| BackgroundTraditional spinal fusion surgery is considered as classic surgical procedures to treat lumbar degenerative disease. All sorts of potential complications after spinal fusion, including the loss of activities among the lumbar fusion segment and the acceleration degeneration of adjacent segment. In view of these, scholars have been exploring the new concept of non-fusion technique which is called dynamic fixation system, it can maintain the mobile motion of the spine segment. The purpose is to change the way of mobile segment bearing load, to control the intersegmental abnormal movement, which means that dynamic fixation could reduce pain and prevent degeneration of adjacent segments by means of controlling abnormal movement. However, Interspinous process distraction device (IPD) is a non-fusion technology as a new spinal surgical technique, Its long-term effect is uncertain. And whether they are suitable for Chinese and the influence on the spinal biomechanics post-implanting are still uncertain. In this study, according to the anatomical features of interspinous region of lumbar vertebrae in Chinese men, we would like to choose and assess Wallis's effect on implanted by the biomechanical and the early clinical outcome of Wallis system.Part I Anatomical measurement of the lumbar spinous process and the gapObjective:To supply anatomical basis for the design, optimize-localize and clinical application of interspinous internal fixation instrument of lumbar vertebrae by the technique of three-dimension (3-D)reconstruction. Methods:Fifty volunteers were subjected to CT scanner from T12 to S1 level. CT scan images were imported into Materialise Mimics 10.01 software. Bone organization threshold, outline and edge were defined and edited selectively,then measurement tools were used to measure the following parameters of lumbar vertebrae by the same researcher:the thickness of spinous processes, the height of spinous processes and the distance between two adjacent spinous processes, All the data were analyzed with the SPSS 13.0 statistical software for test of normality and t test. Results:(1) Lumbar spinous thickness:generally, front part>back part>middle part, inferior border> central> superior border. But L5 is more special, middle part and back part of spinous were thicker than superior border and inferior border. Adjacent upper lumbar spinous inferior borderis thicker than down lumbar spinous superior border.(2) L3 has the longgest spinous, Male:superior border(26.62±2.98) mm, central(25.59±2.33) mm, inferior border(22.73±2.40) mm; Female: superior border(23.76±2.47) mm, central (24.49±2.48) mm, inferior border (19.70±2.49) mm; L5 has the shortest spinous.(3) spinous spacing:in male, L2-3 has the biggest space, and minish in turn down, all of them is front part>middle part>back part.Front part (10.39±2.70) mm, middle part(11.15±2.20) mm, back part (9.35±2.17) mm. In female:L1-2 has the biggest space, and minish in turn down,all of them is front part>middle part>back part,too.Front part (10.32±2.10) mm, middle part (12.18±2.58) mm,back part (10.80±2.43)mm.L4-5 has the smallest space.Conclusion:spinous decreased gradually from top down,front part>middle part>back part, in Sagittal plane spinous space is wedge-shape. Spinous maximum length by L3, L5 is minimum. Spinous lengths:superior border>central>inferior border, adjacent upper lumbar spinous length (position inferior with length of lumbar spinous. Spinous thickness: front part> back part>middle part. This study used the thickness three-dimensional CT reconstruction technique has been obtained compatriots lumbar spinous and spinous clearance anatomy parameter for americans, for the lumbar spinous characteristics between the design stretched and clinical application provides anatomical data.PartⅡEstablishment and analysis of finite element model of Wallis non-fusion system for human lumbarObjectiver To establish finite element model and analyze the movement under different physiological stress distribution of Wallis non-fusion system, which provide a foundation of biomechanics for clinical application. Methods:Eight volunteers were subjected to CT scanner. CT scanning images were imported into Materialise Mimics 10.01 software. Bone organization threshold, outline, edge were defined and edited selectively. Three-models of L4.5 lumbar and its disc were reconstructed and saved in STL format. The merging models then transformed into Abaqus 6.9 software for pre-processor, then analyzed the rotation range of activities of lumbar flexion, extension, lateral bending and rotation of L4/5 lumbar segment, and then the results were compared and verified the model validity with the literature results. These models then imported into Materialise 3-Matic 4.3 software for re-meshing. Three-dimensional model of Wallis system were established using auto CAD 2009 software, then established with L4.5 models. The merged models then were transformed into Abaqus 6.9 software for pre-processor, then analyzed the stress changes of lumbar flexion, extension, lateral bending and rotation of lumbar Wallis non-fusion system. Results: Three-dimensional finite element model of lumbar was established and verified, then Wallis finite element model was established,It concluded 3398 nodes and 11857 elements, then merging with L4,5 models. It concluded 51572 nodes and 245295 elements, A realistic appearance and calculation accuracy 3D finite element model of Wallis and L4.5 lumbar were established. Then the stress changes of lumbar flexion, extension, lateral bending and rotation of lumbar Wallis non-fusion system were analyzed. Through the stress contour showed that:Wallis system was involved in the activities of lumbar spine in different directions, a good match with the lumbar spine Wallis system conformed to the four conditions the movement of lumbar spine, located between the upper and lower spinous part of the stress is more concentrated, and the vertebral spinous process with the lower part of the stress of contact with the highest. Conclusion: Applications of sophisticated CT scanning technique, the CT scanner images, Mimics software directly dock with Abaqus software can directly assign values, which make the establishment of three-dimensional finite element model of Wallis and L4,5 lumbar faster and more accurate. The finite element model was validated and could be used on biomechanics test. After surgery fixed with Wallis system, Wallis interspinous distraction device can share the stress of the small joints and the disc. The stresses of Wallis system and spinous processes were increased, and the risk of fracture of spinous process is increased accordingly. PartⅢPreliminary evaluation of Wallis interspinous process distraction device in lumbar degenerative diseaseObjective:To explore the efficiency of the Wallis non-fusion system in the treatment of lumbar degenerative disease by clinical observation. Methods:Between August 2007 and October 2008,31 patients of lumbar degenerative conditions were treated alone by Wallis interspinous dynamic stabilization system or a combination of fixed-fusion cases in Dongzhimen Hospital, Beijing, China. Clinical follow-up was done for 18-40 months respectively after the operation,The time and blood loss of Wallis system operation were recorded, The curative effect was evaluated by ODI dysfunction index, JOA score, VAS score and the Chinese Medical Association Orthopaedic Section of lumbar spinal surgery group standard assessment surgery, The early effect and complications associated with Wallis posterior dynamic lumbar stabilization were recorded. Results:According to surgical planning in all cases the successful completion of surgery, alone Wallis system in the treatment of 19 patients, The average operation time was (75±22) min, The average time of Wallis system implanting was (23±8) min, the average intraoperative blood loss volume was (150±60) ml; Wallis system fixation and fusion surgery with 12 patients, The operation time was (140±45) min, the average Wallis system implantation time was (18±6) min, The average intraoperative blood loss was (350±100) ml. Good wound healing in all patients, schedule stitches. All patients did not occur in the spinous process fracture, nerve damage, implant rupture, infection and other complications Were followed up for 18-40 months, mean 26.8 months, all patients had varying degrees of symptoms and signs of improvement:before and after 2 weeks and the final follow-up VAS pain scores were:7.65±1.30,3.85±1.53,3.75±1.51, JOA scores were:13.50±3.25 24.51±2.22,23.95±2.69, ODI scores were:40.26±3.42,22.05±4.30,22.31±2.89. After 2 weeks and the final follow-up VAS, JOA, ODI score compared with the preoperative difference was statistically significant (P<0.01), the last follow-up pain VAS, JOA. ODI score and after 2 weeks no significant difference (P<0.05), follow-up of all cases were not found in the Wallis system, shift, loosening, fracture, no lumbar kyphosis, spinous process fracture, recurrence of symptoms, etc. The last follow-up of patients overall satisfaction with surgery degree was 92.3%. Conclusion:Combination of clinical and imaging follow-up observation, Wallis system of short-term treatment of lumbar degenerative disease satisfactory outcome, the current can be used as an alternative treatment. The long-term efficacy remains to be further clinical follow-up observation. |
PDF Full Text Request