ACL–PCL and intercondylar notch impingement: magnetic resonance imaging of native and double-bundle ACL-reconstructed knees

Abstract

The purpose of this study was to: (1) define the relationship between the ACL and PCL in normal knees; (2) determine whether ACL-PCL impingement occurs in native knees; and (3) determine whether there is a difference in impingement between double-bundle reconstructed and native knees. Eight subjects were identified (age 20-50; 6 females, 2 males). All were at least 1-year status postanatomic double-bundle ACL reconstruction (allograft; AM=8mm; PL=7mm) and had no history of injury or surgery to the contralateral knee. MRIs of both knees were performed with the knee at 0 and 30° of flexion. The images were evaluated by a non-treating surgeon and two musculoskeletal radiologists. Coronal and sagittal angles of AM and PL bundles, Liu's PCL index and the distance between ACL and PCL on modified axial oblique images were recorded. Impingement was graded (1) no contact; (2) contact without deformation; or (3) contact and distortion of PCL contour. Seventy-five percent (6) of the native ACL's showed no contact with the roof of the intercondylar notch or PCL, compared to 25% (2) of the double-bundle reconstructed ACLs. One double-bundle reconstructed ACL showed intercondylar notch roof and ACL-PCL impingement (12.5%). Significant differences were found between the native ACL and the double-bundle reconstructed ACL for the coronal angle of the AM (79° vs. 72°, p=0.002) and PL bundle (75° vs. 58°, p=0.001). No differences in ROM or stability were noted at any follow-up interval between groups based on MRI impingement grade. ACL-PCL contact occurred in 25% of native knees. Contact between the ACL graft and PCL occurred in 75% of double-bundle reconstructed knees. ACL-PCL impingement, both contact and distortion of the PCL, occurred in one knee after double-bundle reconstruction. This study offers perspective on what can be considered normal contact between the ACL and PCL and how impingement after ACL reconstruction can be detected on MRI. Cohort Study, Level III.