Impingement pressure in the anatomical and nonanatomical anterior cruciate ligament reconstruction: a cadaver study.

Background: Although the literature has extensively discussed impingement after anterior cruciate ligament (ACL) reconstruction, the definition of impingement is vague, and impingement pressure has not been well investigated as a function of tunnel position.

Purpose: To determine the amount of impingement pressure between the ACL and posterior cruciate ligament (PCL) and between the ACL and notch roof in the native ACL, the single-bundle ACL reconstruction with different tunnel placements, and the anatomical double-bundle ACL reconstruction.

Study Design: Controlled laboratory study.

Methods: Fifteen fresh-frozen nonpaired human cadaver knees were used. In each knee, different femoral and tibial tunnels were created, which allowed different graft placements. A single graft was placed in 3 positions: tibial anteromedial (AM) to femoral AM (anatomical), tibial posterolateral (PL) to femoral high AM (nonanatomical/mismatch), and tibial AM to femoral high AM. Double grafts were placed in an anatomical fashion (AM to AM and PL to PL). In each case, pressure-measuring films were inserted between the ACL and roof, the ACL and PCL, and the AM and PL bundles (for double-bundle group only). Knees were then moved with 40 N of force and from full flexion to full extension, and the pressure pattern on the film was analyzed.

Results: Compared with other groups, only the AM-high AM group showed significantly higher roof impingement pressure (P < .05). There was no significant difference in PCL impingement pressure between the intact ACL group and any of the reconstructed groups. No impingement pressure was observed between the grafts in the anatomical double-bundle ACL reconstruction.

Conclusion: This study evaluated the effect of different tunnel placements on the impingement pressure after ACL reconstruction. Anatomical single- or double-bundle ACL reconstruction and nonanatomical tibial PL-femoral high AM ACL reconstruction do not cause roof, PCL, and interbundle impingement.

Clinical Relevance: Surgeons can perform the anatomical double-bundle ACL, anatomical single-bundle, and nonanatomical tibial PL-femoral high AM reconstructions as impingement-free reconstructions.