Influence of Posterior Tibial Slope on Stability after Total Knee Arthroplasty

ABSTRACT

PURPOSE: The purpose of this study was to compare the influence of posterior tibial slope on hyperextension deformities and anterior tibial translation between two types of total knee arthroplasty(TKA); posterior cruciate retaining(CR) and substituting(PS), which have different polyethylene conformity. MATERIALS AND METHODS: 109 consecutive primary TKAs using Nexgen(R)(Zimmer, Warsaw, IN) CR(n=60) and PS (n=49) type prostheses, performed from July 1995 to August 2005 were reviewed. Each group of CR and PS were divided into two categories according to the degree of posterior tibial slope; 0~5 degrees and more than 5 degrees. The amount of hyperextension deformities and anterior tibial translation measured at the immediate and postoperative 2 years radiographs were analyzed in each subdivided groups. RESULTS: The significant amount of hyperextension deformities(p<0.05) and anterior tibial translation(p<0.05) were noted in the CR group. The CR group with more than 5 degrees of posterior tibial slope was more prone to develop the hype- rextension deformities(p=0.003) and anterior tibial translation(p=0.007) compared with the group that has posterior tibial slope less than 5 degrees. But in the PS group, there was no significant difference related with hyperextension deformities (p =0.240) and anterior tibial translation(p=0.204) between the two groups. CONCLUSION: The posterior tibial slope more than 5 degrees resulted in increments of the hyperextension and anterior tibial translation in the CR TKA group than in the PS TKA group.