Polished Cobalt-Chrome vs Titanium Tibial Trays in Total Knee Replacement (a Comparison using the PFC Sigma System)

Fixed-bearing total knee arthroplasty components can cause wear debris due to fretting micromotion between the polyethylene insert and the metal tibial tray, possibly leading to osteolysis and implant failure. This study compared the effects of either a highly polished cobalt-chrome (CoCr) or titanium tibial tray in patients receiving the PFC. Sigma� posterior stabilized knee system with a moderately cross-linked polyethylene insert. One hundred five patients with titanium tibial trays and 70 patients with CoCr tibial trays were prospectively enrolled at the time of follow-up of at least 4 years from surgery. There were two revisions with implant removal in each group. On blinded radiographic review, osteolysis was observed in three of 105 knees in the titanium group and three of 70 knees in the CoCr group. Radiolucent lines were categorized in accordance with the Knee Society roentgenographic evaluation system. In the titanium group 18% showed no radiolucent lines, 65% scored four or less (nonconcerning), and 17% scored between five and nine (requires observation for progression). In the CoCr group 24% showed no radiolucencies, 61% scored four or less, and 14% scored between five and nine. None of the knees in either group scored greater than 10 (possible or impending failure). Knee society scores and radiographic alignment were statistically similar between groups. These results suggest that there may not be a difference in clinical or radiographic midterm outcome between titanium and CoCr tibial trays in total knee arthroplasty.