Imaging Studies
Traditional facial radiographs have limited usefulness in the diagnosis of zygomaticomaxillary complex (ZMC) fractures. The submental-vertex view offers excellent resolution of the zygomatic arches; however, the Townes, anteroposterior, and Waters views offer much less information. Gross bony disruption of the orbital rim or opacification of the maxillary sinus can be diagnosed; however, the dense temporal bone makes subtle findings difficult. Even if a facial fracture is diagnosed using plain radiographs, a CT scan usually is needed to determine the extent of the injury. [29]
CT scans, depicted in the images below, are considered the criterion standard for radiologic diagnosis of ZMC fractures. [5, 6]
Coronal CT scan demonstrating displaced right zygomaticomaxillary complex fracture. Note the associated orbital floor fracture.
Axial CT scan demonstrating zygomaticomaxillary complex fracture on right with severe displacement.
A three-dimensional CT scan of a right displaced zygomaticomaxillary complex fracture. Courtesy of the UC Davis Otolaryngology Image Library.
The CT scan helps the physician make a more accurate preoperative diagnosis and guides decisions about the operative treatment. Patients with traumatic injuries frequently require CT scans of the brain to evaluate intracranial injuries. If significant clinical suspicion of a facial fracture exists, the images can be continued through the facial bones. Modern helical scanners can reformat thin cut (1- to 1.5-mm) axial images into coronal and sagittal cuts with acceptable resolution to avoid neck flexion and extension.
Other Tests
Visual acuity: Any injury resulting in significant disruption of the bony orbit requires an ophthalmologic evaluation. This evaluation allows dilated funduscopic examination for retinal detachment from the trauma or hyphema. Either of these findings likely delays immediate surgical fracture reduction until the intraorbital injuries are managed.
Extraocular motion: Function of the extraocular muscles is evaluated with concentration on potential entrapment of the inferior or medial rectus muscle by an orbital floor or medial orbital wall fracture, respectively.
Infraorbital nerve dysfunction: The presence or absence of skin sensation to light touch should be documented, accounting for the function of the infraorbital nerve.
Forced-duction tests: Forced-duction testing can be used to determine the presence of mechanical restriction of globe motion. This test must be performed bilaterally to compare the uninjured and injured sides. It is generally performed with the patient under general anesthesia because most patients cannot relax enough to allow accurate testing.
Diagnostic Procedures
Unfortunately, the diagnostic studies available to differentiate muscle contusion from muscle entrapment (eg, thin-cut CT scans, forced-duction testing) are not 100% accurate. These tests are quite specific when muscle entrapment is observed; however, they often are not sensitive enough to rule out entrapment in subtle cases. Therefore, diagnostic surgical exploration must be considered for patients with significant orbital disruption and extraocular muscle dysfunction, even if gross muscle entrapment cannot be identified clearly. Transmaxillary endoscopic evaluation of the orbital floor is a relatively new technique that can also be used to assess the integrity or the orbital floor.
Axial preoperative CT scans do not clearly define the extent of orbital blowout fractures. Patients with facial traumatic injuries with suspected cervical spinal cord injuries cannot hyperextend their head for coronal CT scan, and thin cut reconstructions are not always available. Consequently, the degree of orbital floor disruption is not known until the time of surgery. Before the surgical endoscope, evaluation of the orbital floor necessitated a lid or rim incision to evaluate the extent of disruption. In such cases, the risk of orbital exploration must be weighed against the risk of missing an occult injury to the orbital floor and orbital contents. The exacerbation of an orbital floor injury after reduction of the zygomaticomaxillary complex should also be considered. A large lateral movement of the ZMC may actually widen a small orbital floor disruption requiring an orbital exploration for diagnosis and treatment.
The endoscope can be used to evaluate the orbital floor (ie, the roof to the maxillary sinus) by passing it through preexisting fractures in the face of the maxilla. When gross disruption of the anterior maxillary face is not present, a 4-mm osteotome is used to open a small maxillary sinusotomy, taking care not to injure the infraorbital. A Kerrison can then be inserted into the sinusotomy and an antrostomy 1.5 cm by 2.0 cm can be performed (ie, Caldwell-Luc sinusotomy). When the endoscope is then inserted into the maxillary sinus, the integrity of the orbital floor can be evaluated from below. [30, 31]
Gentle pressure on the globe (ie, pulse test) exaggerates any significant prolapse of the orbital contents into the maxillary sinus. After the evaluation is complete, the sublabial incision is closed in the traditional fashion. Repair of the Caldwell Luc sinusotomy is not necessary.
This technique involves a significant learning curve, and surgeons are encouraged to continue using a standard approach to these injuries to confirm what is noted on endoscopy. Once experience is ample, the surgeon can confidently identify smaller, inconsequential orbital floor defects and avoid a formal orbital exploration.
Intraoperative radiologic assessment of the reduction of these fractures has been documented using a C-arm [32] or intraoperative CT scanning Advantages include immediate visualization of the fracture reduction and necessary revision without waking the patient from anesthesia. Disadvantages included increased radiation dosages and costs that may be prohibitive.
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Axial CT scan demonstrating zygomaticomaxillary complex fracture on right with severe displacement.
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Intraoperative photograph of a titanium plating for rigid fixation of a zygomatic-maxillary buttress fracture in a complex maxillary fracture.
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Coronal CT scan demonstrating displaced right zygomaticomaxillary complex fracture. Note the associated orbital floor fracture.
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A three-dimensional CT scan of a right displaced zygomaticomaxillary complex fracture. Courtesy of the UC Davis Otolaryngology Image Library.
