This study shows that several changes in the PR of JIA subjects (erosion, altered condylar morphology, the disproportion between COP and CRP, and accentuated curve of antegonial notch) were statistically more frequent in patients than in control subjects. We observed different sensitivities and specificities depending on the radiographic alteration; however, the disproportion and the altered condylar morphology were the most sensitive findings, and the presence of altered condylar morphology and erosion the most specific. The presence of several alterations in the PR increased the likelihood of these findings being related to JIA, to varying degrees.

These TMJ changes are often asymptomatic, which means that they could not be considered as involved in the JIA patient’s clinical evaluations. This can lead us to classify the patient as having oligoarticular JIA when, in reality, he would present polyarticular subtype if we consider this involvement or to classify the patient as inactive when he presents TMJ active involvement. However, it is worth noting that even if alterations are present on the patient’s PR, this should not be considered sufficient to change their status from “inactive disease” to “active disease”. The changes found on the PR may reflect disease activity, or alternatively, represent sequelae of previous inflammatory status. This study tried to answer questions that are still poorly defined: How often these frequent alterations in PR of JIA subjects are present in healthy children? Which changes or combinations among them are specifically associated with TMJ involvement in JIA? Once these alterations or combinations are present, in which cases is there a justification for a referral to a pediatric rheumatologist?

We observed that alterations in the PR of subjects with JIA are persistent findings. When comparing to the control group, we found a difference in all the evaluated findings, which shows that these changes are rarely present in images of healthy individuals. This observation agrees with other studies that found PR alterations in only 6 to 20% of the control participants [11, 16].

We found low sensitivity and high specificity of the presence of these radiographic alterations. This trend is accentuated when we associated two, three, and even four findings in the same participant. It means that many patients with JIA will not have identifiable alterations in their PR, but when these findings are present there is a higher likelihood of being related to JIA. Our findings are in agreement with those of Im et al. [21]. They demonstrated in adult individuals that PR had limited diagnostic accuracy and acceptable reliability in the TMJ’s detection of bone lesions [21].

In the logistic regression, it is evident that alterations in PR are factors to be considered since individuals with the presence of erosion, altered condylar morphology, disproportion between CRP and COP and accentuated curve of antegonial notch are more likely to be patients than controls. We propose that PR should be used as a diagnostic tool for assessing TMJ, always considering its limitations, but using it as an important tool that indicates a higher likelihood of being a patient than a variation in normality.

The rationale of this study was based on the advantages of PR (low cost, low dose of radiation exposure, and ease of access), turning this imaging into an important screening tool. However, it has limitations related to early structural changes, as it can only detect them at a later stage.

In a survey of 87 centers on how pediatric rheumatologists diagnosed TMJ involvement in JIA subjects, 33 centers answered that they still used PR, although the low sensitivity of this imaging modality to identify early changes in TMJ arthritis is well known [22]. This study showed that for 24.6% of the professionals, PR was the first imaging option.

Although MRI is considered the gold standard in the diagnosis of early TMJ involvement in JIA patients [7, 8], the study of Abramowicz et al. [23] shows that the presence of alterations in the condylar morphology in PR is highly sensitive and specific and could reflect the occurrence of synovitis in MRI. These authors compared PR findings with TMJ contrast-enhanced MRI findings. The combination of altered condylar morphology and accentuated curve of antegonial notch in the PR was correlated with the presence of synovitis in the MRI. It confirms the importance of using this imaging modality [23]. The use of MRI in detecting active inflammatory process in this joint is essential, in the presence of significant changes in the mandible head, on the PR of subjects with a confirmed diagnosis of JIA.

We have as strengths of this study the sample size, its prospective nature, and the presence of a control group.