[Anti-rotation biomechanical study of wire and various cable system in the posterior brooks instrumentation for atlantoaxial instability].

Objective: To compare the anti-rotation biomechanical performances of wire and various cable fixation devices currently used in the posterior Brooks instrumentation for atlantoaxial instability.

Methods: In this experiment,six specimens of the atlantoaxial complex (Occipital-C3) were used. The models of the normal complex,unstable complex (type II odontoid fracture) and fixed complex were established. On the WD-5 mechanics experimental machine,the parameters including the strength and rigidity of anti-rotation were quantified for the normal complex (group N),the atlantoaxial instability complex (group M), the new type Titanium cable (group A), Atlas titanium cable (group B), Songer Titanium cable (group C), stainless wire(group D).

Results: The max strength of A, B, C, D groups was 12.5, 11.3, 11.52, 11.55 N x m respectively, the max rigidity was 58.81, 53.17, 54.11, 54.35 N x cm/deg respectively. The strength and rigidity of anti-rotation, compare to the unstable atlantoaxial complex which were fixed by the new double locking Titanium cable fixation system were superior to those of normal complex, instability complex, Songer or Atlas Titanium cable (P < 0.05).

Conclusion: Having been changed the locking method, the anti-rotation biomechanical characteristics of the new type double locking Titanium cable fixation system are superior or similar to the traditional Songer or Atlas Titanium cable.