RIGHT SIZING OF THE FEMORAL COMPONENT IN TOTAL KNEE REPLACEMENT

Abstract

In Total Knee Replacement, over-sizing the femoral component may restrict knee flexion. If the AP dimension of the existing femur is in between component sizes, you should down-size the femoral component whenever possible.

Using the Triathlon Knee System the femoral and tibial component sizes were recorded for 140 consecutive knee replacements. For each procedure, the femoral component size was compared to the tibial component size and recorded as same size, one size down or one size up. The author’s component selection was then compared with 500 Triathlon knee replacements carried out during the same period by other surgeons

In the authors 140 cases, the femoral component was the same size in 96(68%), one size down in 33(24%) and one size up in 11(8%). This compared with other users (500 cases) where the femoral component was the same size in 360(62%), one size down in 51(10%) and one size up in 89(18%). Compared with other users, the author was more likely to downsize the femoral component 24% v 18% and less likely to upsize 8% v 18%. These differences were significant, p< 0.05.

Conclusion: Fear of “notching” the anterior femur may influence femoral component selection in TKR. This fear has been overstated and discourages surgeons from correctly sizing the femoral component to facilitate knee flexion.