个体定制化人工半膝关节的快速设计制造与临床试用

目的]建立以计算机辅助设计（CAD）和快速成型（RP）技术为核心的人工半膝关节个体定制化设计方案和快速制造方法，通过临床试用探讨半膝关节置换术的应用和假体设计制造技术。方法]以患者CT扫描和三维重建等临床影像学资料为数据源，利用图像处理技术获取关节形状的数据，采用NURBS算法在Surface软件下重构出关节曲面，在计算机上完成半膝关节假体及其辅助装置的三维设计。采用RP技术制作出原型并通过精密铸造等手段完成实体制造。将假体与大段异体骨移植联合应用，对1例股骨下段肿瘤患者进行了肿瘤切除、人工膝关节置换术。结果]全部设计和制造过程可在1周内完成。计算机分析表明，所设计的关节面CAD模型与原始数据的最大误差〈1mm，在屈、伸、旋转等状态下与胫骨关节面匹配良好，应力分布均匀。通过RP和精密铸造技术制作的假体及其辅助装置符合设计要求，可与大段异体骨装配。植入患膝后假体位置准确，能够实现与对侧胫骨关节面的良好匹配，关节间隙正常。术后患者无不良反应，可早期功能锻炼。随访1年，患者膝关节功能恢复满意，未见关节脱位、慢性疼痛等。结论]通过CAD和RP技术制造的定制化半膝关节在特定病例中具有一定的临床实用价值。

Custom design and rapid fabrication of artificial semi-knee joint and its clinical application

Objective] To present a custom design and rapid fabrication method for artificial semi-knee joint based on computer aided design (CAD) and rapid prototyping (RP) technique and to evaluate the clinical application value of semi-knee arthroplasty and the role of CAD/RP technique in the design and fabrication of the prosthesis are. Methods] The scanning information of computer tomography (CT) and three dimensional reconstruction image of the patient were obtained as basic data by graphics processing software. The curved surface of knee joint was reconstructed by means of Non-uniform Rational B-Spline (NURBS). Based on the reconstructed surface, three dimensional CAD model of semi-knee prosthesis and related connecting implements including intramedulltary pin, fusion cages and positioning device were designed. The prototypes of these models were made by laser prototyping system rapidly and then the prosthesis was fabricated by investment casting for high quality. The prosthesis was used in 1 case of a young patient whose distal femur was destroyed by osteosarcoma, the semi-knee arthroplasty was performed with allograft to evaluate the clinical applicaton value of prosthesis. Results] All the design and fabrication process could be acompleted, the maxium error was less than 1 mm as analysed by computer. Simulating by CAD model of joint, the femur surface could perfectly match the tibia surface in each position including flexion, extension and rotation, The prosthesis made by RP and investment casting could meet design requirements and could be installed in allograft bone precisely. After operation, the prosthesis was in right position and could match the joint surface of tibia accurately without any adverse effect. After operation and followed-up for one year showed that the function of the knee was recovered satisfactorily without dislocation. The patient could walk, partially squat and climb stairs without any pain. Conclusion] CAD and RP are advanced and excellent techniques on fabricating custom designed prosthesis, the operation of semi-knee arthroplasty is an effective therapeutic means for some special patients and can be used in the clinic.