The effect of a sagittal cutting error of the distal femur on the flexion-extension gap difference in total knee arthroplasty.

The aim of this study was to determine how much a distal femoral cutting error would affect the flexion-extension gap difference (flexion gap minus extension gap) in total knee arthroplasty (TKA). We evaluated 15 knees using a computer-simulation technique. Bone cutting errors of -2°, 2° and 4° of extension were simulated in three TKA systems. A distal femoral cutting error of 2° of extension or flexion caused a change in the difference between the flexion and extension gaps of approximately two mm in all three TKA systems. Surgeons should recognize that distal femoral cutting errors have a significant effect on the flexion-extension gap difference in TKA and pay particular attention to the alignment of the distal cutting surface.