Predictive factors of total hip replacement due to primary osteoarthritis: a prospective 2 year study of 505 patients

To determine the 2 year total hip replacement (THR) rate and to identify factors predictive of THR due to primary osteoarthritis (OA).

A 2 year prospective cohort study. Inclusion criteria were primary hip OA, with a history of pain for 6 months, and patients' pain assessment of > or =30 mm on a visual analogue scale (0-100 mm). Predictive factors of THR were identified by univariate then multivariate analysis using logistic regression. Potential predictors considered were demographic, radiographic (localisation and severity of OA), and patients' assessment of symptomatic severity of OA.

Of the 741 patients enrolled, 505 (68.2%) patients, mean (SD) age 64.0 (10.1) years, mean (SD) disease duration 4.7 (5.2) years, had complete 2 year data. There was no difference between the completer and non-completer groups. During follow up, 189/505 (37.4%) patients had a first THR. By multivariate analysis, predictors of THR were Kellgren-Lawrence radiographic grade (grade III: odds ratio (OR) = 3.3 (95% confidence interval (95% CI) 1.7 to 6.4); grade IV: OR = 5.3 (95% CI 2.6 to 10.8)), high mean patient global assessment during the first 6 months (OR = 2.2 (95% CI 1.4 to 3.2)), and previous non-steroidal anti-inflammatory drug (NSAID) intake (OR = 1.5 (95% CI 1.0 to 2.4)). For two of these factors together, OR = 3.0 (95% CI 1.6 to 5.9), for three factors together, OR = 5.6 (95% CI 2.6 to 12.2).

The 2 year rate of THR was high in this group of patients with painful hip OA: 37.4%. Radiological grade, mean patient global assessment, and the need for NSAIDs were predictive of THR.