The Biomechanical Study On The Stress Change Of The Adjacent Superior Intervertebral Space After Artificial Cervical Disc Replacement And Clinical Study Of Byran Disc

Cervical disc degenerative diseases are common medical conditions treated by spine surgeons. Many operative ways are used to treat this kind of diseases, such as anterior discectomy, disc decompression/excision and discectomy with interbody fusion, microendoscopic discectomy, automated percutaneous cervical discectomy, drugs injection in intervertibra, prosthetic cervical nucleus, artificial disc replacement(ADR) et al. Up to now, artificial disc replacement has become a focus of spine surgery, and preliminary reports have been reported by many surgeons.Cervical disc exists between interbody from C₂ to T₁, the intervertebral disc is composed of three elements: nucleus pulposus,annulus fibrosus and cartilaginous plate. The nucleus pulposus locates at the meta-rear of center, which is surrounded by annulus fibrosus as a thick envelope, and cartilaginous plate situates in superior and inferior side of the adjacent vertebral bone. Discectomy possibly lead to segment instability, vertebral spinal stenosis and degeneration of facet joints. Cervical interbody fusion changes the biomechanical environment and sacrifices motion function of the segment fused. It also leads to increased stress and range of motion(ROM) of the adjacent segement, which can accelerate its degeneration. The cervical disc arthroplasty is the important technique in modern times. With development of the cervical artificial disc technique and its success on clinical patients, more and more patients accept this operation. Weather the artificial disc replacement can preserve the function of cervical spine, and weather it can affect on the adjacent disc, especially the superior disc, is unreported.In this thesis, the cyclo-shaped migration sensor was used to measure stress change of the intervertebral space during the biomechanical test. In order to reveal the impaction on the superior adjacent intervertebral space, the models of discectomy, intervertebral fusion and artificial disc. replacement between C_5/6 were set up, and stress changes of intervertebral space between C_4/5 were measured during axial, flexion, extension, lateral bending load. Then the premilinary clinical results about Bryan artificial disc replacement treating the different disc degenerative diseases was reported, the data of thirty patients whose follow-up time varied from 3 to 18 months was evaluated by the score of JOA and scale of Odom, and the clinical results of the different time were evaluated. The report give the clear evidence for the use of Bryan artificial disc.Chapterâ… :The biomechanical research of the stress in the superior intervertebral space after artificial disc replacementObjective To compare stress changes of C_4/5 intervertebral space before and after C_5/6 discetomy, artificial disc replacement, and intervertebral fusion during the different load conditions, and to provide a basis on application of the ADR..Method Eleven healthy adult fresh-frozen multisegmental cervical spine segments (C₃ to T₁) were utilized in this investigation and biomechanically evaluated under the following C_5/6 conditions:(1)intact spine;(2)discectomy;(3)the Bryan Disc prosthesis implantation;(4)the interbody fusion. The testing was performed by using INSTRON computed mechanics test system. Under the condition of axial, flexion, extension, and lateral bending load whose load amount were increased gradually(axial load 25-150N, unaxial load 0.25Nm-1.5 Nm), stress change of the superior (C_4/5) intervertebral space was tested by modified cyclo-shaped miniature transducer. The data was analyzed by SPSS 12.0 and the statistic significance was set atα=0.05.Result 1. Under axial ,flexion,extension and lateral bending loading, the disectomy indicated a significant increase of stress in the superior (C_4/5) intervertebral space compared to intact condition(P＜0.05).(2)Under axial, flexion, extension and lateral bending loading, the interbody fusion resulted in significant increase of the stress in the superior (C_4/5) intervertebral space compared to intact condition(P＜0.01).(3)Under axial ,flexion,extension and lateral bending loading, the Bryan Disc prosthesis implantation indicate minor increase of the stress in the superior (C_4/5) intervertebral space compared to intact condition(P＞0.05) .(4)Under axial ,flexion, extension and lateral bending loading, there was significant difference of stress in the superior (C_4/5) intervertebral space between ADR and discectomy (P＜0.05). (5)Under axial,flexion, extension and lateral bending loading, there was significant difference of stress in the superior (C_4/5) intervertebral space between ADR and interbody fusion (P＜0.01).(6)Under axial,flexion, extension and lateral bending loading, interbody fusion resulted in significant decrease of the stress in the superior (C4/5) intervertebral space ,compared to discectomy (P＜0.05).Conclusion 1. It was the first time to compare the effect on the adjacent superior intervertebral space among the ADR, discectomy and intervertebral fusion group by the biomechanical method: there was no difference between the ADR and intact spine group, the intervertebral fusion and discectomy can increased stress in the superior intervertebral space. The result proved that ACDR can preserve motion function of cervical spine and accord with biomechnics of cervical spine, which supported the clinical use of the cervical disc prosthesis. 2. Discectomy and intervertebral fusion can improve stress in adjacent superior intervertebral space, which may be one reason of cervical degeneration or degeneration acceleration.Chapterâ…¡The associated clinical researchObjective To determine whether new functional intervertebral cervical disc prosthesis can provide relief on objective neurologic symptoms and signs, improve the ability of daily living, alleviate the pain of patients, and maintain the stability and segmental motion of cervical vertebrae.Method Thirty cases (thirty-there discs ,male21, female 9, age from 30 to 56 years, mean age 41.5 years) who underwent artifical cervical disc replacement from september 2004 to octember 2005 were followed-up. The follow-up time varied from 3 to 18 months, the averge time was 11months. Among the cases, there were 6 cases of cervical spondylotic myelopathy and 22 cases of cervical disc herniation, 2cases of complex. 24 cases were replaced at single level, 3 cases were replaced at double level. 3 cases who were replaced single level accompanied with fusion. The score of JOA, the scale of Odom, the X-ray film of preoperation, 3, 6, 12 months after operation were collected. The clinical effects were evaluated through analyzing the score of JOA and scale of Odom with the paired-sample T test. The data was analyzed by SPSS 12.0, Paired-samples T Test was used to detect the difference among the different groups, the statistic significance was set at α=0.05.Result (1)The neurological or vascular complications were not observed during or aider operation. According to the score of JOA, there, was significant difference between pre-operation and post-operation, while the clinical result had no significant change in 3, 6 ,12 months followed up postoperatively. (2) According to the scale of Odom, all patients's function was improved, and 15 patients was excellent, 11 good and 4 fair. Their excellent and good rate was 86.6%.Conclusion It is a good early outcome for artifical cervical disc replacement. Discectomy and implantation of the device alleviated neurologic symptoms and signs ,and radiographic evidences proved that the ROM of cervical was maintained. To assess the long-term function of the prosthesis and its influence on adjacent levels, at least 5 years follow- up time should be needed.