Measuring the anterior cruciate ligament's footprints by three-dimensional magnetic resonance imaging

The purpose of this study was to compare 3D MR imaging and open cadaveric measurements of the ACL's footprints to see whether 3D MR imaging measurements are accurate enough to be used for preoperative templating in anatomic ACL reconstruction.

Eight formalin-injected cadaveric knees were scanned by rapid acquisition isotropic 3D MR imaging. The femoral and tibial footprints were measured on MR imaging and compared with cadaveric dissection. Bland-Altman plots were used to assess the level of agreement.

The AM and PL bundles were clearly appreciated in each specimen by 3D MR imaging and cadaveric dissection. The average paired difference in the femoral and tibial footprint measurements was 2, 1, 2, and 2 mm for the femoral footprint length, femoral footprint width, tibial footprint length, and tibial footprint width, respectively. The individual paired measurements were all within the mean difference ± two standard deviations of the difference in the Bland-Altman plot showing strong agreement.

Measuring the ACL's footprint by 3D MR imaging or open cadaveric dissection has strong agreement and can be used interchangeably. 3D MR imaging has the potential to allow surgeons to: (1) tailor ACL reconstruction technique or graft choice based on ACL footprint size, (2) plan for selective bundle ACL reconstruction for partial tears, and (3) preoperatively template tunnel position according to the patient's individual anatomy.