Anatomical studies show that the native ACL consists of two distinct functional bundles, termed the anteromedial (AM) and
posterolateral (PL) bundles. The utility of using routine magnetic resonance imaging (MRI) to distinguish the individual bundles
of the ACL has not been evaluated. The purpose of this study was to evaluate the intra- and inter-observer agreement for assessment
of the AM and PL bundles using MRI in the axial, coronal, and sagittal viewing planes. We identified a series of patients
seen in the senior author’s clinic during a 16-month period. Images were independently evaluated in blinded fashion at two
separate time points by a musculoskeletal radiologist and two orthopaedic residents. The AM bundle was detected in most planes
of view with high frequency and reliability, while detection of the PL bundle was less frequent and had a lower associated
reliability. Our results indicate that it is difficult to reliably detect both the AM and PL bundles using a low-field strength
magnet with standard planes of view. It has been demonstrated that the ACL may be imaged effectively in planes that are based
on the natural course of the ligament, and it is likely that this will also facilitate visualization of the individual AM
and PL bundles. The use of additional oblique planes of view offers a potential approach for improved evaluation of the ACL,
even with low field strength magnets. Future work in this area may assist in the pre-operative assessment of isolated AM or
PL bundle injuries, facilitating a more anatomic approach to ACL reconstruction.
Keywords Anterior cruciate ligament - Magnetic resonance imaging - Double-bundle - Pre-operative evaluation - Anatomic reconstruction