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.
The study hypothesis was that all four devices show ≥450N 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™); Bio-Intrafix® (Mitek™); Translig® (SBM™); RIGIDfix® (SBM™). For each system, four models were tested using an Instron 5566® traction machine, allowing 100mm/min stretching up to breakage. Study parameters comprised: pull-out strength, maximal whole assembly slippage, stiffness at breaking point, and type of break.
Mean pull-out strength was 450±24N (range, 421–488N) for Ligafix®, 415±60N (327–454N) for Bio-Intrafix®, 539±66N (449–636N) for RigidFix and 1067±211N (736–1301N) 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 450N 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.
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.Le texte complet de cet article est disponible en PDF.
Keywords : Biomechanics, Fixation, Tibia, Anterior cruciate ligament reconstruction, Pull-out strength