Background Joint destruction in RA includes both bone and cartilage lesions. By X-ray examination, cartilage destruction is evaluated as a joint space narrowing (JSN). However, joint space narrowing is not a direct evaluation of cartilage.
Objectives We aimed to examine the finger joint cartilage thickness (CT) by ultrasound (US) imaging and clarify its clinical significance in patients with RA.
Methods We enrolled 121 RA patients in low disease activity or clinical remission (DAS28-CRP <2.7) in this study. The CT of metacarpophalangeal (MCP) and proximal interphalangeal (PIP) joints of 2nd to 5th fingers was bilaterally visualized and measured at the middle portion of MCP and PIP joints from a longitudinal dorsal view, with approximately 90 degrees flexion. In addition, JSN of finger were scored by van der Heijde- modified Sharp method for patients who had a hand X-ray within 2 months.
Results CT in MCP joints ranged from 0.0 to 1.1 mm (median 0.5 mm), and CT in PIP ranged from 0.0 to 0.6mm (median 0.3mm), respectively. The sum of total CT from 8 fingers ranged from 4.0 to 9.4 mm (median 6.9 mm), and there was a significant difference in total CT, but not in JSN score, between male and female patients (7.4 versus 6.7, p=0.006; and 11 versus 10, p=0.899, respectively). CT was well correlated with JSN (ρ=-0.589, p<0.001; ρ=-0.595, p<0.001 for MCP joints andρ=-0.448, p<0.001 for PIP joints), and both CT and JSN were significantly correlated with disease duration (ρ=-0.282, p=0.002, andρ=0.286, p=0.005, respectively). Notably, CT of MCP, but not of PIP, was inversely correlated with disease duration (ρ=-0.328, p<0.001). Height was correlated with CT (ρ=0.244, p=0.008), but not with JSN (ρ=-0.057, p=0.589). CT and JSN were not correlated with age, functional disability, and seropositivity.
Conclusions A direct visualization and quantification of finger joint CT, especially MCP joints, by US is valid and useful in RA.
Disclosure of Interest None declared