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


METHODS
Seven sheep tibiae were tested in compression (1000N), bending and torsion (6Nm) 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.


CONCLUSIONS
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.
Biomechanics and Implants Research Group, The Medical Device Research Institute, School of Computer Science, Engineering and Mathematics, Flinders University, Bedford Park 5042, South Australia, Australia. Electronic address: john.costi@flinders.edu.au.
John J
JJ
Costi
Biomechanics and Implants Research Group, The Medical Device Research Institute, School of Computer Science, Engineering and Mathematics, Flinders University, Bedford Park 5042, South Australia, Australia.
Richard M
RM
Stanley
School of Mechanical Engineering, The University of Adelaide, Adelaide, South Australia, Australia.
Boyin
B
Ding
Centre for Orthopaedic and Trauma Research, The University of Adelaide, Adelaide, South Australia, Australia; Department of Orthopaedics and Trauma, Royal Adelaide Hospital, Adelaide, South Australia, Australia.
Lucian B
LB
Solomon
D000818:Animals; D001858:Bone Nails; D016025:Bone Transplantation; D004548:Elasticity; D005594:Fracture Fixation, Intramedullary / Q000295:instrumentation*; D008422:Materials Testing / Q000295:instrumentation / Q000379:methods*; D012756:Sheep; D013977:Tibia / Q000293:injuries* / Q000601:surgery*; D014783:Viscosity
Bending stiffness; Biomechanical testing; Bone allograft; Compression stiffness; Fixation stability; Fracture stability; Impaction bone grafting; Phase angle; Segmental defect; Sheep; Tibia; Torsion stiffness