Ultrasound examination can be used to differentiate physiologic channels from bone erosions in rheumatoid arthritis (RA), according to study results published in Rheumatology. In a multisite imaging study, ultrasound displayed excellent specificity for erosions and physiologic bone channels in patients with RA and healthy control participants.

Investigators enrolled patients with RA and healthy control participants from outpatient clinics in Germany and France. All patients with RA fulfilled the American College of Rheumatology/European League Against Rheumatism classification criteria for RA. Demographic and clinical data were captured at the time of ultrasound assessment, including age, sex, disease duration and activity, and current medications. All study participants underwent bilateral ultrasound evaluation of the metacarpophalangeal (MCPJ) and proximal interphalangeal joints (PIPJ), with technicians blinded to the clinical status of participants. Ultrasound examinations were performed both in B- and Power Doppler-mode. A subset of the patient and control group also underwent high-resolution peripheral quantitative computer tomography (HR-pQCT) of the hand, data from which were used to validate the lesion classification results from ultrasound examination.

A total of 38 patients with RA and 43 control participants were included in the study, with the majority of participants from both groups being women. Overall, the researchers examined 771 MCPJ and 638 PIPJ by ultrasound, and 94 and 51, respectively, by HR-pQCT. Among patients with RA, ultrasound-defined cortical bone lesions were most commonly clustered in the lateral part of the MCPJ (50%) and the dorsal part of the PIPJ (66.7%). Ultrasound-defined physiologic bone channels were most commonly observed in the palmar parts of the MCPJ and PIPJ in both patients (78.8% and 100%, respectively) and control participants (51.8% and 80.0%, respectively). On ultrasound, the widths and depths of erosions were significantly larger than those of physiologic bone channels (P <.000001 for all dimensions). In addition, erosions were more likely to be observed at the radial and ulnar sites, whereas physiologic bone channels were localized at palmar sites. The specificity of ultrasound was excellent for physiologic channels and pathologic erosions across joints (range, 0.89-1.00). Incorrect classification was more likely at the radial and ulnar sites of joints, where pathologic breaks resembling erosions were most prevalent.

“Overall, this study suggests that it is possible to discriminate between [physiologic] channels and [pathologic] cortical breaks resembling bone erosions using [ultrasound],” the investigators wrote. Localization and size may be essential to distinguishing cortical breaks from erosion. 


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Reference

Finzel S, Aegerter P, Schett G, D’Agostino M-A. Identification, localization and differentiation of erosions and physiological bone channels by ultrasound in rheumatoid arthritis patients [published online May 17, 2020]. Rheumatology (Oxford). doi:10.1093/rheumatology/keaa183