Biomechanical evaluation of three different fixation methods for treating displaced tibial avulsion fracture of the posterior cruciate ligament: a finite element analysis.

Abstract

Displaced tibial avulsion fractures of the posterior cruciate ligament (PCL) significantly compromise knee stability; however, existing clinical data regarding treatment and prognosis are limited. There exists a paucity of biomechanical research concerning various surgical methods for tibial avulsion fractures of the PCL, and optimal management remains controversial. Therefore, the objective of this study was to investigate the biomechanical stability of displaced tibial avulsion fracture using suture bridge fixation, screw fixation, and TightRope fixation at varying flexion angles. Finite element analysis was employed to evaluate the biomechanical stability of three surgical approaches. A type III PCL tibial avulsion fracture model was established, followed by the assembly of models for suture bridge fixation, screw fixation, and TightRope fixation. Varying angles of knee flexion were simulated, and the stress distribution on the implant, the PCL, and the bone fragment, as well as the displacement of the fragment, were assessed. The findings indicated that the peak stress distribution on the implant for screw fixation was the highest, occurring near the midsection and tail of the implant, followed by TightRope fixation, which occurred near both ends of the fixation. In contrast, suture bridge fixation exhibited the lowest stress, occurring near the junction between the anchor and the suture. The stress distribution of the PCL in screw and TightRope fixation was slightly higher than that observed with suture bridge fixation. This stress was primarily concentrated in the upper portion and gradually increased, reaching a maximum at 120° The peak von Mises stress (VMS) on the bone fragment in the suture bridge fixation group was the highest, followed by the screw fixation group, and subsequently the TightRope fixation group. Furthermore, the displacement of the bone fragment was comparable among the three fixation methods across various angles of knee flexion. The biomechanical properties of suture bridge fixation are superior to those of both TightRope and screw fixation. They are all alternative surgical treatment methods for displaced tibial avulsion fractures of the PCL. The ideal surgical approach should be selected based on the clinical context and a comprehensive evaluation.