Concise Review Randomization Procedures in Orthopaedic Trials Pietro Randelli, M.D., Paolo Arrigoni, M.D., James H. Lubowitz, M.D., Paolo Cabitza, M.D., and Matteo Denti, M.D. Abstract: 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. Com- mercially available computer software facilitates randomization. Key Words: Allocate—Block— Randomization—Selection bias—Simple—Stratify. A prospective, randomized controlled trial (RCT) is an essential tool for comparing the efficacy of surgical treatments and provides the highest level of evidence when attempting to resolve a primary re- search question. With proper randomization, treatment is not known to the researcher at the time a patient is registered for a trial; thus, selection bias (bias result- ing from patients in different treatment groups having differing prognoses) is minimized, because random- ization results in a balance of unknown (as well as known) prognostic variables when patients are as- signed to various treatment arms. Review of the surgical 1-3 and orthopaedic surgical 4 literature reveals that few published studies (3% to 6%) represent RCTs, and a minority of trials employ proper methods of randomization. A review of pub- lished “RCTs” of upper extremity disorders reveals that only 43% were truly randomized; of these, 23% described an inappropriate randomization method, and in 34%, the randomization method was not described. 5 The purpose of this review is to concisely consider and suggest an ideal method of randomization for orthopaedic surgical trials. RANDOM NUMBERS Randomization is ideally based on a table of random numbers, which is readily generated by computer. Such a table consists of a group of digits that are completely independent of one another, such that knowledge of proceeding digits of a series does not allow prediction of the next digit, because each digit has an equal chance of appearing in each position. A simple way to obtain such a list of random numbers is to use the “Randbe- tween” worksheet function provided in Microsoft Ex- cel (version 2003; Microsoft, Redmond, WA). From the Dipartimento di Scienze Medico-Chirurgiche (P.R., P.A., P.C.), Università degli Studi di Milano, IRCCS Policlinico San Donato, Milan, Italy; Taos Orthopaedic Institute (J.H.L.), Taos, New Mexico, U.S.A.; and the Centro di Traumatologia dello Sport (M.D.), Istituto Ortopedico Galeazzi, Milan, Italy. The authors report no conflict of interest. Address correspondence and reprint requests to Pietro Randelli, M.D., IRCCS Policlinico San Donato, Via Morandi 30 20097, San Donato Milanese, Milan, Italy. E-mail: pietro.randelli@tin.it © 2008 by the Arthroscopy Association of North America 0749-8063/08/2407-0822$34.00/0 doi:10.1016/j.arthro.2008.01.011 834 Arthroscopy: The Journal of Arthroscopic and Related Surgery, Vol 24, No 7 (July), 2008: pp 834-838