Abstract
Malrotation of tibial components is one of the important causes of failure in total
knee arthroplasty. The aim of this study is to determine the relationship between
tibial rotational positioning and coverage of the tibial surface during the operation,
using a symmetric and newly introduced asymmetric medial pivot tibial components.
The coverage and overhang were compared between a symmetric component (Advance medial
pivot) and a newly introduced asymmetric medial pivot tibial component (Evolution
medial pivot) in 31 knees during the operation. When the tibial component was placed
parallel to the anteroposterior (AP) axis, the uncovered width in the posteromedial
part using a symmetric design was larger than that using an asymmetric design (p < 0.01). Overhang in the posterolateral part was observed in 42% for a symmetric
design and 3% for an asymmetric design (p < 0.01). When the component was placed in malrotation (10 degrees internal to the
AP axis), overhang in the posteromedial part was observed in 6% for a symmetric design
and in 71% for an asymmetric design (p < 0.01). The tibial rotation parallel to the AP axis and maximizing coverage of the
tibial surface conflict in a symmetric design, but are compatible in an asymmetric
design. An asymmetric tibial component is expected to improve the coverage and the
rotational positioning of medial pivot total knee prosthesis.
Keywords
medial pivot total knee prosthesis - asymmetric tibial component - tibial coverage
- overhang
