STUDY QUESTION What are the rates of serious cardiovascular events in those who undergo primary total joint arthroplasty (TJA) compared with those who do not within three years of initial assessment?
SUMMARY ANSWER Undergoing elective primary TJA within three years of initial assessment was associated with a significant 12.4% absolute reduction in subsequent risk of serious cardiovascular events.
WHAT IS KNOWN AND WHAT THIS PAPER ADDS Osteoarthritis is associated with increased mortality, particularly secondary to cardiovascular disease, with the risk for mortality proportional to the degree of disability secondary to the arthritis. This study suggests that management of hip or knee osteoarthritis with arthroplasty decreases the risk for subsequent serious cardiovascular events.
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Participants and setting
We utilised baseline questionnaire data from the Ontario Hip/Knee Study (1996-98), a population based cohort of 2411 adults aged 55 or more with disabling hip or knee arthritis and living in Ontario, Canada. 153 participants (88.4%) who underwent a primary, elective TJA during the exposure period were matched to a participant who did not.
Design, size, and duration
We carried out a propensity score matched landmark analysis. Entry to the cohort occurred on completion of the baseline questionnaire. We chose a landmark date of three years after completion of the questionnaire. Those who experienced a primary elective TJA during this period were considered exposed and those who did not were considered unexposed (regardless of whether they underwent TJA after the landmark date). We excluded participants who had a cardiovascular event or died during the exposure period. A propensity score for undergoing a TJA within the exposure period was determined from information on sociodemographics (age, sex, body mass index, education, income), health status (comorbidities, SF-36 general health score, pre-existing cardiovascular disease, depression, smoking status, use of non-steroidal anti-inflammatory drugs), and arthritis severity (Western Ontario and McMaster Universities arthritis index, troublesome hips and knees). We matched exposed to unexposed participants in a ratio of 1 to 1.
Main results and the role of chance
111 (36.3%) cardiovascular events occurred in our matched cohort (153 pairs) over a median follow-up period of seven years. The TJA group were less likely to experience a cardiovascular event during follow-up (hazard ratio 0.56, P<0.001). The absolute risk reduction was 12.4% and the number needed to treat was eight.⇓
Bias, confounding, and other reasons for caution
A theoretical unmeasured confounder, if not collinear with other covariates, would have to have had a prevalence of at least 75% in one group, and be completely absent from the other group, with a relative risk ratio of at least 0.65 (if found only among the TJA group) or 1.50 (if found only among the non-TJA group) to account for the observed TJA effect. Potential unmeasured confounders included motivation, self efficacy, hyperlipidaemia, and renal insufficiency.
Generalisability to other populations
This study used a true population based cohort of people with osteoarthritis. Further study is required to confirm our results.
Study funding/potential competing interests
BR is supported in part by a doctoral award from the Canadian Institutes of Health Research. PCA is supported in part by a career investigator award from the Heart and Stroke Foundation. GAH is supported in part by the FM Hill chair in academic women's medicine. ICES received support from the Ministry of Health and Long-Term Care (Canadian Institutes of Health Research grant No MOP-15468).
This is a summary of a paper that was published on bmj.com as BMJ 2013;347:f6187