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BACKGROUND: The edge load contact caused by joint separation causes great stress concentration and then produces a large amount of wear. The edge contact caused by hip joint separation is a dynamic process of femoral head touching the rim of the acetabulum and sliding into the acetabulum quickly, so a dynamic contact mechanical model is needed. OBJECTIVE: To obtain the dynamic mechanical simulation model of ceramic acetabulum under the edge load contact, so as to provide the contact mechanics foundation for the wear analysis of hip joint under the condition of edge load, and provide theoretical basis for prosthesis design and surgeon operation. METHODS: By using 3D modeling software SolidWorks and dynamic simulation software ADAMS, edge load contact dynamics simulation model of ceramic femoral head and acetabular cup was established to verify the edge load contact deformation by numerical method. The effects of acetabular abduction angle and initial separation distance on edge load contact were analyzed. RESULTS AND CONCLUSION: (1) The contact stiffness coefficient used in the model is reasonable and effective. This model can be used to study the parameters that influence the edge load contact of hip joints. (2) The excessive cup inclination angle and initial separation distance will increase the severity of the edge load. (3) Acetabular cup inclination angle and initial separation distance are two important factors that affect the edge load contact. [ABSTRACT FROM AUTHOR]

BACKGROUND: The biomechanical properties of the hip bone are complex in vivo that requires a more efficient and accurate method for the finite element analysis. OBJECTIVE: To develop a musculoskeletal multi-body dynamic model of the patient-specific hip joint after surgery and simulate gait, and to explore the biomechanics of the hip joint. METHODS: CT data of the patient's hip joint postoperatively were collected, three-dimension reconstruction underwent in MIMICS, and materialization and position matched on Geomagic Studio and meshed on Hypermesh. A musculoskeletal multi-body dynamic model of the patient-specific hip joint was established using AnyBody software and simulated the normal movements during walking, then export the muscle force, oint forces, joint moment as the Boundary conditions in finite element analysis. Then, the muscle forces, joint forces and torque were obtained and imported to be the boundary conditions for finite element analysis. The stress and strain values and concentration parts were measured on Abauqus during walking. RESULTS AND CONCLUSION: (1) The maximum value of the joint force in the three directions of the hip joint was 600, 2 000, 100 N at 2.1 seconds. (2) The ilium force was almost only in the Y direction, and the maximum value was 1 000 N. (3) The maximum stress on the hip joint was about 12 MPa at 30% of the gait cycle and the maximum relative displacement was 0.5 mm. (4) To conclude, the stress of the hip after surgery is mainly concentrated on the vicinity of the sacroiliac joint, postersuperior of the acetabulum, middle region of iliac bone, and upper zone of pubic bone; the stress of the hip is higher than that of the normal hip, and the activity intensity should be paid attention during rehabilitation. [ABSTRACT FROM AUTHOR]

BACKGROUND: A large number of preclinical experimental data have shown that stem cells can regulate the immune function, and serve the function of cell replacement. OBJECTIVE: To summarize the anti-inflammatory effects of stem cells in the treatment of ischemic stroke, based on which, we further discuss the specific mechanisms. METHODS: We conducted a systematic and comprehensive search in PubMed, Elsevier, Springer, Wiley, Ovid, EBSCO databases. The range of retrieval time was from 2012 to 2017. The keywords were “stem cells, stroke, inflammation, immune”. Totally 110 articles were retrieved initially, and 47 articles were included in result analysis. RESULTS AND CONCLUSION: By reading extensive literature, we analyzed and summarized the research status quo of the anti-inflammatory effects of neural stem cells, mesenchymal stem cells and endothelial cells in the treatment of ischemic stroke. The mechanisms mainly include reducing focal inflammation, immune regulation, promoting the secretion of various neurotrophic factors, reducing secondary cell death, protecting neurons and promoting cell function recovery and further promoting the recovery of nerve function. The mechanisms underlying local immune regulation and anti-inflammatory effects of stem cells are mainly described as the shift from M1 to M2 macrophages under the intervention of stem cell factors, to intervene secreted immune cytokine profiles and exert effects on inhibition and polarization of glial cells. Further investigation is required on the anti-inflammatory effects and immune regulation of stem cell therapy for stroke. [ABSTRACT FROM AUTHOR]