ABSTRACT
BACKGROUND: Three-dimensional finite element analysis has been used by many scholars from department of orthopedics, but the results of postoperative evaluation of hip preserving treatment for osteonecrosis of femoral head are different. OBJECTIVE: To study the biomechanical changes of the femoral head and the biomechanical changes of the proximal femur after greater trochanter bone flap for the treatment of femoral head necrosis using three-dimensional finite element method, and to verify the mechanical safety and effectiveness. METHODS: One case of unilateral femoral head necrosis in ARCOIII stage undergoing parallel vascularized greater trochanter bone flap transplantation was selected. Computed Tomography data of proximal femur were collected before and 6 months after the operation, and preserved in DICOM format. With the aid of computer technology, professional medical modeling software, MIMICS and HYPERMESH, were used to establish the three-dimensional geometric models of the proximal femur. These models were divided into normal group, necrosis group and repair group. Finite element analysis software ANSYS was utilized to simulate human body standing and movement in different situations. The model was divided by free mesh, and given material parameters to establish normal proximal femur, femoral head necrosis and bone defect. Greater trochanter bone flap was applied in repairing three-dimensional finite element model of bone defect. Loads were loaded on different finite element models. The maximum displacement of the femoral head and the stress distribution in the proximal femur of the three groups were observed under different loading models. RESULTS AND CONCLUSION: (1) Under the same load, the maximum displacement of the three sets of models was 0.61 mm in the normal group, 0.66 mm in the necrosis group, and 0.61 mm in the repair group, respectively. Maximum Von Mises stress was greater in necrosis model than in the normal molding. The maximum Von Mises stress gradually decreased in the repair model, and was close to normal value. (2) Three groups of models showed stress concentration above the rotor in femoral neck region. The maximum stress in the trochanteric position was higher in necrosis models than in normal models. The maximum stress in this region gradually increased after repair, but was still lower than the failure stress of bone. (3) The results confirm that the maximum stress and the maximum displacement are closer to the normal value after greater trochanter bone flap for treatment of osteonecrosis of the femoral head. The greater trochanter is safe and reliable for repairing bone defect of femoral head.
ABSTRACT
@#BACKGROUND: Acute kidney injury following percutaneous coronary intervention (PCI) is associated with a worse outcome. However, the risk factors and outcomes of acute kidney injury (AKI) in patients after intracoronary stent implantation are still unknown. METHODS: A retrospective case control study was done in 325 patients who underwent intracoronary stent implantation from January 2010 to March 2011 at the Drum Tower Hospital of Nanjing University School of Medicine. Those were excluded from the study if they had incomplete clinical data. The patients were divided into a normal group and a AKI group according to the standard of post-operation day 7 to identify AKI. The parameters of the patients included: 1) pre-operative ones: age, gender, hypertension, diabetes mellitus, cerebrovascular disease, left ventricular insufficiency, peripheral angiopathy, creatinine, urea nitrogen, estimated glomerular filtration rate (eGFR), hyperuricemia, proteinuria, emergency operation, hydration, medications (ACEI/ARBs, statins); 2) intraoperative ones: dose of contrast media, operative time, hypotension; and 3) postoperative one: hypotension. The parameters were analyzed with univariate analysis and multivariate logistical regression analysis. RESULTS: Of the 325 patients, 51(15.7％) developed AKI. Hospital day and in-hospital mortality were increased significantly in the AKI-group. Univariate analysis showed that age, pre-operative parameters (left ventricular insufficiency, peripheral angiopathy, creatinine, urea nitrogen, estimated glomerular filtration rate, hyperuricemia, proteinuria, hydration), emergency operation, intraoperative parameters (operative time, hypotension) and postoperative hypotension were significantly different. However, multivariate logistic regression analysis revealed that increased age (OR=0.253, 95％CI=0.088–0.727), pre-operative proteinuria (OR=5.351, 95％CI=2.128–13.459), pre-operative left ventricular insufficiency (OR=8.704, 95％CI=3.170–23.898), eGFR≤60 ml/min/1.73 m2 (OR=6.677, 95％CI=1.167–38.193), prolonged operative time, intraoperative hypotension (OR=25.245, 95％CI=1.001–1.034) were independent risk factors of AKI. CONCLUSIONS: AKI is a common complication and associated with ominous outcome following intracoronary stent implantation. Increased age, pre-operative proteinuria, pre-operative left ventricular insufficiency, pre-operative low estimated glomerular filtration rate, prolonged operative time, intraoperative hypotension were the significant risk factors of AKI.