ABSTRACT
PURPOSE: We wanted to evaluate the effects of a preoperative posterior tibial slope of more than 10degrees on the extension gap and patellar height during posterior substituted total knee arthroplasty. MATERIALS AND METHODS: One hundred ten posterior substituted total knee arthroplasties were divided into group I (more than 10degrees of preoperative posterior tibial slope, n=56) and group II (less than 10degrees of slope, n=54). Each group was evaluated to compare the frequency of additional distal femoral resections due to an insufficient extension gap and the correlation with the decrease of the patellar bone height. RESULTS: In each group, the preoperative tibial slope was 12.77degrees (+/-3.22degrees) vs. 6.72degrees (+/-2.58degrees), respectively (p=0.000) and the decrease of the posterior slope was 10.74degrees (+/-3.54degrees) vs. 4.78degrees (+/-2.66degrees), respectively, (p=0.000). The frequencies of additional distal femoral resection were 54.5% vs. 46.1%, respectively, (p=0.448) with flexion contracture and 11.8% vs. 34.1%, respectively, (p=0.022) without flexion contracture. The decrease of the patellar bone height was 0.35 (+/-4.79) mm vs. 1.99 (+/-4.78) mm, respectively, (p=0.075). There was weak correlation between the decrease of the patellar bone height and the decrease of the posterior tibial slope (r=-0.253, p=0.016). CONCLUSION: In the group having more than 10degrees of preoperative posterior tibial slope without flexion contracture, the decrease of the posterior tibial slope had to be considered as one of the factors that affected making the extension gap significantly greater during the gap technique and to preserve the patellar bone height.