Clinical Study And Stress Analysis Of Cervical Spinal Curvature After Two Surgical Treatments For Cervical Spondylotic Myelopathy

ObjectiveTo investigate whether there is a difference between Zero-P and PCC system in the improvement and maintenance of postoperative cervical curvature in the treatment of cervical spondylotic myelopathy,and analyze the biomechanical properties of Zero-P and PCC systems.MethodsTo ollect the data of 108 patients who underwent single-level or double-level anterior cervical decompression and fusion from January 2016 to January 2019 in the Department of Ridge and column of the First Affiliated Hospital of Guangzhou University of Traditional Chinese medicine,which internal fixator is ZERO-P or PCC system.Patients were treated with internal fixation device as Zero-P in Group A(Group A of single segment:46 cases,Group A of double segment: 22 cases).and patients in Group B(Group B of single segment: 20 cases,Group B of double segment: 20 cases)were treated with PCC system.Age,sex,operative segment,follow-up time,operative time,amount of intraoperative bleeding,JOA score,VAS score,Cobb-c,Cobb-s,T1 S,and the height of intervertebral space were compared between the two groups,and at the last follow-up,patients were evaluated for complications such as dysphagia and sink of the fusion cage.The following 4 models are established by finite element analysis:(1)single-level cervical spine-anterior plate internal fixation model;(2)single-level cervical spine-Zero-P internal fixation model;(3)double-level Cervical spine-anterior plate internal fixation model;(4)double-level cervical spine-Zero-P internal fixation model.Results(1)There were no significant differences in age,sex,follow-up time and segmental distribution among the 4 groups(P>0.05).There were no significant differences between single-segment group and double-segment group(P>0.05).At the last follow-up,Joa score and VAS score were improved in all 4 groups(P< 0.05).(2)Cobb-c and Cobb-s were improved in all 4 groups at the end of follow-up(P<0.05),but Cobb-c and Cobb-s were decreased in all groups at the end of follow-up.T1 S of single segment Group A,single-segment Group B and double-segment Group B were increased after operation and at last follow-up(P<0.05),and T1 s of double-segment Group A was increased after operation(P< 0.05).However,there was no significant difference in T1 s at the last follow-up compared with that before operation(P=0.100).(3)The postoperative and final follow-up results showed that the height of intervertebral space of all patients was higher than that before operation(P<0.05).In Group A,both single-level and double-level showed a decrease in the level of intervertebral space after the last follow-up operation(P<0.05).In Group B,single-level and double-level follow-up did not decrease the level of intervertebral space significantly(P>0.05).(4)In single segment Group A,10 cases(21.74%)had fusion cage subsidence,and in single segment Group B,1 case(5%)had fusion cage subsidence.There was no significant difference between two groups(P=0.094).(5)The stress of the cervical vertebra-anterior plate internal fixation model is mainly concentrated in the fusion cage and plate,and the stress load of the plate is larger than that of the screw.The stress of the cervical vertebra-Zero-P internal fixation model is mainly concentrated in the screw,and mainly concentrated in the anterior middle of the screw,and the stress load of the screw is larger than that of the front baffle and fusion cage.All the four groups of models showed greater stress concentration under the condition of extension,especially in the model of cervical vertebra-anterior plate internal fixation.No matter single segment or double segment,the maximum stress of cervical vertebra-anterior plate internal fixation model was larger in extension and rotation conditions,and the maximum stress value of cervical vertebra-Zero-P internal fixation model was larger in flexion and left flexion conditions.(6)Under flexion,extension,and lateral flexion,the range of motion of the operative segment of the cervical vertebra-anterior plate internal fixation model was lower than that of the cervical vertebra-Zero-P internal fixation model.Among all the models,the range of motion of the operative segment was the lowest in the flexion condition and relatively high in the extension condition.In the model of the same internal fixation,the range of motion of the two-segment operative segment was higher than that of the single segment under all working conditions.(7)In terms of TCM syndrome types,the liver and kidney deficiency type is the most common type,followed by the phlegm-dampness-blocking type.In the Qi stagnation and blood stasis type and the phlegm-dampness blocking collaterals type,the majority are women,and the liver and kidney deficiency type is more common in men.In each age group,the most common type is liver and kidney deficiency.ConclusionsIn general,zero-notch anterior cervical interbody fusion is a safe and effective method for the treatment of cervical Spondylotic myelopathy.Compared with PCC system,the clinical effect is similar.Zero-P can reduce the incidence of dysphagia and adjacent segment degeneration after operation.Through clinical study and finite element analysis,we found that plate-Cage internal fixation has better biomechanical stability,and PCC system may have more advantages in maintaining postoperative cervical curvature.At the same time,Zero-P has a high sinking rate of fusion cage,which may have a secondary effect on the postoperative cervical curvature.In cervical spondylotic myelopathy,liver and kidney deficiency is the most common type.Therefore,the method of replenishing liver and kidney should be used for patients after cervical spondylotic myelopathy.