In Vivo Comparison of Knee Kinematics for Subjects Having Either a Posterior Stabilized or Cruciate Retaining High-Flexion Total Knee Arthroplasty

The objective of this study was to determine the in vivo kinematics for subjects having either a fixed posterior stabilized (PS) or cruciate retaining (CR) high-flexion total knee arthroplasty (TKA). Three-dimensional kinematics from full extension to maximum flexion were determined for 30 subjects (15 PS, 15 CR) using fluoroscopy. On average, the PS subjects demonstrated 112° of weight-bearing (WB) flexion, −6.4 mm of posterior femoral rollback, and 2.9° of axial rotation. The CR subjects averaged 117° of WB flexion, −4.9 mm of posterior femoral rollback, and 4.8° of axial rotation. Posterior femoral rollback of the lateral condyle occurred for all PS TKAs and in 93% of the CR TKAs. Only 2 subjects in each group experienced greater than 1.0 mm of condylar lift-off. Subjects in both TKA groups demonstrated excellent WB ranges of motion and kinematic patterns similar to the normal knee, but less in magnitude.