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: Acetabular defect is one of the typical characteristics of adult developmental dysplasia of the hip. The acetabular defect caused an insufficient coverage to the femoral head, which means the contact area between them decreased and the pressure increased. Stress concentration could quicken hip wear and lead to arthritis or dislocation of the hip. Till now, there is no accepted objective criterion about what degree defect could lead to biomechanics changes in the hip. OBJECTIVE: To analyze the influence of different degrees of acetabular defect on the stress distribution of hip joint by using three-dimensional finite element method, and provide theoretical guidance for clinical treatment of hip dysplasia. METHODS: CT thin layer scanning data of normal adult hip were selected. Hip dysplasia models with varying degrees of bone defect were built by using Mimics15.0 and Hypermesh software. Von Mises stress distribution on the subchondral bone of the hip was analyzed by using Ansys10.0 software in the case of single foot touchdown. RESULTS AND CONCLUSION: Each model result was consistent with the actual situation. The maximum Von Mises stress value appeared at the top of the acetabulum dome and medial posterior femoral neck. When simulating one leg standing, the smaller the CE angle, the greater the maximum Von Mises stress on femoral head was; and acetabulum increased from 2.768 MPa and 3.029 MPa with 30° CE angle to 11.075 MPa and 15.322 MPa with 5° CE angle. This change was more obvious when CE angle was less than 15°. These findings confirmed that acetabular defect increases the peak stress of the hip joint, and the greater the defect, the greater the stress was. It is suggested that clinical intervention should be done as early as possible in patients with acetabular defect.
ABSTRACT
<p><b>BACKGROUND</b>The prevalence of developmental dysplasia of the hip (DDH) is unknown in China. We aimed to determine the prevalence of DDH in Chinese adults.</p><p><b>METHODS</b>In this study, we performed a cross-sectional survey of a nationally representative sample of Chinese adults. All participants underwent questionnaire investigation, physical examination, and X-ray examination. Factors associated with DDH were analyzed with logistic regression.</p><p><b>RESULTS</b>We invited 29,180 individuals aged 18 years and over to participate, randomly selected from 18 primary sampling units (street districts in urban areas and townships in rural areas). The survey and examination were completed in 25,767 people (10,296 men and 15,471 women). DDH was diagnosed in 391 people, yielding an overall DDH prevalence of 1.52%. Based on this information, we estimate the number of individuals with DDH in China to be approximately 16.05 million. DDH prevalence increased with age (odds ratio = 1.53 [1.03-2.27], P = 0.036), was significantly higher among women than men (2.07% vs. 0.75%, P< 0.001), and was higher among rural residents than urban residents (1.75% vs. 1.29%, P< 0.001). Economic development was independently associated with the presence of DDH. There was no evidence of an association between body mass index alone, education, or current smoking or drinking and risk of DDH (P > 0.05).</p><p><b>CONCLUSIONS</b>DDH has become an important public health problem. Special attention should be paid to residents with DDH. Screening for DDH should be performed in China.</p>