BACKGROUND Extension stems provide stability to revision total knee arthroplasty (RTKA). Little is known regarding the relationship between stem characteristics and RTKA stability. We aimed to identify the relationship between canal filling ratio (CFR) and aseptic loosening following RTKA. METHODS We retrospectively reviewed demographics, radiographic parameters, and outcomes associated with RTKA performed between 2008 and 2013 in a tertiary hospital. The inclusion criteria were: revision for aseptic loosening, hybrid fixation, minor bone defect, Zimmer® LCCK prosthesis, and follow-up > 24 months. Using the modified Knee Society radiographic scoring system, radiographic prosthesis loosening was defined as a radiolucent line (RLL) score ≥ 9 on the femoral side or ≥ 10 on the tibial side. We utilized receiver operating characteristic (ROC) curve analysis to evaluate the cutoff value for stem length and diameter in terms of prosthesis loosening or not. Furthermore, CFR-related parameters were analyzed with logistic regression to clarify their relationships with prosthesis loosening. RESULTS Prosthesis loosening was detected in 17 of 65 patients included. On logistic regression analysis, male sex and severity of the tibial bone defect were associated with loosening. On multivariate analysis, male sex and bone defect severity were associated with loosening on the femoral side, while malalignment was associated with loosening on the tibial side. Protective factors included femoral CFR > 0.85, CFR > 0.7 for > 2 cm, and CFR > 0.7 for > 4 cm, as well as tibial CFR > 0.85. CONCLUSIONS To minimize loosening post-RTKA, femoral CFR > 0.7 for > 2 cm and tibial CFR > 0.85 are recommended. Risk factors may include male sex, bone defect severity, and malalignment.

中文翻译：

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延伸茎长度和直径对翻修全膝关节置换术的临床和放射学结果的影响。

背景技术延长杆为翻修全膝关节置换术（RTKA）提供稳定性。关于茎特征和RTKA稳定性之间的关系知之甚少。我们的目的是确定RTKA后根管充盈率（CFR）与无菌性松动之间的关系。方法我们回顾性回顾了2008年至2013年在三级医院进行的人口统计学，放射学参数和与RTKA相关的结局。纳入标准为：修订无菌性松动，混合固定，轻微骨缺损，Zimmer®LCCK假体以及随访> 24个月。使用改良的Knee Society放射线评分系统，将放射线修复体松动定义为股骨侧的射线可透线（RLL）得分≥9或胫骨侧的≥10。我们利用接收器操作特性（ROC）曲线分析来评估假体是否松动的茎长度和直径的截止值。此外，通过逻辑回归分析了CFR相关参数，以阐明它们与假体松动的关系。结果包括65名患者中的17名患者检出了假体松动。通过逻辑回归分析，男性和胫骨骨缺损的严重程度与松弛有关。在多变量分析中，男性和骨缺损的严重程度与股骨侧的松动有关，而畸形与胫骨侧的松动有关。保护性因素包括股骨CFR> 0.85，> 2 cm CFR> 0.7，> 4 cm CFR> 0.7以及胫骨CFR> 0.85。结论为了最大程度地减少RTKA后的松动，建议股骨CFR> 0.7（> 2 cm），胫骨CFR> 0.85。危险因素可能包括男性，骨缺损严重程度和错位。