Objective?To discuss the clinical application of total hip arthroplasty (THA) with collum femoris preserving (CFP) prosthesis and to analyze the mid-term effectiveness.?Methods?Between January 2004 and February 2007, 45 patients (48 hips) underwent THA with CFP prosthesis. There were 29 males (31 hips) and 16 females (17 hips) with an average age of 48.8 years (range, 38-60 years), including 20 left hips, 22 right hips, and 3 bilateral hips. The causes of hip replacement were osteoarthritis (20 cases), avascular necrosis of femoral head (13 cases), dysplasia (4 cases), rheumatoid arthritis (3 cases), post-traumatic osteoarthritis (2 cases), ankylosing spondylitis (2 cases), and Perths disease (1 case). The average disease duration was 6.1 years (range, 2-13 years). Harris scores, visual analogue scale (VAS) score, and the hip range of motion (ROM) were recorded at pre- and post-operation. The X-ray films were taken at pre- and post-operation to observe the position, loosening of the prosthesis, and ectopic ossification. The gait of patients were also evaluated during follow-up. Short-form 36 health survey scale (SF-36) was used to evaluate the life quality of patients.?Results?All 45 patients were followed up 5-8 years with an average of 6.4 years. All the incisions healed by first intention. No infection, hip dislocation, nerve injury, or deep vein thrombosis occurred. Six cleavage fractures (13.3%) of the lateral femoral diaphysis at the distal prosthesis occurred during operation, which healed at 8 months postoperatively without any treatment. Mild ectopic ossification occurred in 4 patients (8.9%) who had no discomfort. Five patients (11.1%) had bone mineral density loss in the region of the proximal femur. The survival rates of the cups and stems were all 100% at last follow-up. The results of Harris score, VAS score, and ROM of the hip joint at 1 year postoperatively and last follow-up were significantly better than preoperative ones (P lt; 0.05). No significant difference was found in VAS score and ROM of the hip joint between at 1 year postoperatively and at last follow-up (P gt; 0.05) except the Harris score (P lt; 0.05). According to Harris functional assessment at last follow-up, the results were excellent in 31 hips, good in 11 hips, and fair in 6 hips with an excellent and good rate of 87.5%. The physiological role, body pain, and total health scores were significantly lower than the reference value of urban men from Sichuan province (P lt; 0.05), but no significant difference was found in the other scores of the SF-36 when compared with the reference value (P gt; 0.05).?Conclusion?THA with CFP prosthesis is a good option for the young patient with complete collum femoris and without osteoporosis, and can achieve good mid-term effectiveness.