压配型髋臼假体置换后骨性髋臼的微有限元分析

目的探讨压配型髋臼假体置换术后骨性髋臼皮质骨和松质骨的骨小梁应力分布模式及松质骨是否参与承载负荷。方法应用显微CT扫描骨性髋臼的骨小梁,建立骨性髋臼的三维微有限元模型。计算压配型髋臼假体置换后骨性髋臼骨小梁的应力和应变,分析骨性髋臼骨小梁应力、应变的生物力学特征。结果当压配型金属髋臼假体植入髋臼后,骨性髋臼外表面的最高应力区位于耻骨区,最高应力为1.389 MPa。在臼顶区,高应力区的面积最大。在骨性髋臼内部的松质骨,高应力区主要分布在臼顶区,分布区域相对较广。当施加1.372 k N载荷后,骨性髋臼外表面面积较大高应力区位于臼顶区域和耻骨区域,臼顶区的最高拉应力为0.604 MPa,耻骨区骨小梁出现微损伤。在骨性髋臼内部的松质骨,面积较大高应力区主要分布在臼顶区和耻骨区。结论高应力区沿着骨性髋臼外表面呈现3点式环形分布,集中分布于耻骨区、坐骨区、臼顶区;髋臼内部松质骨骨小梁通过形变导致应力分布更加均匀。髋臼松质骨具有承受载荷功能。     

COA:Effect of impaction on gene modified cells seeded on granular bone allograft in vitro and in vivo

Background Impaction bone grafting during revision joint surgery to restore bone stock may result in slow and limited allograft incorporation into host bone. A new approach has been proposed by gene modified bone marrow stromal cells (BMSCs) in combination with impaction bone grafting may effectively restore bone stock and improve allograft incorporation. This study aims to investigate the effect of impaction on gene modified BMSCs seeded on granular bone allograft in vitro and in vivo. Methods Deep frozen granular cancellous bone allograft from canine was prepared to serve as cell delivery scaffold, which was seeded with green fluorescent protein (GFP) genetically modified BMSCs to construct cell allograft composites. The composites were impacted in a simulative impactor model and treated with successive incubation under the standard condition after impaction in vitro. Four Beagle dogs, treated with bilateral uncemented proximal tibial joint hemiarthroplasty with prosthesises, were implanted with autologous GFP gene modified cell allograft composites to repair the bone cavity around the prothesis to mimic impaction bone grafting in vivo. Results Significant reduction of viable cells was observed after impaction under fluorescence microscope in vitro, but a proportion of GFP positive cells remained alive and functionally active to secret GFP protein in vitro and in vivo. Conclusions Gene modified bone marrow MSCs seeded on granular allograft will withstand the forces of impaction and maintain their normal functions in vitro and in vivo in spite of partial loss.