Diagnosis of Midface Fractures with CT: What the Surgeon Needs to Know 1

Note: This copy is for your personal non-commercial use only. To order presentation-ready copies for distribution to your colleagues or clients, contact us at www.rsna.org/rsnarights. EDUCATION EXHIBIT 783 Diagnosis of Midface Fractures with CT: What the Surgeon Needs to Know 1 ONLINE-ONLY CME See www.rsna.org/education /rg_cme.html. LEARNING OBJECTIVES After reading this article and taking the test, the reader will be able to: Describe the buttresses of the midfacial skeleton. Discuss the major fracture patterns of the midfacial buttresses. Identify surgically relevant and emergent patterns of midface fractures. TEACHING POINTS See last page Richard A. Hopper, MD Shahram Salemy, MD Raymond W. Sze, MD Computed tomography is commonly used to evaluate patients with blunt facial trauma. With the high definition of the current scanners, even small fractures of the facial skeleton can be visualized. In complex midface injuries, it can be difficult for the radiologist to know which fractures are important to point out to the surgeon. An understanding of the anatomically relevant and surgically accessible craniofacial buttresses is critical for management of these injuries. Naso-orbitoethmoid fractures are classified according to the degree of injury to the medial canthal attachment. If the nasofrontal ducts are disrupted, surgical obliteration of the frontal sinus is needed to prevent formation of a mucocele. Displaced fractures of the zygomaticomaxillary complex often increase orbital volume due to angulation of the lateral orbital wall at the zygomaticosphenoid suture. If the zygomatic arch is severely comminuted or angulated, surgical exposure is indicated. In orbital fractures, the position and shape of the medial and inferior rectus muscles can indicate whether entrapment and diplopia are likely. Pediatric trapdoor orbital fractures and fractures of the orbital apex associated with decreasing vision represent surgical emergencies. Le Fort fractures involve disruption of the pterygoid plates from the posterior maxilla; any combination of Le Fort I, II, and III patterns can occur. RSNA, 2006 Abbreviations: NOE naso-orbitoethmoid, ZMC zygomaticomaxillary complex 2006; 26:783 793 Published online 10.1148/rg.263045710 Content Codes: 1 From the Departments of Surgery (R.A.H., S.S.) and Radiology (R.W.S.), University of Washington, Seattle, Wash. Received May 3, 2004; revision requested August 18; final revision received July 22, 2005; accepted July 22. All authors have no financial relationships to disclose. Address correspondence to R.A.H., Division of Craniofacial, Plastic and Reconstructive Surgery, Children s Hospital and Regional Medical Center, 4800 Sand Point Way NE, 6E-1, Seattle, WA 98105-0371 (e-mail: richard.hopper@seattlechildrens.org). RSNA, 2006

784 May-June 2006 RG f Volume 26 Number 3 Figure 1. Drawing of the adult skull shows the four paired vertical buttresses and the four transverse buttresses, all of which exist in areas of relative increased bone thickness. Introduction Midface fractures are common sequelae of motor vehicle accidents, falls, assaults, and other blunt trauma (1,2). Computed tomography (CT) has become the imaging standard of reference in evaluating these injuries to determine which patients will require surgical intervention for their bony injuries (3,4). The surgical treatment of displaced craniofacial fractures centers around restoring the preinjury alignment of the skeleton by using rigid fixation (5). To achieve this goal, the facial skeleton can be conceptualized as a series of buttresses that serve to support both the form and function of the face (5). Preoperatively, the surgical team needs to have a thorough understanding of the degree and nature of damage to the facial buttresses in order to plan their exposure and restore them accurately. With the high definition of CT, even minor, clinically irrelevant fractures of the facial skeleton can be visualized. In complex midface injuries with multiple fractures, it is important to distinguish those that have direct surgical relevance (6). The purpose of this article is to describe the major fracture patterns of the midface buttresses and their surgical relevance. The goal is to aid radiologists in the description of complex midface fractures using terms directly relevant to the surgical triage and treatment of the injury. Anatomy of the Facial Buttresses The facial skeleton can be conceptualized as four transverse and four paired vertical buttresses (Fig 1). The buttresses represent areas of relative increased bone thickness that support the functional units of the face (muscles, eyes, dental occlusion, airway) in an optimal relation and define the form of the face by projecting the overlying soft-tissue envelope. Owing to the reliance of facial form and function on these buttresses, as well as the mechanical force exerted on them, the surgeon typically treats any significant buttress displacement using reduction and rigid internal fixation with titanium plates and screws. As structural units that support the face, the buttresses must either directly or indirectly interface with the skull base or cranium as a stable reference (Fig 1). The upper transverse midface buttress runs from the squamosal portion of the temporal bone to the nasofrontal junction across the zygomatic arch and the inferior orbital rim. The posterior extensions of this buttress are the orbital floors. The lower transverse maxillary buttress runs along the maxilla above the alveolar ridge. The posterior extension of this buttress is the hard palate. The paired lateral vertical midface buttresses are the columns of bone from above the posterior maxillary molars across the zygomaticomaxillary suture and body of the zygoma, extending superiorly along the lateral orbital rim and across the zygomaticofrontal suture to the frontal bone. The Teaching Point Teaching Point

RG f Volume 26 Number 3 Hopper et al 785 Figure 2. NOE fracture pattern. Axial nonenhanced CT image shows that the medial vertical maxillary buttresses (*) are posteriorly and laterally displaced due to disruption of the upper transverse maxillary buttress. The medial canthi of the lids are attached to the rims of the lacrimal fossae (black arrows). Widening of the transverse buttress has resulted in telecanthus. The telecanthus was treated with transethmoid wires placed behind the lacrimal fossae to rotate the segments inward and restore the intercanthal distance. The sagittal extension of the medial maxillary buttress along the medial orbital wall has also been disrupted, resulting in exophthalmos from the blow-in fractures (white arrow) and loss of nasal dorsal projection. Reduction and fixation of the frontal process of the maxilla to the frontal bone along with a bone graft to the medial orbital wall were used to treat the orbital relationship; however, a calvarial bone graft to the nasal dorsum was required to restore nasal projection. posterior projections of this buttress include the lateral orbital wall and the lateral wall of the maxillary sinus. The paired medial maxillary buttresses are the columns of bone from the anterior nasal spine, extending along the rim of the piriform aperture, up the frontal process of the maxilla, and across the nasofrontal junction to the frontal bone. The posterior projection of this buttress includes the medial orbital wall, and the anterior projection includes the lateral nasal wall. The paired posterior maxillary buttresses are the columns of bone at the pterygomaxillary junction, where the pterygoid processes of the sphenoid join the posterior maxilla. Facial buttress pearls are as follows: (a) The buttress concept was intended for improved appreciation of facial structure; it does not replace traditional anatomic terms. (b) Buttresses have sufficient bone thickness to accommodate metal screw fixation. (c) Buttresses are all linked either directly or through another buttress to the cranium or cranial base as a stable reference point. (d) Transverse buttress reduction restores facial profile and width; vertical buttress reduction restores facial height. (e) Buttress reduction establishes a functional support for the teeth and globes. Common Buttress Fracture Patterns Naso-orbitoethmoid Fractures Naso-orbitoethmoid (NOE) fractures involve the central upper midface, disrupting the confluence of the medial maxillary buttress with the upper transverse maxillary buttress as well as their posterior extensions along the medial orbital wall and floor. Fractures of the NOE complex can be one of the most difficult fracture patterns to accurately repair. Even if the frontal process of the maxilla (superior portion of the medial maxillary buttress) is anatomically reduced, there can still be a residual rotation deformity that splays the posterior extension of this buttress. This will increase the transverse distance between the medial orbital walls and the attachments of the medial canthi, resulting in telecanthus (increased distance between the inner corners of the eyes) and globe malposition (Fig 2). The eyelids insert

786 May-June 2006 RG f Volume 26 Number 3 Figure 3. Drawings show the Manson classification of NOE fractures. A type I fracture involves a large bone fragment. A type II fracture involves comminution of the bone fragments. A type III fracture is defined by avulsion of the medial canthal ligament from its osseous insertion. Teaching Point Figure 4. NOE fractures. Coronal nonenhanced CT image shows a right-sided Manson type I fracture and a left-sided Manson type II fracture (among other fractures). In the type I fracture, note the large bone fragment (black arrow) with the attachment of the medial canthus. The fragment has been pulled laterally and inferiorly. This segment of the medial vertical maxillary buttress must be accurately reduced and fixated to reestablish intercanthal distance. In the type II fracture, the medial canthal attachment is on a small bone fragment, which is not visualized in this plane. The small bone fragment and tendon must be wired and plated to the defect in the medial vertical buttress (white arrow). around the lacrimal fossa through the medial canthal tendon. If the tendon insertion is not returned to its correct position, the patient loses the normal shadow definition on either side of the nose, the medial corner of the palpebral fissure drifts laterally, and the eyes appear too far apart. The Manson system classifies these fractures into three major subsets based on the medial canthus (Fig 3) (7). In type I, the fractured piece is large, and the medial canthal insertion around the lacrimal fossa is intact. Accurate fixation of the large bone fragment will restore the canthal anatomy (Fig 4). In type II, there is comminution of the buttress and the canthus is attached to a small bone fragment. The type III pattern cannot be diagnosed with imaging; instead, it needs clinical examination to determine if the canthus is avulsed from the bone. Radiologic description of NOE fractures should comment on the degree of comminution of the medial vertical maxillary buttress, specifically in the region of the lacrimal fossa, where the medial canthus attaches. The distance between the two lacrimal fossae in the coronal plane is also important, as it will alert the surgeon to the need for a medial canthoplasty. By definition, NOE fractures include damage to the ethmoid sinus and walls. If there is bilateral comminution and displacement in this region, the nasofrontal ducts that drain the frontal sinus are also likely disrupted (Fig 5). Nasofrontal duct disruption predisposes the patient to future mucocele formation unless the sinus is surgically obliterated. A description of the degree of comminution of the ethmoid sinus in the region of the nasofrontal ducts by the radiologist can be an invaluable reminder to the surgeon. NOE fractures include orbital damage. The description of orbital fractures is given later in a separate section. NOE fracture pearls are as follows: (a) NOE fractures are distinguished from simple nasal fractures by posterior disruption of the medial canthal region, the ethmoids, and the medial orbital walls. (b) Clinically, the most obvious deformity is loss of nasal projection in profile and apparent

RG f Volume 26 Number 3 Hopper et al 787 Figure 5. Nasofrontal ducts. (a) Coronal nonenhanced CT image shows the normal anatomy in the region of the nasofrontal ducts (*). (b) Coronal nonenhanced CT image of a patient with NOE fractures shows comminution of the ethmoid region and likely disruption of the nasofrontal ducts (*). In this situation, the frontal sinus (FS) will be obliterated to prevent postoperative mucocele formation due to inadequate frontal sinus drainage. Figure 6. Drawing shows the quadripod nature of the zygoma. Note the four sutures, in particular the location of the zygomaticosphenoid suture at the lateral orbital wall. increased distance between the inner corners of the eyes. (c) NOE fractures can be classified by the degree of injury to the region where the medial canthus attaches around the lacrimal fossa. (d) Although the frontal sinus may not be directly injured, if the nasofrontal ducts are disrupted, then frontal sinus surgery is needed to prevent a mucocele in the future. Zygomaticomaxillary Complex Fractures The paired zygomas each have two attachments to the cranium and two to the maxilla; they create a large portion of the orbital floors and lateral orbital walls. Therefore, these two cornerstone zygomaticomaxillary complexes (ZMCs) are surgically important in establishing orbital volume and serving as a reference for reduction of maxillary fractures. The two major buttresses of the ZMC are the upper transverse maxillary (across the zygomaticomaxillary and zygomaticotemporal sutures) and the lateral vertical maxillary (across the zygomaticomaxillary and frontozygomatic sutures). Fractures typically occur across these three buttress-related sutures, leading to the term tripod fracture. This term fails to recognize the posterior relationship of the zygoma with the sphenoid bone of the skull base and its extension inferiorly down the lateral wall of the maxillary sinus. A displaced ZMC fracture is a quadripod fracture (Fig 6). If the two buttresses of the zygoma are reduced and fixated, it is still possible to have

788 May-June 2006 RG f Volume 26 Number 3 Teaching Point a rotational deformity of the zygoma about the zygomaticosphenoid suture. The surgeon pays particular attention to the alignment of the zygoma and sphenoid at the lateral orbital wall, since angulation here after fixation of the remaining buttresses reflects a residual rotational deformity and an associated increased orbital volume (Fig 7). A fracture along the zygomaticomaxillary suture from the inferior orbital rim through the lateral maxillary buttress almost invariably traverses the infraorbital nerve foramen. Although the nerve is usually intact, the crush injury can lead to permanent anesthesia or impaired sensation of the cheek and a portion of the upper lip. In a noncomminuted ZMC fracture, the zygomatic arch component of the superior transverse maxillary buttress is typically left unfixated, with the remaining buttresses used as a reference for reduction. However, if the buttresses are comminuted, the surgeon may need to expose and reduce the zygomatic arch via a scalp incision to ensure that the zygoma is adequately anteriorly projected. The typical clinical and radiologic deformity of a ZMC fracture is loss of cheek projection and a resultant increase in facial width. A frequently missed ZMC fracture is at the temporal bone portion of the upper transverse maxillary buttress (Fig 8). If this angulation is not reduced before the remaining fractures are addressed, facial width will be increased and the cheek will be underprojected (Fig 8). The degree of displacement of the zygoma can be described by the impaction of the malar prominence in the axial plane (Figs 8 and 9) and the degree of angulation at the zygomaticosphenoid suture, which is a measure of the rotational deformity (Fig 7). Facial symmetry is achieved by restoring the three-dimensional position of the malar prominence, and orbital volume is restored by alignment of the zygoma with the sphenoid. ZMC fracture pearls are as follows: (a) The ZMC relates to the temporal bone, maxilla, frontal bone, and skull base and is therefore a quadripod structure. (b) Displaced ZMC fractures often increase orbital volume by angulation of the lateral orbital wall at the zygomaticosphenoid suture or blow-out of the orbital floor. (c) The zygomatic arch establishes both facial width and profile. Surgical exposure is indicated if it is severely comminuted or angulated. Figure 7. ZMC fracture. Axial nonenhanced CT image shows a displaced fracture of the left zygoma. The rotational deformity of the zygoma is demonstrated by angulation of the lateral orbital wall at the zygomaticosphenoid suture. The lateral displacement (black arrow) of the lateral vertical buttress (*) has resulted in increased orbital volume and enophthalmos (white arrow). Orbital Fractures Orbital floor fractures can occur in isolation, but they are also commonly associated with posterior propagation of ZMC and Le Fort II fractures (orbital floor fractures) and NOE fractures (medial orbital wall fractures). In severe ZMC fractures, the orbital defect can appear minimal due to impaction of the zygoma. It is important to visualize the defect with the zygoma in its anatomic position to appreciate the true loss of bone support. For orbital floor defects, attention to the shape and position of the inferior rectus muscle on coronal CT scans can provide information regarding the damage to the fascial sling of the globe. If the rectus remains flattened in cross-section and in the correct position, the fascial sling is likely intact and the surgeon will encounter minimal entrapped periorbital tissue (Fig 10a). However, if the inferior rectus is round and inferiorly displaced, the fascial sling is disrupted and the periorbita and muscle have prolapsed into the orbital floor defect (Fig 10b). Entrapment of the inferior rectus in children can be easily missed, since the flexible bone springs back into place like a trapdoor, looking normal at CT except for the entrapped muscle beneath it (Fig 10c). This pediatric trapdoor fracture requires urgent treatment within 24 72 hours to minimize the chance of motility problems (8). Teaching Point

RG f Volume 26 Number 3 Hopper et al 789 Figures 8, 9. ZMC fractures. (8) Axial nonenhanced CT image shows comminuted fractures (black arrows) of the left upper transverse maxillary buttress, with increased facial width and impaction of the malar prominence (white arrows). These are common sequelae of the distracting forces of the masseter muscle. This comminuted and displaced fracture pattern requires a coronal scalp incision for proper exposure, reduction, and fixation of the buttress. (9) Axial nonenhanced CT image shows fractures at the zygomaticotemporal (bottom arrow) and zygomaticomaxillary (top arrow) sutures of the upper transverse maxillary buttress. The lateral vertical maxillary buttress (*) is displaced posteriorly and medially. The pull of the masseter muscle on the body of the zygoma has resulted in a rotational deformity with decreased malar projection. As long as the rotational deformity is corrected and the other maxillary buttresses are fixated by means of limited incisions, the zygomatic arch does not need to be exposed with a coronal scalp incision. Figure 10. Blow-out fractures of the orbital floor. (a) Coronal nonenhanced CT image shows a left orbital floor fracture without evidence of entrapment of the inferior rectus muscle (arrow). The inferior rectus remains flattened in cross-sectional appearance, indicating that the fascial support of the globe is likely intact. (b) Coronal nonenhanced CT image shows a left orbital floor fracture in another patient. The inferior rectus (arrow) is displaced inferiorly into the maxillary sinus. Note that the cross-sectional appearance of the muscle has changed from ovoid to circular. The fascial support has been disrupted, and the muscle is entrapped. (c) Coronal nonenhanced CT image shows a trapdoor fracture of the left orbital floor in a pediatric patient. The orbital floor was disrupted by the impact but then sprang back into place, trapping the inferior rectus (arrow) within the maxillary sinus. Because the bone has returned to its anatomic location, the diagnosis could easily be missed unless attention is paid to the locations of the extraocular muscles. Trapdoor fractures require emergent treatment to optimize the chance of recovery.

790 May-June 2006 RG f Volume 26 Number 3 Figure 11. Fractures of the medial orbital wall with clinical evidence of entrapment of the medial rectus muscle. (a) Axial nonenhanced CT image shows the lamina papyracea impinging on the medial rectus (arrow). This result is evident from the angulation of the muscle in the orbit. (b) Axial nonenhanced CT image shows that the posteromedial bulge of the left lamina papyracea has collapsed toward the midline. This collapse has increased the orbital volume and resulted in enophthalmos, with retroposition of the ipsilateral globe (small arrow) relative to the coronal plane (white line). The affected medial rectus (large arrow) has lost the typical flattened profile seen in the uninjured contralateral orbit (*) and herniated into the fracture site. Figure 12. Orbital apex. (a) Axial nonenhanced CT image shows the normal anatomy of the orbital apices (*) with alignment of the zygoma and sphenoid along the lateral orbital wall (white line). (b) Axial nonenhanced CT image shows impingement of the orbital apex secondary to a sphenoid skull base fracture. The orbital apex fracture was associated with loss of vision secondary to compression of the optic nerve by a fragment of the sphenoid (arrow) with inward angulation of the lateral orbital wall (white line). The fracture was emergently reduced, and the patient regained her vision. Medial orbital wall fractures have a strong association with diploplia due to loss of the posterior-medial bulge of the orbit or mechanical entrapment of the medial rectus muscle (Fig 11). Both blow-in and blow-out patterns can result in muscle entrapment. Orbital apex fractures are fortunately rare; however, they are emergent surgical cases if there is radiologic and clinical evidence of optic nerve impingement (Fig 12) (9). Any radiologic findings of potential damage to the globe or optic nerve, such as a retrobulbar hematoma or an impinging bone fragment, should be communicated to the surgeon, since they require immediate surgical treatment if associated with decreasing vision. Although common in the pediatric population, isolated orbital roof fractures can also occasionally occur in an adult (Fig 13). The injury can be associated with a violation of the dura, necessitating an intracranial approach.

RG f Volume 26 Number 3 Hopper et al 791 Figure 14. Patterns of pterygomaxillary disjunction. (a) Axial nonenhanced CT image shows a right-sided unilateral pterygomaxillary disjunction (white arrows), which has resulted in separation of the posterior vertical maxillary buttress (*) from the rest of the maxilla; this appearance is indicative of a Le Fort fracture. The contralateral pterygomaxillary junction is intact because the fracture exited in the form of a parasagittal palate fracture (black arrow). (b) Axial nonenhanced CT image shows comminuted bilateral pterygomaxillary disjunctions (white arrows) with a sagittal palate fracture (black arrow). There is a complete posterior maxillary fracture with disruption of both posterior vertical maxillary buttresses (*), resulting in separation of the maxilla from its attachment to the skull base. impacted ZMC fractures. (e) Medial orbital wall blow-out fractures cause enophthalmos if the posterior-medial orbital bulge is lost. (f) Orbital apex compression with clinical decreasing vision is a surgical emergency. Figure 13. Orbital roof fracture in an adult. Coronal nonenhanced CT image shows an isolated blow-in fracture of the left orbital roof (arrow). The associated exophthalmos and dural tears were treated with an intracranial approach. Orbital fracture pearls are as follows: (a) Orbital fractures can occur in isolation or with other fracture patterns. (b) The position and shape of the medial and inferior rectus muscles can indicate whether entrapment and clinical diplopia are likely. (c) Pediatric trapdoor orbital fractures are a surgical emergency. (d) The size of the orbital floor defect can be underestimated in severely Le Fort Fractures With the exception of alveolar and palate fractures, fractures involving separation of the maxilla from the skull base are commonly described according to the classification described by Rene Le Fort in 1901. Le Fort fractures involve a separation of all or a portion of the maxilla from the skull base. For this to occur, the posterior vertical maxillary buttress at the junction of the posterior maxillary sinus with the pterygoid plates of the sphenoid must be disrupted. This can occur either through the posterior walls of the sinus or through the plates themselves, as seen at axial CT (Fig 14). Once a pterygomaxillary disjunction has been diagnosed, the remaining facial buttresses are inspected to determine the class of Le Fort fracture (Fig 15). If the inferior portions of both the lateral and medial maxillary buttresses are fractured, a

792 May-June 2006 RG f Volume 26 Number 3 Figure 15. Drawings show the common Le Fort fracture patterns. The Le Fort I pattern involves fractures through the inferior portions of the medial and lateral maxillary buttresses. The Le Fort II pattern involves fractures through the zygomaticomaxillary and frontomaxillary sutures. The Le Fort III pattern involves complete craniofacial dissociation. Le Fort I fracture has occurred, and the maxillary arch (lower transverse maxillary buttress) will move in relation to the rest of the face and skull (Fig 16). If the inferior lateral maxillary buttress (zygomaticomaxillary suture) and the superior medial maxillary buttress (frontomaxillary suture) are fractured, then the entire maxilla will move in relation to the skull base as a Le Fort II fragment (Fig 16). If the upper transverse maxillary buttress (zygomatic arch), superior lateral maxillary buttress (frontozygomatic), and superior medial maxillary buttress (maxillofrontal) are fractured, then craniofacial separation has occurred as a Le Fort III pattern, with the entire face moving in relation to the skull base. The level of fracture through the medial vertical maxillary buttress in a Le Fort II pattern is not always through the nasofrontal junction. It can also occur through the frontal process of the maxilla; however, to distinguish it from a Le Fort I pattern, a portion of the upper transverse maxillary buttress (orbital rim) is involved in the mobile segment (Fig 17). The radiologic diagnostic criteria for Le Fort fractures are summarized in the Table. The hard palate is an important posterior extension of the lower transverse buttress of the maxilla. A displaced unilateral Le Fort fracture is possible only if the palate is fractured sagittally or parasagittally. A palate fracture in association with a Le Fort pattern will widen the maxillary dental arch and retrude the front of the maxilla, causing malocclusion. A dental splint or plate Figure 16. Coronal nonenhanced CT image shows bilateral Le Fort I, II, and III fractures. The lateral and medial maxillary buttresses (white lines) are fractured inferiorly and superiorly (junctions of white lines and black lines). To confirm the diagnosis, pterygomaxillary disjunction and fractures of the zygomatic arches would need to be observed on axial images. fixation through a local incision is often needed to restore the width of the palate and obtain a functional occlusion. Le Fort fracture pearls are as follows: (a) All Le Fort fractures require disruption of the pterygoids from the posterior maxilla, as seen at axial imaging. (b) Any combination of Le Fort I, II, and III patterns can occur. (c) A sagittal or parasagittal hard palate fracture with a Le Fort pattern will result in a widened maxillary arch. (d) Displaced unilateral Le Fort fractures are possible only with a sagittal or parasagittal palate fracture.

RG f Volume 26 Number 3 Hopper et al 793 Criteria for Classification of Le Fort Fractures after Confirmation of Pterygomaxillary Disruption Site of Fracture Inferior medial maxillary buttress (piriform aperture) Upper transverse maxillary buttress (inferior orbital rim) Upper transverse maxillary buttress (zygomatic arch) CT Planes Type of Le Fort Fracture Sites of Confirmatory Fractures Coronal I Inferior lateral maxillary buttress Coronal, axial II Lateral maxillary buttress, orbital floor, nasofrontal junction Axial III Zygomaticofrontal and zygomaticosphenoid sutures, orbital floor, nasofrontal junction for the management of these injuries, for both radiologist and surgeon alike. We have outlined the anatomy of the critical midface buttresses, the common fracture patterns, and their surgical relevance in order to aid the communication between radiologist and surgeon, with the hopes of increasing the speed and accuracy of addressing these injuries. Figure 17. Coronal nonenhanced CT image shows right Le Fort I and bilateral Le Fort II fractures. The right medial maxillary buttress is fractured inferiorly (white arrow), producing a right Le Fort I pattern; it is also fractured superiorly (left black arrow), thus contributing to the bilateral Le Fort II pattern. The leftsided Le Fort II medial fracture (right black arrow) is not at the level of the nasofrontal junction; however, it is distinguished from the Le Fort I pattern in that a portion of the orbit is included in the mobile segment. The inferior portion of the left medial maxillary buttress is intact (*), thus making the Le Fort I pattern unilateral. Conclusions Midface fractures are common in the trauma patient. They require accurate radiologic diagnosis and surgical management to prevent severe functional debilities and cosmetic deformity. An understanding of the anatomically relevant and surgically accessible craniofacial buttresses is critical References 1. Iida S, Kogo M, Sugiura T, Mima T, Matsuya T. Retrospective analysis of 1502 patients with facial fractures. Int J Oral Maxillofac Surg 2001;30(4): 286 290. 2. Gassner R, Tuli T, Hachl O, Rudisch A, Ulmer H. Cranio-maxillofacial trauma: a 10 year review of 9,543 cases with 21,067 injuries. J Craniomaxillofac Surg 2003;31(1):51 61. 3. Cooper PW, Kassel EE, Gruss JS. High-resolution CT scanning of facial trauma. AJNR Am J Neuroradiol 1983;4(3):495 498. 4. Laine FJ, Conway WF, Laskin DM. Radiology of maxillofacial trauma. Curr Probl Diagn Radiol 1993;22(4):145 188. 5. Gruss JS, MacKinnon SE. Complex maxillary fractures: role of buttress reconstruction and immediate bone grafts. Plast Reconstr Surg 1986;78(1):9 22. 6. Daffner RH. Imaging of facial trauma. Semin Musculoskelet Radiol 1998;2(1):65 82. 7. Markowitz BL, Manson PN, Sargent L, et al. Management of the medial canthal tendon in nasoethmoid orbital fractures: the importance of the central fragment in classification and treatment. Plast Reconstr Surg 1991;87(5):843 853. 8. Grant JH 3rd, Patrinely JR, Weiss AH, Kierney PC, Gruss JS. Trapdoor fracture of the orbit in a pediatric population. Plast Reconstr Surg 2002;109(2): 482 489; discussion 490 495. 9. Linnau KF, Hallam DK, Lomoschitz FM, Mann FA. Orbital apex injury: trauma at the junction between the face and the cranium. Eur J Radiol 2003; 48(1):5 16. This article meets the criteria for 1.0 AMA PRA Category 1 Credit TM. To obtain credit, see www.rsna.org/education /rg_cme.html.

RG Volume 26 Volume 3 May-June 2006 Hopper et al Diagnosis of Midface Fractures with CT: What the Surgeon Needs to Know Richard A. Hopper, MD, et al 2006; 26:783 793 Published online 10.1148/rg.263045710 Content Codes: Page 784 The buttresses represent areas of relative increased bone thickness that support the functional units of the face (muscles, eyes, dental occlusion, airway) in an optimal relation and define the form of the face by projecting the overlying soft-tissue envelope. Page 784 As structural units that support the face, the buttresses must either directly or indirectly interface with the skull base or cranium as a stable reference (Fig 1). Page 786 Radiologic description of NOE fractures should comment on the degree of comminution of the medial vertical maxillary buttress, specifically in the region of the lacrimal fossa, where the medial canthus attaches. Page 788 A frequently missed ZMC fracture is at the temporal bone portion of the upper transverse maxillary buttress (Fig 8). Page 788 If the rectus remains flattened in cross-section and in the correct position, the fascial sling is likely intact and the surgeon will encounter minimal entrapped periorbital tissue (Fig 10a). However, if the inferior rectus is round and inferiorly displaced, the fascial sling is disrupted and the periorbita and muscle have prolapsed into the orbital floor defect (Fig 10b).