Abstract
The orbitozygomaticomaxillary complex (OZMC) is a structural foundation for both form and function of the craniofacial skeleton. Due to its anterolateral position and projection, it provides significant strength and stability. Fractures of the OZMC must be optimally diagnosed and classified using necessary imaging, physical examination, and additional established criteria. The interruption of its normal anatomical state results in aesthetic compromise and functional impairments. Various treatment modalities exist, so the uniform implementation of a treatment algorithm has been suggested with the goal of obtaining favorable, predictable, and reproducible results. As in any surgical intervention, even with the latest techniques, materials, precautions, and expertise, acute and long-term complications exist. The craniofacial surgeon constantly seeks the most favorable treatment modality that will lead to optimal results, both functionally and aesthetically, and diminished complications through literature, research, and experience.
Keywords
zygomatic fractures, zygomaticomaxillary fractures, orbital zygomaticomaxillary complex fractures orbitozygomaticomaxillary complex fractures, OZMC, orbital fractures, orbital floor fractures, surgery, fixation, reduction
Background
Because of its prominent position, the zygoma is one of the more frequently injured facial bones. The zygomatic bone is an essential structure of the midface and serves as a foundation, contributing greatly to both form and function. Fractures of the zygoma occur independently and in association with fractures to adjacent bones, such as Le Fort fractures. Since the zygoma constitutes most of the lateral orbital wall and part of the orbital floor, these fractures are sometimes referred to as orbital (orbito-) zygomaticomaxillary complex fractures (OZMC fractures).
Incidence and Etiology
In a study of 362 patients, the age group presenting with zygomatic fractures most heavily represented was between 20 and 29 years of age, at 41% of the patient population, followed by the group between 30 and 39 years of age, at 18% of the patient population. In a separate study conducted by Ozyazgan et al., 689 patients with midface fractures were evaluated. Males constituted 81% and females 19% of these patients. Throughout the majority of the literature most of the patients presented between 20 and 40 years old. The most common causes leading to OZMC fractures are motor vehicle collisions, assaults, falls and sporting injuries. Some variations in incidence and pattern occur with age and geographic location.
Surgical Anatomy
The zygoma or cheek bone is an important foundation structure of the craniofacial skeleton; it is the most anterolateral projection of the midface. This lateral structural pillar helps dissipate forces along the cranial base. In doing so, it provides significant strength and stability to the midface. The zygoma presents as a thick quadrangular bone and constitutes most of the lateral and inferior orbital walls. Its strength comes from its five projections. These projections articulate with the frontal, sphenoid, temporal, maxillary bones, and inferior orbital rim ( Fig. 1.12.1 ) forming the zygomaticofrontal, zygomaticosphenoid, zygomaticotemporal, and zygomaticomaxillary sutures, and inferior orbital rim respectively. Fractures usually occur at or near these five articulations. The articulation at the frontal bone is strongest, often fracturing incompletely, or greensticking. The frontal process of the zygoma may also be displaced behind the zygomatic process of the frontal bone, and thus, impacted.
A comprehensive knowledge and understanding of the surgical anatomy of the orbit is necessary when treating OZMC fractures, as the orbit is frequently involved ( Figs. 1.12.2–1.12.4 ). The lateral orbital wall is formed by both the orbital process of the zygoma and the greater wing of the sphenoid bone. The zygomaticosphenoid suture, the greater wing of the sphenoid, and the zygomatic arch serve as key anatomical landmarks to ensure proper reduction and are especially helpful in treating comminuted fractures.
Another key anatomical landmark is the zygomaticofrontal suture – the site where the frontal bone and the lateral orbital wall meet. This area is usually at least 4 mm thick. The zygomatic arch, which lies lateral to the zygoma, includes the temporal process of the zygoma and the zygomatic process of the temporal bone. In the area where it inserts to the body of the zygoma it is commonly 4 mm or more in thickness. The area of the zygoma that extends medially towards the infraorbital foramen can be as thin as 2 mm. These thicknesses are pertinent as thinner areas correlate with a higher likelihood of fracture and comminution.
The second division of the trigeminal nerve also branches to the zygomatic-facial and temporal branches that exit the foramina in the body and frontal process of the zygoma, and provide sensory innervation in the area adjacent to the zygoma, including a segment of the lateral cheek and anterior temporal region, respectively. Another branch of the maxillary nerve, the infraorbital nerve, exits via the infraorbital foramen after coursing the orbital floor. This nerve provides sensation to the anterior cheek, bilateral nose, upper lip, and through a separate branch in the bone, the anterior maxillary teeth.
Pertinent facial and mimetic muscles in this area include the temporalis, zygomaticus major and minor, the levator labii superioris, and the masseter. The zygomaticus major, minor, and labii superioris are all innervated by cranial nerve VII and are all muscles of facial expression. The temporalis muscle attaches to the zygomatic arch and posterior portion of the body of the zygoma. These muscles and fascia are displaced inferiorly with fractured fragments due to their attachments. The masseter attaches along the inferior zygomatic arch around the temporal surface of the zygoma and plays a role in the inferior displacement of the zygoma following fracture.
Other anatomic landmarks of relevance include Lockwood’s suspensory ligament, Whitnall’s tubercle, and the lateral canthal tendon. The vertical position of the globe is largely determined by the attachment of Lockwood’s suspensory ligament and the lateral canthal tendon to the lateral orbital wall. The lateral canthal tendon is attached to Whitnall’s tubercle, which is located below the zygomaticofrontal articulation and is positioned on the inner medial portion of the frontal process of the zygoma. Inferiorly displaced fractures of the OZMC may result in inferior displacement of the lateral canthus.
Clinical Presentation
OZMC fractures are most commonly attributed to motor vehicle collisions, assaults, falls, and sports injuries. Patients presenting from such trauma should be first evaluated for life-threatening injuries and stabilized. Careful evaluation must be taken of both bony and soft tissue components of the injury. It is critical to evaluate the status of cranial nerves II to VI, eyelids, lacrimal apparatus, canthal tendons, globe, visual function and acuity, diplopia, and retina. An ophthalmology consultation should be considered whenever injury to any part of the ophthalmic apparatus is present. It is also important to record the history: the nature, force, and direction of the causative trauma. The direction of trauma is important as differing directions of impacts create different presentations. Assault usually results in direct lateral blows that typically present with inferomedial fracture and posterior displacement. A direct blow to the side of the head may result in an isolated zygomatic arch fracture. Trauma from a frontal direction often leads to a fracture with posterior and inferior displacement. More severe impact forces cause disruption of muscle attachments and ligaments, creating lateral displacement and more comminution. Displaced fractures may lead to facial flattening on the affected site which is often best appreciated from a superior “bird’s eye” view. This is due to a depression of both the malar eminence and infraorbital rim. Enophthalmos may also be evident especially from an inferior or “worm’s eye” view with the globe positioned inferiorly, posteriorly, and medially. The palpebral fissure may be altered due to the inferior position of the zygoma with its attachment of the lateral canthus. In higher energy fractures, the displacement of the zygomatic body is lateral, and the midface is widened on that side.
Patients with OZMC fractures often present with pain, epistaxis, diplopia, subconjunctival hemorrhage, and periorbital edema and ecchymosis. OZMC fractures typically involve the orbital floor and normally travel through the infraorbital foramen and groove of the infraorbital nerve. Because of this, many patients present with decreased or absent sensation in the areas of distribution of both the zygomaticotemporal and infraorbital nerve. These areas include the cheek, lateral nose, maxillary anterior teeth, and ipsilateral upper lips. Trismus may be present whenever medial displacement causes impingement of the body on the coronoid process of the mandible or may be due to contusion of the masseter muscle. This manifests as limited opening and range of motion of the mandible. Downward displacement of the zygoma of that side can present with an antimongoloid slant of the palpebral fissure because of displacement of the lateral canthus, enophthalmos because of orbital enlargement, and a more pronounced supratarsal fold of the upper eyelid. On clinical examination, physical palpation should be completed and must include the orbital rim, zygomaticofrontal suture, zygoma, zygomaticomaxillary interface, and zygomatic arch. These areas should be assessed for any bone separation, step-offs or tenderness, as these would suggest further radiographical evaluation and indicate the presence of a fracture.
Patients with isolated arch fractures usually have trismus and limited mouth opening. These patients normally present with pain and decreased mandibular motion, but no orbital signs. A depression is often observed over the fracture; however, this may be masked if there is significant edema in the area.
Patients should have a thorough orbital examination, including evaluation of extraocular muscle movements noting incomplete excursion as possible entrapment of the globe. An ophthalmology examination prior to surgery may be necessary based on initial examination and suspected visual loss or globe injury. | A study by Barry et al. found 23 patients out of 138 to have ocular injuries. The most common include diplopia, enophthalmos, retina and pupil injuries (traumatic mydriasis). Jamal et al. evaluated 98 patients and found that 66.6% sustained minor ocular injuries. Studies have shown major ocular injuries such as ruptured globe, retinal hemorrhage or detachment and hyphema occur in approximately 10% of these patients, whereas the incidence of traumatic optic neuropathy is approximately 6%.
Radiological Evaluation
Computed tomography (CT) is the gold standard in the identification and imaging of OZMC fractures. Fracture patterns, as well as displacement and comminution, are readily appreciated on CT. CT also allows for the visualization of soft tissue damage that is sometimes not clinically evident. Often three views – the axial, coronal, and sagittal – and a 3-dimensional reformatted CT scan provide the best imaging for evaluating OZMC fractures. The axial and the 3D views aid in determining the anterior/posterior position of the zygoma and the degree of displacement and rotation. For evaluation of the orbit, the coronal and sagittal views provide the most useful information regarding the internal orbital bony and soft tissue anatomy, especially when determining whether an orbital floor repair will be required and the extent of such repair. Attention should be given to the orbital volume as well as any herniation of orbital contents. Soft tissue windows are useful to evaluate extraocular muscles and to evaluate for herniation of soft tissues into the maxillary sinus. Computed tomography is not only important in identifying the fracture patterns; it is also an important tool in treatment planning, resulting in more adequate treatment and consequently better prognosis. Finally, intraoperative and postoperative CT scans can evaluate the effectiveness of the reduction.
For more complex injuries, including those that present with severe comminution, intraoperative CT may be useful to evaluate the reduction of the repositioned zygoma. The status of the orbital floor can be evaluated following reduction of the zygoma to determine whether the orbital floor should be accessed to avoid postoperative enophthalmos.
Classification
Classification of OZMC fractures is of utmost importance as it sets the foundation for proper treatment planning and in so doing achieves the best possible prognosis. Classification systems have been described in order to predict which fractures would remain stable after certain points of open reduction. These systems of classification have evolved to provide uniformity in diagnosis and treatment. Previous classification systems depended on the direction of displacement seen in a Waters view radiograph. As imaging and techniques improved, so did the classification of these fractures. Manson et al. proposed classifying fractures based on segmentation and displacement patterns. They described low-energy, middle-energy, and high-energy injuries. Low-energy injuries are those with minimal to no displacement. Medium-energy injuries compromise the majority of injuries and present with fracture of all articulations along with moderate displacement. High-energy injuries presented with involvement of the lateral orbit, lateral displacement, and segmentation of the zygomatic arch. Gruss et al. proposed a classification system that expanded the existing system and stressed the importance of recognizing and treating fractures of the zygomatic arch in association with those of the zygomatic body. They also stressed the importance of identifying and treating segmentation, comminution, and lateral bowing of the zygomatic arch. Zingg et al. reviewed 1025 fractures and classified zygomatic injuries into three types – Types A, B, and C. Type A fractures were low-energy incomplete fractures involving only one articulation, either the zygomatic arch, infraorbital rim, or lateral orbital wall. Type B fractures, or monofragment fractures, were complete, nonsegmented fractures with displacement along all four articulations; and Type C included comminuted multifragment fractures, including fragmentation of the zygomatic body.
Classification techniques are helpful to standardize terminology and to aid in developing a surgical plan and in selecting approaches. Common among these classification systems is that as the amount of displacement and comminution increases, the role of open reduction and fixation increases.
Surgical Indications
Treatment of each OZMC fracture should be individualized. Management of these fractures depends on the degree of displacement at each articulation and its predicted aesthetic and functional deficits. Treatment may range from observation of or barely displaced fractures to extensive reconstruction of the zygoma, orbit, and zygomatic arch in severe fractures with lateral displacement at each buttress. The selection of incisions and fixation areas for OZMC fractures ultimately depend on the degree of comminution and stability of the zygoma and its associated structures. Some zygoma fractures are amenable to less invasive treatment with minimal reduction and limited surgical approaches.
The availability of intraoperative CT has the potential to limit the need for additional incisions once the reduction has been confirmed. Each incision considered for access of the fractured zygoma carries with it inherent risks and complications. Incisions providing exposure with less risk should be utilized first. For example, a transoral surgical approach offers good visibility with minimal surgical risk. The upper lid, lower lid, and coronal approaches each carry increasing risk for more visible scarring.
Disruption and displacement of the orbital floor with no or poor reconstruction may result in postoperative enophthalmos. If the orbital floor component does not require repair, a lower eyelid incision may not be required. Over half of zygoma fractures can be treated without internal orbital reconstruction and therefore lend themselves to a less invasive surgical approach. A study by Ellis and Reddy found that in patients with minimal or no soft tissue herniation and minimal disruption of the internal orbit, reduction of the points of the rim of the zygoma alone was adequate. Shumrick and colleagues found that by utilizing preoperative CT they could avoid orbital exploration in 70% of their patients with OZMC fractures. Their criteria for internal orbital reconstruction were cases where greater than 50% of the orbital floor was comminuted and where associated soft tissue prolapse into the sinus was present.
In order to restore proper facial width, height, and projection, especially in patients sustaining multiple/comminuted facial fractures, it can be desirable to expose and plate the zygomatic arch. This important horizontal buttress is better approached through a coronal approach, which also aids in the visualization and reduction of the superior articulations of the zygoma and lateral internal orbit ( Fig. 1.12.5 ).
