Bioabsorbable sutures versus screw fixation of displaced tibial eminence fractures: a biomechanical study.

Background: In 1995, we developed a simple and safe arthroscopic technique of anterograde stable fixation of the displaced tibial eminence fractures using a cannulated screw and washer, allowing immediate mobilisation and weight bearing. Some authors described similar end results by arthroscopic fixation of this abruption with trans-osseous sutures. We proved with the biomechanical study that the fixation with strong trans-osseous sutures provides a comparable stable fixation the same as the cannulated screw and washer. We developed a test machine for cyclic loading and a machine for measuring of the pull-out strength for this study.

Methods: A standard osteotomy of the tibial spine was performed during the cadaveric biomechanical study. We performed an arthroscopic fixation with the cannulated screw and washer in ten knees, and in another group of ten knees, arthroscopic fixation was made using two trans-osseous Orthocord™ sutures. The operating time for each procedure was measured, and any possible technical complications were recorded. One thousand cycles of flexion from 0° to 90° were performed on a special loading device on all knees. The macroscopic dislocation of the fragment was measured. After the cyclic loading, all soft tissue was resected except the anterior cruciate ligament with the fixed fragment. The pull-out strength defined as translation of the tibia in anterior direction by breakage was measured with a custom-made measuring device.

Results: The average time for the screw and washer fixation was 20 min, and average time for the sutures fixation was 48 min. After cyclic loading, we did not see any dislocation of the fragment. Average pull-out strength at which fixation with a cannulated screw and washer fell was 253.42 N and mean pull-out strength at which fixation with trans-osseous sutures fell was 330.32 N. Fixation of the fragment with trans-osseous sutures was statistically significantly stronger-Wilcoxon-Mann-Whitney's test, p = <0.00.

Conclusion: Fixation with strong trans-osseous sutures is stronger than fixation with a cannulated screw and washer on cadaveric knees. It appears that fixation with strong trans-osseous sutures allows immediate mobilisation and weight bearing like fixation with a cannulated screw and washer. Meanwhile, the time for fixation with trans-osseous sutures is significantly longer.