Variation of pain in the first day after surgery. At T0 and T1 no significant differences could be detected in the VAS score but from T2 until discharge from the hospital the study group presented a significant reduction of VAS. T0: before the surgery; T1 3 hours after surgery; T2 6 hours after 318 surgery; T3 12 hours after surgery; T4 24 hours after surgery. (PTN: posterior tibialis nerve; PTA: posterior tibialis artery).