Imaging of Suspected Mandibular Fracture: What is the Best Modality?
Abstract & Commentary
Source: Nair MK, et al. Imaging of mandibular trauma: ROC analysis. Acad Emerg Med 2001;8:689-695.
This paper sought to address the continuing debate as to which approach is superior when imaging the mandible for suspected fracture. In a novel approach, cadaveric specimens were used after fracture had been induced by blunt trauma with a steel pipe in various regions in approximately 50% of mandibles. Fracture existence was verified by examination of defleshed mandibles by an oral and maxillofacial (OMF) radiologist. After being informed of the approximate fracture rate, six trained observers (3 general surgeons and 3 OMF surgeons) interpreted four imaging modalities of the specimens: 1) panoramic view; 2) mandibular series comprised of right and left lateral oblique views, reverse Towne’s views, and an anteroposterior (AP) view; 3) digitized images of the mandibular series; and 4) panoramic view together with an AP view. Plain film images were interpreted with 2X magnification and hot light made available; brightness and contrast manipulation was permitted for the digitized images. Sensitivity, specificity, and receiver operating characteristic (ROC) analysis were calculated for the various imaging modalities.
ROC curve analysis demonstrated the panoramic plus AP view combination to be superior to other modalities, with panoramic view alone being next best, and digitized mandibular series performing worst (see Table).
| Table: Sensitivity and Specificity of Various Modalities | ||
| View | Sensitivity (%) | Specificity (%) |
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|
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| Panoramic | 88 | 94 |
| Panoramic + AP view | 92 | 97 |
| Mandibular series | 74 | 79 |
| Digitized mandibular series | 73 | 82 |
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Further statistical analysis revealed that there was no significant difference between panoramic and panoramic plus AP view. Not surprisingly, condylar and coronoid fractures were the most difficult to detect (P < 0.03). Inter- and intra-observer agreement was high (kw 0.76 and 0.81, respectively). The authors conclude that panoramic imaging is adequate for the detection of uncomplicated mandibular fractures, and that this modality affords greater diagnostic accuracy than does the mandibular series.
Comment by Richard A. Harrigan, MD, FAAEM
Score one for panoramic imaging. Most recently, an emergency department (ED)-based clinical study by Guss and colleagues found panoramic imaging to be statistically equivalent to the mandibular series,1 although the number of fractures detected by the latter was higher. The study by Guss et al was superior to those done previously2-4 in that the methodology was greatly improved, employing prospective analysis for the first time, among other things. Yet it still suffered from a seemingly unavoidable design flaw to which each of these clinical studies fell victim: the lack of a truly satisfactory criterion gold standard. Guss et al used the reading by a neuroradiologist (provided with clinical history) as their gold standard; to be sure, this was an improvement on prior work. Operative evidence of the presence or absence of fracture might be the ideal clinical gold standard, but that benchmark either has been employed inconsistently or not used at all.1-4 Thus, a study, in this case cadaveric, that utilizes verifiable fractures is highly desirous and an important addition to the literature.
The enhancement of radiographic diagnostic accuracy by the addition of an AP view to the panoramic image, although not demonstrating a statistically significant advantage, highlights a clinical take-home point. When using the panoramic view to screen for fracture, if your suspicion is high and yet the panoramic image does not demonstrate a fracture, perhaps an additional AP view will help rule in or rule out a fracture.
References
1. Guss DA, et al. Pantomography vs. mandibular series for the detection of mandibular fractures. Acad Emerg Med 2000;7:141-145.
2. Johnston CC, et al. Clinical trial of pantomography for the evaluation of mandibular trauma. Ann Emerg Med 1980;9:415-418.
3. Moilanen A. Primary radiographic diagnosis of fractures in the mandible. Int J Oral Surg 1982;11: 299-303.
4. Chayra GA, et al. Comparison of panoramic and standard radiographs for the diagnosis of mandibular fractures. J Oral Maxillofac Surg 1986;44:677-679.
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