Stress distribution around a TKR implant: are lab results consistent with observational studies?

Malalignment of Total Knee Replacement prosthesis has been reported to limit the implant survival time. We hypothesized that this may be secondary to excessive stress occurring at the bone-implant interface, resulting from abnormal load transfer across the knee joint. In this study, we conducted Finite Element Analysis of a geometrical model of the knee joint after Total Knee Replacement with different axial alignments. The calculated stresses and displacements were significantly higher with varus knee malalignment than with the valgus one. The stresses are not high enough to pose a serious risk of a crack or a fracture but might be responsible for chronic pain reported by some patients. In cases where optimal implant positioning is not possible, slight valgus malalignment might produce better results than varus.