Research on controlling long-term performance by tensioning post tendon of long-span continuous rigid-frame bridges

The problems like cracking of the girder in the mid-span and the ever-increasing vertical deflection appear during the long term usage of the long-span continuous rigid-flame bridge. Post-tension tendon with re- served duct can increase the pre-stress of the main beam effectively, and decrease the long term span deflection in order to improve the performance of the girder. At the same time, the proper tension position is very crucial to optimise the stress distribution of the bridge and control the deflection increase. Combining with practical en- gineering, the authors analyze the influence of different positions of post-tension tendon （ including top-, web- and bottom plate tendons） on the stress and deflection of the main beam, and find out the optimal position of post tendon.

Five-year oncologic outcomes and prognostic factors for locally advanced low rectal cancer after low anterior resection

Objective： The aim of the study is to investigate the longterm oncologic outcomes including local recurrence, distant metastases and overall survival （OS） for patients with low rectal cancer underwent low anterior resection （LAR） with total mesorectal excision （TME）, and to analyze the prognostic factors for them. Methods： Between January 2001 and December 2009, 147 patients with clinical stage II and III rectal cancers located 3-6 cm from the anal verge underwent LAR with TME without temporary diverting stoma. The median distal resection margin （DRM） was 1.0 （range, 0.3-5） cm. Anastomostic leakage occurred in 29 （19.7%） patients. Thirty patients received surgery alone, 20 patients received preoperative chemoradiotherapy （CRT）, 43 patients received postoperative CRT, and adjuvant chemotherapy was administered for 108 patients. The median cycle of adjuvant chemotherapy was 6 （range, 2-20） cycles. The median followup was 74.8 （range, 30.1-146.3） months. Results： In all patients, 5-year recurrence-free survival （RFS）, disease-free survival （DFS） and OS were 70.4%, 54.2% and 60.5%, respectively. Forty-three （29.3%） patients suffered local recurrence. Patients received preoperative CRT with a downstaging yp0/1 who had a better 5-year RFS, DFS and OS, which were 100%, 90.9%, and 90.9%, respectively. For patients with pathologic stage Ⅱ and stage Ⅲ, the 5-year RFS, DFS, and OS were 79.2% and 60.1%, 67.9% and 39.1%, 72.1% and 48.2%, respectively. On multivariable analysis, RFS was associated with anostomostic leakage, DFS was associated with anastomostic leakage and pathologic N stage, and OS was associated with anastomostic leakage, pathologic N and T stage. For patients with anastomostic leakage, the 5-year RFS, DFS, and OS were 51.7%, 32.4%, and 38.3%, respectively, which were worse than that for patients without anastomostic leakage, the latter were 75.2%, 59.7%, 65.7%, respectively （P 〈 0.05）. DRM and radiotherapy were associated with RFS on univariable analysis （P 〈 0.05）, but not on multivariable analysis. Tumor grade was prognostic factors for RFS and OS on univariable analysis, but not on multivariable analysis. The other factors including sex, age, tumor size and adjuvant chemotherapy were not associated with RFS, DFS and OS on univariable analysis. Conclusion： For patients with low rectal caner underwent LAR and TME, the long-term oncologic outcomes were satisfactory for patients with stage yp0/1, but not for patients with pathologic stage II1. Anastomositic leakage negatively affect long-term oncologic outcomes. Radiotherpy, adjuvant chemotherapy and distal resection margin were not associated with long-term outcomes.