Discussion
Zygomatic arch is the second most common site of facial bone to get fractured and its treatment requires outmost care as it has both cosmetic and functional significance. Conventional plain radiography and computed tomography (CT) scans are the basic diagnostic tools for maxillofacial injuries. Computed tomography (CT) can provide three dimensional assessment of fracture, but high radiation exposure, high cost and difficulty in transporting make its intra-operative use to assess the reduction difficult [4]. Further, it cannot be used in pregnant women and in those with cervical spine injuries. Again, fluoroscan assisted closed reduction using C-arm has the same problem of high exposure to radiation [5] for the use of intra-operatively. Although, the use of USG in dentistry has been increasingly developed and widely studied in recent years and its role in maxillofacial trauma surgery is less recognized [6]. Sonographic evidence may be treated as an alternative diagnostic imaging modality to radiology by which the use of conventional radiographs may not be required [7]. USG has shown high accuracy in the detection of nasal bone fracture with a sensitivity ranging from 90% to 100%, specificity of 98-100% and high predictive value [8] and so it can also be used in assessment of zygomatic arch fracture pre- and post-operatively. In this case report the patient‘s zygomatic arch fracture was observed clearly in USG (Fig:9).
The zygomatic arch fracture is commonly managed by indirect reduction without fixation which is done through various approaches like Gille’s temporal approach [9], BalaSubrahmaniam upper buccal sulcus approach, Quinn approach [10] and Keen’s lateral coronoid approach .The patient in the present case report is also managed by close reduction, but with the guidance of ultrasonogram to confirm the accurate reduction. Although gross swelling and emphysema make the ultrasonographic visualization of bony surfaces difficult, this problem of this was overcome by choosing an ultrasound frequency of 7.5 MHz or less.
Reduction of the zygomatic arch fracture is conventionally done by blind method and the position of the fragments is usually confirmed by radiography or palpation during the operation. Radiography is not always feasible because of difficulties in managing the patient or the risk of X-ray exposure, and palpation by the surgeon is often unreliable [11]. Conversely, ultrasonography is non-invasive, safe, easily reproducible and portable and gives information in real-time, and thus it overcomes the disadvantages of radiography and palpation [11].
In this study, the fracture reduction of zygomatic arch was confirmed by ultrasonography intra-operatively and re-confirmed by submentovertex view post-operatively. Use of USG in fracture reduction was followed in this case as it is simple and relatively easy with minimal or no complications and the armamentarium required for this technique are readily available. Thus, ultrasonography can be a reliable method as an alternative to other imaging modalities in cases of close reduction for zygomatic arch fractures.