Biomechanical evaluation of six femurgraft-tibia complexes in ACL reconstruction

Abstract

Soft tissue graft-tibial tunnel fixation is considered the weak point in reconstruction of the anterior cruciate ligament (ACL). We hypothesized that the biomechanical properties of fixation devices used in ACL reconstruction can be better evaluated by testing complete constructs (femoral tunnel fixation-graft-tibial tunnel fixation). Porcine knees were reconstructed with bovine digital extensor tendons using 6 different commercially available fixation device combinations, and biomechanically tested with cyclic loads (1000 cycles, 0–150 N, 0.5 Hz) and until failure (crosshead speed, 250 mm/min). The device combinations tested (in groups of 6) were EndoButton CL-BioRCI, Swing Bridge-Evolgate, Rifidfix-Intrafix, Bone Mulch- Washerlock, Transfix-Retroscrew, and Transfix-Deltascrew. Ultimate failure load, stiffness, slippage at cycles 1, 100, 500 and 1000 and mode of failure were evaluated. The statistical differences between pairs of groups were assessed with Student’s unpaired t test. The ultimate failure load of complexes made with the Swing Bridge- Evolgate was significantly higher than any other device (968 N; p<0.05), while that of devices made with Transfix-Retrofix was significantly lower than the others (483 N, p<0.05). The stiffness of Swing Bridge-Evolgate complexes was significantly higher than the others (270 N/mm, p<0.05). Regarding mode of failure, Rigidfix-Intrafix complexes showed a failure of the femoral fixation in all specimens. All failures of the other specimens occurred at the tibial side, except one specimen in the EndoButton CL-BioRCI group. Many commercially available tibial fixation devices showed biomechanically appreciable properties, sometimes better than femoral devices.