Relationship Between Preoperative Extrusion of the Medial Meniscus and Surgical Outcomes After Partial Meniscectomy.

BACKGROUND: No previous study has examined arthritic change after meniscectomy with regard to extrusion of the medial meniscus.

PURPOSE: (1) To determine the factors related to preoperative meniscal extrusion; (2) to investigate the relationship between medial meniscal extrusion and postoperative outcomes of partial meniscectomy, and to identify a cutoff point of meniscal extrusion that contributes to arthritic change after partial meniscectomy in nonosteoarthritic knees.

STUDY DESIGN: Cohort study; Level of evidence, 3.

METHODS: A total of 208 patients who underwent partial meniscectomy of the medial meniscus between January 2000 and September 2006 were retrospectively reviewed. The extent of extrusion and severity of degeneration of the medial meniscus as shown on preoperative MRI were evaluated. The minimum follow-up duration was 7 years. Clinical function was assessed with the Lysholm knee scoring scale, the International Knee Documentation Committee (IKDC) subjective knee evaluation form, and the Tapper and Hoover grading system. Radiological evaluation was conducted by use of the IKDC radiographic assessment scale. Regression analysis was performed to identify factors affecting preoperative extrusion of the medial meniscus and factors influencing follow-up results after partial meniscectomy. Receiver operating characteristic curve was used to identify a cutoff point for the extent of meniscal extrusion that was associated with arthritic change.

RESULTS: The mean ± SD preoperative Lysholm knee score was 65.0 ± 6.3 and the mean IKDC subjective score was 60.1 ± 7.5. The mean follow-up functional scores were 93.2 ± 5.1 ( P < .001) for the Lysholm knee score and 89.0 ± 6.2 for the IKDC subjective score ( P < .001). Preoperative extent of meniscal degeneration ( P < .001) and preoperative pattern of meniscal tear ( P < .001) were related to preoperative meniscal extrusion. Preoperative extrusion of the meniscus showed a tendency to increase as the extent of intrameniscal degeneration increased, and the medial meniscus was extruded more in patients with horizontal, horizontal flap, and complex tears. The preoperative extent of meniscal extrusion had a statistically significant correlation with follow-up Lysholm knee score (coefficient = -0.10, P = .002), IKDC subjective score (coefficient = -0.09, P = .007), Tapper and Hoover grade (odds ratio = 1.05, P < .001), and IKDC radiographic grade (odds ratio = 1.13, P < .001) at the mean follow-up period of 88.6 months. The cutoff point for the relative value of preoperative meniscal extrusion associated with arthritic change was 34.6% (sensitivity = 69.3%; specificity = 82.7%; accuracy = 77.9%).

CONCLUSION: The preoperative extent of intrameniscal degeneration and the preoperative patterns of meniscal tear including horizontal, horizontal flap, and complex tears were associated with preoperative extrusion of the medial meniscus. The preoperative extrusion of the medial meniscus was negatively correlated with outcomes of partial meniscectomy. The preoperative extent of meniscal extrusion can be used as a predictive factor for osteoarthritis in partial meniscectomy.