The Biomechanical Study And Clinical Observation Of Preserving Posterior Ligament Complex After Posterior Lumber Surgry

Posterior lumbar interbody fusion has become the routine operation for the lumbar degenerative disease. Sufficient decompression on spinal canal effectively improve the early clinical symptoms.However, a large number of clinical and follow-up data showed that spinal instability and adjacent segment degeneration accelerated after posterior lumbar interbody fusion. The decompression method is the main reason. Whether The Posterior Ligament Complex (PLC) were damaged or not in the decompression process was the key factor. PLC plays an important role in the stability of the posterior column of the spine.At present, the preservation of PLC has become a common sense on posterior lumbar interbody fusion. After the laminectomy, it is necessary to seek the sufficient fusion of interbody which helps to maintain the stability of the spine. However, the fusion rate was decreased after operation in some patients. The initial implant position of cage is main factor.With the development of the digital technology and minimally invasive surgery, the navigation system can guide cage to the position more safely and accurately. It could help to increase the fusion rate and to maintain the overall stability of the spine.Through the continuous study of biomechanics can we grasp the mechanical structure of PLC accurately. The finite element analysis is a part of biomechanical research method.In order to investigate the mechanism of biomechanics and clinical observation, the study are carried out two parts in the following.Part One Finite element analysis the biomechanical effect of preserving posterior ligament complex after posterior lumbar spine surgeryObjective To build a three-dimensional finite element model of spinal L1 to L3, analysis the spinal stability and stress distribution after the total laminectomy and insertion of bilateral pedicle screw using finite element method based on the lack of PLC.Methods A intact L1-L3 three-dimensional finite element model was developed by using the computed tomography scans of a healthy male volunteer. Apply softwares like Mimics14.11,3-matic (V6.0) and ANSYS 15.0 to set up the complete lumbar spine finite element model(Group A), the finite element model of L2 total laminectomy with the lack of PLC (Group B),the finite element mode of total laminectomy and insertion of Bilateral pedicle screw with the lack of PLC (Group C). We used software to simulate flexion, extension, lateral bending and axial rotation.Results Based on the max of Von Mises under different motion state,the maximum stress were significantly lower in group A than in group B (p<0.05), the maximum stress was significantly lower in group B than in group C (p<0.05). Based on the means Deformation under different motion state,the means deformation were significantly lower in group A than in group B (p<0.05), the means deformation was significantly lower in group C than in group B (p<0.05).Conclusion ① The posterior ligament complex structure plays an important role in maintaining the stability of the spine, and the lack of PLC can increase the range of motion and influence the stability of the spine. ②the lack of PLC with pedicle screw can reduce ROM, but the pressure of the adjacent segment is increased, which can accelerate the degeneration of adjacent segment. ③ Too much stress on the pedicle screw system will increase the risk of failure.Part Two Retrospective comparative study of preserving posterior ligament complex in surgical treatment of lumbar degenerative diseaseObjective To compare the clinical outcomes in lumber degenerative diseases patients treatment among traditional laminectomy with lack of PLC, improved laminectomy preserving PLC and improved laminectomy preserving PLC by navigation.Methods From January 2013 to January 2015,98 patients with lumbar degenerative disease underwent among traditional laminectomy with lack of PLC(group A), improved laminectomy preserving PLC(group B) and improved laminectomy preserving PLC by navigation(group C). The clinical outcomes include blood loss, operation time, hospital stay, incremental curvature of lumbar spine, fusion rate, the adjacent intervertebral angle, the depth and the axis deviation of cage, accurate rate of pedicle screw and ODI and VAS scores were used to compare.Results Compared with group A, group B and group C had less blood loss, and the difference was statistically significant(P<0.05). However, the operation time and hospital stay among the three groups had no significant differences. There was a significantly greater improvement in ODI and VAS scores after operation 3 months among the three groups (P<0.05). The change of adjacent intervertebral angle in group A was more obvious than in group B and group C (P<0.05). The depth and the axis of the cage in the group C was superior to group A and group B (P<0.05). The rate of fusion and accurate pedicle screws had no significance among the three groups (P>0.05)Conclusion ①The accelerated adjacent segment degeneration due to the lack of PLC, which is the vital structure of spine. ② All of the improved laminectomy and standard laminectomy could acquire satisfied clinical outcome in lumbar degenerative disease. ③ The navigation can be achieved the implant precisely to be placed under posterior lumbar interbody fusion.