Risk of bias in studies
MINORS scores are presented in table 1. The median MINORS score was 9 (range 6-13) out of a maximal score of 16. In general studies presented clearly stated aims, however lack of clarity on whether consecutive patients were included was a frequent issue. Endpoints were typically well defined, and reporting was unbiased. None of the studies prospectively calculated a study size and there was variable reporting on minimal follow-up periods and attrition rates, thus impacting reliability of extracted survival data.