Page 28 - The value of total hip and knee arthroplasties for patients

Chapter 2
of 7 collaborating hospitals (as such a nested study within the Dutch Arthroplasty Register, LROI). A second aim was to evaluate the preoperative characteristics of the patients willing to provide PROMs.
MATERIALS AND METHODS
Study design
The longitudinal Leiden Orthopaedics Outcomes of OsteoArthritis Study (LOAS) has a multicenter, observational, prospective design (Trial ID NTR3348). Level of Evidence II.The study was approved by the Medical Ethics Committee of the Leiden University Medical Center (NTR3348) and all local hospital research committees in the participating hospitals. Funding was received from the Dutch Arthritis Foundation (LLP13). All patients in the study provided written informed consent. For the current analysis, the data (up to 30 November, 2015) from the patients enrolled during the first 30 recruitment months (June 2012 until December 2014) were used, with the data up to and including 24 months of follow-up being used.
Patients and recruitment
Hospitals were approached by the coordinating investigator. In return for their participation each participating hospital received a report on the results within their centre as well as anonymized data from the other centres (every 3 months), a website in Dutch for participating patients and health professionals (http://www.loas. nl), newsletters (every 3 months) and an annual meeting for the local investigators.
Patients
All patients undergoing primaryTHA orTKA in the participating centers, who were able to complete questionnaires in Dutch and are 18 years or older were considered eligible for participation in the LOAS study. Patients were invited by their treating orthopedic surgeon at their visit to the outpatient clinic prior to surgery. Every week, each hospital send a list of all patients who had been invited to participate in the study to the coordinating researcher, including an additional note if a patient refused to participate. Subsequently, patients who agreed to be approached for the study were further informed about the study by the coordinating researcher.They received an information package by mail, containing a patient information letter, the preoperative questionnaire and an informed consent form. Patients were included
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