2.3. Randomization and Blinding
Randomization in this study utilized computer-generated and centrally administered methods, employing permuted blocks of 5. Participants were randomly allocated at a ratio of 3:2 without any stratification. To enhance willingness to participate, an increased likelihood of randomization to the vitamin D group was implemented.With the exception of MU and the personnel at the data monitoring center located at the Jikei University School of Medicine, who were responsible for preparing the vitamin D or placebo bottles based on the randomized assignment, all other surgeons, the clinical research coordinator, and participants at the International University of Health and Welfare hospital were blinded to the patients’ group assignments.