POS0133 HIGH-RESOLUTION PERIPHERAL QUANTITATIVE COMPUTED TOMOGRAPHY FOR THE EVALUATION OF BONE EROSIONS OF METATARSOPHALANGEAL JOINTS IN RHEUMATOID ARTHRITIS: A PILOT STUDY

Abstract

BackgroundBone erosion in rheumatoid arthritis (RA) is most commonly detected in the wrist, metacarpophalangeal (MCP) and metatarsophalangeal (MTP) joints. High-resolution peripheral quantitative computed tomography (HR-pQCT) has successfully been used to quantify bone erosions in the wrist and MCP joints. A recent study highlights that HR-pQCT of only two MCP joints has equal accuracy to detect erosive disease in RA patients compared to conventional radiography (CR) of the hands, wrists, and feet (44 joints)1. However, no study has evaluated the MTP joints by HR-pQCT.ObjectivesTo characterize the localization, size and frequency of erosions in the 4th and 5th MTP joints. Furthermore, to evaluate the sensitivity for the detection of erosion in the 4th and 5th MTP joints by HR-pQCT, compared to CR.MethodsThis single-centre cross-sectional study included 42 patients with established RA (disease duration ≥ 5 years). The right foot was imaged by HR-pQCT in a 2.7 cm long region corresponding to the 4th and 5th MTP joint. Blinded to patient data, the number and volume of bone erosions by HR-pQCT were measured and scored according to the SPECTRA criteria2. CR of 44 joints was evaluated according to the Sharp/van der Heijde (SHS) method.ResultsThe patients (62% women) had a median disease duration of 12 years (interquartile range (IQR): 7 – 20). HR-pQCT of the 4th and 5th MTP joints identified erosions in 38 (90%) patients. The total erosion volume (Vtot) was 2610 mm3 in all quadrants of the 4th and 5th MTP joints. Erosions were most frequently found at the lateral aspect of the 5th metatarsal head (MH), including 1261 mm3 (48%) of Vtot (Figure 1). CR of 44 joints detected erosions in 30 (71%) patients with a median SHS erosion score of 9 (5 – 28). The sensitivity and specificity (95% CI) of classifying patients with erosive RA by HR-pQCT and CR is displayed in Table 1. McNemar’s χ2 test showed a significantly higher sensitivity of patients classified as having erosive RA by HR-pQCT of the 4th and 5th MTP joints than by CR of 44 joints (4.6, p = 0.03).Table 1.Comparing CR and HR-pQCT for classifying patients as having erosive RA, and for identifying erosions in the 4th and 5th MTP joints.Sensitivity & specificity of classifying patients with erosive RA by HR-pQCT when CR of the hands, wrist and feet was used as referenceCRHands, wrists, and feet Erosive RACRHands, wrists, and feetNon-erosive RATotalSensitivity (95% CI)HR-pQCT4th and 5th MTP jointsErosive RA27113890.0 (73.5 – 97.9)Specificity (95% CI)HR-pQCT 4th and 5th MTP joints Non-erosive RA3148.3 (0.2 – 38.5)Total301242Sensitivity & specificity of classifying patients with erosive RA by CR when HR-pQCT was used as referenceHR-pQCT4th and 5th MTP jointsErosive RAHR-pQCT4th and 5th MTP jointsNon-erosive RATotalSensitivity (95% CI)CRHands, wrists, and feetErosive RA2733071.0 (54.1 – 84.6)Specificity (95% CI)CRHands, wrists, and feetNon-erosive RA1111225.0 (0.6 – 80.6)Total38442Conventional Radiography (CR), High-resolution peripheral Quantitative Computed Tomography (HR-pQCT), Metatarsophalangeal (MTP), Rheumatoid Arthritis (RA), Confidence Interval (CI).ConclusionThis is the first study to evaluate erosions with HR-pQCT of the 4th and 5th MTP joints, including a comparison to CR. Erosions were frequent at the lateral aspect of the MTP joints, suggesting that mechanical and biomechanical demands may play a role in the development of erosions in the MTP joints. The superiority of HR-pQCT compared to CR for detecting erosions provide a basis for larger studies assessing bone changes in the MTP joints.