Background: The results of tibial osteotomy used to treat
osteoarthritis of the medial compartment of the knee deteriorate over time
even when the initial correction is optimal. Studies have shown that tibial
and femoral torsion and the femorotibial index (tibial torsion minus femoral
torsion) contribute, together with coronal malalignment, to the development of
single-compartment knee osteoarthritis. The objective of our study was to
evaluate the impact of femoral and tibial torsion and of coronal realignment
on the long-term clinical and radiographic outcomes of valgus tibial
osteotomy.
Methods: A function score was calculated for sixty-eight patients at
a mean of thirteen years after the osteotomy. Anteroposterior
single-leg-stance radiographs were used to evaluate loss of the femorotibial
joint space. Goniometry was used to measure coronal malalignment
preoperatively, at one year, and at the time of the last follow-up, and
postoperative computed tomography was performed to measure femoral anteversion
and tibial torsion and to calculate the femorotibial index. We looked for
associations linking body mass index, initial loss of joint space, coronal
malalignment, femoral and tibial torsion, the femorotibial index, and
functional outcomes.
Results: Worse outcomes were associated with changes in coronal
alignment (=2°) over time, which were associated with deterioration of
the femorotibial space. Femoral anteversion was significantly greater in
patients in whom valgus increased over time than in those in whom valgus
decreased over time. Stability of coronal alignment seemed to be dependent on
a linear relationship between the femorotibial index and the degree of
postoperative realignment. A body mass index of >25 kg/m2 was
associated with a long-term loss of coronal realignment. Preoperative loss of
the medial femorotibial joint space, coronal alignment at one year, and age
were not associated with secondary malalignment or functional outcomes.
Conclusions: Long-term success of a valgus tibial osteotomy is
related to the stability over time of the postoperative coronal realignment.
Therefore, the results of our study suggest that modifying the realignment
according to the extent of femoral anteversion may improve long-term
outcomes.
Level of Evidence: Prognostic Level II. See Instructions
to Authors for a complete description of levels of evidence.