儿童双运动轨迹半膝关节假体的问题与对策

The problems and countermeasures of children double-acting trajectory hemi-knee prosthesis

背景:应用全膝置换治疗儿童股骨髁部恶性骨肿瘤会破坏胫骨端骨骺而导致儿童生长发育过程中出现双侧肢体不等长。本课题组针对单纯半膝髁表面置换后金属假体对胫骨平台造成磨损的问题,首次提出双运动轨迹半膝关节置换理念。目的:分析儿童双运动轨迹半膝关节假体在临床应用中出现的问题,提出改进意见,并对该假体的具体参数和力学特性进行研究。方法:随机选取2011年7月至2013年3月行双运动轨迹半膝关节置换术的6例患儿,对假体髁部参数进行测量及对术后膝关节AKS评分进行统计学分析。选取1例股骨远端骨肿瘤患儿,采集其健侧膝关节的CT及MR数据,利用Mimics10.01及Geomagic studio 12.0软件进行三维重建及图像配准。结果:6例患儿的术后AKS评分与其使用的假体髁部参数存在线性关系;三维重建的股骨髁及关节软骨的复合模型导入Pro/Engineer 5.0软件中计算膝关节力线及旋转轴,并做韧带打孔及内部结构的设计。结论:假体旋转中心在矢状面的横向及纵向偏移均可引起假体不稳,直接导致术后膝关节功能恢复不佳;新方法制作的双运动轨迹半膝关节假体拥有静力学稳定性,同时可最大程度恢复膝关节的前后向稳定性。

Background：Total knee replacement for children with malignant bone tumor at femoral condyle will ruin the epiphysis of the proximal tibia and lead to unequal length of the bilateral lower limbs in children＇s physical development process.Aiming at the problem that the metal prosthesis will abrade the tibial plateau after the semi-joint prosthesis replacement,this study first put forward the concept of double-acting trajectory hemi-knee prosthesis.Objective：To analyze the problems arose from the clinical application of the customized double-acting trajectory hemi-knee prosthesis,and put forward the improvement suggestions.And,to study the specific parameters and mechanical characteristics of the prosthesis.Methods：Randomly select 6 cases of children who received the operation of double-acting trajectory hemi-knee prosthesis during July 2011 to March 2013,measure their prosthetic condyles parameters and statistically analyzed their postoperative knee AKS scores.Choose one child with distal femoral bone tumor,gather the CT and MR data of his/her normal knee,and use the Mimics 10.01 and Geomagic studio 12.0 software to reconstruct a 3D model and register the image.Results：Linear relationship was found between the postoperative AKS score and the prosthetic condyles parameters.Import the reconstructed 3D composite model of femoral condyle and articular cartilage into Pro/Engineer 5.0 software to find the knee joint force lines and the axis of rotation,and then punch the ligament attachment point and design the internal structure.Conclusions：Both the transverse and longitudinal displacement of the rotation axis in the sagittal plane can cause the prosthesis instability,which will directly lead to poor recovery of the knee joint.The double-acting trajectory hemi-knee prosthesis following the new method have the statics stability,and can achieve maximum recovery of the anterior-posterior stability of the knee.