Biomechanical Research And Clinical Application Of The Dynamic Cervical Implant

Objective: Investigate and evaluate the biomechanical properties of the Dynamic Cervical Implant to provide biomechanical basis for clinical application.Methods: Five types were made in 7 almost fresh adult cadaveric cervical spines (C2-T1): intact condition, simulated vertebral disc removal, DCI non-fusion, merely fusion cage fixation and PCB fixation. Their stability was tested by experimental stress analysis at C56.Result: 1. The cervical spine became unstable with the flexibility and the migration increasing and with the strength and the stiffness decreasing significantly after the removal of vertebral disc. 2. After instrumentation of DCI fixation, the strength increased 29%, the stiffness increased 15%, the flexibility decreased 28% and the migration decreased 13% compared to simulated vertebral disc removal group. There was significant difference between DCI fixation group and simulated vertebral disc removal group (P<0.05). And the range of motion of cervical spine after the insertion of correct size of DCI was similar to that of intact condition. 3. Merely fusion cage fixation group were close to the intact condition group and inferior to the DCI fixation group. 4. The biomechanical properties of PCB fixation group obtained rigid fixation with the strength and the stiffness increasing significantly. But the ROM of upper and lower adjacent segments and the mean strength significantly increased.Conclusions: The DCI occupies the properties of elastic and dynamic stability, perfect axial compliance and the shock absorption, which can effectively protect and maintain the cervical biomechanical characteristics and reconstruct the cervical biomechanical function.Objective: To compare post-operatively short and intermediate-term clinical outcomes and the changes of range of motion (ROM) at adjacent levels between DCI un-fusion group and anterior decompression and fusion (ACDF) group. Try to identify the short and intermediate-term clinical efficacy and find out if there is any statistical difference between the two groups.Methods: From September 2009 to December 2010, we operated on 12 patients with DCI non-fusion, and 15 ones with ACDF. Among the DCI non-fusion group, there were 10 males and 2 females with a mean age of 46 years range from 37 to 59 years. Ten cases were cervical spondylotic myelopathy and 2 cases were spondylitic radiculopathy. Ten patients underwent single segment operation (9 cases C56, 1 case C67), and 2 patients underwent double segments operation (1 case C34/C45, 1 case C56/C67). Ten males and 5 females underwent ACDF with PCB fixation. And all patients underwent single segment operation (3 cases C45, 10 cases C56, 2cases C67) with a mean age of 48 years range from 40 to 60 years.. Preopratively, we evaluated the cervical spondylotic myelopathy patients by JOA scaling, post-operative efficency by Odom grsding and we had all treated patients reexamined with dynamic lateral (full flexion and full extention) views during follow-up at 1.5 months, 3 months, 6 months and 12 months respectively aiming to observe the changes of range of motion (ROM) at adjacent levels of treated levels for both groups.Result: Both the two groups showed good clinical outcomes by JOA scaling and Odom grading, and we found no statistical significance between them (P>0.05). Pre-operatively there was no difference between the two groups concerning range of motion at the levels adjacent to the treated ones (P>0.05). Post-operatively the ROM of levels treated with DCI were increased significantly (P<0.05). The ACDF group did show a marked increase (P<0.05). But in the DCI non-fusion group we found no statistical difference (P>0.05).Conclusions: Based on our datum, we can conclude with some certainty that DCI non-fusion can preserve the range of motion (ROM) at operated levels as well as prevent the compensatory hyper-motion at adjacent levels, as a result, it can greatly decrease the rate of developing degenerative lesions in the long run. But those patients treated with ACDF may have the risk of developing degenerative disease for its not being able to preserve motion at treated levels. So in this retrospective research, DCI non-fusion did have some advantages over ACDF.