Biomechanic Research And Clinical Results Of Expansive Hemi-laminectomy Treating Cervical Spondilotic Myelopathy

Part IAn Experimental Biomechanic Research of Different PosteriorDecompressionTechniques of Cervical SpineObjective:Posterior decompression procedures, such as the laminectomy (laminectomy,expansive hemi-laminectomy,en blok laminectomy) and laminoplasty (single-door laminoplasty,double-door laminoplasty) are generally considered the procedures of first choice for treatment of multilevel cervical spondilotic myelopathy (CSM),development spinal stenonsis and Ossification of the Posterior Longitudinal Ligament (OPLL). But at present there are no experimental studies about the biomechanical difference between expansive hemi-laminectomy and open-door laminoplasty etc. In order to provide the biomechanical theory basis for the clinical selection of posterior decompression Techniques of cervical spine, we compare biomechanical characteristics of different posterior decompression Techniques of cervical spine including expansive hemi-laminectomy,open-door laminoplasty and en blok laminectomy.Methods:12 harmless adult cadaveric spine specimens (C1～T1) from age 21 to 48 (mean 32.9 years old) were harvested and randomly divided into 2 groups. There are 6 specimens in each group. All specimens were evaluated by lateral position and oblique position radio-graphically before experiment to exclude occult malignant disease and osseous structure abnormality. The two sides of the specimen was hold by special clips. The space between the clips and the spine was filled and fixed tightly with auto-coagulate tooth support powder (polymethy methacrylate PMMA) to keep the clips parallel to each other. All the experiments were performed under non-destructive principle. Each specimen served as its own control and was tested in the following sequence:the first group includs A1,A2,A3:Group A1 (intact specimens group):removed all anterior and posterior muscles of the cervical spine, and reserved the integrity of the supraspinous ligament, inter-spinous ligament, flavum ligament and the articular capsules; Group A2 (expansive hemi-laminectomy specimens group):on the base of group Al,we performed expansive hemi-laminectomy; Group A3 (total laminectomy specimens group):on the base of group A2,we performed total laminectomy. the second group includs B1,B2,B3,B4. Group B1 (intact specimens group):removed all muscles of the cervical spine, reserved the integrity of the ligaments and the articular capsules; Group B2 (open-door laminoplasty specimens group): on the base of group Bl,we performed open-door laminoplasty; Group B3 (open-door laminoplasty with hinge side fixed with PMMA) on the base of group B2,we fixed hinge side with PMMA; Group B4 (total laminectomy specimens group):on the base of group B3,we performed total laminectomy; We used electric biomechanical testing machine to test the specimens and performed flexion experiment, compressing extension experiment, left and right axial rotation experiment respectively in each group. We collected and calculated the dispalcement and angle change (Cobb) of the specimen when the loading power what made the specimens was 10N,50N,100N in the flexion and extension experiment, as well we recorded the angle change of the specimen when the torsion loading power what made the specimens was 0.25N.m, 0.5N.m pure moments in left and right axial rotation experiment respectively.The data was analyzed by SPSS 12.0 and the statistic significance was set at a=0.05.Results:The experimental data analysis shows that:1.With deformation of the specimen and loading stress,there was no significant difference of the dispalcement or angle change (Cobb) of the specimen between group A1 and A2 in flexion, compressing extension, left and right axial rotation experiment (P>0.05); 2. There was significant difference of the dispalcement or angle change (Cobb) of the specimen among group Al and A3 in flexion, compressing extension, left and right axial rotation experiment(P< 0.05); 3. There was significant difference of the dispalcement or angle change (Cobb) of the specimen among group B1 and B2 in flexion, compressing extension, left and right axial rotation experiment (P< 0.05);4. There was no significant difference of the dispalcement or angle change(Cobb) of the specimen among group B1 and B3 in flexion, compressing extension, left and right axial rotation experiment (P>0.05); 5.There was significant difference of the dispalcement or angle change(Cobb) of the specimen among group B1 and B4 in flexion, compressing extension left and right axial rotation experiment (P< 0.05);6. With deformation of the specimen and loading stress, there was significant difference of the dispalcement or angle change (Cobb) of the specimen among group A2 and B2 in flexion, compressing extension,left and right axial rotation experiment(P< 0.05).Conclusions:The study shows that the biomechanical stability between pre-operation and post-operation of expansive hemi-laminectomy of cervical spine have no significant difference in flexion, compressing extension,left and right axial rotation experiment; The stability between pre-operation and post-operation of open-door laminoplasty of cervical spine have significant difference, but with bone healing of hinge side (hinge side fixed with PMMA),there were no significant difference between them; There were significant difference of the stability between pre-operation and post-operation of the traditional total laminectomy in the two groups. PartⅡClinical Results And Related Affecting Factors Of Expansive Hemi-Iaminectomy Treating Cervical Spondilotic MyelopathyObjective:To observe the long-term clinical results and its related affecting factors of expansive hemi-laminectomy treating cervical spondilotic myelopathy (CSM)Method:The outcomes of 65 patients (38males and 27 females) with cervical spondilotic myelopathy (CSM) or with development spinal stenonsis and Ossification of the Posterior Longitudinal Ligament (OPLL) and received expansive hemi-laminectomy in Department of Orthopedic Surgery of Beijing Army General Hospital during 1998.1～2004.12 were studied. Their mean age at surgery was 61.3 years, ranging from 39 to 76 years.The follow-up period ranged from 3 years and 11 months to 11 years and 8 months (mean 6 years and 2 months).The mean duration of symptoms was 19.1 months (ranging from 2 months to 8 years). According to Japanese Orthopaedics Association (JOA) 17 scores method and native 40 points score method,Scores of pre-,post-operations and final follow-up were writed down to analysis the long-term results of the surgical treatment on cervical spondilotic myelopathy.Patients were divided into two groups to analysis the factors that affected surgical results according to the improvingrate of JOA score. We compared the defference of the patient age, gender, duration of symptoms, JOA scores before operation, operation time, blood loss, degree of axial symptom, ranges of motion, Pavlov Ratio and compressed degree of myelos etc. Meanwhile,comparing the difference of surgical results between patients that there were T2-weighted in their Magnetic Resonance Images (MRI) and the others.Result:The mean JOA scores before surgery was 8.60±2.49points,and the mean pre-operative the mean post-operative JOA score was 12.6±3.10 points, the JOA recovery rate was 58.5%, The JOA recovery rate among the total patients was classified as exellent in 18,good in 32,fair in 12,poor in 3,the excellent and good rate was 76.9%.the mean Preoperative Final follow-up JOA score was 12.9±2.8 points, the JOA recovery rate was 59.4%, the excellent and good rate was 78.5% The postoperative JOA score improved significantly,and the differences were statistically significant(p<0.05). JOA scores and 40 points score method scores of pre-,post-operations and Preoperative Final follow-up were analysis and showed that the surgical results of expansive hemi-laminectomy for cervical spondilotic myelopathy were positive.Patients in the good group showed yonger patient ages,greater pre-operative JOA scores,shorter duration symptoms,larger Pavlov ratioes,and less compressed degree of myelos,operation time, blood loss and gender have no influence on the surgical results. Loss of ranges of motion was 4.6°±3.0°, loss of cervical curvatureindices was 2.1%±1.6%, The rate of patients with evident axial symptoms was 12.3% in this group, Only one patient (1.3%) had appeared C5 nerve root palsy after operation.Conclusion:Hemi-laminectomy can expand sagittal diameter of intraspinalcanal,relieve spinal pressure directly and keep the steadiness of cervical vertebra, theoperation is simple,less dangerous, lower blood and lower rate of axial symptoms,and need no special instrument。The post-operation and long-term results of surgical treatment on CSM with expansive hemi-laminectomy are definite according to Japanese Orthopaedics Association 17 scores method and native 40 points score method, so it is an effective method for treating CSM.The patient ages, duration of symptom,pre-operative JOA score,Pavlov ratio and compressed degree of myelos can influence the treatment results.while gender,operation time and blood loss do not influence the results。A high-signal abnormalities on T2-weighted images can not be predictive for the surgical outcome of CSM.