Tibial tray stability in three cementless total knee arthroplasty systems

Area of Science:

• Biomechanical engineering
• Orthopedic surgery
• Materials science

Background:

• Initial stability of cementless total knee arthroplasty (TKA) tibial trays is crucial for successful bony ingrowth and long-term implant survival.
• Understanding the micromotion and displacement patterns of different TKA tibial tray designs under physiological loading is essential for optimizing fixation.

Purpose of the Study:

• To quantify and compare the three-dimensional (3D) micromotion and displacement of three distinct cementless TKA tibial tray systems.
• To evaluate the influence of implant design (symmetric, asymmetric, anatomic) on initial stability during simulated physiological loading.

Main Methods:

• Robotically applied physiological loading (walking, stair descent) to cementless tibial trays in foam tibia models.
• Tested three TKA systems with keeled and pegged cementless tibial trays from two manufacturers.
• Measured relative displacement at ten peripheral locations using an optical system to characterize micromotion.

Main Results:

• All tested TKA systems exhibited posterior tibial tray movement with posterior loading and anterior movement with anterior loading.
• The anatomic tibial tray design showed significantly less micromotion during walking (84 ± 22 μm) compared to asymmetric (205 ± 54 μm) and symmetric (229 ± 30 μm) designs (p < 0.001).
• The anatomic design also demonstrated less micromotion during stair descent (92 ± 18 μm) than the symmetric design (165 ± 17 μm) (p < 0.002).

Conclusions:

• Total knee arthroplasty system design significantly influences the initial stability of keeled cementless tibial trays.
• Anatomic tibial tray designs offer superior initial stability compared to symmetric and asymmetric designs under simulated gait conditions.
• These findings highlight the importance of implant geometry in achieving robust cementless fixation in TKA.