High-resolution peripheral quantitative computed tomography for the evaluation of bone erosions of metatarsophalangeal joints in patients with rheumatoid arthritis

Objectives: To compare if the 4th and 5th metatarsophalangeal (MTP) joints evaluated by high-resolution peripheral quantitative computed tomography (HR-pQCT) could classify more patients with erosive rheumatoid arthritis (RA) compared with conventional radiography (CR) of the hands, wrists, and feet. Furthermore, we characterize and quantify bone erosions in the two MTP joints by HR-pQCT. Methods: This single-center cross-sectional study included patients with established RA (disease duration ≥5 years). Blinded to patient data, the number and volume of erosions in the 4th and 5th MTP joints were measured by HR-pQCT, whereas the erosive scores by CR of 44 joints in the hands, wrists, and feet were assessed according to the Sharp/van der Heijde method. Results: Among 42 participants, 30 patients were classified with erosive RA and 12 with non-erosive RA by CR. HR-pQCT of two MTP joints could classify more patients with erosive RA compared with CR of 44 joints (p =.03). The optimal cut-off value for the number and volume of erosions per patient in the 4th and 5th MTP joints by HR-pQCT was 7.5 erosions and 11.7 mm 3 , respectively, for detecting erosive disease by CR. Erosions in the two MTP joints by HR-pQCT were found most frequently and were largest at the lateral quadrant of the 5th metatarsal head. Conclusion: The superiority of HR-pQCT of the 4th and 5th MTP joints compared with CR of 44 joints for classifying erosive RA provides a basis for larger studies evaluating if HR-pQCT could be used for diagnosing erosive RA in the future.