A Biomechanical And Clinical Study On The Stress Of Inferior Intervertebral Space After Double Segments Cervical Artificial Disc Replacement

Cervical syndrome is a common and frequent disease in orthopedics,the age of onset it is younger and younger, it is significantly to study on it.Intervertebral disc degeneration is the core pathology basis to theoccurrence and development of cervical syndrome, therefor, researcheson disc can prevent, diagnose early and cure cervical syndrome possiblyand fundamentally. To those patients who had been treated withconservative therapy strictly and had no effect, anterior surgeries to thedisc, decompression/excision of discectomy with interbody fusion was aclassic method to cervical spondylotic myelopathy and radiculopathy.Unfortunatly, the traditional anterior surgery managements lost themotions of fusion segment, leaded to adjacent segment stress focused,instability and accelerat to its degeneration. The more segments had beenfusioned, the degeneration of adjacent segment were more significant,and the recurrence rate of syndrome were higher.How to recover and reconstruct the function of degenerated disc is ahard and hot focuse in orthopedics researches. Based on the idea ofcervical arthroplasty, cervical artificial disc replacement (CADR) is a newtechnique and developed quickly in the past few years. It can recover theoperated disc's founction, decrease its degeneration and approved a newmethod to treat cervical syndrome. Because the higher occurrent place ofCDDD is C_4/5, C_5/6 and C_6/7 segment, it can possess 80.7% of all patientsand always appear with C_5/6 disc herniation compared with one or twoadjacent discs herniation. But whether CADR, especially in the treatmentto the higher occurrence in clinical practice of C_4/5 and C_5/6 doublesegments CDDD, can reconstruct the normal biomechanical performationof cervical spine and fulfill the function of the disc, decrease the sideeffect on adjacent segments? The effect of its clinical therapy is excellent or poor? Unfortunatly, all of those had few been reported in the past years.There is no basic and clinical researches on compare analyze to the stressof inferior intervertebral space after C_4/5 and C_5/6 double segmentsdiscectomy, fusion and CADR.In our study, measured the anterior, media and posterior heights ofsagittal plane of vertebral body and intervertebral disc by X ray, SCT andfresh cadaver practice measurement firstly, in order to explore a sensitiveindication to diagnosis cervical syndrome. Then, builted C_4/5 and C_5/6double segments intervertebral disc complete, discectomy, CADR andfusion model, analyzed the inferior intervertebral space (C_6/7) stresschange during the biomechanical test with different load. Finally,followed-up the clinical cured effect of 5 patients of C_4/5 and C_5/6 doublesegments CADR and 30 cases of fusion, approach the two surgerytreatment to the effects of adjacent inferior intervertebral space. In a word,approve experiment and clinical evidence to choice which operation totreat C_4/5 and C_5/6 double segments CDDD.Chapterâ… X ray, SCT and entity measurement and itssignificance to the heightsof inferior cervical spinal vertebral body and spaceObjectives In order to measure the heights of inferior cervicalspinal vertebral body and space in normal Chinese adult, and comprehendthe morphous of Chinese cervical spine, approve morphous evidence totreat CDDD and approach a new sensitive radiographic indication todiagnosis cervical syndrome.Methods 9 fresh cervical specimens from young adultcadavers(C₃～C₇) were measured by X ray, SCT and fresh cadaver entitymeasurement. In sagittal plane of vertebral body and space, measured andanalysised its anterior, media and posterior heights and calculate the rate of space and body. All datas were analyzed with SPSS.Results 1. The measurement of X ray to the sagittal heights ofvertebral body is higher than SCT and entity method, while the space ofcervical spine and the rate of space and body are lower then them, thedifference is significant(P＜0.05). The datas between SCT and entity haveno significance changes(P＞0.05). 2. The heights of media vertebral bodyis the lowest than anterior and posterior, while, the anterior and posteriorhas no difference. The heights of space in media is the highest, andanterior is the second, posterior is the third. 3. The rate of anterior spaceand body heights in SCT and entity measurement show that from C₃ to C₇are 0.336±0.027(0.333±0.029), 0.448±0.053(0.447±0.054), 0.511±0.054(0.508±0.048), 0.456±0.043(0.453±0.042), 0.372±0.032(0.369±0.030).The rate of media space and body heights in SCT and entity measurementshow that from C₃ to C₇ are 0.454±0.038(0.449±0.036), 0.611±0.091(0.614±0.086), 0.789±0.137(0.791±0.135), 0.680±0.086 (0.685±0.077),0.542±0.078(0.536±0.071). The rate of posterior space and body heightsin SCT and entity measurement show that from C₃ to C₇are0.249±0.015(0.245±0.016), 0.261±0.021 (0.261±0.023), 0.277±0.021(0.280±0.026), 0.263±0.023(0.259±0.027), 0.248±0.015(0.247±0.012).The ratio of media C_5/6 space/C₅ body in SCT and entity is 0.789±0.137(0.791±0.135), is the highest in all segment and location(P＜0.05).Conclusions 1. SCT can measure the vertebral body and spacemore really than computed X ray. 2. In normal cervical spine, the heightsof media vertebral body is the lowest, anterior and posterior is similar.The heights of space in media is the highest, anterior is the second,posterior is the third. 3. The rate of C_5/6 space/C₅ body in SCT is maybea sensitive indication to reflect CDDD. Chapterâ…¡A biomechanical study on the stress of inferiorintervertebral space after C_4/5and C_5/6 double segments CADRObjectives To observe the biomechanical effect and compare thestress changes of C_6/7 intervertebral space pre- and post C_4/5 and C_5/6double segments discectomy, CADR and intervertebral fusion, provide abasic theory evidence to application of the C_4/5 and C_5/6 double segmentsCADR.Methods Eleven healthy adult fresh-frozen cadavers cervical spinesegments were utilized in this research. Builted the models of C_4/5 andC_5/6 double segment disc complete spine, discectomy, the Bryan Discprosthesis implantation, inter body fusion. The stress changes of theinferior (C_6/7) intervertebral space was tested by modified cyclo-shapedminiature transducer, the load including axial, flexion, extension, andlateral bending were applied in each group. The data was analyzed bySPSS for windows 13.0.Results 1. Under axial, flexion, extension and lateral bendingloading, the stress in inferior intervertebral space were increased with theloads.2. In C_4/5 and C_5/6 double segment disc intact and CADR samples,the stress in flexion condition was the highest, while lateral bending wasthe second, axial was the third and extension was the lowest (P＜0.05). 3.In double discectomy samples, the stress in lateral bending was thehighest, while extension was the second, flexion was the third and axialwas the lowest. 4. In inter body fusion samples, the stress in axialcondition was the highest, lateral bending was the lowest, while it wassimilar in flexion and extension conditions. All difference was significant(P＜0.05). 5. The stress of discectomy group was lower than disc intactand CADR groups in axial and flexion conditions, while it was higherthan them in lateral bending and extension conditions. 6. In anterior inter body fusion group, the stress in the inferior space was increased whencompared to disc intact, discectomy and CADR groups (P＜0.05). 7. Thestress had no difference in C_4/5 and C_5/6 double segment disc intact andCADR samples in those four conditions (P＞0.05).Conclusions 1. The specially modified cyclo-shaped pressuretransducer is a excellent tool in this biomechanical study, and canmeasure the stress change of intervertebral space fidelity and correctly. 2.C_4/5, C_5/6 double segments discectomy and intervertebral fusion havechanged the stress distribution in inferior intervertebral space, whencompared to the disc intact samples. 3. Double segments discectomycompared to disc complete group, had lower stress in the inferior spacewhen loaded lateral bending and extension conditions, and had higherstress in the space when loaded axial and flexion conditions, the stressdistribution confused, which will leads to cervical spine degenerated oraccelerated it. 4. In the double inter body fusion groups, the stressincreased significantly, and it is also one of the reasons lead to cervicalspine degenerate or accelerate it. 5. C_4/5 and C_5/6 double segments CADRcan remain the stress and its distribution in inferior space similar to discintact condition, indicate that double segments CADR can retain thenormal biomechanical performs in cervical spine perfectly.Chapterâ…¢The clinical research of the effect of adjacentinferior segment after C_4/5 and C_5/6 double segments CADRObjectives To investigate the clinical outcome of the patient whoaccepted the C_4/5 and C_5/6 double segments Bryan artificial discreplacement and cervical inter body fusion, so can approve evidence forclinical application of double segments replacement. Methods From January 1998 to February 2006, 35 patients withcervical C_4/5 and C_5/6 double segments disc degenerative disease wereenrolled in this study. According to different operations and the length offollow-up, those patients were divided into 3groups. In group one, fivecases were treated with double segments CADR, which were followed-up12 months to 22 months, average 14.66 months. In group two or fusiongroupâ… , 15 patient who had been treated with anterior inter body bonegraft fusion and inter fixation, had been followed-up 12 months to 30months, average 15.75 months. In group three or fusion groupâ…¡, 15patient who had been treated with anterior bone graft fusion and interfixation, had been followed-up 5 years to 8 years, average 6.75 years.Record those JOA score, Odom scale, the ratio of vertebral body andspace height in X ray film, the range of flexion-extension, curvature ofadjacent inferior segment, calculated the ratio of disc degeneration, inpro- and post operation 6 months, 12 months, 2 years and 5 years. Thedata was analyzed by SPSS for windows 13.0.Results 1. In the follow-up of each groups, the score of JOA, scaleof Odom, were higher than pre-operation, the difference was significant(P＜0.05). 2. Compared CADR group and fusion groupâ… , the JOA score,Odom scale, the rate of vertebral body and space height in X ray film, therange of flexion-extension, curvature of adjacent inferior segment,calculated the ratio of disc degeneration, in pro- and post operation 6months, 12 months, they were similar, the difference has no significant(P＜0.05). 3. In group three or fusion groupâ…¡, when compared the 5 yearseffect to post operation, 6 months, 12 months and 2 years, the JOA scoreand Odom scale reduced, the range of flexion-extension rised, curvatureof adjacent inferior segment and rate of vertebral body and space heightin X ray film decreased, the ratio of disc degeneration increased. All ofthem showed significant difference (P＜0.05). Conclusions 1. his study has shown that the C_4/5 and C_5/6 doublesegments CADR and intervertebral fusion are good choice to CDDD, thetherapy effect is excellent and the morphous and function of the adjacentinferior intervertebral space can be maintained well in the near future.2.The therapy effect of interbody fusion decreased in long time follow-up,it can leads to the heights of adjacent inferior disc decrease, range ofmotion increase, curvature of the space reduce and accelerated spacedegenerate. 3. The effect of C_4/5 and C_5/6 double segments CADR in longtime fellow-up should been studied forward.