MRI studies on the effects of symptomatic discoid lateral meniscus injury on the morphology and signal of the anterior cruciate ligament in adults

Objective To report the morphologic,orientation and signal characteristics of the anterior cruciate ligament(ACL) in adults with symptomatic discoid lateral meniscus(DLM) injury.Methods From May 2009 to May 2012,36 knees(the DLM injury group) in adults with symptomatic DLM injury confirmed by the arthroscopy and Magnetic Resonance Imaging(MRI) examination,and 36 knees(the control group) in adults without DLM injury confirmed by the MRI examination were included in this study.General Electric(GE)Healthcare Centricity Radiology Information System(RIS) / Picture Achiving and Communication System(PACS)was used to measure the length,tibial attachment width and body width of the ACL on coronal and sagittal MR images in both groups,and the data were compared.The following MRI characteristics such as orientation changes,discontinuousness,indistinction,diminution and enlargement of single-bundle or double-bundle ACL were taken as the evaluation criteria for abnormal morphology.The abnormally high signal on T_2WI of the ACL was taken as the evaluation criterion for abnormal signal.And then the incidences of abnormal morphology and abnormal signal of the ACL were calculated in both groups,and the differences were compared between them.Results The body width of the ACL on coronal images in the DLM injuries group(4.89±1.02) mm was significantly smaller than that in the control group(5.77±1.13) mm(P=0.004).The length and tibial attachment width of the ACL on coronal images were(19.33±1.49) mm and(7.11±1.19) mm respectively,and the length,tibial attachment width and body width of the ACL on sagittal images were(33.55±2.76) mm,(15.68±1.40) mm and(9.78±1.07) mm respectively,with no statistically significant differences when compared with those in the control group(P0.05).The incidence of normal orientation and morphology of the ACL in the DLM injury group was 30.6%,which was significantly lower than 77.8%in the control group(P=0.000).The incidences of abnormal orientation and morphology of the ACL on coronal and sagittal images were 52.8%and 41.7%in the DLM injuries group,which were significantly increased when compared with 13.9%and 11.1%in the control group(P0.05).The incidence of abnormal signal of the ACL in the DLM injuries group was 33.3%,which was also higher than 11.1%in the control group(P=0.023).Conclusions Compared with the adults with intact DLM,the adults with symptomatic DLM injuries could have abnormal morphology,abnormal orientation and signal changes of the ACL,which seems to be related to the extrusion of the ACL caused by DLM injuries and displacement.