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Unilateral cervical facet dislocation: biomechanics of fixation
Neil Duggal1, Robert H Chamberlain, Sung Chan Park
1London Health Sciences Centre London, Ontario, Canada.
Study Design:
Unilateral facet dislocation was created in human cadaveric cervical spines. Specimens were sequentially instrumented with posterior or anterior screws and plates, and studied biomechanically.
Objective:
To determine the biomechanical differences between anterior and posterior fixation for stabilization of a reduced unilateral cervical facet dislocation.
Summary Of Background Data:
Although previous studies have compared anterior to posterior instrumentation, no data exist on the biomechanics of either type of stabilization after this particular injury.
Methods:
In 6 human cadaveric cervical spine segments, a reproducible unilateral facet dislocation was created and then unlocked (reduced). Nondestructive torques were applied to specimens that were intact, injured-reduced, fixated using posterior nonlocking lateral mass plates, and fixated using a bone graft plus an anterior nonlocking plate. Flexion, extension, lateral bending, and axial rotation were measured stereophotogrammetrically.
Results:
Lateral mass plating was more effective than anterior plating in limiting motion after reduction of a unilateral facet dislocation. Averaged, over all loading directions, lateral mass plates reduced the range of motion to 17% of normal; anterior plates reduced range of motion to 89% of normal. In all loading directions, lateral mass plates performed significantly better than anterior plates (P < 0.05, paired Student t-tests).
Conclusions:
Anterior and posterior plating effectively stabilized a reduced unilateral facet dislocation. Lateral mass fixation provided better immobilization than anterior graft and plate.
