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Preoperative Medial Meniscal Extrusion Is Associated With Patient-Reported Outcomes After Medial Opening Wedge High Tibial Osteotomy

Background: Although the medial compartment continues to sustain some loading after medial opening wedge high tibial osteotomy (MOWHTO) in varus-deformed knees, no studies have examined the relationship between medial meniscal extrusion (MME) and patient-reported outcome measures after MOWHTO. Purpose: To examine whether compartmental baseline MME was associated with patient-reported outcome measures after MOWHTO. Study Design: Cohort study; Level of evidence, 3. Methods: This retrospective study was composed of 149 MOWHTOs in 147 patients with clinical and radiological assessments. Patients were grouped according to severity of MME in the medial compartment at the time of surgery. MME was categorized into 4 groups according to MOAKS (MRI [magnetic resonance imaging] Osteoarthritis Knee Score) criteria and relative value of MME. We compared preoperative characteristics, including Kellgren-Lawrence (KL) grading scale, meniscal tear pattern, and postoperative Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) subscores. Associations between extent of MME and WOMAC subscores at postoperative 1 and 2 years were assessed with generalized linear models. Results: Pattern of meniscal tear (P < .05) and KL grade (P < .05) were associated with MME. Patients with KL grades 3 and 4 at the time of surgery had significantly greater MME than those with KL grade 2 (P < .05). When patients were divided into 4 groups according to MOAKS criteria at the time of surgery, there were significant differences in WOMAC pain scores among groups at 1 and 2 years after the operation (all P < .05). The WOMAC function score also differed among groups at postoperative 1 year (P < .05) but not postoperative 2 years (P > .05). When patients were divided into 4 groups according to relative MME at the time surgery, the WOMAC pain score differed significantly among groups at postoperative 1 and 2 years (all P < .05). Analysis of WOMAC pain score as the dependent variable in multivariate analyses revealed that severity of absolute and relative MME and KL grade were independent predictors of worse WOMAC pain score at postoperative 1 and 2 years (all P < .05). Conclusion: Greater preoperative MME at the time of surgery was associated with inferior patient-reported outcomes, especially pain, in patients with MOWHTO at 1 and 2 years after surgery.