[Biomechanical performance of different wires and cable fixation devices in posterior instrumentation for atlantoaxial instability].
OBJECTIVE
To compare the biomechanical performances of different wires and cable fixation devices in posterior instrumentation for atlantoaxial instability, and test the effect of different fixation strengths and fixation approaches on the surgical outcomes.


METHODS
Six specimens of the atlantoaxial complex (C0-C3) were used to establish models of the normal complex, unstable complex (type II odontoid fracture) and fixed complex. On the wd-5 mechanical testing machine, the parameters including the strength and rigidity of anti-rotation, change and strength of stress, and stability were measured for the normal complex, atlantoaxial instability complex, the new type titanium cable fixation system, Atlas titanium cable, Songer titanium cable, and stainless wire.


RESULTS
The strength and rigidity of anti-rotation, change and strength of stress, stability of flexion, extension and lateral bending of the unstable atlantoaxial complex fixed by the new double locking titanium cable fixation system were superior to those of the Songer or Atlas titanium cable (P<0.05) and medical stainless wire (P<0.05). Simultaneous cable fastening on both sides resulted in better fixation effect than successive cable fastening (P<0.05). Better fixation effect was achieved by fastening the specimen following a rest (P<0.05).


CONCLUSIONS
The fixation effects can be enhanced by increased fastening strengths. The new type double locking titanium cable fixation system has better biomechanical performance than the conventional Songer and Atlas titanium cables. Fastening the unstable specimens after a rest following simultaneous fastening of the specimen on both sides produces better fixation effect.
Liu
Tie-long
TL
General Hospital of PLA, Beijing 100853, China.
Yan
Wang-jun
WJ
Han
Yu
Y
Ye
Xiao-jian
XJ
Jia
Lian-shun
LS
Li
Jia-shun
JS
Yuan
Wen
W
D001268:Atlanto-Axial Joint / Q000503:physiopathology / Q000601:surgery*; D001696:Biomechanical Phenomena; D001864:Bone Wires; D002102:Cadaver; D006801:Humans; D016268:Internal Fixators; D007593:Joint Instability / Q000503:physiopathology / Q000601:surgery*; D009984:Orthopedic Fixation Devices