Implant migration and failure in total knee arthroplasty is related to body mass index and tibial component size.

Aseptic loosening of knee implants is multifactorial. The purpose of this study was to examine the role of body mass index and tibial component size on loosening and migration of total knee arthroplasty (TKA) implants. Six thousand five hundred forty-eight primary TKAs (anatomic graduated components) were studied with aseptic loosening as the end point. A second cohort of 81 TKAs (anatomic graduated components) had radiostereometric analysis beads implanted, permitting implant migration assessment. Patient mass and tibial component surface area were used to calculate potential tibial stresses. We found that higher potential stresses were associated with increased rates of loosening in both metal-backed and all-polyethylene designs. Increased tibial implant migration, in both the varus-valgus and anterior-posterior directions, was associated with higher estimated stresses. We found an increased rate of tibial component loosening and implant migration in patients with a higher mass and smaller tibial component size.