American Journal of Sports Medicine

Miura K, Brinkley R, Noorani S, Fu YC, Woo SL-Y


Background: In double-bundle ACL reconstruction (DB-ACLR), overloading either one of the two grafts should be avoided to decrease the risk of graft failure.

Hypothesis: Overloading of the posterolateral (PL) graft may occur when it is fixed at 30 degrees of knee flexion because the PL bundle is elongated as the knee approaches extension.

Study Design: Controlled laboratory study.

Methods: Ten human cadaveric knees were tested at 1) intact, 2) ACL-deficient, 3) DB-ACLR with the anteromedial (AM) and PL grafts fixed at 60 degrees and full extension, respectively (Fixation 60/FE) and 4) DB-ACLR with both grafts fixed at 30 degrees simultaneously (Fixation 30/30). By means of a robotic/UFS testing system, two external loading conditions simulating clinical examinations: 1) 134 N anterior tibial load and 2) combined rotatory loads of 10 N-m valgus and 5 N-m internal tibial torques were used. Data on resulting knee kinematics and in situ forces in the two bundles of the intact ACL and the respective grafts were obtained.

Results: In response to 134N anterior tibial load, knee kinematics and overall in-situ force in the grafts were similar to the intact knee for both fixation protocols. However, the force in the AM graft for Fixation 60/FE was 34% higher, while the PL graft for Fixation 30/30 was 46% higher, compared to the intact AM and PL bundles, respectively. In response to combined rotatory loads, the PL graft for Fixation 30/30 carried 67% higher load than the intact PL bundle.

Conclusion: Fixation 30/30 caused overloading of the PL graft, while Fixation 60/FE overloaded the AM graft.

Clinical Relevance: In DB-ACLR, even though overall forces in the graft are the same as intact ACL, the force distributions may not be the same as the intact bundles and overloading of one of the two grafts may occur.