Purpose: The revision of any total knee replacement is carried out in a significant
number of cases, due to the excessive internal rotation of the tibial component. The
goal was to develop a personalized method, using only the geometric parameters of
the tibia, without the femoral guidelines, to calculate the postoperative rotational
position of tibial component malrotation within a tolerable error threshold in every
case.
Methods: Preoperative CT scans of eighty-five osteoarthritic knees were examined by
three independent medical doctors twice over 7 weeks. The geometric centre of the
tibia was produced by the ellipse annotation drawn 8 mm below the tibial plateau,
the sagittal and frontal axes of the ellipse were transposed to the slice of the tibial
tuberosity. With the usage of several guide lines, a right triangle was drawn within
which the personalized Berger angle was calculated.
Results: A very good intra-observer (0.89-0.925) and inter-observer (0.874) intra-class
correlation coefficient (ICC) was achieved. Even if the average of the personalized
Berger values were similar to the original 18° (18.32° in our case), only 70.6% of
the patients are between the clinically tolerable thresholds (12.2° and 23.8°).
Conclusion: The method, measured on the preoperative CT scans, is capable of calculating
the required correction during the planning of revision arthroplasties which are necessary
due to the tibial component malrotation. The personalized Berger angle isn’t altered
during arthroplasty, this way it determines which one of the anterior reference points
of the tibia (medial 1/3 or the tip of the tibial tuberosity, medial border or 1/6
or 1/3 or the centre of the patellar tendon) can be used during the positioning of
the tibial component.
Level of evidence: Level II, Diagnostic Study (Methodological Study).
Keywords: Tibial component malrotation, Revision TKR, Revision planning, Revised Berger
method, Personalized Berger method
