Introduction: Extracortical fixation techniques in anterior cruciate ligament reconstruction bear the risk of tunnel enlargement, while close-to-aperture fixations often show lower failure loads. The purpose for this study was to investigate the biomechanical benefits of a novel implant-free combination of an extra-cortical and close-to-aperture fixation.
Materials and methods: Quadrupled human cadaveric semitendinosus tendons were fixed to 30 porcine tibiae with either a cannulated interference screw (I), an implant-free post-fixation (S), or a novel pull-press fixation (P). Specimens were cyclically loaded 20 times between 20 and 60 N followed by 500 cycles with 60-200 N, followed by a load-to-failure test with 1 mm/s.
Results: The mean elongation of the tendons in the P-group during the 500 cycles between 60 and 200 N was significantly lower (5.69 ± 2.16 mm) compared to 9.20 ± 3.21 mm in S-group and 9.37 ± 3.1 mm in the I-group (p < 0.05). The mean maximum load-to-failure was significantly higher in the P-group (728.2 ± 76.4 N) compared to 476.4 ± 68.8 N in the S-group and 625.9 ± 82.5 N in the I-group (p < 0.05). Stiffness of the constructs in the P-group was significantly higher (121.7 ± 44.9 N/mm) compared to 46.2 ± 17.7 N/mm in the S- and 72.8 ± 29.8 N/mm in the I-group (p < 0.03).
Conclusions: This study indicates superior biomechanical properties of a novel implant-free tibial pull-press fixation to conventional implant-free and close-to-aperture interference screw fixations in terms of cyclic elongation and maximum load-to-failure.
Level of evidence: Not applicable, basic science study.
Keywords: ACL reconstruction; Hamstring tendons; Implant-free reconstruction; Pull-press fixation.