<qa>  What is the name of the group assigned to the patients?This study is a prospective, randomized, open-label clinical trial. The study will be performed in patients after obtaining informed consent. Group assignment is by drawing a sealed envelops based on random table. 1 Group 1: Experimental group 30 cases, Aclasta Zoledronic acid 5mg100ml is given intravenously on the 4th postoperative day and one year after the total hip replacement, 2 Group 2: Control group, 30 cases, no bisphosphonate is given to the patients. Only the unilateral coxarthrosis will be recruited for the study. Patients will be analyzed with 1 DXA study 2 Clinical assessment Harris hip score and SF-12 3 X-ray 4 serum marker of bone turnover. Patients will be scheduled for specified examinations preoperatively, postoperatively 6 weeks, 3 months, 6 months, 12 months, and 24 months. 