BACKGROUND:Femoral neck fracture is mainly fixed by three inverted triangle cannulated screws. Scholars have proposed to add a cannulated screw to enhance the fixation strength of femoral neck fracture of Pauwels III type based on three cannulated screw fixation, but the stability is not verified. OBJECTIVE:To analyze the biomechanical stability and stress of the three and four cannulated screws for the treatment of the Pauwels III femoral neck fractures. METHODS:The CT imaging results of the fourth generation of artificial bone sawbones were imported into the Mimics software wherein a three-dimensional finite element model of the proximal femur was prepared and introduced in the 3-matic software. Models of middlesegment of femoral neck with Pauwels III fractures were established. Cannulated screw models were established with UG 8.0 software and introduced in the fractures models. Finally, finite element models of Pauwels III femoral neck fractures fixed with three and four screws were established. In the same condition, an axial load of 411 N was applied on the femoral head with Abaqus software. The displacement of two markers of the broken ends and internal fixation system Von Mises stress distribution were compared between the two models. RESULTS AND CONCLUSION:(1) The displacement was 0.42 mm in three screws model, and 0.17 mm in the four screws model. (2) Von Mises stress peak was 547 MPa and 27.8 MPa in both models. The peak value was lower in models of fourscrews than that of three screws. Stress concentration position was at the fracture site in both models. The stress range of models of four screws was more extensive and scattered. (3) Finite element analysis results demonstrated that four-screw implantation for Pauwels III femoral neck fractures had strong anti-shearing force and biomechanical stability. Clinical advantages need further clinical comparative study.

OBJECTIVE: To investigate the clinical features, the CT, MRI features and therapeutic strategy of nasal neuroendocrine carcinoma (NEC). METHOD: A retrospective study was carried out on 6 cases of NEC. 2 were female and 4 were male. Routine preoperative CT and MRI examination were performed. In one case,the tumor had invaded the brain and then was treated in department of oncology. Five cases were undertaken tumor resection under nasal endoscope, and combined with postoperative chemoradiation therapy. RESULT: The postoperative pathological report of 1 cases was large cell type, the remaining 4 cases were small cell type. One case treated in department of oncology had lived for 2 month with tumor in his body. One cases relapsed and died at 4 month after postoperation, 1 case was lost and 3 case did not relapse till now. CONCLUSION NEC of paranasal sinuses is malignant, but early detection, early diagnosis and treatment can improve the prognosis of this disease. For limited lesion of NEC, nasal endoscopic operation is an effective, safe and minimally injury method.
Adult ; Carcinoma, Neuroendocrine ; diagnosis ; pathology ; surgery ; Endoscopy ; Female ; Humans ; Male ; Middle Aged ; Paranasal Sinus Neoplasms ; diagnosis ; pathology ; surgery ; Prognosis ; Retrospective Studies