The aim of this study was to investigate radiographic factors relevant to predict surgical outcomes of arthroscopic partial meniscectomy (APM) in elderly patients with mild osteoarthritis (Kellgren-Lawrence grades 1 and 2). Data of 172 consecutive patients aged >70 years who underwent arthroscopic meniscal surgery were reviewed retrospectively. The patients who met the inclusion criteria were classified into two groups based on the minimal clinically important difference value of the Lysholm knee scoring scale comparing the score of the last visit with that of the preoperative period: group 1 (with clinically significant improvement) and group 2 (without clinically important change). Radiographic factors assessed on X-ray and magnetic resonance images were evaluated using bivariate and logistic regression analyses. A total of 73 patients were included in this study. Bivariate analysis revealed that the extent of meniscus extrusion (p = 0.031), meniscus extrusion ratio (p = 0.001), and grade of meniscus degeneration (p = 0.019) were significantly different between the groups. Multivariate logistic regression analysis showed that the meniscus extrusion ratio was the most important independent predictive factor for surgical outcomes with clinically important changes (coefficient = 0.159, p = 0.009). On receiver operating characteristic (ROC) curve analysis, the cutoff point of the meniscus extrusion ratio discriminating the two groups was 34.2% (sensitivity: 79.3%; specificity: 68.6%; accuracy: 72.6%). Meniscus extrusion ratio was the most relevant predictive factor for discriminating patients with clinically important change. Meniscus extrusion ratio, with the cutoff point of 34.2%, could serve as a guide to determine whether to perform APM in elderly patients with mild osteoarthritis. This is a Level IV, therapeutic case series study.
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