Load transfer characteristics of a noncemented total knee arthroplasty

This study evaluated load transfer characteristics of femoral and tibial components of a total knee prosthesis that was designed to achieve distal femoral and proximal tibial compressive load-bearing. Strain gauge readings were highest on the cortex of the tibial metaphyseal flare. Roentgenograms of 110 patients with noncemented total knee arthroplasty (TKA) with follow-up periods of 12-24 months were evaluated. Cancellous bone hypertrophy bridging from the undersurface of the tibial component to the metaphyseal cortical bone was noted on all roentgenograms at six months, suggesting stress transfer through cancellous bone to this area. Anterolateral sinking was noted in six of the first 46 patients but was not seen again in the series after a design change was made to more rigidly fix the stem in the bone of the upper tibia. Roentgenograms of the femoral components demonstrated distal bone hypertrophy suggesting compressive load bearing. None of the femoral components migrated or sank.