Three-dimensional photoelasticity analysis of Nitinol Patellar Concentrator for treating patellar fractures

ood results are got when the patellar fractures aretreated by Nitinol Patellar Concentrator (NT-PC )L','],and the NT-PC is appraised to .be the idealest one amongall the methods on treating patellar fractu.,L3]. The objective of our experiment is to study the distribution of stressin patellar when it is fi-cated by NT-PC, which is made ofNi-Ti shape memory alloy. The biomechanical elements ofit in treating codrinuted patellax fractUres and distal polecoconuted patellar fractIJres is il…     

枕寰枢复合体后路螺钉固定技术的应变电测研究

目的比较4种植入方式的枕颈部螺钉在施加生理载荷时所承受的拔出应力,评价其各自在生理环境中的机械性能。方法对12具新鲜人体枕颈部标本(含Oc~C3),依次采用后路经关节螺钉固定和SUMMIT枕颈部内固定系统固定。对固定后的Oc-C1经关节螺钉(Oc-C1组)、C1,2经关节螺钉(C1,2组)、枢椎椎弓螺钉(C2IS组)和枕骨螺钉(OcScrew组)在生理载荷下三维六自由度运动时,运用电测法进行应变电阻测定4种螺钉的拔出应力,并对结果进行统计处理。结果侧屈状态下,电测法测得的所有螺钉局部应变均接近于0。在前屈、后伸、左旋和右旋运动时,随着加载载荷增大,测得的应力均逐步增大。在前屈和旋转时,螺钉均承受不同程度拉伸应力;在后伸时,螺钉所受的力均为压应力。枕骨螺钉(OcScrew组)在屈伸和旋转运动状态下,在所有3种载荷下所承受的应力均大于其它3种植钉方法,存在统计学意义(P<0.05)。结论枕骨螺钉承受的拔出应力最大,生理环境下枕骨螺钉可能更易出现内植物相关并发症,具体应用时应结合临床实际。     

枕颈部后路不同内固定的生物力学比较

目的评价不同内固定重建枕颈部稳定性的生物力学性能。方法12具新鲜人体枕颈部标本,在标本完整、枕寰枢不稳、枕颈部植骨块钛缆固定(A组)、枕颈部经关节螺钉内固定(B组)、SUM-MIT枕颈部内固定系统固定(C组)五种状态下,依次用脊柱三维运动测量系统测试其OcC1、C1,2节段的运动参数。同时对固定后的OcC1经关节螺钉(OcC1TA组)、C1,2经关节螺钉(C1,2TA组)、枢椎椎弓螺钉(C2IS组)和枕骨螺钉(Oc Screw组)在生理载荷下三维六自由度运动时,运用电测法测定四种螺钉的拔出应力,并行统计学分析。结果在OcC1节段,B组在屈伸运动中的运动范围和中性区显著大于C组。在侧屈和旋转运动中,A组的运动范围和中性区均明显大于B、C组。在C1,2节段,B组各方向运动的运动范围和中性区均明显小于A组。B组在旋转运动中的运动范围和中性区均显著小于C组。电测法结果显示,侧屈状态下所有螺钉局部应变均接近0;前屈和旋转时螺钉承受不同程度的拉应力,后伸时螺钉承受压应力。Oc Screw组在屈伸和旋转运动状态下,所承受的任何载荷应力均大于其他三种置钉方法。结论枕颈部后路经关节螺钉内固定和SUMMIT枕颈内固定在控制旋转和侧屈的稳定性上有优点。枕骨螺钉承受的拉应力最大,生理环境下枕骨螺钉可能更易发生松动和断裂。     

医用直线加速器的研究进展

本文简介了医用直线加速器的发展情况，重点介绍了常规放射治疗设备（Conventional radiation therap）的特点，3D适形放射治疗设备（3-dimensional conformal），3D适形调强放射治疗设备（3D Oonforma]and Intensity Modulation—IMRT），还有图像引导设备（Image Guide Radio Therapy—IGRT）的研究现状，最后指出医用直线加速器的发展方向。     

Comparative study of various internal fixation methods for treating patellar fractures by three-dimensional photoelasticity

Objective: To compare the biomechanical basis of 3 different internal fixation methods: nitinol patellar concentrator (NT-PC),tension band and wire circle in treating patellar fractures. Methods:The epoxy resin three dimensional photoelasticity patellar models were made by precise moulding, and were fixated by nitinol patellar concentrator (NT-PC) , tension band and wire circle respectively. The patellar models with frozen stress stripes were put into the polarized light field and the stress distributions were compared. As for the model fixated by NT-PC, by dividing layer, photographing and tracing, we used the iterative method to calculate the stress value of every internal node of the epoxy resin patellar model, and the character of stress was analyzed. Results:An overall stress field was yielded when the patellar model was fixated by NT-PC, and the stripes were more than that of tension band model and wire circle model, which have only few stress stripes in the fixated layers. Further analysis indicated that there were continuous fixated stresses in the facies articularis and distal pole of patella, and the character of stresses produced by NT-PC were mainly in longitudinal direction, then in transverse direction. The shearing stresses were small. Conclusion: The initiative and continuous memorial stress of NT-PC and its overall stress distribution character are the essence of NT-PC distinguished with tension band and wire circle in treating patellar fractures. The stress character produced by NT-PC is good for the stability of fracture site and prompts fracture healing.     

天鹅型记忆接骨器治疗肱骨骨折和骨不连的生物力学研究

目的：研究天鹅型记忆接骨器（SMC）治疗骨折骨不连的生物力学特征。方法：利用电测、二维（2D）、三维（3D）光弹性技术,通过贴片,标定电测得到SMC的载荷－应变曲线,并通过固定新鲜人体肱骨,计算SMC的动态记忆持骨力值;通过2D光弹性技术计算SMC鹅颈加压部动态记忆加压力值,用精密浇铸法得到肱骨环氧树脂3D光弹性模型,模仿临床使用,得到SMC固定下的肱骨模型3D应力场分布,同时利用Leize偏光显微镜结合三维光弹法,计算肱骨模型考察点3D应力场中的6个应力分量。结果：电测SMC动态记忆持骨的生物学力值为110．35N。2D光弹测得纵向动态记忆加压力为163．88N。3D光弹测得SMC的鹅颈－加压部、鹅体－接骨板部、鹅翼－持骨部三部相互协调,记忆持骨,形成动态3D立体固定,产生全场应力分布。3D应力分离表明SMC固定后骨折端的应力基本为正应力。结论：SMC空间立体记忆固定的应力场,有利于骨折、骨不连的治疗、允许早期功能锻炼并促进骨愈合。     

后路枕颈部4种螺钉技术的应变电测研究

目的：比较枕颈部后路4种不同植入方式的螺钉在施加生理载荷时所承受的应力,评价各自在生理环境中的机械性能。方法对16例新鲜人体枕颈部标本（含Oc-C3）,采用后路枕寰枢复合体经关节螺钉固定和SUMMIT系统枕颈固定。对固定后的经寰枕关节螺钉（Oc-C1组）、经寰枢关节螺钉（C1-C2组）、枢椎椎弓螺钉（C2 PS组）和枕骨螺钉（Oc Screw组）在生理载荷下三维六自由度运动时,运用应变电阻测定法测定4种螺钉的应力,数据进行统计学处理。结果在侧屈状态下,电测法测得的4种螺钉局部应变均接近于0。在前屈、后伸、左旋和右旋运动时,随着加载载荷增大,测得的应力均逐步增大。在前屈和旋转时螺钉不同程度承受拔出应力,在后伸时,螺钉所受的为压应力。枕骨螺钉（Oc Screw组）在屈伸和旋转运动状态下,在所有3种载荷下所承受的应力均大于其它3种植钉方法,差异有统计学意义（P＜0.05）。结论生理环境下,枕骨螺钉承受的拔出应力最大,其可能更易出现内植物相关并发症,具体应用时应结合临床实际。