Pull-out strength of four tibial fixation devices used in anterior cruciate ligament reconstruction

  • Chivot Mathieu
  • Harrosh Sylvain
  • Kelberine François
  • Pithioux Martine
  • Argenson Jean-Noël
  • Ollivier Matthieu

  • Fixation
  • Anterior cruciate ligament reconstruction
  • Tibia
  • Biomechanics
  • Pull-out strength


Introduction: In reconstructions of the anterior cruciate ligament (ACL), tibial fixation can be the weak point in the assembly during the early postoperative period. The present study sought to compare pull-out strength between four tibial fixation systems used in ACL reconstruction. Hypothesis: The study hypothesis was that all four devices show ≥ 450 N pull-out strength with comparable biomechanical breakage characteristics. Material and methods: An experimental study used a mechanical model to perform axial traction on a synthetic ligament (polypropylene cord folded in four) implanted in an artificial tibia (Sawbones Proximal Tibia # 1116-2: model: normal anatomy; solid foam; size: medium) using four tibial fixation systems: Ligafix ® interference screw (SBM TM); Bio-Intrafix ® (Mitek TM); Translig ® (SBM TM); RIGIDfix ® (SBM TM). For each system, four models were tested using an Instron 5566 ® traction machine, allowing 100 mm/min stretching up to breakage. Study parameters comprised: pull-out strength, maximal whole assembly slippage, stiffness at breaking point, and type of break. Results: Mean pull-out strength was 450 ± 24 N (range, 421–488 N) for Ligafix ® , 415 ± 60 N (327–454 N) for Bio-Intrafix ® , 539 ± 66 N (449–636 N) for RigidFix and 1067 ± 211 N (736–1301 N) for Translig ® , and was significantly greater for Translig ® than for the other devices (p = 0.02), which did not significantly differ from one another. The expected maximal load of 450 N was reached in 100% of cases with Translig ® and RIGIDfix ® and in 50% of cases with Bio-Intrafix ® and Ligafix ®. There were no significant differences regarding stiffness. Ligafix ® showed significantly less slippage than the others (p = 0.006), with breakage caused by the ligament sliding between bone and implant. Discussion: In this in-vitro study, the Translig ® fixation device showed better pull-out strength than the other three devices tested. Type of study and level of evidence: Comparative laboratory study. Level II.