Objective:To study the biomechanical effects of reconstruction of the posterior cervical ligamentous complex on open-door laminoplasty in sheep cervical spine.Method:24 fresh cervical sipne specimens of sheep were separated into three groups with 8 specimens in each group.Group A,all anterior elements of the cervical spine removed,leaving the posterior muscles intact.Group B,based on the protocol of group A,open-door laminoplasty with reconstruction of posterior cervical ligamentous complex was performed.Group C,based on the protocol of group A,traditional expansive open-door laminoplasty was performed.Lateral bending axial extension and compression were performed respectively in each group under electric multipotential machine.Result:With deformation of the specimen in flexion experiment when it was straight,there was no significant difference between group B and group A,but the deformation of group C was significantly smaller than those of group B and group A(P<0.05).When loading stress made the specimen straight in flexion experiment,the difference between group B and group A was not significant,while that in group C was significantly lower than those in group A and group B(P<0.05).When loading stress made the specimen straight in axial extension experiment,group B was significantly lower than group A(P<0.05),group C was significantly lower than group A(P<0.01),group C was also significantly lower than group B(P<0.05).In anterior loading experiment when the loading value was 10N,group B was significantly higher than group A(P<0.05),the difference between group C and group A was significant(P<0.01),the difference between group C and group B was also statistical(P<0.05).Conclusion:With respect to anterior flexion and physical curve of cervical spine,the cervical laminoplasty plus reconstruction of posterior ligamentous complex is superior over traditional open-door laminoplasty alone.