The influence of stem design on strains and micromotion in revision Total Knee Arthroplasty: Finite element analysis

The main objective of this study was to compare the effect of tibial stem design on load transfer, strains and relative micromotion between the tibial tray and bone. Attempts were also made to correlate FE results with clinical findings, like bone resorption, fibrous layer formation, radiolucencies and pain. The effect of the medial position of the tibial tray to obtain good alignment with press-fit long stems provoked higher strains when compared with the model where the stem was shifted medially. Cemented stems reduce load transfer by the tibial tray to proximal bone while pressfit stems transmit higher percentage of load. The idea that orthopaedic surgeons have that this kind of stems reduce load transmitted to the proximal bone is according to this study a wrong one. The hypothesis that load transferred at the distal tip of the press-fit stems occurs is true in an immediately pos-operative situation if micromotion is minimised due to an adequate press-fit. However, in the middle and long term, the share of load at the distal bone cannot not achieved. FE results demonstrated potential mechanical-clinical relations relative to bone resorption, radiolucencies and pain.