Recruitment challenges in surgical trials: lessons from the crisp trial

Background The results of surgical trials are often challenged because of concerns about the experience and skill of the surgeons taking part. When well-established alternative surgical procedures exist, individual surgeons are usually more proficient in, and favour, a single approach. Conventional within-surgeon randomisation requires surgeons to be proficient in both procedures, which may skew the surgical expertise towards one technique. Expertise-based randomisation overcomes this limitation. We describe our experience of implementing expertisebased randomisation in the context of the CRISP trial to compare on-pump and off-pump CABG in high-risk patients.