The effects of varus tibial alignment on proximal tibial surface strain in total knee arthroplasty: The posteromedial hot spot.

Abstract

The aim of this study was to determine the effect of varus tibial alignment on proximal tibial strain in total knee arthroplasty. Fourteen paired fresh-frozen cadaver tibiae had photoelastic coating applied. The right tibiae were cut in neutral alignment, and the left tibiae were cut in 5 degrees of varus. Components were cemented and loaded with 3 x body weight, varying medial to lateral load. Surface microstrain was measured. There was a statistically increased hot spot of highly concentrated strain in the posteromedial quadrant of the proximal tibia in varus-cut bones (P<.05). In neutral alignment, the strain was nearly equal medial and lateral. The increased strain observed helps elucidate the mechanism of increased failure rates of a total knee arthroplasty inserted in varus alignment. Neutral alignment may have a protective effect.