Background RA has fairly consistently been reported to be associated with low bone mineral density (BMD) and increased risk of fracture to the hip and wrist. However, new effective treatments for RA have now existed for some 15 years, and there is only limited and conflicting evidence of the fracture risk in patients with OA. There is a need to gain new knowledge based on more robust data of the actual fracture risk in both these diseases, preferably using a cohort analysis type of approach with less potential for selection bias than classic case-control study designs.
Objectives To determine the rate ratio of hip and distal radius fracture in patients with rheumatoid arthritis (RA), hip osteoarthritis (OA) and knee OA, respectively.
Methods Cohort study using healthcare data (1998-2012) covering the entire population of Skåne region, Sweden (1.3 million 2012). We identified all RA, hip OA and knee OA patients aged ≥45 years, who we followed until their first hip or distal radius fracture, death, relocation, or end of study period. We calculated the age-standardized fracture-rate ratio (SFR) compared to the general population.
Results We identified 741 598 subjects aged 45 or older at the time of inclusion eligible for the study population. The mean (SD) age at the beginning of the follow-up period was 57.7 (13.1) years and 52% were women. We identified 8467 patients with RA, 29 706 patients with hip OA and 55 753 patients diagnosed with knee OA at risk for hip fracture and similar numbers for radius fracture.
We found a significantly increased rate of hip fracture in both female (SFR=1.54; 95% confidence interval [95%CI] 1.40, 1.70) and male RA patients (SFR=1.81; 95% CI 1.51, 2.17). The hip fracture rate in female hip and knee OA patients, respectively, was reduced (SFR=0.81; 95% CI 0.74, 0.89 and SFR=0.89; 95% CI 0.85, 0.93), but not in men when subjects with total hip replacement were censored (Table 1). In OA patients, the rate ratio of trochanteric fracture tended to be higher compared cervical fracture. The rate of distal radius fracture in both female and male knee OA patients tended to be slightly increased compared to the general population (SFR=1.11; 95% CI 0.97, 1.26 and 1.05; 95% CI 1.00, 1.11, respectively).
Conclusions In RA and OA there are distinctly different risks of sustaining fragility fractures. The 50 to 80% increased rate of hip fracture adds to the total burden of RA while the shifted distribution of cervical/trochanteric fracture types in OA patients are in support of subchondral bone alterations.
Disclosure of Interest None declared