The effects of length of femoral stem on aseptic loosening following cemented distal femoral endoprosthetic replacement in tumour surgery

Purpose Aseptic loosening is a common prosthetic failure mode. The purpose of this study was to identify dose-response relationship between length of femoral stem and aseptic loosening. Methods We collected data of patients who underwent distal femoral prosthetic replacements at our institution from 2001 to 2017. Cox regression and two-piecewise regression model were used to analyze the associations between stem length and aseptic loosening. Results Significant association of length of femoral stem with aseptic loosening was observed in multivariate model and a non-linear relationship could be found from the smoothed curve. In two-piecewise model, an inflection point was calculated to be 143 mm. On the left of the inflection point, every 1 mm increase in the length of stem indicated that the risk of aseptic loosening could be reduced by 6%. Conclusion There was a significant non-linear relationship between the length of femoral stem and aseptic loosening, and the inflection point was 143 mm.