Analysis of differences in bone removal during femoral box osteotomy for primary total knee arthroplasty.

PURPOSE this study was conducted to compare the quantity of intercondylar bone removed during femoral box osteotomy for implantation of three contemporary posterior stabilized (PS) total knee arthroplasty designs: Sigma PS (DePuy), Vanguard (Biomet) and Persona (Zimmer). METHODS we compared the maximum volumetric bone resection required for the housing of the PS mechanism of these three designs. Bone removal by each PS box cutting jig was three-dimensionally measured. The differences between the three designs were analyzed by the Kruskal-Wallis test. The Mann-Whitney U-test was used for pairwise comparisons. The level of significance was set at p<0.05. RESULTS for small-size implants, the average box osteotomy volume of Persona was significantly smaller than the Vanguard and Sigma PS volumes (p=0.003). The mean difference between Vanguard and Sigma PS (p=0.01) was also significant. For medium size implants, the mean difference between Persona and Sigma PS (p=0.008) and the mean difference between Vanguard and Sigma PS (p=0.01) were statistically significant. For large size implants, the mean difference between Vanguard and Sigma PS (p=0.01) and the mean difference between Sigma PS and Persona (p=0.008) were statistically significant. CONCLUSIONS irrespective of implant size, the Persona cutting jig always resected significantly less bone than did Vanguard and Sigma PS. CLINICAL RELEVANCE although this study does not establish any clinical relevance of removing more or less bone at primary TKA, its results suggest that if a PS design is indicated, it is preferable to select a model which resects less distal femoral bone.