Objective To assess the clinical efficacy of percutaneous iliosacral screwing versus reconstruction plating in the treatment of pelvic posterior ring fractures of Tile C.Methods The authors retrieved the randomized controlled trials (RCTs) and clinical controlled trials (CCTs) comparing percutaneous iliosacral screwing versus reconstruction plating for Tile C pelvic posterior ring fractures from the Cochrane library,Medline,Embase,CNKI,Wanfang Data and Chinese Biomedical Database by computer and from major Chinese orthopedic journals by hand.Qualified data were extracted by statistical software Revman 5.2 for meta-analysis.Results 334 cases were included in this Meta-analysis from one RCT and 3 CCTs.Of them,162 underwent percutaneous iliosacral screwing and 172 reconstruction plating (including 66 cases of percutaneous reconstruction plating and 106 ones of anterior reconstruction plating).There was no significant difference between percutaneous iliosacral screwing and reconstruction plating in operation time (P =0.16).Percutaneous reconstruction plating consumed significantly less operation time than anterior reconstruction plating (P ＜ 0.001).Percutaneous iliosacral screwing decreased significantly incision length and intraoperative blood loss than both methods of reconstruction plating (P ＜ 0.001),but significantly increased times of X-ray exposure than percutaneous reconstruction plating (P ＜ 0.001).There were no significantly differences in the good to excellence rates by Matta scores and Majeed scores between percutaneous iliosacral screwing and percutaneous reconstruction plating (P ＞ 0.05),but percutaneous iliosacral screwing performed significantly better than anterior reconstruction plating (P ＜ 0.001).Percutaneous reconstruction plating led to significantly fewer postoperative complications than anterior reconstruction plating (P ＜ 0.001) but similar incidence of postoperative pain at the sacroiliac joint compared with percutaneous reconstruction plating (P =0.30).Conclusion Compared with anterior reconstruction plating,pereutaneous iliosacral screwing and percutaneous reconstruction plating may lead to better clinical efficacy and fewer complications.Percutaneous iliosacral screwing may be superior in incision length and intraoperative blood loss,but it requires more intraoperative X-ray exposure and more demanding technical skills.

OBJECTIVE：To identify the main unknow impurity of Oxiracetam capsule and determine its content ，so as to improve the standard of quality control. METHODS ：Two-dimensional UPLC -IT-TOF-MS was adopted to qualitatively analyze the unknown impurity. One-dimensional liquid chromatogram analysis was performed on ST PAK C 18 ES column with mobile phase consisted of 0.02 mol/L sodium dihydrogen phosphate solution at the flow rate of 0.5 mL/min. The column temperature was set at 30 ℃，sample size was 20 μL. The detection wavelength was set at 210 nm. Two-dimensional liquid chromatogram analysis was performed on Techmate C 18-STⅡ column with mobile phase consisted of 0.02 mol/L ammonium acetate solution at the flow rate of 0.5 mL/min. The column temperature was 30 ℃. Mass spectrometry was adopted （electropray ionization source ，MS+ and MS － mode data acquisition ）. After the target impurity was located by one-dimensional liquid chromatography ，it was transferred to two-dimensional liquid chromatography-mass spectrometry system for qualitative analysis. The unknown impurity structure was inferred by means of molecular formula prediction module “Accurate Mass Calculator ”in LCMS Solution ，and the refined impurity products by preparation and purification were standardized and confirmed . The impurity content was determined by HPLC （with the same condition of one-dimensional liquid chromatography for qualitative analysis ）. RESULTS ：The main unknown impurity in Oxiracetam capsules is oxiracetam acid. The content of the refined product was 99.5％ after preparation and purification. The contents of oxiracetam acid in 9 batches of Oxiracetam capsules were 0.05％ -0.14％ . CONCLUSIONS ：The established two-dementional UPLC-IT-TOF-MS method can accurately locate the peak position of the impurity oxiracetam acid ，and analyze its structure，while the corresponding content determination method can better separate the impurity from the main drug and other components，with good sensitivity ，precision，repeatability，stability and accuracy. The quality of the finished product of Oxiracetam capsules can be well controlled by using above method .