Abrasion and biomechanics of reconstructed posterior cruciate ligament under different clinical operations

The killer turn and critical corner effects in posterior cruciate ligament (PCL) reconstruction techniques significantly influence graft abrasion and biomechanics. However, the mechanisms of graft failure under physiological loading, considering both killer turn and critical corner effects, have not been thoroughly investigated. 24 porcine knee specimens and 32 grafts were randomly assigned to three different PCL reconstruction techniques. The reconstructed knees underwent 300,000 cycles of gait loading using a knee simulator, followed by load-to-failure tests. Finite element (FE) models of PCL-reconstructed knees were developed to further evaluate the killer turn and critical corner effects on graft biomechanics, focusing on graft-to-bone tunnel contact. Reconstructed grafts using the transtibial technique with anatomic tibial tunnel (ATT: 530.5 N ± 176.3 N) and transtibial technique with a lower tibial tunnel (LTT: 564.3 N ± 249.2 N) demonstrate significantly lower maximum load compared to the tibial inlay technique (TI: 920.7 N ± 201.7 N) (P < 0.05) and the non-operated tissues (1077.8 N ± 127.6 N) (P < 0.001). No significant differences were observed between ATT and LTT grafts (P = 1.000) or between TI grafts and non-operated ones (P = 0.695). FE simulations suggest that the reduced strength of ATT grafts may result from increased contact pressure at the killer turn, while the reduced strength of LTT grafts may be attributed to the heightened windshield wiper effect at the critical corner, induced by the longer graft path. Graft failures in ATT commonly occurred at the killer turn, while LTT and TI grafts failed at the critical corner. The TI technique demonstrates superior abrasion resistance compared to both ATT and LTT techniques.