No relationship between postoperative changes in bone density at the proximal tibia and the migration of the tibial component 2 years after total knee arthroplasty

The relationship between changes in bone mineral density (BMD) in the proximal tibia and fixation of the tibial component during 2 years postoperatively was investigated in 28 knees. BMD was measured using dual-energy x-ray absorptiometry, and fixation was determined using radiostereometric analysis. BMD decreased at 3 months and returned to baseline level at 24 months, but with large variations on an individual basis. Most of the prosthetic migration occurred within the initial 3 months. The results show that the bone remodeling that occurs during the 2 years after operation has no relation to the migration of the tibial component. The early migration seems to be related more to local activities at the interface rather than to changes in BMD assessed below the interface. The changes in BMD during 2 years reflect the bone remodeling caused by the normalization of alignment after operation and are not related to the implant fixation.