Randomization, allocation and blinding
Patients were randomly assigned to paravertebral block or control group at a 1:1 ratio based on the results of a computerized randomization program generated by a statistician. The allocation results were sealed in opaque envelopes and stored in the research center. Analgesic pumps with either ropivacaine or saline were prepared by nurses uninvolved in any other part of the study. The patients, surgeons, anesthesiologists and postoperative follow-up assessors were blinded to the group assignments. Unmasking was performed after the completion of statistical analysis.