While recent publications have demonstrated the analgesia effectiveness of femoral nerve block and fascia iliaca block for hip fractures,(18) there are not references in the literature analyzing the effectiveness of a single shot, ultrasound-guided, femoral nerve block in primary hip arthroplasty. This fact opens up the possibility to continue researching the analgesic effectiveness of this block in a population where the options for handling postoperative pain are limited widely for its side effects together with the use of anticoagulant and anti-thrombotic therapy.