There have been questions recently concerning the posterolateral (PL) bundle of the ACL. The responses to these questions, including the indications to reconstruct, as well as possible causes for failure, are included here:

We observed some failures of the PL bundle in early cases and have subsequently made adjustments after several observations.

There are 5 important things to consider in the process of deciding whether to reconstruct the PL bundle:

1. Anatomy.
Every ACL surgery, whether single- or double-bundle, should be performed according to the double-bundle concept. In other words, we should aim to re-create the double-bundle anatomy of the ACL regardless of whether two or four drill holes are used. Both the AM and the PL bundle should be placed anatomically within the native footprint. Using the native footprint and anatomical bony landmarks (intercondylar ridge, bifurcate ridge, etc.) for tunnel placement prevents the graft from being placed either “too high” or “too low.”

2. Insertion Site Size.
With a tibial insertion site size of less than 14 mm in the sagittal direction, 2 tunnels may be sufficient to recreate the double-bundle anatomy. In addition, a small femoral insertion site for the PL bundle may be a contraindication to performing a PL bundle reconstruction.

3. Notch Width.
A notch width of less than 12 mm is typically a contraindication to drilling 4 tunnels in a traditional double-bundle reconstruction.

4. Graft Tensioning.
The PL bundle should be tensioned in full extension to allow rotation to occur. If tensioned in flexion, the graft may be susceptible to stretch out, or even tear.

5. Graft Healing.
The AM and PL bundles must heal together so that they can act synergistically, which requires a longer time to healing and a careful rehabilitation process. In Pittsburgh, we instruct our patients to wait 6-9 months for return to sports with autograft and 1-year with allograft. If the patient wants to return at 6 months or earlier, we first order an MRI to assess healing of the graft.

All in all, we should allow the double-bundle concept to guide us when performing anatomic ACL reconstruction. This requires placing the tunnels in an anatomical position, reproducing the native graft tension patterns, individualizing graft selection and allowing time for the graft to heal.

Does an understanding of the anatomical double-bundle concept assist you in successfully reconstructing the PL bundle?