The biomechanical effects of patient bone osteoporosis on tibial prosthesis fixation in total knee arthroplasty

Osteoporosis is a prevalent comorbidity among patients with knee osteoarthritis. This study employed finite element analysis to investigate the biomechanical effects of tibial osteoporosis on prosthetic fixation in total knee arthroplasty (TKA) by simulating varying degrees of osteoporosis through adjustments in material properties. The results indicated that as the tibial elastic modulus decreased, the maximum von Mises stress of the tibia was reduced, whereas the prosthetic stress increased. The contact pressure on the tibial tray stem diminished, and the tibial tray baseplate displacement, cement shear stress, and micromotion at the fixation interface were elevated. Notably, when the modulus was reduced to 60% of its initial value, the tilting of the tibial tray baseplate increased by 33.72%. Under these conditions, the cement shear stress reached -4.22 MPa, approaching the fatigue limit of 5 MPa, and the peak interface micromotion attained 66.2 μm, exceeding the optimal threshold for bone ingrowth. These findings underscore the necessity for surgeons to assess bone quality before TKA. With progressive osteoporosis, the risk of stress shielding increased significantly, while the risk of bone fracture became inevitable. These findings indicated that patients with severe osteoporosis may face challenges in achieving fixation stability. Consequently, we advocate for the consideration of full cement fixation and/or the utilization of an extended stem to restore initial stability for patients with severe osteoporosis. • Studied biomechanical effects of tibial osteoporosis on TKA prosthetic fixation; • Cement shear stress neared the fatigue limit at 60% elastic modulus; • Micromotion exceeded the bone ingrowth threshold at 60% elastic modulus; • Severe osteoporosis can challenge the achievement of stable fixation.