Tibial tray stability in three cementless total knee arthroplasty systems

Initial stability of cementless total knee arthroplasty tibial trays is necessary for bony ingrowth. The purpose of this study was to characterize the patterns and magnitudes of displacement of three implant systems during physiological loading in terms of tibial tray movement and 3D micromotion.

Physiological loading (walking and stair descent) from a representative subject was robotically applied to cementless tibial trays implanted in foam tibia models. Three commercially available total knee arthroplasty systems with cementless tibial trays with keels and peripheral pegs from two different manufacturers were tested including symmetric, asymmetric and anatomically shaped tibial trays. Relative displacement between the foam tibia model and tibial tray in response to loading was measured at ten peripheral locations using an optical measurement system.

All systems showed inferior movement of the posterior tibial tray in response to posterior located tibiofemoral loading, and superior movement of the anterior tibial tray. The system with an anatomic tibial tray design had significantly less micromotion than the systems with an asymmetric and symmetric tibial tray designs during walking (symmetric: 229 ± 30 μm, asymmetric: 205 ± 54 μm, anatomic: 84 ± 22 μm; p < 0.001) and less micromotion than the symmetric tibial tray during stair descent (symmetric: 165 ± 17 μm, asymmetric: 151 ± 65 μm, anatomic: 92 ± 18 μm; p < 0.002).

Total knee arthroplasty system design had an impact on keeled cementless tibial tray initial stability during simulated walking and stair descent in this biomechanical model.