Assessment of the initial viscoelastic properties of a critical segmental long bone defect reconstructed with impaction bone grafting and intramedullary nailing

Introduction: This study compared the initial viscoelastic properties of a segmental tibial defect stabilized with intramedullary nailing and impaction bone grafting to that of a transverse fracture stabilized with intramedullary nailing. Materials and methods: Seven sheep tibiae were tested in compression (1000. N), bending and torsion (6. Nm) in a six degree-of-freedom hexapod robot. Tests were repeated across three groups: intact tibia (Intact), transverse fracture stabilized by intramedullary nailing (Fracture), and segmental defect stabilized with a nail and impaction bone grafting (Defect). Repeated measures ANOVA on the effect of group on stiffness/phase angle were conducted for each loading direction. Results: The Intact group was significantly stiffer than the Fracture and Defect groups in bending and torsion (p< 0.022 for both loading directions), and was marginal for the Defect group in compression (p= 0.052). No significant differences were found between the Fracture and Defect groups (p> 0.246 for all loading directions) for stiffness/phase angle. In compression and bending, phase angles were significantly greater for the Fracture and Defect groups compared to Intact (p< 0.025), with no significant differences between groups in torsion (p= 0.13). Sensitivity analyses conducted between the Fracture and Defect group differences found that they were not of clinical significance. Conclusion: The initial properties of a segmental defect stabilized with intramedullary nailing and impaction bone grafting was not clinically significantly different to that of a transverse fracture stabilized with intramedullary nailing.