Arthroscopic Analysis of Lateral Meniscal Variants

ABSTRACT

PURPOSE: We classified lateral meniscal variants according to types and tear pattern, and compared MR images with arthroscopic findings. MATERIALS AND METHODS: We reviewed 164 consecutive cases (158 patients) of arthroscopic examination for lateral meniscal variants during last ten years. We classified lateral meniscal variants into four types of arthroscopic appearance by modified Watanabe 's classification, and into six tear patterns by modifying O 'Connor 's classification. RESULTS: Regarding four types, 131 cases were complete; 25, incomplete; 4, Wrisberg, and 4, ringshaped. Six tear patterns were as follows: 33 simple horizontal, 21 complicated horizontal, 37 longitudinal, 27 central, 14 complex, and 12 radial. Among 31 cases with central tear or ring-shaped meniscus, we reviewed 25 MR images. Fifteen (60%) MRI 's were interpreted as displaced meniscal tear(bucket handle tear), 7 (28%) as discoid meniscal tear, and other 3 (12%) as simple tear: misinterpretation rate was 72%. Twelve patients (13 cases, 7.9%) had osteochondritis dissecans of lateral femoral condyle: nine patients (10 cases) of them had central tear, two patients (2 cases) had simple horizontal tear, and one patient (1 case) had ring-shaped meniscus. CONCLUSION: MR findings of ring-shaped meniscus or central tear should be differentiated from displaced meniscal tear(bucket-handle tear) considering history of trauma.