计算机辅助设计兔解剖型人工膝关节假体

The design of anatomic knee prostheses for rabbits with computer aided design

目的设计与制作不同型号兔解剖型人工膝关节假体。方法将新西兰大白兔按体重分为A、B、C3组,对应体重(m)分别为2.0 kg≤m<2.5 kg、2.5 kg≤m<3.0 kg、3.0 kg≤m<3.5 kg,每组5只;采用螺旋CT对兔膝关节和人膝关节假体进行扫描,并行三维重建;应用Freeform自由造型系统将重建图像进行模型修改、表面划分、切割标记,将人膝关节假体模拟安装至兔膝,并根据标记雕刻修整,获得与兔膝关节完全匹配的模型;测量兔膝关节各参数,设计出不同型号假体,利用快速成型技术制作出相应假体并植入兔膝关节内。结果 3组兔膝关节各参数:股骨前髁上下径、内外径,股骨远髁前后径、内外径,股骨后髁矢状径、内外径,胫骨平台前后径、内外径、厚度、胫骨平台下1 cm髓内径,A组最小,B组居中,C组最大,3组间比较差异均有统计学意义(P<0.05);股骨干轴线与前髁夹角α、股骨前髁与远髁夹角β3组间比较差异均无统计学意义(P>0.05);股骨前髁上下径、股骨远髁前后径、股骨后髁矢状径、胫骨平台前后径、胫骨平台内外径与体重呈正相关(P<0.05),α角、β角与体重无相关(P>0.05)。将设计大、中、小号假体植入兔膝内,1个月存活率达93%,膝关节活动功能良好。结论利用计算机辅助设计、快速成型技术研发不同型号兔解剖型膝关节假体,手术植入方法简单,术后功能良好,适用于人工膝关节置换手术的相关基础研究。

Objective To design and manufacture different sizes anatomic knee prostheses for rabbits. Methods New Zealand rabbits were divided into 3 groups according to the weight （n =5; Group A： 2.0 kg≤m 〈2. 5 kg, Group B： 2. 5 kg≤m 〈3 kg, Group C： 3 kg≤m 〈3.5 kg）. By the means of spiral CT scanning, the knee joints of all 15 rabbits and a knee prosthesis of human were scanned and reconstructed in 3D by Mimics 9. 1, and the surface was modified by the software of Freeform. By the measurement of knee parameters in different groups, different sizes of knee joint pros-thesis, including large, median and small were designed and printed out by rapid prototyping technology. The function was observed after the prosthesis installed. Results The parameters of keen joint, including height and left - right diameter of paracondyloid, anteroposterior length and left - right diameter of distal end of condyle, left - right and sagittal diameters of posterior condyle, anteroposterior length, left - right diameter, sagittal diameter and medullar diameter 1 cm below of tibial plateau, were significantly increased with the weight under certain weight range （ P 〈 0. 05 ） , and significantly positively correlated with weight （P 〈0. 05） ; but there was no significant difference in the angle α and β （P 〈 0. 05 ）, nor significant correlation was found between them and weight （P 〉 0. 05）. One month after installation, the knee function of pros-thesis was well. Conclusion The knee joint prosthesis for rabbits made by the technology of the spiral CT scanning, 3D reconstruction and CAD technologies have the advantages of high precision and easy operation. It can be used in the study of knee arthroplasty in rabbits.