Review Question - QID 214085

The posterolateral (PL) bundle of the anterior cruciate ligament (ACL) is primarily responsible for rotational stability. The footprints of this bundle is denoted by A + C in Figure A (answer choice 1).

The ACL is organized into two primary bundles, the anteromedial (AM) bundle (AM) and the PL, which are reflective of their tibial insertions. On the femur, the AM bundle originates more proximally than the PL bundle. While the AM bundle is the main restraint to anterior tibial translation, the PL bundle provides rotational stability, especially during knee extension when it is most taut, and is examined by the pivot shift test. A positive pivot shift test post-operatively indicates persistent rotatory instability and has been associated with functional instability with cutting activities.

Dhawan et al. reviewed anatomic tunnel placement in ACL reconstruction. They reported that native ACL kinematics is optimized with independent femoral drilling techniques that recreate a central footprint single-bundle ACL reconstruction or double-bundle reconstruction, both of which have been supported in comparison to a transtibial drilling technique. They concluded that the complex nature of the native ACL has made it difficult for any available surgical technique to replicate the nuances of complex fiber orientation, rotation, and cross-sectional dimensions.

Kraeutler et al. reviewed the anatomy, biomechanics, and surgical implications of the native and reconstructed ACL. They reported that technical errors (i.e. nonanatomic tunnel placement) are among the most common causes of graft failure after ACL reconstruction, and that no clinical superiority has been demonstrated for double-bundle versus single-bundle ACL reconstruction. They concluded that regardless of the technique utilized, surgeons should avoid placement of a vertical or low femoral tunnel, as this results in abnormal knee kinematics.

Kopf et al. reviewed the femoral origin and tibial insertion morphology of the ACL. They reported that when using the anatomic double bundle structure of the ACL, the entirety of both tibial insertion and femoral origin of both AM and PL bundles may be restored. They concluded that given the large variability in the size and the anatomy of the femoral origin and tibial ACL insertions, it is of paramount importance to understand the individual variations in size and shape of the ACL bundles footprints.

Figure A depicts the femoral and tibial footprints of the anterior cruciate ligament bundles with A, B, C, and D representing the femoral footprint of the PL, femoral footprint of the AM, tibial footprint of the PL, and tibial footprint of the AM bundles, respectively.

Incorrect Answers:
Answer 2 and 3: These are not footprints of the AM and PL bundles of the ACL, respectively.
Answer 4: This represents the AM bundle, which primarily restricts anterior tibial translation.
Answer 5: This is incorrect. The PL bundle provides rotational stability.