The medial open-wegde osteotomy generates progressive intrameniscal integrity changes in the lateral knee compartment: a prospective MR-assessment after valgic osteotomy in the varus gonarthritic knee

Purpose Meniscal changes in the lateral knee compartment after medial-opening high tibial osteotomy (HTO) with valgic overcorrection have not been investigated clinically with magnetic resonance imaging (MRI). The hypothesis of this study was that HTO with valgic overcorrection affects the lateral compartment due to the change in the bearing axis and the shift in the pressure load from the medial to the lateral compartment. This should lead to an accelerated degeneration of the lateral compartment. Methods Twenty-four patients (mean age, 45.7 ± 7.6 years) were prospectively and longitudinally monitored with MRI after medial-opening high tibial osteotomy. The degeneration of the meniscus was assessed at the anterior horn, pars intermedia, and posterior horn using the Stoller classification. The morphological changes were also assessed at the anterior horn, pars intermedia, and posterior horn using the relative vertical and transverse diameters of the examined part of the meniscus, according to the ratio maximal meniscal diameter/maximal tibial width. These parameters were analyzed preoperatively and at follow-up (mean 5.3 ± 1.5 years after surgery). Results During the follow-up period, there were no significant morphological changes in either the anterior horn, pars intermedia, or posterior horn. Nor were there any correlations between the morphological parameters, bodyweight, and the follow-up period. Despite these findings, an MRI evaluation showed progressive degeneration in every part of the meniscus according to the Stoller classification, and this was significant at the anterior horn ( p < 0.01), pars intermedia ( p = 0.021), and posterior horn ( p < 0.01). Conclusion High tibial osteotomy did not lead to morphological changes in the external meniscus over a follow-up period of 5.3 ± 1.5 years. However, progressive degeneration of the meniscus was observed in the imaging data. Further research is required to confirm the observed degeneration and to evaluate the consequences of the observed degeneration.