Influence of single centers in a multicenter trial on robot-assisted therapy?

Stroke is one of the leading causes of disability, and advances in neurorehabilitation bring new therapy forms that aim to enhance recovery after stroke. In a multicenter clinical trial, we tested whether robot-assisted therapy of the arm with the therapy robot ARMin is superior to conventional therapy with regard to improvement in arm motor function. In this article, we describe differences in motor function gains among the four participating centers. Three centers showed a tendency favoring robotics whereas one center showed the converse. Results might be accidental considering the small and different number of patients within the centers. However, it indicates that not only study procedures but soft factors that are generally not taken into consideration when planning a multicenter study, such as therapeutic attitude or center differences, might influence the study outcome.