An evaluation of reconstructed ACL impingement on PCL using MRI

Using magnetic resonance imaging (MRI), we evaluated 42 reconstructed anterior cruciate ligaments (ACLs) for impingement on corresponding posterior cruciate ligaments (PCLs) in the knee-extended position.Thirty-one single-bundle ACL reconstructions and 11 double-bundle ACL reconstructions were performed. MR examinations were performed at 3 and 12 months after arthroscopic ACL reconstructions.Using oblique axial MRIs of reconstructed ACLs, we evaluated the shape of the PCL and divided them into two groups: an impingement-positive group and an impingement-negative group. Using sagittal images, we measured the PCL index (Liu's method) and examined the correlation between the degree of impingement and the index.At 3 months after surgery, 14 of 31 single-bundle ACL reconstructions and 5 of 11 double-bundle ACL reconstructions were regarded as positive impingement on PCLs. At 12 months after surgery, 17 of 31 single-bundle ACL reconstructions and 5 of 11 double-bundle ACL reconstructions were regarded as positive impingement on PCLs. At 3 months in single-bundle reconstructions and at 3 and 12 months in all reconstructions, the PCL index of the impingement-positive group was significantly lower than that of the negative group.This study indicated that reconstructed ACLs in the impingement-positive group pressed the PCLs more posteriorly than did the impingement-negative group.