Study on the effect of sequential section of posterior spinal structures on low lumbar stability.

Abstract

Objective To study the effect of sequential section of L5.6 posterior spinal structures on lumbar mechanical stability using constant displacement testing method by measuring vertebral segmental motion on 6 degrees of freedom. Methods Forteen fresh segments of L4-L7 were selected as spinal speci-mens from healthy female Small-Tailed Han sheep. The sequences were procedured as follows: Ⅰnormal→Ⅱ total laminectomy→Ⅲ half-resection of left facet joint→Ⅳ fuU-resection of left facet joint→Ⅴ half-resection of right facet joint→Ⅵ full-resection of right facet joint. Instron 8874 was used for testing six sequences. Then the mean stiffness of every sequence were recorded and analyzed. SPSS 11.5 statistical package was used for ANOVA. Results The resection of posterior ligaments as well as left facet joint had some effect on the stability of flexion/extension, but the mechanical instability did not occur (P>0.05). Plus the half-resec-tion of right facet joint, the mechanical instability appeared (P 0.05). The resec-tion of posterior ligaments led to the mechanical instability of left/right axial torsion(P<0.05). The mean stiff-ness decreased 26.13% and 26.20% respectively. Facet joints had important sense on torsional stability, es-pecially on the opposite side. Conclusion Under conditions of insuring the field of vision, we must carry out microinvasive operation and preserve the integrity of posterior spinal structures as far as possible during performing posterior approach of lumbar. Key words: Lumbar vertebrae; Zygapophyseal joint; Biomechanics