Acetabular cup migration after primary cementless total hip arthroplasty in rheumatoid arthritis and its influencing factors: a comparative study with osteoarthritic hip

Purpose To compare the radiographic migration profiles of primary cementless total hip arthroplasty (THA) between patients with rheumatoid arthritis (RA) and those with osteoarthritis (OA). Methods A total of 197 patients (215 hips) who underwent cementless THA for RA or OA between January 2001 and January 2013 and followed up for a minimum of 5.5 years were included. Ninety-four RA patients (109 hips) were compared with 103 OA patients (106 hips). Radiological evaluation was performed for acetabular cup loosening, and cup migration was measured using Einzel-Bild-Rontgen-Analyse (EBRA) software. Multiple variables were assessed to identify influencing factors for cup migration. Results Early cup migration was observed in 13 hips (11.9%) in the RA group and four hips (3.8%) in the OA group, showing a significant difference (p = 0.041). Acetabular cup loosening occurred in three cups (2.8%) in the RA group and in one cup (0.9%) in the OA group, showing no significant difference (p = 0.321). Total cup migration was higher in the RA group (2.62 mm) than in the OA group (1.44 mm, p = 0.005). Total cup migration was significantly higher in patients aged < 50 years than in those aged > 50 years (p = 0.005). Rheumatoid factor (RF) and anti-cyclic citrullinated peptide (anti-CCP) antibody influenced total cup migration. Patients with seropositive RA showed significantly higher total cup migration and early cup migration incidence than those with seronegative RA (p = 0.005, p = 0.038, respectively). Conclusions Acetabular cups in primary cementless THAs of RA patients were less stable in terms of cup migration compared with that of OA patients.