A Prospective Randomised Controlled Clinical Trial: Three Cancellous Screws Versus Four Cancellous Screws for Fixation of Femoral Neck Fractures

This is a prospective randomized controlled clinical trial. All patients will be randomly divided into 2 groups at a ratio of 1:1. The investigators will use three screws for internal fixation in the first group, and four screws for internal fixation in the second group. The relevant parameters of the sample calculation are α = 0.05 (one-sided) and β = 0.2. PASS 15 was used for calculation, and the final sample size was 290, 145 for each group. Subjects who meet all the inclusion conditions but do not meet any exclusion conditions and have signed the informed consent will be randomized, and each patient will be assigned a unique patient identification number, which will be used throughout the study. Using a computer random allocation system, eligible patients were randomly divided into the two groups at a ratio of 1:1. The investigators will perform preoperative preparations, intraoperative operations, and internal fixation in accordance with the instructions provided in the internal plant product packaging. The investigators only plan to include cases in which closed reduction can be successfully performed, so the investigators will exclude cases that require open reduction. For the three-screw group, three cancellous screws with an inverted triangle pattern are used to fix the fracture of femoral neck. For the four-screw group, the fourth screw will be implanted in the horizontal direction of the femoral distance on the basis of the three screws. After the operation, the subjects will be managed according to the standard nursing and rehabilitation procedures at the experimental site and the results of laboratory examinations will be recorded. Regular follow-up evaluations will be carried out after the operation until the end of the two-year follow-up or the end of the study. In this study, the internal fixation failure rate (IFFR) will be used as the main research endpoint, which is defined as the total incidence of cutouts, fractures. The results of the radiographic examination, the lateral X-ray film and computed tomography(CT), will be evaluated by an independent radiologist to determine whether there are cut-out or fracture of the internal plant. Secondary endpoints include: 1. Bone nonunion after 36 weeks: evaluate bone healing according to the lateral X-ray examination. According to the regulations of Food and Drug Administration of the US, it is defined as nonunion if there are no obvious signs of fracture healing 9 months after the fracture, or if there is no obvious difference in fracture space after three consecutive months. 2. Garden classification proportion, and Garden index for reduction assessment. 3. Clinical prognosis: o A 12-Item Short-Form Health Survey (SF-12) o Harris hip score. 4. Operation time, from the incision to internal fixation implanted. 5. The times of intraoperative fluoroscopy, average 25 milliseconds per X-ray shot, record the number of X-ray shot. 6. Postoperative adverse events within 2 years, including ipsilateral femoral head avascular necrosis, infection, wound hematoma, ipsilateral coxa vara, and ipsilateral limb shortening. In this study, it is difficult to blind anyone to randomization. However, considering that most of the patients may not have medical expertise, if the researchers do not inform them, the patients are the only people who may be blind. Investigators will try their best to reduce human-induced bias in experimental results. Investigators will use one-sided α = 0.05 for statistical tests and confidence interval calculations. P value <0.05 is considered statistically significant. SPSS (latest version: SPSS Inc., Chicago, IL, USA) will be used to analyze the results.