Patients in GroupTizanidine will receive 4 mg tizanidine per oral twice a day during the postoperative first week and the first dose will be administered 1 hour before surgery, patients in Group Placebo will receive the same treatment with a placebo pill concurrently with a standard analgesic treatment: dexketoprofen trometamol; 25 mg intravenous (iv) before the induction of anesthesia and 25 mg per oral 3 times a day-1 week and acetaminophen; 1 g iv at the end of surgery. All patients will be instructed to use acetaminophen 500 mg up to 4 times a day for rescue analgesia and to contact the hospital if they have pain despite all three medications.