To the Editor:

I would like to thank Dr. Fox for her question which allows me to explain our randomization method. In our study the patients were selected in the following way:

Each patient on a waiting list of our Clinic that is in a public hospital was called by a resident. The waiting list includes more than 1300 patients who are waiting for different types of surgeries by nine different orthopaedic surgeons. . The patient's registration number determined the graft choice: odd numbers were allotted to receive a BPTB graft while even numbers underwent hamstring reconstruction.

The patients were investigated preoperatively by the same independent observer who evaluated them at the follow-up. (Dr. Giron);

Each patient was informed about the study and signed an informed consent form. They were aware that the only difference in the procedure was the type of the graft employed. They did not know which graft would be used for their reconstruction but they were informed about our percentage of success with each graft based on previous studies.

Patients who refused to take part in the study or wanted to personally choose the graft were not included in the study.

5. The surgeon (Prof. Aglietti) performed the surgery and selected the type of graft on the basis of the patient's registration number on the waiting list. He met the patients in the OR and was not able to influence the selection. The procedures were performed alternately (odd and even numbers sequentially) up to 120.

There are several way to allocate patients in clinical studies, but I think that this method of allocating the patients (registration number in a general waiting list including also other patients undergoing different types of surgeries) could be reasonably considered "randomized" and not "deterministic" because at the time of registration in the waiting list each patient had the same probability of receiving an odd or an even number.

Sincerely yours,

Francesco Giron, MD

To the Editor:

We read with interest the excellent article by Aglietti et al [1]. However we feel that it cannot be described as a "randomized" trial. Randomization was achieved be a "strictly alternating" pattern of treatment allocation, which is open to sources of potential bias. Despite this method of allocation the two groups are very well matched, although there is no discussion in the article as to whether a stratification process was used to achieve this.

The term 'randomized' has a precise statistical meaning in that each patient has the same probability of receiving either treatment, independent of the previous patients allocation [2]. this is clearly not the case here. In addition, the term "strictly" is difficult to interpret. Although the procedure performed at each successive operation may have alternated, we feel further information should be supplied concerning the processes of entering patients into the trial. In particular, the surgeon's role in influencing the treatment received, and whether allocation was by third party. In addition there is no information about the patients who declined entry into the study or withdrew once they knew which treatment arm they had been allocated to, again both potential sources of bias. Using alternation to allocate treatment is thus better described as 'deterministic' and the term 'randomized' should not be used.

We note a previous study by the same author [3] used the same method of treatment allocation, however this was not described as 'randomized' but more appropriately as a "prospective comparative study". Interestingly, subsequent papers refering to this study have inadvertently described it as randomized [4,5].

Since the CONSORT guidelines [6] were published, there has been an increased recognition of the importance of methodology, and its justification in research, and there has been a greater emphasis on the reporting of randomized controlled trials. Unfortunately, despite being an otherwise excellent study, this work has left itself open to criticisms of the allocation method used, and thus the potential for bias.

1. Aglietti P, Giron F, Buzzi R et al. Anterior cruciate ligament reconstruction: Bone-patellar tendon-bone compared with double semitendinosus and gracilis tendon grafts. JBJS-A 2004; 86A: 2143-55.

2. Altman D. Practical statistics for medical research-chapter 5. Chapman & Hall 1991.

3. Aglietti P, Buzzi R, Zaccherotti G et al. Patella tenodn versus doubled semitendinosus and gracilis tendons for anterior cruciate ligament reconstruction. Am J Sports Med 1994; 22(2): 211-8.

4. Erikson K, Anderberg P, Hamberg P et al. A comparison of quadruple semitendinosus and patella tendon grafts in reconstruction of the anterior cruciate ligament. JBJS-B; 83B: 348-54.

5. Shaieb MD, Kan DM, Chang SK et al. A propsective randomised comparison of patella tendon versus semitendinosus and gracilis tendon autografts for anterior cruciate ligament reconstruction. Am J Sports Med 2002; 30(2): 214-21.

6. Begg C, Cho M, Eastwood, S et al. Improving the quality of reporting of randomized controlled trials: the CONSORT statement. JAMA 1996; 276: 637-9.