Radiographic Imaging of the Mandible for Suspected Fracture
abstract & commentary
Source: Guss DA, et al. Pantomography vs. mandibular series for the detection of mandibular fractures. Acad Emerg Med 2000;7:141-145.
In cases of possible mandibular fracture, the emergency physician (EP) can choose between two screening imaging modalities: the traditional mandibular series (bilateral obliques, anterior-posterior, and reverse-Towne views, yielding four images) and panoramic or pantomographic imaging (yielding one image). Which is better? In this prospective study, two EPs and one radiologist reviewed individual films independently while blinded to patient data; the reading of a neuroradiologist (not blinded to clinical information, and viewing both sets of films from the patient together) was used as the gold standard reference criterion. After excluding 17 patients for incomplete data availability, the study group comprised 54 patients ages 14 and older. Of these, 30 patients had a total of 47 fractures.
For each blinded reader, mandibular series detected more fractures than did pantomography, but the difference was not statistically significant. In all cases, combining the two modalities increased the number of fractures detected, a difference that was statistically significant for the radiologist and one of the the EPs when comparing fractures detected by either modality with those seen on pantomography. There was no significant difference in fracture detection sensitivity between the EPs and the radiologist, and kappa statistics revealed significant reliability among evaluators for both imaging modalities. The authors conclude that mandibular series and pantomography are equally effective in detecting mandibular fractures.
Comment by Richard A. Harrigan, MD, FAAEM
The literature in this area of emergency radiography has been sparse and flawed; the current study is the best thus far published. Prior studies have suffered from methodologic flaws, including: retrospective design;1,2 invalid end point ("ease of interpretation");3 the use of residents to read the films;2 unequal numbers of subjects with both imaging modalities;1 and lack of blinding to clinical data and the other imaging study.1 This study addressed all of these problems effectively. The gold standard in this study seemed reasonable. One could argue that pathological (i.e., surgical) evidence of fracture might be a more accurate assessment of true fractures. These data, if available, would be interesting to compare to the nonblinded neuroradiologist’s readings. The gold standard in this study, however, is certainly a "working" gold standard—one that is "real world" for the EP. Other studies used final diagnoses from the medical record as the gold standard—commendable, if it included surgicopathologic data, but this was not specified in the methodology sections of these papers.1,2
There will be times when both films may be used to rule out or better characterize a fracture. Different views have their strengths and weaknesses. For example, the reverse Towne view visualizes the ascending rami of the mandible quite well, and the anterior mandible is at times difficult to visualize by pantomography.4 On occasion, when clinical suspicion is high, an alternate modality may be necessary. Moreover, pantomography requires that the patient sit upright and immobile during a prolonged imaging time—demands that may be ill-advised or impossible in certain patient populations.
References
1. Moilanen A. Primary radiographic diagnosis of fractures in the mandible. Int J Oral Surg 1982;11:299-303.
2. Chayra GA, et al. Comparison of panoramic and standard radiographs for the diagnosis of mandibular fractures. J Oral Maxillofac Surg 1986;44:677-679.
3. Johnston CC, et al. Clinical trial of pantomography for the evaluation of mandibular trauma. Ann Emerg Med 1980;9:415-418.
4. Hodgkinson DW, et al. Maxillofacial radiographs. BMJ 1994;308:46-51.
27. Which of the following is true regarding radiographic imaging of suspected mandibular fractures?
a. Pantomography is more sensitive than mandibular series.
b. Mandibular series is more sensitive than pantomography.
c. Pantomography and mandibular series are equivalently sensitive.
d. Pantomography is more sensitive in the supine patient.
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