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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: There are many studies on the marginal integrity of all ceramic crowns with different resin adhesives, or different shoulder, different polymerization angles, but there is no research on whether different methods of redundant bonding will affect the marginal integrity of all ceramic crowns. OBJECTIVE: To analyze the effect of removing excess resin adhesive on the marginal integrity of all ceramic crowns with different marginal gaps. METHODS: Totally 40 extracted third molars were prepared with all ceramic crowns and randomly divided into groups A, B, C, and D (10 teeth in each group). After the model scanning was completed, the edges of restoration in groups A, B and C were lifted at 30, 60 and 90 µm respectively by computer control, while those in group D were not raised. Procera alumina CAD-CAM all ceramic crowns were made. Then, the four groups of groups A, B, C and D were randomly divided into two subgroups. In one subgroup, a large amount of excess resin adhesive was removed with a small brush, and then the light was illuminated for 40 seconds after the full crown bonding. Subsequently, a small amount of resin adhesive was scraped off with sickle scalpel (small brush group). The sample in the other subgroup was exposed to light for 2 seconds, scraped off with sickle scalpel, and then illuminated for 40 seconds (sickle group). The marginal integrity and surface quality of the adhesive were observed by scanning electron microscope. RESULTS AND CONCLUSION: (1) Scanning electron microscope showed that the continuity of the bonding interface was better in the small brush group. Different degrees of adhesive defects were found in the sickle group. Under the same marginal gap, the defect rate of cement in the small brush group was lower than that in the sickle group (P < 0.05). Under the same adhesive removal method, there was no significant difference in the defect rate of cement between groups A, B, C, and D (P > 0.05). (2) Results indicate that the method of using small brush to remove excess adhesive, then lighting for 40 seconds, and finally using sickle scalpel to remove the remaining small amount of adhesive is more suitable for clinical practice. [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: Vertebroplasty (PVP) and kyphoplasty (PKP) are important methods for the treatment of osteoporotic vertebral compression fractures in the elderly. Although bone cement has certain liquidity and vertebral fractures are often in different situations, bone cement leakage rate is still high. OBJECTIVE: Based on the theoretical discussion and clinical analysis, to study the theoretical causes of bone cement leakage and effective prevention methods. METHODS: A total of 162 cases (186 vertebrae) were treated with three methods of vertebroplasty. Group A: 64 cases with 78 vertebrae were treated with conventional cemented vertebroplasty; Group B: 57 cases with 65 vertebrae were treated with cemented vertebroplasty using cement pump; Group C: 41 cases with 43 vertebrae were treated with balloon kyphoplasty. The leakage of bone cement was observed in three groups. RESULTS AND CONCLUSION: Of the 186 vertebrae, postoperative bone cement leakage occurred in 25 vertebrae, with the leakage rate of 13% (25/186). Group A had bone cement leakage in 11 vertebrae, and the leakage rate was 14% (11/78). Group B had bone cement leakage in 8 vertebrae, and the leakage rate was 12% (8/65). Group C had bone cement leakage in 6 vertebrae, and the leakage rate was 14% (6/43). There was no significant difference among the three groups in the leakage rate of bone cement (P > 0.05). That is to say, the causes of bone cement leakage are not completely controllable, and the leakage position has some randomness. Strict and careful imaging monitoring is an intuitive method to prevent bone cement leakage. [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]