Risk of Venous Thromboembolism After Knee, Hip or Shoulder Replacement: A Retrospective Cohort Study Using Linked Hospital and Primary Care Data

Date of Approval
Application Number
Technical Summary

Venous Thromboembolism (VTE), a term including both deep vein thrombosis and pulmonary embolism, can be a serious complication after joint replacement surgery. UK studies to measure the risk of VTE after joint replacement surgery have thus far looked exclusively at hospital data. However, using hospital data alone may substantially underestimate post-surgical VTE risk [1,5]. This retrospective cohort study will therefore use three data sources combined to better estimate the VTE risk after joint replacement surgery: hospital data (Hospital Episode Statistics), primary care data (Clinical Practice Research Datalink) and death certificate information (Office of National Statistics).

This study has two main aims. The first is to provide comprehensive, joint-specific estimates of VTE risk in the six months after primary knee, hip and shoulder replacement surgery, and to explore changes in risk over time. Logistic regression will be used to investigate temporal variations in VTE risk from October 2007 to February 2020, including potential seasonal patterns and step changes in risk due to National Institute of Health and Care Excellence (NICE) guideline updates (e.g. NG89, released in March 2018, covering the assessment and management of VTE risk in hospitals).

The second aim of this study is to better understand patient specific VTE risk in the six months after primary knee, hip or shoulder replacement surgery. VTE risk will be related to patient covariates, region and date of surgery using a random forest model (RFM) in order to allow for complex, interactive and nonlinear relationships. The relationship between risk and patient attributes will be explored, as will regional and temporal variations in risk when holding patient attributes constant. We will also use the similarity matrix resulting from the RFM to cluster patients into groups of relatively homogenous risk, which could provide important information for future NICE guideline updates.

Health Outcomes to be Measured

Venous Thromboembolism (deep vein thrombosis; pulmonary embolism) recorded in primary care, secondary care or on death certificate in the 6 months after joint replacement surgery.


John Powell - Chief Investigator - University of Oxford
Nadja Leith - Corresponding Applicant - University of Oxford
Clare Bankhead - Collaborator - University of Oxford
Cynthia Wright Drakesmith - Collaborator - University of Oxford
Jonathan Rees - Collaborator - University of Oxford
Sarah Brown - Collaborator - University of Oxford
Subhashisa Swain - Collaborator - University of Oxford


HES Accident and Emergency;HES Admitted Patient Care;HES Outpatient;ONS Death Registration Data;Patient Level Index of Multiple Deprivation