Effect of bending direction on the mechanical behaviour of interlocking nail systems.
OBJECTIVE
To compare the mechanical properties of various interlocking nail constructs in medio-lateral (ML) and cranio-caudal (CC) bending.


METHODS
Synthetic bone models simulating a severely comminuted tibial fracture were treated with either screwed or bolted, 6 or 8 mm standard interlocking nails (ILN), or an angle-stable ILN (AS-ILN), after which they were then sequentially tested in ML and CC bending. Construct compliance, maximum angular deformation (MaxDef) and slack were statistically compared (p<0.05).


RESULTS
The compliance of all constructs was significantly greater in CC than in ML bending. However, due to the presence of a greater slack in the ML plane, standard ILN constructs sustained significantly more deformation in that plane. Maximum deformation of the novel AS-ILN constructs was the smallest of all constructs and consistently occurred without slack regardless of bending direction.


CONCLUSIONS
This study suggested that standard ILN construct overall deformation and acute instability (slack) may be more critical in ML than in CC bending. Conversely, the small MaxDef and the absence of slack in both bending planes seen in novel angle-stable AS-ILN may provide optimal construct stability and in turn may be more conducive to bone healing.
Déjardin
L M
LM
Department of Small Animal Clinical Sciences, College of Veterinary Medicine, Michigan State University, East Lansing, MI, USA. dejardin@cvm.msu.edu
Guillou
R P
RP
Ting
D
D
Sinnott
M T
MT
Meyer
E
E
Haut
R C
RC
D000818:Animals; D001696:Biomechanical Phenomena; D001858:Bone Nails / Q000662:veterinary*; D001842:Bone and Bones / Q000502:physiology*; D004285:Dogs; D005593:Fracture Fixation, Internal / Q000662:veterinary; D008954:Models, Biological; D013314:Stress, Mechanical