Abstract:Objective〓The primary objective of this study is to delineate the morphological disparities between complete lateral discoid meniscus (CDLM) and the standard lateral meniscus on sagittal magnetic resonance imaging (MRI) views.Additionally,the study aims to elucidate the underlying mechanisms leading to CDLM rupture by comparing anatomical features among ruptured,unruptured CDLM,and normal lateral meniscus cases.Methods〓A retrospective analysis was conducted on the records of patients who underwent knee arthroscopic meniscus surgery at The First Affiliated Hospital of University of South China from January 2017 to December 2020.A total of 99 knees from 95 patients (36 males with 38 knees and 59 females with 61 knees) fulfilling the inclusion criteria were included in the study.The patient age range was 18~55 years,with a mean age of (45.63±6.81)years.These knees were classified into three groups:30 knees (from 29 patients) with ruptured CDLM (Group A),16 knees (from 16 patients) with unruptured CDLM (Group B),and 53 knees (from 51 patients) with normal lateral meniscus (Group C).MRI scans were utilized to measure two key parameters:The anteroposterior diameter (APD) of the meniscus and the proximal anteroposterior tibia diameter (TD).The intraclass correlation coefficient (ICC) was employed to assess inter-observer reliability,and the average of two measurements was recorded for analysis.Statistical comparisons were performed among the three groups for APD,TD,and the ratio of APD to TD (APD/TD),with the intention of identifying significant differences that might elucidate the mechanisms behind CDLM rupture.Results〓The inter-observer reliability for measuring the APD and proximal anteroposterior TD was high,with ICC values of 0.782 and 0.972 respectively.Comparing the three groups,there was no statistically significant difference in APD between ruptured (Group A) and unruptured CDLM (Group B) (P>0.05).However,both Group A and Group B had significantly smaller APDs compared to the normal lateral meniscus group (Group C) (P<0.05).Similarly,TD did not differ significantly between Group A and Group B (P>0.05),but Group A had a lower TD than Group C (P<0.05).Notably,the APD/TD ratio was significantly higher in Group A compared to Group B (P<0.05),indicating an increase in relative APD post-rupture,while Group B had a significantly lower APD/TD ratio compared to Group C (P<0.05).Conclusion〓The study demonstrates that complete lateral discoid meniscus (CDLM) exhibits smaller anteroposterior (APD) and proximal tibial (TD) dimensions compared to normal lateral meniscus.Furthermore,CDLM rupture is associated with an increase in the relative APD (APD/TD ratio),suggesting morphological alterations that may contribute to its susceptibility to rupture.
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