Loss to follow-up in orthopaedic clinical trials: a systematic review

Purpose: The rate of patients lost to follow-up may contribute to bias in randomized controlled trials (RCTs). Methods: We systematically reviewed orthopaedic RCTs from 2008 to 2011, including 559 RCTs with 131,836 enrolled subjects. The loss to follow-up rates and minimum follow-up times were recorded for each trial. Orthopaedic subspecialty, country of origin, number of enrolled patients, patient age, follow-up strategy, and funding type were also recorded. Results: Loss to follow-up was not reported in 111 of these studies (20 %). Mean loss to follow-up was 10.4 %. No orthopaedic subspecialty demonstrated significantly different follow-up rates. Remote follow-up strategies did not reduce the loss to follow-up rate. Studies with a minimum follow-up length of three years showed significantly higher loss to follow-up rates compared with studies with shorter minimum follow-up time (14.8 % versus 9.8 %, p = 0.01). Studies performed in the United States had a significantly higher rate of loss to follow-up compared with non-United States studies (13.8 % versus 9.4 %; p = 0.01). Conclusions: Loss to follow-up rates in published orthopaedic randomized controlled trials is overall relatively low. A substantial portion of publications does not adequately report follow-up data. Studies performed in the United States and studies with longer follow-up periods seem to be at higher risk for loss to follow-up.