Review Question - QID 218032

Excessive posterior tibial slope (>12°) increases the risk of failure in the setting of revision anterior cruciate ligament (ACL) reconstruction and should be addressed at the time of revision surgery.

ACL rupture is a common occurrence, with the primary treatment being ACL reconstruction. As the number of these procedures increase, ACL re-rupture has become increasingly recognized and ACL revisions have increased in number. In the setting of primary ACL reconstruction failure, surgeons should scrutinize their surgical technique and graft selection, but should also be aware of other anatomic considerations that may increase the risk for re-rupture, principally malalignment. Malalignment can occur in the coronal or sagittal planes, with sagittal plane abnormalities mainly due to excessive posterior tibial slope (>12°). If identified, this abnormality should be addressed at the time of revision ACL reconstruction, with a high tibial osteotomy (HTO). HTOs can be performed as opening and closing wedge osteotomies and can have some degree of biplanar correction depending on the amount of concomitant coronal plane malalignment. It is thought that the lateral closing wedge HTO is more effective at decreasing the tibial slope than the opening wedge HTO. In the setting of pure sagittal plane malalignment, a slope reducing anterior closing wedge HTO may also be utilized.

Cantivalli et al. evaluated a combined HTO and ACL reconstruction in patients with medial compartment arthritis, varus malalignment, and anterior instability. They also highlighted its usefulness in patients with excessive tibial slope > 12°. They delved into further detail regarding the specific types of osteotomies that would be performed for specific indications such as varus malalignment, excessive tibial slope, etc.

Loia et al. reviewed the use of HTO in varus knees and discussed the indications and limits of the procedure. They specifically reviewed the opening wedge, valgus producing HTO and noted that it can be used to address straightforward varus malalignment as well as 'double' and 'triple' varus malalignment. In the setting of ACL injury (double varus), they recommend concomitant HTO with ACL reconstruction, but do note that posterior slope is affected by the positioning of the plate and recommend avoiding placing the plate too anterior.

Incorrect Answers:
Answer 1: Tunnel widening is a risk factor for ACL re-rupture after revision ACL as it decreases the contact of the graft to the tunnel and negatively impacts healing. However, most agree that tunnel widening >15 mm leads to the greatest risk increase.
Answer 3: Prior posterolateral corner reconstruction would not necessarily increase his risk for failure, as there is no mention of coronal limb malalignment in this question.
Answer 4: Use of autograft tissue for revision ACL reconstruction is advised, as re-rupture rates are increased >2x with the use of allograft.
Answer 5: Transtibial drilling technique can lead to "non-anatomic," tunnel placement, but if performed correctly, does not have significantly higher rates of failure.