Few reports have focused on the distal interphalangeal (DIP) joint in patients with rheumatoid arthritis (RA). The purposes of this study were to evaluate the frequency of bone erosion of the DIP joint, and to determine the factors associated with its deformity.
This study reviewed 204 patients with RA in whom radiographs of hands were obtained. According to the presence/absence of bone erosion of the DIP joint, patients were divided into two groups (DIP-positive and DIP-negative groups). Additionally, wrist, metacarpal phalangeal (MP), thumb interphalangeal (IP), and proximal interphalangeal (PIP) joints were evaluated. Clinical variables such as age, sex, body mass index, disease duration, disease activity (DAS28-CRP), and drug use were investigated.
Regarding the radiological findings of the DIP joint, 32 patients (15.7%) were allocated to the DIP-positive group and 172 patients (84.3%) to the DIP-negative group. The mean age, disease duration, DAS28-CRP, and the rate of corticosteroids usage were significantly higher in the DIP-positive than in the DIP-negative group (p = 0.0031, 0.0062, 0.0342, and 0.0011, respectively). Radiologically, concomitant bone erosions of the wrist, MP, thumb IP, and PIP joints were significantly more common in the DIP-positive than in the DIP-negative group (p < 0.01 for all four joints). Multivariate analysis demonstrated that advanced age, long disease duration, and the presence of radiological bone erosion of the PIP joint were independently associated with bone erosion of the DIP joint (p = 0.0480, 0.0307, and 0.0021, respectively). Accordingly, in patients with DIP erosions, mean DAS28-CRP was significantly higher in patients with <5 years (n = 10) than in those with ≥5 years of disease duration (n = 22, p = 0.0088).
Bone erosion can be observed at the DIP joint in patients with RA, and these cases frequently shows bone erosions of other finger joints, such as PIP joint. In addition, bone erosion can be observed soon after the onset of RA caused by uncontrolled disease activity in some patients with RA.