Vertebral Reconstruction Through The Pedicle Channels: A Experimental Study And Clinical Observation

Background As the China's national economic development and social aging population growth, industrial and mining injuries, traffic injuries geriatric spinal fractures caused by injury were increased year by year. Thoracolumbar spinal fractures are common injuries, accounting for 10% to 20% of the spinal injuries in recent years. Traditional treatment of thoracolumbar fractures is to use the short-segment pedicle instrumentation(SSPI), which restore vertebral height, correct spinal deformity and stretch the posterior longitudinal ligament to make the spinal canal bone to reaches a certain level of reduction and decompression. But the loss of angle and height of postoperative and the higher failure rate of the fixation in the treatment of thoracolumbar fracture were facing enormous challenges, which caused the increasing attention by the experts. Biomechanics experiments and imaging studies have shown that the different force vectors can be caused by vertebral compression fractures, when the vertebral fractures occur, the damage is not only in the external cortex, trabecular bone within the vertebral body was also compressed. Pedicle screw was used to the anterior and posterior longitudinal ligament and intervertebral disc annulus fibrosus for reduction, although this can basically restore the vertebral height and shape, but the internal vertebral trabecular bone reduction effect was very weak[2]. Vertebral fractures after pedicle screw reduction, which remained noticeable gap in both was average 5.25cm3, accounting for 13.9% of the total volume of vertebral body,and the CT scan after pedicle screw reduction found that all the internal of the bursting vertebral fractures, especially vertebral pedicle level, remained bone defect area in the front of the vertebral body, its volume is about a quarter size of vertebral body, which was namely the formation of "eggshell-like" hollow vertebrae, the presence of lacunar means that the vertebral height may be missing after load, vertebral endplate will collapse,and the intervertebral disc annulus fibrosus without effective support. The lost intervertebral height of the spine will break the integrity of the front and middle column of the spine. Without an effective reconstruction, internal fixation over a long time to bear load, prone to the failure of internal fixation, vertebral collapse and loss of correction in later period. Vertebral reconstruction is through the vertebral pedicle channel to complete endplate reset, and fill into the different filling materials into the injured vertebra vertebral body cavity to restore the biomechanical properties of vertebral, maintain the form of vertebral body, reduce the internal fixation the stress load, thereby reducing the incidence of postoperative complications. At present, the SSPI combined with vertebral reconstruction is major in treatment of thoracolumbar burst fractures; The percutaneous vertebroplasty (PVP) and percutaneous kyphoplasty (PKP) were major in used to treatment of osteoporotic compression fractures. The two technologies are used the pedicle channel to complete the vertebral reconstruction, rehabilitation of the mechanical properties of injured vertebral and reduce pain, but each has its indications.This study was discussed the reconstruction of the vertebral body through the pedicle channel, which were range of the anatomical studies of the pedicles channels, biomechanics research of the treatment of thoracolumbar vertebral reconstruction caused by traumatic compression fractures, the animal experimental and histological study of the different filling materials repair sheep vertebral bone defect and clinical research of the vertebral reconstruction in treatment of thoracolumbar vertebral fractures and self-designed kyphoplasty Device. This study is aimed to provide experimental evidence and clinical supervisors for vertebral reconstruction through the pedicle channels to treatment of thoracolumbar vertebral fractures.Part 1 Vertebral reconstruction through the pedicle channels:A anatomical studyObjective:To evaluate the line and the area of thoracolumbar (T10-L2) vertebral pedicle channel for vertebral reconstruction.Methods:Five fresh specimens of human thoracolumbar vertebrae (T10-L2), take the lateral of X-ray and CT scan, slice thickness of 0.625mm without interval, the CT date were inputed into Mimics 10.0 and then using the measurement tool in the Mimics to measure each vertebral body pedicle axis length(L), pedicle length(L0), width(W) and height(Ho), vertebral height(H), pedicle entry point in the sagittal plane angle (a) and the pedicle entry point in the cross-section angle (β), and further calculated the volume through vertebral pedicle channel for vertebral reconstruction.Results:The average thoracolumbar (T10-L2) vertebral pedicle axis length were 32.64±5.66mm,31.80±6.41mm,38.46±3.52mm,40.31±4.39mm and 42.72±3.36mm. The average vertebral pedicle length were 12.38±2.06mm,11.77±2.15mm,14.63±2.34mm,15.46±3.04mm and 14.37±1.64mm; The average pedicle width were 5.09±0.26mm,5.79±1.10mm,7.35±1.87mm,7.17±0.69mm and 7.14±0.84mm; The average pedicle height were 9.76±1.43mm,10.83±0.77mm,11.16±0.78mm,11.33±1.26mm and 11.16±0.96mm. The average vertebral height were 18.12±0.88mm,19.48±1.02mm,21.25±1.27mm,22.88±0.68mm and 23.20±0.93mm. The averageαangle were 25.06±3.84°,30.87±7.284°,25.12±5.18°,20.55±1.54°and 21.74±2.58°; The averageβangle were 43.6±4.52°,49.48±10.30°,41.97±5.19°,40.29±6.49°and 42.85±6.47°. The average volume of one side of vertebral body after vertebral reconstruction respectively were 1.02±0.36cm3,1.30±0.43cm3,1.96±0.67cm3,1.84±0.48cm3 and 1.94±0.41cm3, the corresponding percentage of total vertebral volume were 53.95%,55.68%, 52.67%,49.5% and 48.14%.Conclusion:It's possible to use the pedicle channels for vertebral body reconstruction, reduction the end-plates and filling bone graft inside vertebral body.Part 2 Vertebral reconstruction in the treatment of thoracolumbar fractures:A biomechanical StudyObjective:To discuss the changes of biomechanical and morphological with different filling materials in combination with vertebral reconstruction in the treatment of thoracolumbar fractures.Methods:Six fresh specimens of human thoracolumbar vertebrae (T12-L2), using the INSTRONI8874 as prepared by biomechanical testing mechanism of traumatic compression fracture of L1 vertebral body were randomly divided into two group:the acrylic bone cement group and allograft bone group, and then reconstruction of vertebral. To test the stiffness, elastic modulus and ultimate compression strength at the state of integrity, injury and immediately vertebral reconstruction. At the same time take the X-ray film in order to observe the imageology changes of vertebral compression fractures, reduction and reconstruction. By the end of the test, two groups were randomly selected specimens of the L1 vertebral body with a cross-sectional, observing morphological changes of L1 vertebral body.Results:98.95% of the height of L1 vertebral body was restored by the two kinds of filling materials in combination with vertebral reconstruction(P>0.05). The stiffness and elastic modulus of the acrylic bone cement group and allograft bone group were significantly between the immediately state after the vertebral reconstruction and the state of integrity and the damage (P<0.05); The stiffness and elastic modulus of the immediately state after the vertebral reconstruction were not statistically significant between the two groups (P>0.05). The ultimate compressive strength of the acrylic bone cement group and allograft bone group were statistically significant between the immediately state after the vertebral reconstruction and the integrity state(P<0.05); The ultimate compressive strength was statistical significance between the two groups(P<0.05). The imaging of the vertebral reconstruction shows that the vertebral body height can be effective restoration to achieve anatomic reduction. The CT scan after reconstruction and vertebral cross-sectional sample profile showed no bone cement fracture, and bone allograft can be seen in close embedded.Conclusion:Acrylic bone cement or allograft bone injuries of vertebral reconstruction can effectively maintain the reduction of traumatic compression fractures and biomechanical strength. Part 3 Different filling materials in the repair of bone defects in sheep vertebral:A histological studyObjective:To observe characteristics of the bone absorption and formation with different filling material in the repair of bone defects in sheep vertebral body.Methods:Six adult healthy goats, revealed the rear structure after general anesthesia, using the curette to scrape off as much as possible the vertebral trabecular bone to form the bone defects through the bilateral pedicle channels. Each of the L1-6 vertebral were divided into four groups:sheep allogeneic bone group, acrylic bone cement group and Cem-OsteticTM artificial bone group. T12 vertebral body is not filled as a blank control. To execute two animals after four, eight and twelve weeks, remove the vertebral body tissue to prepare for decalcified tissue section, and then taking the HE staining for histological observation.Results:All animals are survived, at 12 weeks, the histological observation found that in the blank control group the fibrous connective tissue structure can be seen, and none of trabecular bone structure. The trabecular bone, osteoblasts and osteoclasts can be seen at the junction of normal trabeculae and defect area; The defects in the sheep allogeneic bone group absorbed significantly, there are a large number of osteoblasts and trabeculae bone, which arranged in a certain direction; In acrylic bone cement group, the cement-trabecular bone interface shows a large number of defects and scattered pink dye homogeneous structure without any cellexistence, surrounded by a large number of inflammatory cells; The defects in the Cem-OsteticTM artificial bone group can be seen scattered trabeculae, surrounded by a large number of osteoblasts and osteoclasts, including a part of remodeling trabecular bone.Conclusion:In addition to acrylic bone cement group, the other two kinds of material within the bone defect filled with vertebral body could be seen biodegradable and osteogenic presence, can be used as bone defect filling materials, and the allograft bone is more significant. There was no trabecula bone in the defect of the blank control group, which was filling with fibrous connective tissue.Part 4 Vertebral reconstruction in the treatment of thoracolumbar fractures:A clinical StudyChapter 1 Pedicle fixation and vertebral reconstruction for treatment of thoracolumbar fracturesObjective:To evaluate the posterior instrumentation combined with the vertebral lifted bone grafting to treat thoracolumbar fractures.Methods:Thirty patients (34 vertebrae) with thoracolumbar fractures were treated with posterior instrumentation fixation, which restored the anterior and middle column height of vertebral body and inserted the bone graft through the pedicle. There were 23 males and 7 females with an average age of 40.8 years (range,24-77 years). All patients were traumatic fractures (6 patients with osteoporosis). The bone grafting included Cem-OsteticTM 3 cases, autograft 17 and allograft 10 cases. The visual analogue scale (VAS) score and imageology changing were followed up.Results:All patients were follow-up for 12-24 months (average,18 months). Pre-operation, one week postoperatively and final follow-up, the average anterior height of vertebral body were 15.5±3.8mm,23.3±5.7mm and 22.5±5.1mm; and the average posterior height of vertebral body were 25.8±3.4mm,28.6±2.0mm and 28.3±2.2mm; the average Cobb angle were 23.5°±7.6°, 14.3°±7.1°and 15.7°±7.5°. The average VAS score were 7.57±1.45,2.57±0.65 and 2.07±0.62. All indexes above were significantly improved, there was a statistically significant difference between pre-operation and on week postoperatively (P<0.05), but no significant difference between final follow-up and 1 week postoperatively (P>0.05). All patients were cured and instrumentations were not loosed and broken. The bone mineral density of all fractured vertebral bodies was equal or higher than the adjacent levels.Conclusion:For restoring and maintaining the height of vertebral body and improving the density of the vertebral body, the posterior instrumentation combined with the vertebral lifted bone grafting is an ideal method to treat thoracolumbar fractures, especially for stability of the anterior and middle column of vertebral body.Chapter 2 Posterior paraspinal muscle approach for thoracic and lumbar spine fractures: compareed with the traditional surgical approachObjective:To evaluate the posterior paraspinal muscle approach treatment of thoracic and lumbar spine fractures (T2-L5) of the surgical methods and compared with conventional approach.Method:From October 2006 to October 2008,a total of 52 cases of non-neurological symptoms consecutive patients with thoracic and lumbar spine fractures were included in the study, including 37 male and 15 female with an average 46.5 years(from 18 to 59 years). Accordding to the Denis fracture classification, there were 17 compression fractures and 35 burst fractures with spinal space-occupying less than 1/3,including 1 T4 fractures,2 T7 fractures,1 Tg fractures,3 T10 fractures,5 T11 fractures,14 T12 fractures,16 L1 fractures,9 L2 fractures,1 L3 fractures. The patients are randomly divided in two group,20 cases with the traditional approach, and the other 32 cases with the posterior paraspinal muscle approach. All the patients were given pedicle screw fixation, partly with posterolateral fusion. Results:The posterior paraspinal muscle approach to the traditional after the surgery has no significant difference in time, but in the amount of bleeding, postoperative drainage, duration of recumbence and visual analogue pain score (VAS) significant advantages, the difference was statistically significant (P>0.05). All patients were follow-up for 9-24 months (average,15.6 months).Till the last follow-up, all patients with vertebral fractures were healed. No loosening or breaking of internal fixation.Conclusions:The posterior paraspinal muscle approach for thoracic and lumbar spine fractures, retain the posterior ligament complex, is an effective and minimally invasive treatment, with less trauma, less bleeding, the advantages of reliable clinical results.Chapter 3 Self-designed adjustable kyphoplasty device for a biomechanics testObjective:To develop a new type of titanium alloy adjustable kyphoplasty devices used to explore the feasibility of the vertebral reconstruction.Methods:Using of the rigid and flexible of titanium alloy, the equipment is composed of lantern-shaped metal pieces. Using the adjustable rotating precession devices to make the metal balls expansion and retraction, the device for vertebral reconstruction in the fresh human body of thoracolumbar spine specimens (T12-L2) for a feasibility test. Applications INSTRON5544 test the maximum stress load of metal balls by self-designed test equipment.Results:The initial diameter of lantern-shaped metal ball was 6.0mm, which formed from the titanium alloy, can pass the thoracolumbar pedicle channels into the vertebral body inside, and then rotating the adjustable device to adjust the metal ball to expanse, which reached maximum diameter was 12mm, while producing a strong distraction force, the biomechanical testing show that the maximum stress load of a single piece was 56.96±3.21N, the stress is 9.48±0.53 Mpa.Conclusion:The Self-designed adjustable kyphoplasty device can combinated with PKP or combinated with posterior pedicle screw fixation for the treatment of various types of fractures, including osteoporotic vertebral compression fractures, complete vertebral reconstruction. But its clinical application still need further study.SUMMARY1. To use the CT scanning and computer-aided technique to measure the related-lines and angles of the fresh human thoracic spine specimens (T10-L2). Through the measurement of the sagittal plane angle we have found that through the pedicle channels can be achieved the reduction of the endplate. At the same time, to calculate the volume of the vertebral reconstructtion through the pedicle channel, to provides a theoretical basis for the reduction of endplate and vertebral reconstruction.2. By simulating traumatic vertebral compression fractures, filled with allograft bone and bone cement through the pedicle channel to test biomechanical properties in the state of the integrity, damage and injuries immediately after the reconstruction. We confirmed that two different filling materials can be effectively maintain the reduction of vertebral injury, which has the same biomechanical properties of the integrity vertebral body.3. By filling with the different graft material to the sheep vertebral bone defect, which confirmed that in the blank control group the fibrous connective tissue structure can be seen, and none of trabecular bone structure. The trabecular bone, osteoblasts and osteoclasts can be seen at the junction of normal trabeculae and defect area; The defects in the sheep allogeneic bone group absorbed significantly, there are a large number of osteoblasts and trabeculae bone, which arranged in a certain direction; In acrylic bone cement group, the cement-trabecular bone interface shows a large number of defects and scattered pink dye homogeneous structure without any cellexistence, surrounded by a large number of inflammatory cells; The defects in the Cem-OsteticTM artificial bone group can be seen scattered trabeculae, surrounded by a large number of osteoblasts and osteoclasts, including a part of remodeling trabecular bone.4. Posterior pedicle screw fixation combined with vertebral body lifted, which can effectively replace endplate, restore vertebral height and angle, filled with different bone graft materials to maintain reduction and biomechanical properties, has a simple and economical features, which is improved based on the traditional surgical treatment and provided a new surgical option of the surgical treatment of thoracic and lumbar fractures.5. Compared with traditional surgical approach, the posterior paraspinal muscle approach retains the integrity of posterior ligament complex, greatly reducing the surgical trauma and shorten the operation time. Operating under direct vision surgery, without a large amount of X-ray fluoroscopy, and has the same surgical level, which compared with percutaneous minimally invasive surgery, is less than percutaneous pedicle screw system at the facet of the cost, operation time and the learning curve, has great relevance. This surgical approach provide a minimally invasive treatment for vertebral fractures from T1 to L5, which is confirmed by the anatomy and clinical research.6. The self-designed and developed by adjustable kyphoplasty devices and biomechanics test in vitro study confirmed that the device in the treatment of vertebral fractures of vertebral reconstruction is feasible and safe, which is simple operation, can be reused, saving the cost of surgery. Its can be applied to vertebral reconstruction in percutaneous or combination with pedicle screw fixation in the treatment of various types of vertebral fractures, including osteoporotic vertebral compression fractures.