Biomechanical Analysis of Tibial Strength After Harvest of Unicortical Tibial Grafts from Two Different Sites

Abstract

Background: Use of tibial strut grafts has several potential advantages over other donor sites and would be ideal as a harvest site for bone grafts if there are minimal or no resulting risks to tibial stability. Methods: Ten matched-pair cadaver tibiae were randomized to have a 1.5 × 4.0 cm cortical graft harvested from the tibial crest or 1 cm posterior to the tibial crest. Both locations were 6 cm distal to the tibial plateau. The grafts were removed using a high-speed oscillating saw, and each end of the tibia was mounted for testing and loaded onto a servohydraulic test frame. The samples were axially loaded with 720 N (162 lbs) of force, and an external rotational torque was applied at 5 degrees per second to failure. Failure torque for each tibia was recorded. A paired Student's t-test was used to determine whether any observed differences in failure torques were significant. Results: The torque to failure range for on-crest grafts was 11.65 to 81.76 Nm (average, 44.53 Nm; SD, 22.82 Nm). The torque to failure range for the tibiae with the graft 1 cm off-crest was 13.30 to 70.45 Nm (average, 41.64 Nm; SD, 17.83 Nm). All fractures were spiral, included the distalmost anterior corner of the donor site, and extended distally. There was no significant difference in torque to failure between the two donor sites ( p = 0.22). The grafts varied consistently in quality. Conclusion: Considering that there was no statistically significant difference in torque to failure between the two groups of tibiae, the site for tibial bone graft can be selected based on the shape of the cortical graft necessary for each specific surgery.