BACKGROUND: Most current studies of orthopedic screw parameters focus on mechanical properties but lack biocompatiblllty assessment. OBJECTIVE: To Investigate the Influence of geometric parameters and material properties of orthopedic screws on blomechanical compatibility, explore the optimal combination of various factors and parameterization levels, providing a theoretical reference for the design of orthopedic screws. METHODS: An orthogonal experiment protocol was designed according to the five factors and three parameterization levels of orthopedic screws. Factor A was the screw diameter (4.5, 5.5, 6.5 mm), factor В was thread profile (rectangular, trapezoidal, triangular), factor С was screw pitch (1.75, 2.25, 2.75 mm), factor D was the thread depth (0.5,1.0,1.5 mm), and factor E was elastic modulus (45,110, 200 GPa). The blomechanical finite element analysis of the three-dimensional bone-nail model under different sets of screw parameters was carried out. Stress distribution and two experimental indicators (the stress transfer parameter STPa between the cortical bone and the screw, and the stress transfer parameter STPß between the cancellous bone and the screw) under different experimental schemes were obtained. The weighted matrix analysis method was used to analyze the orthogonal experimental data to obtain the influence law and the optimal combination. RESULTS AND CONCLUSION: Different levels of different factors have different degrees of influence on biocompatiblllty. Among them, the screw material properties are the most Important factors, followed by the thread profile, pitch and thread diameter, and the last was the thread depth. The thread profile, pitch, and thread diameter had similar influence on biocompatiblllty. The optimal combination of the orthogonal experiment was an orthopedic screw with a large diameter of 6.5 mm, a trapezoidal thread, a pitch of 2.75 mm, a thread depth of 0.5 mm, and an elastic modulus of 45 GPa.

Objective To understand the distribution and drug resistance of pathogens from patients with anastomotic fistula infection after esophageal cancer surgery, and provide basis for clinical diagnosis and treatment.Methods Patients were admitted to a hospital due to anastomotic fistula after esophageal cancer surgery between January 2012 and December 2015, microbial culture and antimicrobial susceptibility testing results of patients were retrospectively analyzed.Results 1 986 patients underwent radical resection of esophageal cancer within 4 years, 148 of whom developed anastomotic fistula, 104 (70.27％) were with positive microbial culture.A total of 197 pathogenic strains were isolated, 52(26.40％)and 145 (73.60％)strains were isolated from intrathoracic anastomotic fistula and cervical anastomotic fistula respectively;127 (64.47％)strains were gram-negative bacteria, the major were Pseudomonas aeruginosa, Klebsiella pneumoniae, and Acinetobacter baumannii, 62(31.47％) strains were gram-positive bacteria, the major were Staphylococcus aureus, Enterococcus spp., and Streptococcus viridans, 8 strains (4.06％) were fungi.49(47.12％) cases were with mixed pathogenic infection.The resistance rates of gram-negative bacteria to imipenem were 17.86％-47.62％, to polymyxin B was 0, resistance rates of Pseudomonas aeruginosa to other antimicrobial agents were all<50％, Klebsiella pneumoniae to piperacillin and aztreonam were both>70％, Acinetobacter baumannii to most antimicrobial agents were all>50.00％;resistance rates of gram-positive bacteria to clindamycin and tetracycline were both>50.00％, to linezolid, vancomycin, and teicoplanin were all 0, resistance rates of Staphylococcus aureus to penicillin, oxacillin, and ciprofloxacin were all>60％,resistance rate of Enterococcus spp.to quinupristin/dalfopristin was 100.00％.Conclusion Postoperative anastomotic fistula combined with infection can affect the prognosis of patients after esophageal cancer surgery, regular monitoring on distribution and drug resistance of pathogens can provide the basis for initial empirical treatment, and is conducive to the early treatment and rational use of antimicrobial agents.

Objective To investigate the risk factors of cervical esophagogastric anastomotic fistula after esophagectomy of esophageal cancer.Methods The retrospective case-control study was conducted.The clinicopathological data of 956 patients who underwent esophagectomy and cervical esophagogastrostomy from January 2012 to December 2016 in the First Affiliated Hospital of Zhengzhou University were collected.Patients underwent Sweet or Mckeown surgery.Observation indicators:(1) intra-and post-operative situations;(2) the risk factors analysis of cervical esophagogastric anastomotic fistula after esophagectomy;(3) follow-up situations.Follow-up using outpatient examination and telephone interview was performed to detect the esophagogastric anastomotic stenosis of patients up to February 2017.Measurement data with normal distribution were represented as the (x)±-s.Univariate analysis and comparison of count data were done using the chi-square test or Fisher exact probability method.Multivariate analysis was done using the Logistic regression model.Results (1) Intra-and post-operative situations:all the 956 patients underwent successful operations,including 107 with Sweet operation and 849 with Mckeown operation.Of 956 patients,336 received thoracotomy and 620 received thoracoscopic surgery.Tumors located in upper,middle and lower esophagus were respectively detected in 143,627 and 186 patients.Operation time,volume of intraoperative blood loss and number of lymph node dissected in 956 patients were (274 ± 67) minutes,(210 ± 167) mL and 18 ± 11,respectively.Of 956 patients,117 had cervical esophagogastric anastomotic fistula,with an incidence of anastomotic fistula of 12.24％ (117/956).Of 117 patients with cervical esophagogastric anastomotic fistula,2 had early stage fistula,110 had middle stage fistula and 5 had later stage fistula;12 were cured by two-tube method (stomach tube and nutrition tube),24 were cured by three-tube method (stomach tube,nutrition tube and chest tube or mediastinal tube),43 were cured by open neck incision dressing,15 were cured by fistula cavity drainage and 17 were cured by esophageal stent implantation.Sixteen patients died in hospital postoperatively,including 6 with cervical esophagogastric anastomotic fistula and 10 without cervical esophagogastric anastomotic fistula.Duration of hospital stay of 956 patients was (16± 11)days,and durations of hospital stay of patients with and without cervical esophagogastric anastomotic fistula were (39± 19) days and (13±6) days.Postoperative pathological examinations:873,9 and 74 patients were respectively diagnosed with squamous cell carcinoma,adenocarcinoma and other types of cancer.TNM staging:stage 0,Ⅰ,Ⅱ,Ⅲ,Ⅳ and unidentified stage were respectively detected in 135,110,325,376,1 and 10 patients.(2) The risk factors analysis of cervical esophagogastric anastomotic fistula after esophagectomy:univariate analysis showed that gender,age,history of diabetes,surgical method,tubular stomach production,operation time,postoperative pulmonary infection and postoperative aspirating sputum through fiberbronchoscope were risk factors affecting cervical esophagogastric anastomotic fistula after esophagectomy,with statistically significant differences (x2 =4.179,6.174,4.427,4.377,6.266,7.057,55.036,51.806,P＜ 0.05).Multivariate analysis showed that tubular stomach production,postoperative pulmonary infection and aspirating sputum through fiberbronchoscope were independent risk factors affecting cervical esophagogastric anastomotic fistula after esophagectomy,with statistically significant differences (OR =1.922,2.907,2.323,95％ confidence interval:l.203-3.070,1.682-5.023,1.235-4.370,P＜0.05).(3) Follow-up situations:908 of 956 patients were followed up for 2-62 months,with a median follow-up time of 28 months.During the follow up,21 of 111 patients with cervical esophagogastric anastomotic fistula were complicated with cervical esophagogastric anastomotic stenosis,59 of 797 patients without cervical esophagogastric anastomotic fistula were complicated with cervical esophagogastric anastomotic stenosis,showing a statistically significant difference in cervical esophagogastric anastomotic stenosis (x2-16.803,P＜0.05).Conclusion Tubular stomach production,postoperative pulmonary infection,postoperative aspirating sputum through fiberbronchoscope are independent risk factors affecting cervical esophagogastric anastomotic fistula after esophagectomy.

In order to evaluate the biomechanical stability of titanium alloy screw with different structural parameters under bone remodeling, some three-dimensional finite element models were established and the bone remodeling process after implanting the screw was simulated. Three-dimensional finite element models consist of bone and screw with different lengths and diameters. Bone remodeling process was simulated by user-defined subroutine. It is found that the stress on the bone is concentrated on the groove and root of the internal thread. The screw stress is mainly on the beginning of the thread, and the whole stress decreases along the long axis of the screw. The stress distribution trend of bone and screw did not change significantly during the bone remodeling. The maximum equivalent stress value was different, the maximum equivalent stress on the screw and cancellous bone increased while the maximum equivalent stress value on the cortical bone decreased.
Biomechanical Phenomena ; Bone Remodeling ; Bone Screws ; Finite Element Analysis ; Stress, Mechanical ; Titanium

Objective To explore the effects of screw configurations on bone healing, so as to provide the basis for related fracture treatment. Methods The process of bone healing under different screw configurations was studied by finite element method, and the change in the process of callus growth during healing periods was simulated by interfragmentary strain theory (IFS). The iterative process for renewing callus modulus in every finite element was conducted by the second-developed ABAQUS based on Python scripting language, thus the process of fracture healing was simulated. Results The effect from different numbers of screws on bone healing was smaller than that from different working length of bone plates. On the premise of stable fixation, given the certain working length of bone plates, the effect from different screw numbers on stress distributions in plates or screws was relatively small, while the effect from different working length on stress distributions in plates or screws was relatively large, and the stress distribution in plates was larger than that in screws at different working length. Conclusions It is necessary to take more consideration on working length of bone plates than the number of screws when they are under a stable fixed situation, and it is a wise choice to reduce the screw numbers and choose a suitable working length for bone healing process.