Can kinematic tibial templates assist the surgeon locating the flexion and extension plane of the knee?

PURPOSE

We performed virtual feasibility and in-vivo validation studies to test whether the use of a kinematic tibial template (KTT) assists the surgeon in accurately locating the orientation of the F-E of the knee with low bias and high precision.

METHODS

With use of 166 3-dimensional bone models of normal knees, we designed seven KTTs that located the orientation of the F-E plane of the knee when best-fit within the cortical edge of the tibial resection. The virtual feasibility study asked 11 evaluators with different levels of surgical experience to use software and select, orient, and best-fit the KTT within the tibial resection of each bone model. The in-vivo validation study analyzed tibial component rotation on postoperative CT scans of 118 consecutive patients after one surgeon set the I-E rotation of the tibial component with a KTT when performing kinematically-aligned TKA. Bias and precision were computed as the mean and standard deviation of the differences between the A-P axis of the KTT and the F-E plane of the knee.

RESULTS

For the virtual feasibility study, the bias was 0.7° external and the precision was ±4.6° for 1826 KTT fittings, which were not affected by the level of surgical experience. For the in-vivo validation study, the bias was 0.1° external and the precision was ±3.9°.

CONCLUSIONS

The virtual feasibility and in-vivo validation studies suggest a KTT can assist the surgeon in accurately setting the I-E rotation of the tibial component parallel to the F-E plane of the knee when performing kinematically-aligned TKA.