| Part 1 Biomechanical analysis of adjacent unstable segment intradiscal pressure in an anterior cervical discectomy modelObjective: Anterior cervical decompression and fusion(ACDF)is one of the common surgical methods for the treatment of cervical degenerative disease(CDD).However,A large number of studies have shown that the incidence of adjacent segment degeneration(ASD)become very high after ACDF.In this study,we established a cervical instability animal model and adopt biomechanical experiment to analyze the intradiscal pressure of adjacent unstable segment before and after ACDF operation.Methods: 12 adult male goats were randomly divided into 2 groups:experimental group(n=6)and the control group(n=6).The experimental group was established cervical instability model by transecting the posterior muscles of neck and supraspinous and interspinous ligament at C4-5.The goats of control group were only cut the skin of posterior part of neck,and then sutured them.After the successful establishment of the cervical instability model in the experimental group,all the goats' cervical spine specimens(C3-T1)were underwent the single segment ACDF operation of C5-6.Testing was performed in displacement control under flexion,extension and axial rotation loading modes.Intervertebral disc pressures were recorded at adjacent intervertebral disc(C4-5)before and after ACDF operation.Results: The flexion and extension activity of C4-5 in the experimental group was significantly higher than that of the control group at fourth months after the operation(P < 0.05),which proved that the C4-5 instability model was successfully established.The experimental group was called unstable group,and the control group was called stable group.Under flexion,extensionand axial rotation loading modes,the C4-5 intervertebral disc pressures after operation were significantly higher than that before operation in both groups(P< 0.05).Before operation,under flexion and extension loading modes,the C4-5 intervertebral disc pressures in unstable group were significantly higher than that in stable group(P<0.05),but under axial rotation loading modes,there was not significantly difference in the C4-5 intervertebral disc pressures between two groups(P<0.05).After operation,under flexion,extension and axial rotation loading modes,the C4-5 intervertebral disc pressures in unstable group were significantly higher than that in stable group(P<0.05).Conclusion: This study found that during cervical flexion and extension,the intervertebral disc pressure of adjacent segment with instability was significantly higher than that without instability both before and after cervical fusion surgery.Theoretically,it can be considered that the degenerative speed and severity of intervertebral disc of adjacent segment in CDD patients with adjacent segment instability are higher than those patients without adjacent segment instability.Part 2 Effect of lower cervical instability on adjacent segment disease after anterior cervical discectomy and fusionObjective: There are many factors that influence the occurrence of adjacent segment degeneration(ASD)after anterior cervical discectomy and fusion(ACDF),and adjacent segment degeneration is one of them.The purpose of this study is to investigate the intervertebral disc degeneration of adjacent segment,symptomatic adjacent segment disease(SASD)and additional operation situation after single level ACDF,if adjacent segment exist instability before surgery.Methods: We enrolled 138 patients who had undergone single level ACDF for cervical myelopathy and/or radiculopathy at our hospital from June2005 to December 2010.According to the absence/presence of adjacent segment instability,all patients were divided into two groups: unstable group(n=56)and stable group(n=82).According to the modified Pfirrmann gradingsystem for disc degeneration,all the adjacent intervertebral discs were graded.The average value of the upper and lower adjacent discs degeneration grade was taken as the degeneration grade of adjacent intervertebral discs.Preoperative,postoperative and the final follow-up sagittal alignment of the cervical spine(SACS)were measured and compared between two groups.The preoperative and the final follow-up and the change of adjacent intervertebral discs degeneration grade were compared between stable group and unstable group.The incidence of symptomatic ASD and additional surgery were compared between two groups.Results: There was not significantly difference in Preoperative,and postoperative SACS between two groups(P >0.05),but the final follow-up SACS in unstable group was significantly less than that in stable group(P<0.05).The postoperative and final follow-up SACS were significantly more than that of peroperation in both groups(P <0.05).The final follow-up SACS was significantly less than that of postoperation in unstable group(P <0.05).The final follow-up and the change of adjacent intervertebral discs degeneration grade in unstable group were significantly higher than that in stable group(P <0.05).The incidence of symptomatic ASD and additional surgery were significantly higher than that in stable group(P <0.05).Conclusion: After single level ACDF surgery,the degenerative speed of intervertebral disc of adjacent segment and the incidence of symptomatic ASD and additional surgery were higher in CDD patients with adjacent segment instability than those patients without adjacent segment instability.Part 3 The effect of degenerative lower cervical instability on the operative effect of single segment cervical spondylotic myelopathyObjective: Cervical degenerative changes are the most common cause of cervical spondylotic myelopathy(CSM)and lower cervical instability.The purpose of this study was to investigate the incidence of increased signal intensity(ISI)of the spinal cord on MRI T2 and the associated factors of prognosis in single segmental CSM accompanied by lower cervical instability.Methods: A retrospective study of 122 single segmental CSM patients treated with anterior cervical discectomy and fusion(ACDF)from January2010 to July 2013 at our hospital was performed.According to the absence/presence of lower cervical instability,patients were divided into the unstable group(n=43)and the stable group(n=79).Age,sex,follow-up period,duration of symptoms,number of physical signs,incidence of ISI of the spinal cord,JOA score and JOA recovery rate were compared between groups.Multivariate Logistic regression analysis was used to analyze the risk factors related to JOA recovery rate and to calculate OR and 95%CI.Results: The occurrence rate of ISI of the spinal cord was 72.1% in the unstable group and 44.3% in the stable group,and the difference was significant(P <0.05).There were significant differences in duration of symptoms,and number of physical signs between the two groups(P <0.05).There were significant differences in JOA score of preoperation,postoperation and at the final follow-up between the two groups(P <0.05).The recovery rate of the JOA score in the unstable group was significantly lower than in the stable group(P <0.05).The result of multivariate stepwise logistic regression showed that longer duration of symptoms(OR= 1.158,95%CI=1.014-1.273,P< 0.001),lower preoperative JOA score(OR= 2.369,95%CI=1.328-3.764,P <0.001),and more preoperative physical signs(OR= 3.477,95% CI = 2.358-5.235,P = 0.004)were significant risk factors for lower JOA recovery rate.Conclusion: Patients suffering from CSM with lower cervical instability have higher incidence of ISI of the spinal cord.Longer duration of symptoms,lower preoperative JOA score,and more preoperative physical signs were highly predictive of poor surgical outcomes for patients with single segmental CSM with lower cervical instability. |
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