Preoperative medial meniscus extrusion on magnetic resonance imaging is associated with a tendency toward varus shifting of open-wedge high tibial osteotomy

Abstract

PurposeTo investigate serial changes in postoperative alignment over 5 years after open-wedge high tibial osteotomy (OWHTO) and to identify risk factors associated with alterations in the postoperative weight-bearing line WBL ratio. MethodsPatients who underwent OWHTO during 2011–2017 were retrospectively reviewed. Inclusion criteria were (1) follow-up duration ≥5 years and (2) serial postoperative long-standing hip-to-ankle radiographs to evaluate alignment alterations. The WBL ratio was measured preoperatively and at 3 months, 6 months, 1 year, and 5 years postoperatively to evaluate serial changes. Alterations in the WBL ratio were analyzed using a linear mixed model, considering potential risk factors including International Cartilage Repair Society (ICRS) grades of each compartment, and medial meniscus extrusion (≥3 mm). Clinical outcomes were assessed using the Knee Society (KS) objective and functional scores, and the correlations between clinical outcomes and alignment alteration were examined. ResultsA total of 78 knees were investigated. During the study period, the overall WBL ratio decreased by 5.5 ± 7.2%, signifying varus shifting, from 58.6 ± 11.5% at 3 months post-surgery to 51.5 ± 12.7% at 5 years post-surgery. Based on univariate regression analyses, ICRS grade of the medial compartment and medial meniscus extrusion were included in a linear mixed model regarding alignment alteration. The model identified medial meniscus extrusion as a significant risk factor after adjusting for time (p <0.001). Medial meniscus extrusion also had a significant interaction with time (p <0.001), indicating greater alignment alteration in cases of medial meniscus extrusion. The extrusion was noted in 68 out of 78 knees. ConclusionIn the midterm following OWHTO, the overall alignment had a tendency toward varus shifting. A linear mixed model found that preoperative medial meniscus extrusion on magnetic resonance imaging is associated with the tendency.