Objective To discuss biomechanical mechanism of reconstructed joint capsule ligament stabilizing hip joint by means of three-dimensional finite element analysis.Methods A finite element model of total hip arthroplasty(THA)including ischiofemoral ligament reconstruction was construtted by using finite element analysis software Unigraphics NX 2.0 and SolidWorks 2006 to simulate seated leg crossing and obtain peak resisting moment and range of motion prior to impingement.Results The current form of finite element model was characterized by large deformation multi-body contact,large interfacial sliding and high elasticity and could clearly reflect real anatomy and biomechanical behavior of ischiofemoral ligaments.Compared with model with only metal,model of ischiofemoral ligament reconstruction could reduce the peak polyethylene stress at the impingement site and at the head egress site by typically 17%and 31%respectively,increase peak resisting moment by nearly 57%and provide 2.29-fold stability.Conclusions As a discrete structure within the posterior capsule of the hip joint,the ischiofemoral ligament may be the most important contributor to the mechanical integrity of the posterior stability structure.The joint capsule ligament must be reconstructed in hip arthroplasty.

Objective:To explore diagnostic value of magnetic resonance apparent diffusion coefficient(ADC)combined with dynamic enhanced magnetic resonance imaging(DCE-MRI)for parotid lymphoma of parotid gland.Methods:Clinical data of 74 patients with tumors of parotid gland who admitted to Hainan Western Central Hospital from September 2021 to September 2023 were selected to carry out retrospective analysis,and they were divided into malignant tumor group(15 cases)and benign tumor group(59 cases)according to the diagnosis of surgical pathology.And then,the benign tumor group was further divided into two subgroups according to the result of surgical pathology,which included pleomorphic adenoma group(35 cases)and"parotid lymphoma of parotid gland"group(24 cases).The differences in ADC values and DCE-MRI parameters(Ve,Kep,Ktrans)were compared between malignant tumors and benign tumors,and between pleomorphic adenoma and parotid lymphoma of parotid gland.The efficacies of ADC values and DCE-MRI parameters in diagnosing malignant tumors were analyzed by means of the receiver operating characteristics(ROC)curve.Results:The ADC value,Ve value and Kep of benign tumor group were respectively(1.17±0.41)×10-3 mm2/s,(0.46±0.15)and(1.56±0.57)min,which were significantly higher than those[0.86±0.19× 103mm2/s,0.35±0.08,and 0.80±0.27 min]of malignant tumor group(t=2.841,2.733,5.004,P＜0.05),respectively.Results of binary logistic regression analysis showed that ADC,Ve and Kep were respectively influence factors on benign and malignant parotid tumors(OR=0.045,0.001,0.004,P＜0.05).ROC curve analysis showed that the AUC values of single ADC,Ve,Kep,and the combination of them were respectively 0.726,0.715,0.903 and 0.915 in diagnosing benign and malignant parotid tumors.There was not significant difference in Ktrans value between pleomorphic adenoma group and"parotid lymphoma of parotid gland"group(P＞0.05).The ADC value and Ve value of"parotid lymphoma of parotid gland"group were lower than those of pleomorphic adenoma group,while Kep value of"parotid lymphoma of parotid gland"group was higher than that of pleomorphic adenoma group,and the differences of them between two groups were significant(t=4.568,4.897,4.805,P＜0.05),respectively.Binary logistic regression analysis showed that ADC,Ve and Kep were influential factors of occurring parotid lymphoma of parotid gland(OR=0.042,0.000,13.452,P＜0.05),respectively.ROC curve analysis showed that the AUC values of single ADC,Ve and Kep,and the combined diagnosis of them were respectively 0.742,0.784,0.763 and 0.959 for parotid lymphoma of parotid gland.Conclusion:Magnetic resonance ADC value and DCE-MRI parameter have favorable value in identifying benign and malignant parotid tumors,and in identifying and diagnosing parotid lymphoma of parotid gland and pleomorphic adenoma,and the combined diagnosis has higher diagnostic value.