Protruding anterior medial meniscus and posterior tibial translation as secondary signs of complete and partial posterior cruciate ligament tear.

OBJECTIVE:To evaluate whether measurement of protruding anterior meniscus in the medial compartment (PAMM) and posterior tibial translation (PTT) can be used as a secondary sign of posterior cruciate ligament (PCL) tear for differential diagnosis of partial or complete tear. METHODS:21 cases with complete PCL tear, 35 cases with partial PCL tear, and 55 normal cases were reviewed in this retrospective study. PTT and PAMM were measured from the MR images associated with each case. Non-parametric data were evaluated using the Kruskal-Wallis test and the Mann-Whitney U-test with Bonferroni correction to compare differences among the three groups: complete tear, partial tear, and controls. RESULTS:There were significant differences in the median values of PAMM among the three groups, and with PAMM increasing as the grade of PCL injury increased. However, there were no significant differences in median PTT among the three groups. Median PAMM in the partial and complete tear groups was significantly higher than in subjects without PCL rupture (adjusted p-value <0.05). Although median PAMM in subjects in the complete tear group tended to be higher than in those with a partial tear, this difference was not statistically significant (adjusted p-values ≥0.418). CONCLUSION:PAMM is more useful finding than PTT and can predict PCL tear with or without posterior instability. However, PAMM cannot differentiate partial tear and complete tear of the PCL. ADVANCES IN KNOWLEDGE:PAMM is more useful finding than PTT and can predict PCL tear with or without posterior instability. However, PAMM cannot differentiate partial tear and complete tear of the PCL.