Biomechanical Study On The Cervical Stability Of Cervical Spinous Process Fracture(Extension Into The Lamina )with Posterior Ligamentous Complex Injury

Objective 1.To establish a valid finite element model of cervical spinous process fracture(extension into the lamina)and assure its influence to cervical stability through the comparison of ROM and Von Mises stress between the fracture model and the normal control model.2.To investigate the effect of cervical spinous process fracture(extension into the lamina)with posterior ligamentous complex(PLC)injury on biomechanical stability of the cervical spine in sheep specimen in vitro,and evaluate the role of the posterior spinous process and PLC in maintaining the stability of the cervical spine.Methods 1.A 21 years old male normal volunteer was chosen and the CT scan data were collectedBy using specially designed modeling system,a high quality finite element model of complete cervical spine is generated.Based on the normal model,a finite element model of cervical spinous process fracture(extension into the lamina)was developed according to a clinical case.The range of motion(ROM)under flexion,extension,lateral-bending and axial rotation and Von Mises stress were measured and analyzed in the normal and fracture model.2.Twenty-four fresh goat cervical spine C3~6 specimens were randomly and evenly divided into 3 groups: control group(group A),simple cervical spinous process fracture(extension into the lamina)group(group B)and cervical spinous process fracture(extension into the lamina)with PLC injury group(group C).Under loading of 1.5 N·m torque,the range of motion(ROM)in each group was respectively measured under six working conditions:including flexion,extension,bilateral lateral bending and axial rotation,and the ROM differences among 3 groups were compared by using One-Way ANOVA analysis.Results 1.The finite element model of cervical spinous process fracture(extension into the lamina)was similar to the clinical fracture.The range of motion(ROM)on C6~C7 segment under each movement in fracture model was less than normal model(flexion,lateral-bending and axial rotation).In the C7~T1 segment,the ROM of flexion,lateral-bending and axial rotation were larger than the normal model(from 0.91~3.53 degrees),and the degree of change was significant(unilateral rotation activity increased by 36.7%).The Von Mises stress value of the vertebral body and intervertebral disc was higher than that of the normal model in lateral bending and axial rotation,but the stress concentration point had no obvious displacement.2.Simple cervical spinous process fracture has little effect on the stability of cervical spine and there was no significant difference in ROM between group B and control group(P>0.05)under all working conditions.Compared with control group,the ROM in flexion,extension and axial rotation significantly increased in group C(P<0.05),and no significant ROM difference was found in lateral bending between control group and group C(P>0.05).Conclusion 1.The finite element model can be used to simulate the biomechanics of cervical spinous process fracture(extension into the lamina),indicating the evidence of local instability,but the overall stability has not been destroyed.2.Simple cervical spinous process fracture(extension into the lamina)does have no effect on the overall stability of the cervical spine.Cervical spinous process fracture(extension into the lamina)with PLC injury is more likely to cause cervical instability than simple cervical spinous process fracture(extension into the lamina),and surgical intervention is required in cervical spinous process fracture with PLC injury.