Review Question - QID 1431

The clinical presentation is consistent with a ACL reconstruction with a malpositioned femoral tunnel at the "12 o'clock" position. ACL reconstruction with 12 o'clock femoral fixation would lead to a vertically placed graft and result in continued instability with cutting activities, and a positive pivot shift exam due to failure to reconstruct the posterolateral bundle of the ACL.

Current standards for anatomic ACL reconstruction stress the importance of more horizontal graft placement (10:30 in a right knee vs 1:30 in the left knee. This attempts to reconstruct both the anteromedial bundle, which provides anterior-posterior stability, and the posterolateral bundle, which provides rotational stability. Improper femoral graft placement is one of the most common reasons for ACL revision surgery.

Scopp et al studied the effect of ACL femoral fixation in the coronal plane for patellar tendon autografts in a biomechanical model. In their study, they review that non-anatomic tunnel positioning of the femoral tunnel accounts for most of all technical failures and continued knee rotational instability. Their results supported that oblique femoral fixation as opposed to vertical femoral fixation of the ACL lead to more normal knee rotational stability.

Incorrect Answers:
Answers 1 and 3: A positive Lachman or anterior drawer would not be present with a vertically placed femoral tunnel since the graft would still provide resistance to anterior-posterior translation .
Answer 2: A positive external rotation dial test at 30 degrees would be present with a posterolateral corner injury.
Answer 4: A positive posterior drawer sign would be present with a PCL injury.