Review Question - QID 5535

This patient has a vertical femoral tunnel position with rotatory instability. The most likely cause of his symptoms is a femoral tunnel placement that did not restore the posterolateral bundle.

An anterior cruciate reconstruction (ACL) surgery with vertically placed grafts will result in persistent knee instability. Complaints will be mainly related to activities that require twisting or cutting movements. Physical examination will likely reveal a positive pivot shift exam due to the failure to reconstruct the posterolateral bundle of the ACL. Current standards for anatomic ACL reconstruction stress the importance of more horizontal graft placement (for example, 10:30 in a right knee vs 1:30 in the left knee). This allows for more rotational stability, while maintaining anterior stability. Improper femoral graft placement is one of the most common reasons for ACL revision surgery.

Noyes et al. looked at patients undergoing revision ACL surgery with the use of patellar bone-tendon-bone (BTB) autograft. They showed the rate of graft failure to be three times higher than their reported failure rate after primary ACL reconstructions.

Driscoll et al. performed a biomechanical study comparing 2 femoral tunnel locations in anatomic single-bundle anterior cruciate ligament reconstruction. They found that a femoral tunnel positioned in the anatomic center of the femoral origin of the ACL, as opposed to the anteromedial position, provides the greatest amount of rotatory and anterior stability.

Figure A shows AP and lateral radiographs of the knee. Note there is a autograft ACL reconstruction with vertical placement of the femoral and tibial tunnel.

Incorrect Answers:
Answer 1: Physical examination revealed a negative external rotation dial test which would likely rule out a posterolateral corner injury.
Answer 2: Femoral tunnel placement that did not restore the anteromedial ACL bundle would result in greater anteroposterior instability.
Answer 3: A tibial tunnel that was positioned too anterior would cause the knee to be tight in flexion with impingement in extension.
Answer 5: A tibial tunnel that was positioned too posterior would cause significant knee instability with a grossly positive Lachman and Pivot shift.