Involvement of different risk factors in clinically severe large joint osteoarthritis according to the presence of hand interphalangeal nodes.

OBJECTIVE: To quantify the differences in risk factors influencing total hip replacement (THR) and total knee replacement (TKR) based on the presence versus absence of multiple interphalangeal nodes in 2 or more rays of the fingers of each hand in patients with large joint osteoarthritis (OA).

METHODS: A group of 3,800 patients with large joint OA who underwent total joint replacement (1,201 of whom had the nodal phenotype) and 1,906 control subjects from 2 case-control studies and a population-based cohort in the UK were studied. Odds ratios (ORs) and 95% confidence intervals (95% CIs) were calculated for the risk of total joint replacement in association with age, sex, body mass index (BMI), height, and prevalence of the T allele in the GDF5 rs143383 polymorphism. ORs for total joint replacement were compared between cases of nodal OA and cases of non-nodal OA and between patients who underwent TKR and those who underwent THR.

RESULTS: Age, sex, and BMI had significantly higher ORs for an association with total joint replacement in nodal OA cases than in non-nodal OA cases. The GDF5 polymorphism was significantly associated with THR in cases of nodal OA, but not in cases of non-nodal OA, and increased height was a risk factor for THR in non-nodal OA cases only. Female sex was a protective risk factor for TKR in non-nodal OA cases (OR 0.60, 95% CI 0.52-0.70) but was predisposing for TKR in the nodal form of OA (OR 1.83, 95% CI 1.49-2.26). The nodal phenotype was associated with a significantly higher risk of undergoing both THR and TKR (OR 1.46, 95% CI 1.09-1.94) and also a significantly higher risk of bilateral TKR (OR 1.70, 95% CI 1.37-2.11), but, paradoxically, was associated with a lower risk of bilateral THR (OR 0.72, 95% CI 0.56-0.91).

CONCLUSION: Nodal and non-nodal forms of large joint OA have significantly different risk factors and outcomes, indicating a different etiology for the 2 forms of OA. With regard to the likelihood of undergoing THR, this appears to be, at least in part, genetically determined.