Lateral meniscocapsular separation in patients with tibial plateau fractures: detection with magnetic resonance imaging.

OBJECTIVE: This study aimed to retrospectively evaluate magnetic resonance imaging findings for the detection of lateral meniscocapsular separation (LMCS) in patients with tibial plateau fractures. We hypothesize that patients with LMCS have greater perimeniscal abnormal signal or greater distance between the lateral meniscus (LM) and the lateral collateral ligament (LCL) than patients without LMCS.

METHODS: The study group included 16 patients with LMCS and 11 patients with normal LMCS who underwent surgery due to tibial plateau fracture. Magnetic resonance images were assessed for the width of perimeniscal abnormal signals on 3 orthogonal planes. The distance between LM and LCL was measured on coronal images. Nonparametric tests were performed.

RESULTS: The thickness of perimeniscal abnormal signals was increased in the patient group than in control group (median, 10.00 [interquartile range, 9.00-12.70] mm vs 3.39 [2.45-3.67] mm at axial images [P < 0.001]; 8.60 [3.75-11.26] mm vs 2.73 [1.64-4.38] mm at coronal images [P = 0.015]; 13.57 [9.50-15.04] mm vs 4.65 [0-5.89] mm at sagittal images [P = 0.002], respectively). Sixteen patients in the patient group had involvement around the whole LM, whereas none of the patients in the control group had involvement around the whole LM (P < 0.001). The distance between LM and LCL was increased in the patient group than in the control group (9.00 [7.47-10.75] mm vs 5.11 [4.38-7.07] mm [P = 0.002], respectively). The cutoff value of 7 mm thickness of abnormal signal and distance between LM and LCL showed an accuracy of 96% (26/27 patients) and 85% (23/27 patients), respectively.

CONCLUSIONS: Patients with perimeniscal signal greater than 7 mm or distance between LM and LCL greater than 7 mm have high likelihood of LMCS.