The best position of bone grafts in the medial open-wedge high tibial osteotomy: A finite element analysis.

BACKGROUND AND OBJECTIVE: The application of wedge-shaped bone grafts can increase the biomechanical stability of knee during the medial open-wedge high tibial osteotomy (MOWHTO) by reducing the von Mises stress of the medial plate and lateral cortical hinge area. However, the optimal position of bone grafts it remains unclear, so we aimed to determine search for the optimal position of the bone grafts in MOWHTO by using finite element analysis. METHODS: In the finite element analysis, MOWHTO models were established with three different osteotomy distraction heights and assembled into four groups according to different conditions, including the no bone grafts (NBG) group, the anterior bone grafts (ABG) group, the middle bone grafts (MBG) group, and the posterior bone grafts (PBG) group. Based on previous studies, 600 N and 1800 N loads were applied to the knee joint to simulate the static forces during a double and single leg stance to measure the von Mises stress of the medial implant area and lateral hinge area, the maximum displacement of different models, the relative displacement of the osteotomy area and the stress distribution in the bone grafts. RESULTS: Compared to the NBG and ABG groups, the stress of the lateral cortical hinge area and the medial implate area was significantly lower in the PBG group. For example, under the 600N force load, when the height of the osteotomy area was 10 mm, 15 mm, and 20 mm, the maximum von Mises stress of the medial implate area and lateral cortical hinge area in the NBG group were 140, 141, 172, and 53, 57, 60 MPa, respectively. Compared with the NBG group, the maximum von Mises stress of the medial implate area and lateral cortical hinge area in the PBG group were reduced by 45%, 56%, 63% and 14%, 39%, 68% at distraction height of 10 mm, 15 mm, and 20 mm, respectively. The bone grafts in the posterior parts provide the best stability,with the stress of the middle and posterior bone grafts are mainly concentrated in the edge. CONCLUSIONS: The posterior part of the osteotomy area is the best position for bone graft placement since it provides optimal stability and reduces von Mises stress in the medial plate and lateral cortex hinge area, with the stress of the posterior bone grafts mainly concentrated in the edge. These findings guide bone graft placement sites in clinical surgery and are a basis for future research on bone graft materials and structures in MOWHTO.

Mangiferin inhibits apoptosis and oxidative stress via BMP2/Smad-1 signaling in dexamethasone-induced MC3T3-E1 cells.

Mangiferin is a xanthone glucoside, which possesses antioxidant, antiviral, antitumor and anti-inflammatory functions, and is associated with gene regulation. However, it remains unknown whether mangiferin protects osteoblasts, such as the MC3T3-E1 cell line, against glucocorticoid-induced damage. In the present study, MC3T3-E1 cells were treated with dexamethasone (Dex), which is a well-known synthetic glucocorticoid, in order to establish a glucocorticoid-induced cell injury model. After Dex and/or mangiferin treatment, cell viability, apoptosis and reactive oxygen species (ROS) production was measured by Cell Counting kit-8 (CCK-8) and flow cytometry, respectively, and the concentration of tumor necrosis factor (TNF)-α, interleukin (IL)-6 and macrophage colony-stimulating factor (M-CSF) was measured by ELISA. The expression of bone morphogenetic protein 2 (BMP2), phosphorylated­SMAD family member 1 (p-Smad-1), t-Smad-1, osterix (OSX), osteocalcin (OCN), osteoprotegerin (OPG), receptor activator of nuclear factor-κB (RANK), RANK ligand (RANKL), B­cell lymphoma 2 (Bcl-2) and Bcl­2­associated X protein (Bax) was measured by real-time PCR and/or western blot analysis. The results indicated that pretreatment of MC3T3-E1 cells with mangiferin for 3 h prior to exposure to Dex for 48 h significantly attenuated Dex-induced injury and inflammation, as demonstrated by increased cell viability, and decreases in apoptosis, ROS generation, and the secretion of TNF-α, IL-6 and M-CSF. In addition, pretreatment with mangiferin markedly reduced Dex-induced BMP2 and p­Smad-1 downregulation, and corrected the expression of differentiation­ and apoptosis­associated markers, including alkaline phosphatase, OSX, OCN, OPG, RANK, RANKL, Bcl-2 and Bax, which were altered by Dex treatment. Similar to the protective effects of mangiferin, overexpression of BMP2 suppressed not only Dex-induced cytotoxicity, but also ROS generation, and the secretion of TNF-α, IL-6 and M-CSF. In conclusion, the results of the present study are the first, to the best of our knowledge, to demonstrate that mangiferin protects MC3T3-E1 cells against Dex-induced apoptosis and oxidative stress by activating the BMP2/Smad-1 signaling pathway.

[Pressure interlocking intramedullary nailing fixation and bone grafting for treatment of tibial fracture nonunion].

OBJECTIVE: To explore the curative effect of intramedullary nailing pressure within a fixed period with a bone graft taken from the opening of intramedullary nailing on tibial fracture nonunion. METHODS: From February 2008 to October 2010, 18 patients with nonunion of tibial shaft were treated by pressurized intramedullary nail fixation and bone grafting taken from the opening of intramedullary nailing. They included 12 males and 6 females ranging in age from 31 to 67 (mean 42) years. The time from injury to surgery was 6-18 months (mean 8 months). There were 11 cases of nonunion and 7 cases of delayed union. After operation, the knee function was evaluated according to HSS scoring. The therapeutic effect was assessed by Tenny-Wiss scoring system. RESULTS: All patients were followed up for 12-36 (mean 18) months. The wound healed well without infection or skin necrosis. All patients had no nonunion, infection, deformity, and re-fracture. The bone healing time was from 4 to 8 months (mean 6 months). The HHS score of knee function 1 year after surgery averaged (89.97 +/- 3.21). The effect result of Tenny and Wiss scoring system was excellent in 16 cases and good in 2 cases. CONCLUSION: Open reduction by intramedullary nail fixed within a period with bone graft (from the opening of intramedullary nailing) for treatment of nonunion and delayed union of tibial fracture can improve the fracture healing rate, avoid complications from iliac bone grafting, and reduce medical expenses.