Biomechanical comparison of three techniques for fixation of tibial avulsion fractures of the anterior cruciate ligament

Purpose: To evaluate the initial stability of a suture anchor fixation and to compare this with a screw fixation and pull-out suture fixation for anterior cruciate ligament tibial avulsion fracture. Methods: The initial fixation strength of 3 different fixation techniques, antegrade cannulated screw fixation, pull-out suture fixation with Ethibond and bioabsorbable knotless suture anchor fixation, was evaluated. Using 14 fresh cadavers (28 knees), the strength to failure, initial displacement and mode of failure were measured. Results: The strength to failure of the suture anchor fixation was not significantly different from that of the screw fixation and was higher than that of the pull-out suture fixation. The initial displacement of the suture anchor fixation was lower than that of the screw fixation and the pull-out suture fixation. The majority of the suture anchor fixations and the screw fixations were failed by pull-out from the bone. Eight of the 56 suture anchor fixations failed by pull-out of the suture from the ligament proper. And, one of the 7 screw fixations failed due to fracture of the avulsed bony fragment. All of the pull-out suture fixations failed by suture material rupture. Conclusions: These biomechanical results suggest that the initial fixation strength of suture anchor fixation was not less than that of screw fixation or pull-out suture fixation. And, the initial displacement of suture anchor fixation was lower than that of screw fixation or pull-out suture fixation. The suture anchor fixation appears to be a good alternative fixation technique for repair of anterior cruciate ligament tibial avulsion fracture.