Is radiological shortening of the ramus a reliable guide to operative management of unilateral fractures of the mandibular condyle?

Several studies have published measurements of the height of the ramus on orthopantomographic (OPT) images of patients with unilateral fractures of the mandibular condyle as a possible quantitative measure for making decisions about treatment. However, we know of no studies that have described the accuracy and validity of such measurements. The aim of the present study was to assess the shortening of the ramus in patients with such fractures, and compare them with differences found in a control group. Seventy-four patients and 74 controls were studied. The height of the ramus on the fractured was less than that on the uninjured side, although this was not statistically significant (p=0.25). In the control group, 50 subjects (68%) had a difference in the ramal height of more than 2mm. Of 74 patients, 25 (34%) had a shorter, uninjured ramus on the opposite side. A Bland and Altman scatterplot showed 23 outliers (31%) among the patients, which exceeded the mean (SD 1.96) of the control group. The interobserver and intraobserver reliability both showed excellent agreement for all measurements made. Shortening of the ramus can be measured on OPT images. However, in a control group there was a large mean difference in height. Among the patients, 25/74 (34%) also had an uninjured ramus on the opposite side that was shorter than that on the fractured side. Measurement of the difference in height on an OPT image cannot be relied on as an absolute indication for intervention.