Introduction: Although studies have demonstrated similar outcomes between ultracongruent (UC) and traditional bearings, debate exists regarding the optimum bearing surface. We sought to determine whether preoperative factors may predict use of a UC bearing when compared to a standard cruciate retaining (CR) group.
Materials and methods: The study cohort consisted of 117 patients who underwent primary total knee arthroplasty (TKA). The implants utilized were either the CR or UC polyethylene components of the Zimmer Persona® Total Knee System. Patient demographics and comorbidities were documented. Intraoperative variables and postoperative outcomes were recorded. We calculated change in tibial slope and femoral condylar offset from pre- to post-surgery and computed the percentage of patients for whom an increase in tibial slope or femoral condylar offset was determined. All dependent variables were compared between patients who received the UC component and those with a CR component using either independent samples t-tests or chi-square test of independence.
Results: Thirty-nine patients received a UC insert and 78 patients received a CR insert. Mean length of stay (p=0.017), estimated blood loss (p=0.021), and tourniquet time (p=0.032) were greater for the UC group. Intraoperative implant variables were not different between the groups. However, the proportion of patients for whom tibial slope increased postoperatively was greater for the UC group compared to the CR group (p=0.018).
Conclusion: Our results showed that no preoperative medical comorbidities or demographic factors predicted use of the UC bearing; however, postoperative tibial slope was increased for a greater number of patients who received the UC implant.