数字化导航模板辅助全膝关节置换的模拟研究

A computer simulation study of total knee arthroplasty assisted by digital navigation templates

目的探讨数字化导航模板辅助全膝关节置换的准确性和可行性。方法取成年尸体下肢标本20具，随机分为导航模板组和传统方法组，每组10具20个膝关节。导航模板组术前行下肢全长CT扫描，利用逆向工程软件对CT数据进行处理，设计与股骨远端和胫骨近端匹配的可定位截骨平面和外旋轴的导航模板，通过快速成型机制作模板实物用于尸体标本的全膝关节置换手术操作。传统方法组按常规全膝关节置换手术操作。术后通过CT扫描比较两种方法定位的截骨准确性。结果导航模板与股骨髁和胫骨平台贴合紧密，无明显移动。导航模板组18个膝关节的股骨远端和胫骨近端截骨面与下肢机械轴垂直，2个膝关节内翻；17个膝关节后髁截骨面与通髁轴完全平行，3个膝关节有成角。传统方法组20个膝关节均出现下肢机械轴内外翻，其中5个膝关节大于5°；20个膝关节均出现后髁截骨面与通髁轴成角，其中10个膝关节大于3°。结论导航模板法的股骨远端、胫骨近端和股骨外旋截骨准确性均高于传统手术方法。

Objective To investigate the accuracy and feasibility of total knee arthroplasty （TKA） assisted by a computer assisted navigation templates in cadaveric knee joints. Methods Forty fresh cadaveric legs were randomly divided into two groups of 20 specimens each. Computer-assisted navigation templates were used for TKA in group 1, whereas conventional extramedullary tibial and intramedullary femoral guiding systems were used in group 2. ACT scan was performed preoperatively on the lower limb for navigational group. The computer generates a model of the lower extremity by using the reverse-engineering software to process the CT data, then a navigational template was constructed as the inverse of the distal femur and proximal tibia surface with an osteotomy gap and two drill guides to define the rotational alignment of the femur in the computer. The navigational templates produced an accurate model using a rapid prototyping （RP） technique to assist cadaveric TKA. The conventional method for cadaveric TKA was performed accord- ing to routine operation. CT scans were performed postoperatively to evaluate the osteotomy accuracy of the two TKA methods. Results The navigational template fit tightly with the femur condyle and tibia plateau. In the navigational group, eighteen knee osteotomies of the distal femur and proximal tibia were perpendicular to the mechanical alignment, two knee joints were found to have genu varum malalignment; seventeen knee osteotomies of the posterior condylar surface were parallel to the transepicondylar axis, three knee joints have an included angle. In the conventional group, all twenty knee joints show genu varum or genu valgum deformity; five knee joints of these deformities were more than 5°. All twenty knee osteotomies of the posterior condylar surface have an included angle with the transepicondylar axis; ten knee joints of these were more than 3°. Conclusion Computer-assisted digital navigation templates in total knee arthroplasty may be used as a novel method for its advantage of safety, feasibility, simple operative procedure and alignment accuracy.