All the anesthetics procedures were realized by the same anesthetist. The standard anesthesia for the procedure was spinal anesthesia with injection of 12 to 15 mg of 0.5% isobaric bupivacaine. Patients of the control group (group A) were submitted to spinal anesthesia with 0.5% isobaric bupivacaine, in isolation. Punctures in the femoral and popliteal areas were made to mask the femoral and sciatic block, respectively, with no infusion of any medication. The patients of the group B received, furthermore the standard anesthesia, the block of the femoral nerve guided by ultrasonography (Nemio 17 - Toshiba Systems Co. - Japan) and neurosimulation (Stimuplex HNS 12 - Braun - Germany) with 1 Hz stimulus frequency, 1.2 to 0.5 mA energy. The technique used was femoral area puncture, at the level of the crural fold of skin, with a 0.5% (125mg) ropivacaine associated to 75 mcg of clonidine. For the patients of the group C, in addition to the femoral blocking, the anesthesia of the sciatic nerve at the top of the popliteal fossae was realized, also guided by ultrasonography (Nemio 17 - Toshiba Systems Co. - Japan) and neurosimulation (Stimuplex HNS 12 - Braun - Germany) with 1 Hz stimulus frequency, 1.2 to 0.5 mA energy. 0.5% ropivacaine was injected associated to 75mcg clonidine. As an adjuvant for analgesia, all the patients received analgesic and anti-inflammatory permanently in postoperatory, with availability of opioids for rescue if needed. The necessity of its use and eventual complications were registered until hospital discharge.