Mobile-bearing TKA improved the anteroposterior joint stability in mid-flexion range comparing to fixed-bearing TKA

Proper anteroposterior (AP) joint displacement is an important indicator of good clinical outcome following total knee arthroplasty (TKA). We hypothesized that a newly introduced mobile-bearing posterior stabilized (PS) prosthesis reduces the AP joint displacement. The aim of this study is to compare the AP joint displacement between a newly introduced mobile-bearing PS TKA in one knee and a conventional fixed-bearing PS TKA in other knee. 82 knees in 41 patients who had bilateral TKAs were investigated. All the patients received a conventional fixed-bearing PS prosthesis in one knee and a highly congruent mobile-bearing PS prosthesis in the other knee. AP joint displacement was measured using the KT-2000 arthrometer, at 30A degrees and 75A degrees in flexion, at average of 3.3 years after the operation. AP joint displacements at 30A degrees in flexion were 6 +/- A 3 mm in the knees with the mobile-bearing PS prosthesis and 9 +/- A 4 mm in the knee with fixed-bearing PS prosthesis (p < 0.001). AP joint displacements at 75A degrees in flexion were 4 +/- A 2 mm in the knees with the mobile-bearing PS prosthesis and 6 +/- A 3 mm in the knee with fixed-bearing PS prosthesis (p < 0.001). This study suggested that the design of the prosthesis can improve the AP joint stability in mid-flexion range.