| Objective1.To analyze the relationship of bone mineral density(BMD)with the type and degree of femoral neck fracture in the elderly by a prospective clinical research,to find out the rule of the influence of BMD in femoral neck fracture and to verify its predictive role in the fracture type and fracture degree,so as to provide clinical basis and methods for the treatment of fracture.2.To verify the effect of BMD on the type and degree of femoral neck fracture in elderly patients,a three dimensional finite element model of proximal femur with different BMD and more close to the real human body biomechanical structure was established.Meanwhile,fracture mechanics experiment was performed by using finite element software,results of fracture mechanics of the two models were compared at the same time,including fracture type and degree of damage.Above investigation was conducted to determine the influence of different material properties in fracture mechanics,and to lay the experimental foundation for the study of biomechanical mechanisms of osteoporotic femoral neck fracture in the elderly.Methods1.Clinical researchA total of 50 elderly patients with femoral neck fractures were selected who were admitted to the trauma department of orthopedics in the First Affiliated Hospital of Guangzhou University of Chinese Medicine from July 2016 to February 2017.After admission,BMD of lumbar vertebrae in each patient was determined by DXA bone densitometer,patients were divided into group A(T-Score?-2.5g/cm2)and group B(T-Score>-2.5g/cm2),25 patients in each group(25 hips).Among the involved 50 patients,there were 24 male patients and 26 female patients,aged between 60 to 91 years,with a mean age of(76.38±9.57)years old.All patients were diagnosed with closed fracture,including 20 patients with left hip fracture and 30 patients with right hip fracture.Following the identification of fracture classification(Garden classification)by hip X-ray and CT,information were recorded,such as age,gender,injury side,fracture type and BMD.Statistical analyses were carried out using SPSS 17.0 to analyze the relationship of BMD with age,gender,injury side,and the relationship between BMD and fracture types.2.Experimental studyCT image data of bilateral hips was collected from one eligible patient with femoral neck fractures in clinical.The finite element Mimics15.0 software was used complete relevant steps,such as region growing and lacuna filling,aimed at the establishment of the finite element model of the proximal femur of the uninjured side.Then,data was imported to Hyermesh13.0 software by using tetrahedral mesh technology,the model was assigned with two kinds of bone density material properties,respectively(C1 model:material property of compact bone entirely;C2 model:material properties of cancellous bone and compact bone),two finite element models of the proximal femur were developed to simulate the physiological and mechanical properties of real human body.After the determination of failure parameters,interface properties,analysis steps,boundary constraints and load,the finite element post-processing software LS-DYNA was introduced for calculation to obtain the fracture model of femoral neck fracture based on the stress-strain curve.Furthermore,above results were compared with clinical fracture lines to analyze and compare the stress,strain,crack propagation and fracture classification of the two models.Results1.The mean age of group A and group B was(81.7±8.12)and(71.2±8.09)years old,respectively,there was statistical difference according to the results of t test between groups(t=-4.520,P<0.0).In addition,the mean BMD was(-3.7 ± 0.54)g/cm2 and(-1.58 ± 1.18)g/cm2 in group A and group B,respectively,showing statistical difference by using t test between groups(t=8.399,P<0.05).The above results indicated that threshold setting of BMD was reasonable in both groups,baseline characteristics were comparable between groups,and there was positive correlation between BMD and patients'age.2.In group A,Garden classification results showed that there were 8 cases with Garden ?-? type fracture,17 cases with Garden ?-? type fracture;meanwhile,in group B,15 cases were detected to have Garden ?-? type fracture,and 10 cases with Garden ?-? type fracture.There were some differences between groups with different BMD,indicating statistical significance by X2 test(X2=3.945,P=0.047<0.05).These results suggest that BMD could affect fracture types,which could predict fracture type and severity to some extent.Meanwhile,the fracture line of group A was smoother than that in group B.3.Three dimensional finite element model of proximal femur and femoral neck fracture model were established based on the finite element software and two kinds of bone density material properties,corresponding effectiveness had been confirmed accordingly.4.Crack propagation and crack trend were not completely consistent when fracture occurred in C,and C2 models,which were significantly flatter and smoother in the former model when compared to the latter model,very similar with previous clinical studies.5.Under the same boundary,direction,load and unit time,the yield stress in C,model was obviously larger than that in C2 model,but the damage degree of fracture was greater in C2 model.Conclusion1.Through the finite element fracture mechanics analysis,three dimensional finite element model of femoral neck fracture is established to be true and reliable based on clinical data,which can be a good simulation of femoral neck fracture and contribute to dynamic visual restoration of the whole process of femoral neck fracture,and can also applicable for fracture mechanics analysis,providing experimental basis for the study of the mechanical mechanism of femoral neck fracture under different external forces.2.BMD has effective influence in mechanical properties of bone stress and strain,which can affect the type of femoral neck fracture in the elderly to some extent and to predict the type and degree of femoral neck fracture,providing potential basis and methods for the prevention and treatment of hip fracture. |
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