The impact of knee replacement on mortality in the presence of chronic disease

Date of ISAC Approval: 
Lay Summary: 
There are more knee replacements being performed each year, but it is unclear whether they decrease the likelihood of death for people with knee osteoarthritis. We propose a study to determine whether knee replacement improves the life span of people with osteoarthritis in the knee, taking into consideration their other illnesses.
Technical Summary: 
Knee osteoarthritis (KOA) is a leading cause of disability1 and has been associated with morbidity and mortality2. Currently, knee replacements (KR) are the only known effective long-term intervention for end-stage knee osteoarthritis. Consequently, the prevalence of KRs is escalating worldwide3. Whether total KR can reverse the increased risk of mortality among people with KOA is currently unclear. While it is hypothesized that KR would have a favorable effect on mortality, likely through promoting increased mobility1 and thereby improved health, studying this question is methodologically challenging due to the difficulty in controlling for confounding by indication. Patients with KOA undergoing KR may be healthier than those who do not undergo a KR. We plan to conduct a cohort study in a population of patients with knee osteoarthritis (KOA) to assess mortality rates in patients with and without a knee replacement (KR). From among all patients with KOA we will identify people with a first primary KR code on or after the date of cohort entry (date of first KOA). Each KR patient will be matched to a non-KR patient on year of birth and sex. Each patient will then be followed from their index date (date of KR or a randomly assigned index date for non-KR patients), to censor date (date of death or end of record whichever comes first). We will calculate incidence rates and hazard ratios for death in the two cohorts. We will also identify a second a propensity score matched cohort of non-KR patients to control for health status in KR compared to non-KR patients since the is a chance that patients who have a KR are healthier that those who do not.
Health Outcomes to be Measured: 
1) Primary outcome: Death 2) Secondary outcomes: Chronic comorbidities including cardiovascular disease, diabetes, hypertension, congestive heart failure, cognitive illness, depression, infectious diseases, kidney disease, mental illness, peripheral vascular disease, pulmonary disease, and gastrointestinal disease.

Dr Susan S Jick - Chief Investigator - BCDSP - Boston Collaborative Drug Surveillance Program
Jessica Maxwell - Collaborator - BCDSP - Boston Collaborative Drug Surveillance Program
Dr Susan S Jick - Corresponding Applicant - BCDSP - Boston Collaborative Drug Surveillance Program