Randomization procedures in orthopaedic trials.

Historically, the surgical literature has lacked in reports of randomized clinical trials. This deficit is now being addressed, but the best methods are not always followed. One opportunity for improvement is in the area of randomization. Randomization is of central importance in clinical trials because it reduces bias and represents a basis for ensuring the validity of data analysis using statistical testing. Randomization requires a table of random numbers. Simple randomization is adequate for large trials. Block randomization is a method of balancing equal numbers of patients in each treatment group. Stratification allows balanced distribution of one or more confounding prognostic variables among treatment groups to ensure that groups have similar prognoses (minimizing selection bias). Block randomization and stratification improve validity in trials with fewer patients. Commercially available computer software facilitates randomization.