s / Osteoarthritis and Cartilage 20 (2012) S54–S296 S177 Therefore, we assessed whether HRT use is associated with reduced implant failure rates in a community-based cohort. Methods: Study population: Female participants in the General Practice Research Database undergoing a TKA or THA from 1986 to 2006 were included. Revision surgery was identified using READ codes. In order to identify arthroplasties indicated for osteoarthritis, we excluded patients aged 80%) adherence were identified as HRT users. Three sensitivity analyses were carried out, where we explored the association between HRT use for 12 months, HRT adherence and cumulative use, and time to failure. We used time varying Cox Models to account for the immortal time till met definition of HRT use. Statistical analysis: Time-varying Cox models were used to estimate hazard ratios (HR) for HRT users versus non-users matched by propensity score to minimize for confounding by indication. Potential confounders were: age, gender, body mass index, joint replaced (hip/knee), year of surgery, OA indication, fracture history, anti-osteoporosis medication use, oral glucocorticoids, smoking, alcohol intake, multiple deprivation index, UK region, co-morbid conditions, and use of drugs which can affect bone metabolism. Results: Of 24,733 eligible women included, 3,644 met the definition of HRT user and the remaining 21,089 were non-users. From the propensitymatching, 2,700 HRT users and 3 comparable controls (8,100women)were selected. The median (interquartile range) follow-up was 3.3 (1.5-6.1) years after surgery. Despite matching, HRT users were more likely to be taking drugs with increase fracture risk. A total of 168 (1.56%) participants underwent revision surgery during the period of followup. The cumulative failure rate was significantly lower in HRT users than non-users (27(1.00%) vs 141(1.74%, p1⁄40.007)). HRT use for 6 months was associated with a lower risk of revision (HR 0.61 (0.41 to 0.93)) [Figure]. Both higher adherence (p1⁄40.007) and longer therapy duration (p1⁄40.008) led to further reductions in revision rates. [Table]. Sensitivity analyses: effect of adherence and cumulative use of HRT on implant surv