Mechanical evaluation of posterior wiring as a supplement to anterior cervical plate fixation.
METHODS
An in vitro experimental study was performed to examine 3-dimensional biomechanical stability of cervical fixations.


OBJECTIVE
To determine whether posterior interspinous wiring contributes to the rigidity of a single-level motion segment that has been plated anteriorly, and to determine the effects of this combined fixation on intradiscal pressure and spinal motion at the adjacent segments.


BACKGROUND
Combined anterior and posterior column fixation is being increasingly used in a variety of clinical situations that do not involve complete disruption of the motion segment. The biomechanical validity of combined anterior posterior fixation in the absence of overt posterior ligamentous disruption has not been studied.


METHODS
Six human fresh-frozen cadaveric cervical spines (C3-T1) were used. Three-dimensional intersegmental motion and intradiscal pressure were measured while the spine was loaded in flexion, extension, lateral bending, and torsion (up to 2.5 Nm). Fixation stability at the operative level (C5-C6) and influence of the fixation on adjacent segments were evaluated after an anterior plating procedure and combined anterior plating and posterior wiring.


RESULTS
Comparing the combined approach with anterior plating alone, significant reductions in C5-C6 motion was noted: 49% in flexion (P <0.05), 48% in extension (P <0.003), and 33% and 39%, respectively, in left and right torsion (P <0.05). Reduction in the left and right lateral bending was not significant (18% and 12%, respectively). The improved fixation had minimal influence on the adjacent segments.


CONCLUSIONS
Combined anterior posterior fixation further reduces the segmental motion by almost 50% in flexion and extension, 33% and 39% in torsion, and does not significantly alter intradiscal pressure and spinal motion at adjacent segments.
Department of Orthopaedic Surgery, Medical College of Wisconsin, Milwaukee 53266-0099, USA. rrao@mcw.edu
Raj D
RD
Rao
Mei
M
Wang
Manoj D
MD
Singrakhia
Linda M
LM
McGrady
D000368:Aged; D001860:Bone Plates; D001864:Bone Wires; D002574:Cervical Vertebrae / Q000601:surgery*; D017586:Diskectomy; D006801:Humans; D016059:Range of Motion, Articular; D013314:Stress, Mechanical