likelihood of dural tears.
Midface fractures
Midface fractures are very difficult to manipulate once healed. Although it may be obvious where the fracture points are, the combination of the buttresses with the thin laminar bone tends to fuse relatively quickly. The most straightforward is the Le Fort 1 type fracture. If these bones have healed and there is a need to correct occlusion, osteotomies can either follow existing fracture lines, or new osteotomies can be performed.
ZMC and NOE fractures are far more difficult to deal with after they have healed. The NOE is difficult because of the inability to access and mobilize the segments. The globe is ever present along with the medial canthal tendon and the nasolacrimal apparatus. All of these important structures do not allow for easy manipulation of the bony segments or placement of osteotomes to mobilize the segments.
The ZMC fracture is particularly difficult due to the presence of four processes. In order to manipulate a malunion of a ZMC, all four processes must be exposed, and all areas must be osteotomized to mobilize the complex. Even when all four processes are osteotomized, oftentimes the orbital floor and lateral wall of the orbit are not easily accessible and do not allow for easy mobilization of the complex.
Mandible
Mandibular fractures are likely the easiest region to manipulate when bones have healed. Here any access traditionally used to treat fractures can be used to osteotomize and manipulate healed fractures. Generally, controlled forces can be used to separate the segments with the assistance of osteotomes. The only important structure that needs to be protected is the inferior alveolar nerve, and with the use of the dentition for IMF, mandibular fractures can be osteotomized, manipulated, reduced, and fixated even when treatment is delayed.
Fixation
The purpose of internal fixation is to stabilize bony segments to allow for normal bone healing. The commonly accepted theory of bone healing for facial fractures is fixation osteosynthesis. This concept is a departure from rigid fixation, which represents absolute immobility, and compressive fixation, which represents no gap between the bony segments. The concept is based on normal physiologic fracture healing dependent on vitality, stability, and minimal distance between fractured segments.
Fixation plates are available in a variety of conformations and range in thickness from 0.5 mm for non–stress-bearing regions of the midface to 3.0 mm in profile for mandibular reconstruction plates utilized for continuity defects. There are three different categories of plating: non–stress-bearing midface, stress-bearing midface, and the mandible. In general, the fixation has the lowest profile in the frontal area, and as the fractures progress inferiorly, the plate profile generally increases. Figure 1-12 generally summarizes the profile of the fixation plates used for different facial fractures.
Fig 1-12 Guidelines for plate profile/thickness based on location on the facial skeleton.
Plates should always be aligned along the dense facial buttresses. The buttresses offer cortical bone and greater thickness to allow the fixation screws to engage. The mandible is the exception because the entire bone consists of a dense cortical shell. Figure 1-13 summarizes the ideal locations for fixation plates of the various midface facial fractures.
Fig 1-13 Ideal placement of the fixation plates for the midface. Plates are placed on the horizontal and vertical buttresses.
Traditionally, for both the midface and mandible, it is very common to use monocortical plates, and therefore the 5-mm screw length is frequently utilized. In addition, 1.5-mm-diameter screws are used for the midface, and 2.0-mm-diameter screws are used for the mandible. Finally, it is ideal to place three screws on each side of the fracture. However, if the placement of three screws requires excessive dissection, excessive retraction, or potential iatrogenic injury, then two screws are adequate for midface fracture fixation. In stress-bearing areas including the mandible, two screws on each side of the fracture for each plate is acceptable; however, more than one plate is necessary for appropriate stability when using low-profile miniplates.
Postoperative Assessment
One of the most significant advancements in the management of facial trauma from a technical perspective is the postoperative CT assessment. While maxillofacial CT images have generally been obtained for preoperative evaluation, postoperative reduction traditionally has been assessed using plain radiographs. Radiographs reveal plate positioning based on bony landmarks, but plain films are not capable of providing detailed 3D imaging of fractured segments after reduction and reconstruction.
Nonetheless, plain films remain useful for fractures of the mandible based on their dependence on occlusion. Because the successful reduction of mandibular fractures is determined primarily by the restoration of function, when occlusion has been restored, there is an inherent assurance that the fractures of the mandible are adequately reduced. The presence of a slight gap between bony segments or a misalignment of the inferior border is usually inconsequential to the establishment of function as long as the dentition is aligned to allow for maximal intercuspation with the condyles in the appropriate position. This is the rationale for obtaining postoperative panoramic radiographs for mandibular fractures, because the visualization of the true 3D positioning is inconsequential to the successful re-establishment of function. Therefore, the fundamental purpose of a plain film becomes plate positioning relative to alignment of different landmarks of the face, screw positioning, and the relationship of plates to fractures and fracture segments to each other.
Management of the midface differs in principle from that of the mandible, and thus the postoperative assessment is not equivalent. For all midface fractures aside from a Le Fort type, occlusion is not a factor in the assessment of successful reduction and fixation. A 2D postoperative image of midface fractures is insufficient to determine appropriate reduction and fixation of the fractures. Immediate postoperative clinical assessment is not valuable because oftentimes the postoperative edema is greater than the postinjury presurgical edema, and accurate assessment of facial structures and globe position cannot be determined. In addition, the midface fracture does not have the luxury of a functional component to allow the surgeon to assess the immediate postoperative results. Therefore, a postoperative CT is essential in the assessment of appropriate facial bone reduction. With the benefit of accompanying analytical software, multiple accurate measurements can be made on the CT images to assess for facial symmetry and re-establishment of projection and preinjury contours.
The objective of postoperative imaging involves the analysis of surgical success to restore facial fractures to the preinjury state. The short-term benefit of the CT imaging and the associated 3D reconstruction is the immediate assessment rather than the “wait-and-see” approach of the clinical examination. If appropriate reduction is achieved with adequate restoration of projection and symmetry, the patient can be notified of the successful results and anticipate an acceptable outcome. Conversely, if the reduction is inadequate or the orbital floor plate is inappropriately positioned, the patient may undergo immediate modification to remedy the less than ideal results.
Due to the severity of many of the fractures encountered, and because patients do not customarily have baseline intact CT scans of their face, an evaluation of symmetry to the contralateral aspect of the face represents the best means to assess appropriate fracture reduction. Four measurements can be made on a CT image: linear distance, angle measurement, surface area, and extrapolated volume (see Figs 1-14 to 1-20). Multiple aspects of the face can be assessed using these four tools of measurement, including anterior facial projection, transverse facial projection, enclosed areas of the face (orbit, infrazygomatic space), and orbital volume.
Fig 1-14 Linear measurements: (a) transverse dimension; (b) anterior projection.
Fig 1-15 Angle measurement: orbital floor.
Fig 1-16 Angle measurements: (a) root of zygomatic arch; (b) angle of zygomatic arch.
Fig 1-17 Increased posterior width of the mandible based on the angular displacement of the symphysis area. A small angular displacement in the symphysis will lead to a significant increase in the transverse dimension.
Fig 1-18 Surface area of the coronal orbit.
Fig 1-19 Infrazygomatic space.
Fig 1-20 (a and b) Orbital volume.
Facial projection is an important component of successful facial bone reduction. With the understanding of force transmission on the face, any blunt trauma propagating posteriorly will lead to posterior displacement of the vertical buttresses of the face (see Fig 1-4). For a Le Fort, NOE, or ZMC fracture, the vertical buttress at the ZF, the piriform aperture, and the maxillary buttress are often affected. The posterior displacement at these buttresses leads to deficiency in anterior projection and also results in an increase in orbital volume. This may lead to decreased clinical facial projection at the malar prominence or telecanthus and possible dystopia and enophthalmos, depending on which buttresses are affected.
For the transverse dimension, horizontal buttresses flare laterally when a posterior vector of force is applied (see Fig 1-3). This is most obvious for the zygomatic arch when a ZMC is sustained, or when there is a symphysis fracture of the mandible. The horizontal buttresses are in the shape of an arc, and therefore when fractured, the zygomatic arch displaces laterally, as does the posterior mandible when the symphysis of the mandible is fractured (see Fig 1-3). Although not a buttress, the NOE fracture follows the same principle of arc displacement. In a type 2 or 3 NOE, the central fragment is fractured in multiple segments. The central fragment is then displaced posteriorly as a continuation of the vertical buttress of the piriform, but it also displays a posterior splaying of the bony segments. This splay or displacement at the posterior aspect of the NOE leads to the clinical manifestation of the telecanthus. This is another characteristic of facial fractures that can manifest as an obvious deformity on the clinical examination.
Finally, globe position is a relatively common deformity associated with the midface fracture. The reason for this is related to the fact that almost all midface fractures have an orbital rim component: ZMC with the lateral orbit and inferior rim, NOE with the inferior rim and medial wall, and Le Fort 2 and 3 with the medial or inferior section of the rim. In addition, all ZMC, NOE, and Le Fort 2 and 3 fractures affect the orbital floor or medial wall of the orbit. Any displacement of the rim components will lead to projection deficiencies and direct increases in orbital volume. This altered orbital volume, which can be as little as a 6.3% increase, may lead to the retraction and inferior displacement of the globe and thus the clinical manifestation of dystopia and enophthalmos.
The evaluation of postoperative CT imaging comparing linear measurements, facial angles, and surface and volumetric dimensions can assess the success of facial fracture reduction. However, it is the clinical manifestation that is of utmost importance and the only factor that truly dictates the success of the surgical intervention. If the facial bone structures are not restored to the appropriate position, the soft tissue drape cannot be positioned to the preinjury state, and there will be a subsequent acquired facial deformity.
Nevertheless, the postoperative CT analysis holds another significant benefit for the surgeon: It influences and assists the surgeon by improving future preoperative treatment planning and execution of surgery. The assessment of postoperative CT results also has a direct influence on how future preoperative CT scans are evaluated. Any subsequent treatment planning including the access selection, the election to intervene, the sequence of reduction, and the anticipated outcome can be influenced by the observed results from a postoperative CT. If a surgeon can objectively assess his or her postoperative results, over time there will be a far greater understanding of surgical maneuvers and techniques and their effects on radiographic and clinical outcomes. Having a means to assess surgical results in an objective manner identifies deficiencies in technique or materials and initiates improvement based on necessity.
CT Assessment
Linear measurements
Although the facial skeleton is a 3D structure, specific factors such as anterior and lateral projection directly influence the surgical and esthetic outcome. When assessing a preoperative or postoperative CT scan, a direct measurement can be made on an axial or coronal image to determine both the degree of fracture displacement on the preoperative CT scan and the success of reduction on the postoperative CT scan (Fig 1-14). Utilizing a ZMC fracture as an example, the position of the complex can be evaluated on an axial CT scan using the Frankfort horizontal as the plane of reference. In this plane, posterior displacement of the complex and lateral displacement of the arches can be measured and compared to the contralateral side. Measurements of lateral arch displacement can be made using the midsagittal plane as the fixed midline reference. Additional anteroposterior (AP) measurements can be made using a fixed skull base reference that exists on both sides of the midline, such as the carotid canal or the posterior aspect of the glenoid fossa. Although the measurements cannot be directly translated into the surgical intervention, evaluation of the preoperative position of the fracture segments would assist the surgeon in determining the access needed and the degree of manipulation required for appropriate reduction. For the postoperative evaluation, the same AP and lateral measurements can be made to assess the successful reduction of the facial fractures.
Angle measurements
In addition to linear measurements, angles can also be measured to determine surgical plans and assess surgical results. There are multiple facial angles that have been assessed in order to assist in achieving optimal results in trauma management. The first involves the angle created between the anterior wall of the maxilla and the orbital floor in the sagittal plane. Orbital floor reconstruction is a difficult procedure, especially in combination with a ZMC fracture. The dissection necessary to establish support for the alloplastic implant is tedious, and when areas of support are missing, the implant must be cantilevered to achieve the appropriate support for the globe contents. In general, the inclination from the anterior wall of the maxillary sinus to the posterior shelf of the orbit measures an approximate 90-degree angle (Fig 1-15). Like all anatomy, there is always variability, and without the appropriate CT study of a large number of anatomical specimens, the 90-degree reference would only represent a recommendation. However, when reconstructing an orbital floor with minimal support for the implant, being aware that the orbital floor must be reconstructed with at least a 90-degree inclination will allow the surgeon to reconstruct the orbital floor in a more accurate position.
The second set of relevant angles that can be measured on the CT scan involves the zygomatic arch and any fractures involved with the arch. The zygomatic arch directly affects the transverse dimension of the face. When a patient sustains a ZMC or a Le Fort 3 fracture, the arch or zygomaticotemporal junction is always affected. Due to the arcuate form, there is often telescoping and lateral displacement of the arch. First, if the zygomatic process of the temporal bone is fractured, there will be a flare to the posterior aspect of the arch. This flare will invariably lead to a widening of the face, and the greater the angle of displacement (Fig 1-16a), the greater the lateral displacement of the complex based on the length and anterior extension of the zygomatic arch. The second angle that can be measured on the arch is the transition between the posterior and anterior aspect of the arch (Fig 1-16b). The zygomatic arch tends to be more linear than it is initially perceived during the reduction and fixation process. The posterior third of the zygomatic arch extends laterally, and as the arch extends anteriorly, an approximate 120- to 140-degree angle is created as it comes together with the maxillary buttress. If this angle is not preserved and a general curve is placed on the arch during fixation, the transverse dimension will be inaccurate, and the patient will manifest with a widened appearance of the midface.
Finally, the third angle that is often relevant in the planning and assessment stages of trauma surgery is the angle created from mandibular fractures. Like the zygomatic arch, the mandible is a horizontal buttress and exists in an arcuate form. When there is trauma directed at the anterior mandible, there is posterior displacement in the anterior segments and a flare of the posterior segments. The principle of overbending plates in the anterior mandible is based on the tendency for the posterior segments to flare after reduction and fixation of the anterior cortex of the mandible. Similar to the zygomatic arch, an angle of displacement is initially formed, and as the mandible extends posteriorly, the insignificant angle translates to an increased transverse dimension (Fig 1-17). The increased transverse dimension can usually be corrected with IMF or an occlusal splint against an intact maxilla; however, if the patient is edentulous, if there is a concomitant maxillary palatal fracture, or if there are additional fractures in the subcondylar area, there will be a widening of the patient’s face.
Surface area
The next measurement that can be obtained from the CT scan is surface area. Surface area measures are not as critical in preoperative assessment but offer greater benefit when determining the accuracy of postoperative reduction. Surface area can be calculated for confined areas of the facial skeleton such as orbits and has been commonly used for lesions and pathology in the head and neck area. Surface area on a CT scan is calculated based on the delineation of a region of interest. Once the region is defined, the pixels are counted within the region, and an algorithm converts the pixels to square centimeters. Surface area is complicated by the limitation of its benefit. For any given enclosed space, if a certain dimensional aspect is reduced while another is increased to the same degree, the absolute surface area will not change. The most ideal manner in which surface area is truly informative is if the two areas are overlaid on each other and observations are made to determine the location of the variability.
There are two areas that can be assessed when determining the success of postoperative reduction. One involves the reconstruction of the periorbital framework for a midface fracture. By assessing the surface area of the anterior orbit, the surgeon can determine if the framework was reestablished (Fig 1-18). In the event that the patient develops a dystopia postsurgery, if the framework is appropriately re-established, a determination can be made to modify the floor component. However, if the framework is not reduced appropriately, then the inadequacy would be related to both the reduction of the complex and the orbital floor.
Fig 1-19