Biomechanical evaluation of cervical spine fixation after healing in a destabilized cervical spine model in sheep: a comparison of the anterior plating and posterior wiring techniques.
BACKGROUND
We conducted biomechanical evaluation of the anterior plating and posterior wiring techniques for cervical spine stabilization after a course of healing in sheep.


METHODS
Seventeen sheep were included, and six of which underwent sham operations (group A, n=6). The other eleven received complete C2-C3 destabilization, followed by intervertebral bone grafting and cervical stabilization either with anterior plating (group B, n=5) or posterior wiring (group C, n=6) techniques. These animals were killed 6 months later. Ligamentous spines (C1-C5) were subjected to the relevantly applied loads. The load-deformation data of the C2-C3 and C3-C4 functional units were recorded and analyzed.


RESULTS
At the C2-C3 functional unit, group B had the least motion ranges in flexion, lateral bending, and rotation loads than did the other two groups. Significantly smaller motion ranges of lateral bending and rotation loads were found in group B than in group C (p<0.05). Compared with group A, group C had a decreased motion range in flexion load but showed increased motion range in rotation load. Consequently, group B had superior intervertebral fusion and less osteophyte than did group C. At the C3-C4 functional unit, group B showed significantly decreased motion ranges in extension and lateral bending loads (p<0.05), while group C did not.


CONCLUSIONS
The results indicated that the anterior plate-stabilized spines were more stable over time than did the posterior-wired spines. This biomechanical advantage eventually resulted in superior intervertebral fusion masses in the former, although it also induced a slightly decreased motion range at the contiguous functional unit. In exclusively posterior wired-spines, the weakness for opposing rotation loads might contribute to the formation of osteophytes at the fusion functional unit. These data point out that the mode and stability of implant fixation systems greatly influence the biomechanical redistribution and bone-adaptive remodeling process during healing, which are closely related to the bone graft maturation and osteophytic formations at the fusion level and the occurrence of stiffening problems at the contiguous levels.
Lee
Ming-Yang
MY
Department of Surgery & Institute of Biomedical Engineering, Neurophysiology Laboratory, Neurosurgical Service, National Cheng Kung University Medical Center & Medical School, Tainan, Taiwan.
Chang
Guan-Liang
GL
Chang
Jia-Hao
JH
Hung
Yu-Chang
YC
Chang
Ching-Hong
CH
Lee
E-Jian
EJ
D000818:Animals; D001696:Biomechanical Phenomena; D001860:Bone Plates; D001864:Bone Wires; D002574:Cervical Vertebrae; D007405:Intervertebral Disc Displacement / Q000473:pathology / Q000601:surgery*; D011187:Posture; D016059:Range of Motion, Articular; D012756:Sheep; D013123:Spinal Fusion / Q000379:methods*