Objective To compare the biomechanical properties of the anterior transpedicular screw-artificial vertebral body (AVB) and conventional anterior screw plate system (AP) in lower cervical spine by finite element study. Methods CT images (C1-T1) were obtained from a 38-year-old female volunteer. The models of intact C3-7 (intact group), AP fixation (AP group), and AVB fixation (AVB group) were established and analyzed by Mimics 14.0, Geomagic Studio 2013, and ANSYS 14.0 softwares. The axial force of 74 N and moment couple of 1 N·m were loaded on the upper surface and upper facet joint surfaces of C3. Under conditions of flexion, extension, lateral bending, and rotation, the Von Mises stress distribution regularity and maximum equivalent stree of AP and AVB groups were recorded, and the range of motion (ROM) was also analyzed of 3 groups. Results The intact model of lower cervical spine (C3-7) was established, consisting of 286 382 elements and 414 522 nodes, and it was successfully validated with the previously reported cadaveric experimental data of Panjabi and Kallemeyn. The stress concentrated on the connection between plate and screw in AP group, while it distributed evenly in AVB group. Between AP and AVB groups, there was significant difference in maximum equivalent stress values under conditions of 74 N axial force, flexion, extension, and rotation. AVB group had smaller ROM of fixed segments and larger ROM of adjacent segments than AP group. Compared with intact group, whole ROM of the lower cervical spine decreased about 3°, but ROM of C3, 4 and C6, 7 segments increased nearly 5° in both AP and AVB groups. Conclusion As a new reconstruction method of lower cervical spine, AVB fixation provides better stability and lower risk of failure than AP fixation.
Objective To assess the cl inical significance of transpedicular screw insertion in lower cervical vertebra assisted by multi-spiral CT (MSCT) three dimentional (3D) image reconstruction techniques. Methods Eight cervical vertebra specimens were examined by MSCT, and the messages were sent to SGI02 Workstation; according to the parameter requirements of lower cervical pedicle fixation, by using post-process of volume rendering (VR) the condition was judged and multi-plannar reformation (MPR) was used to do individual analysis; and the ideal path of screw insertion was obtained andthe related parameters were measured. After preoperative plan being finished, referring to these measured parameters, 3.5 mm screws were inserted into C3-7 pedicles of these 8 specimens. After insertion of screws, MSCT scanning and 3D reconstruction were performed again to evaluate the accuracy of lower cervical pedicle screw inserting. From May 2007 to November 2009, 28 patients who received screw insertion in lower cervical spines were given MSCT scanning and 3D reconstruction to evaluate the illness situation, to confirm shortest fixation volumes, and to collect the parameters of aim pedicle screw insertion. Results The time of insertion for each screw was (392 ± 62) seconds. It was found that one pedicle was clausura (1.25%, 1/80) and five pedicle diameters in coronal view were less than 3 mm (6.25%, 5/80), which all were not fit for screw insertion. A total of 74 screws were placed successfully. One-time success rate of screw insertion was 95.95% (71/74). The total accuracy rate was 91.89% (68/74). Six screws penetrated (8.11%). According to the Richter penetrating classification: grade one was 6.76% (5/74) and grade two was 1.35% (1/74). There were significant differences (P lt; 0.05) in penetrated rate between our study and anatomic landmark local ization (47.37%), Miller methods (25.00%), and there was no significant difference (P gt; 0.05) when compared with Abumi method (6.70%), hopper method (7.10%), pipel ine deoppilation method (5.20%) and navigation technique (11.30%). In cl inical 28 cases, 121 screws were inserted; one pedicle was clausura and one was fissure fracture, which all were unfit for insert screw in preoperative plan, the surgery project was adjusted. After operation, 17 patients (76 screws) were given MSCT scanning again. A total of 67 screws (88.16%) were placed successfully. Nine screws (11.84%) penetrated, grade one was 7.89% (6/76) and grade two was 3.95% (3/76). Conclusion It is accurate to apply MSCT 3D reconstruction techniques to measure the ideal screw canal in preoperative individual ized plan. Strictly following individual quantitative data, the safety and accuracy of the surgery can be improved. And it is feasible and available to use MSCT MPR imaging to evaluate the accuracy of pedicle screw insertion.
Objective To discuss the selection of anterior or posterior or a combination of anterior and posterior surgical treatment of lower cervical dislocation. Methods A retrospectively study was performed on 28 patients with lower cervical dislocation who received operative treatment between January 2005 and October 2008. There were 19 males and 9 femaleswith an average age of 38 years (range, 19-57 years), including 21 cases of fresh dislocation and 7 cases of old dislocation. The time from injury to hospitalization was 3 hours to 58 days. According to Allen classification, all cases had flexion injury, including 19 cases of degree I dislocation, 2 cases of degree II, 5 cases of degree III, and 2 cases of degree IV. At admission according to Frankel classification, 7 cases were rated as grade A, 4 as grade B, 9 as grade C, 3 as grade D, and 5 as grade E. All patients received open reduction, internal fixation, and il iac bone graft spinal fusion. Of them, combined anterior and posterior approach operation were given in 4 cases, single anterior operation in 22 cases, and single posterior operation in 2 cases. Results All operations were completed successfully and the spinal cord injury did not deteriorate after operation. Esophageal fistula occurred in 1 case receiving anterior approach operation and was cured after 1 month. Infection of wound occurred in 1 case and was cured after dressing change. The other incisions healed by first intention. One case (Frankel grade A) died of pulmonary infection 6 weeks after operation. Twenty-seven patients were followed up 21-38 months. Two cases suffered from shoulder pain 12 months after operation. X-ray films showed complete reduction, normal height of vertebral space and normal sequence of cervical spine after operation. All cases obtained bone fusion after 3.5-6.0 months of operation (4.2 months on average). Frankel grades were improved in different degrees after operation. Conclusion The operation plan of lower cervical dislocation should be determined by the neurologic status of the patient, and the classification of the injury as a unilateral or bilateral dislocation. Anterior cervical discectomy, fusion, and fixation were available in the lower cervical dislocation.
Objective To establ ish sophisticated three-dimensional finite element model of the lower cervical spine and reconstruct lower cervical model by different fixation systems after three-column injury, and to research the stress distribution of the internal fixation reconstructed by different techniques. Methods The CT scan deta were obtained from a 27-year-old normal male volunteer. Mimics 10.01, Geomagic Studio10.0, HyperMesh10.0, and Abaqus 6.9.1 softwares were usedto obtain the intact model (C3-7), the model after three-column injury, and the models of reconstructing the lower cervical spine after three-column injury through different fixation systems, namely lateral mass screw fixation (LSF) and transarticular screw fixation (TSF). The skull load of 75 N and torsion preload of 1.0 N•m were simulated on the surface of C3. Under conditions of flexion, extension, lateral bending, and rotation, the Von Mises stress distribution regularity of internal fixation system was evaluated. Results The intact model of C3-7 was successfully establ ished, which consisted of 177 944 elements and 35 668 nodes. The results of the biomechanic study agreed well with the available cadaveric experimental data, suggesting that they were accord with normal human body parameters and could be used in the experimental research. The finite element models of the lower cervical spine reconstruction after three-column injury were establ ished. The stress concentrated on the connection between rod and screw in LSF and on the middle part of screw in TSF. The peak values of Von Mises stress in TSF were higher than those in LSF under all conditions. Conclusion For the reconstruction of lower cervical spine, TSF has higher risk of screw breakage than LSF.
OBJECTIVE: To investigate surgical reconstruction of stability of lower cervical spine in children suffering trauma, tuberculosis and tumor. METHODS: From January 1998 to September 2001, 8 cases of unstable lower cervical spine were treated by operations, of anterior decompression, massive iliac bone grafting, posterior fixation with spinous process tension band wiring, and fusion with heterogeneous iliac bone grafting. RESULTS: With an average following up of 1 year and 9 months (6 months to 4 years and 3 months), 3 cases recovered excellently, 4 cases recovered well and 1 case died of pulmonary infection. CONCLUSION: The above results indicate that anterior decompression, massive iliac bone grafting, posterior fixation with spinous process tension band wiring and fusion with heterogeneous iliac bone grafting can be used as one of the methods to reconstruct the stability of lower cervical spine in children.
This study aims to investigate the range of motion (ROM) and the stress variation in the intervertebral disc and the vertebral body on adjacent segments and the influence of force transmission mode after the dynamic cervical implant (DCI) surgery. Two types of surgery, DCI implantation and interbody fusion were used to establish the finite element model of the cervical C5, 6 segment degeneration treatment. The ROM and the adjacent discs and vertebral body stresses of two procedures under flexion, extension, lateral bending and axial rotation working conditions were analyzed. The results showed that ROM of the surgical segment in DCI model was well preserved and could restore to the normal ROM distributions (reduction of the amplitude was less than 25%), and the kinetic characteristics of adjacent segments was less affected. In fusion surgery model, however, ROM of the surgical segment was reduced by 86%-91%, while ROM, disc stress and vertebral stress of adjacent segments were increased significantly, and stress of the C5 vertebral body was increased up to 171.21%. Therefore DCI surgery has relatively small influence on cervical ROM and stress. The study provides a theoretical basis for DCI and fusion surgery in clinic.
This study aims to develop and validate a three-dimensional finite element model of inferior cervical spinal segments C4-7 of a healthy volunteer, and to provide a computational platform for investigating the biomechanical mechanism of treating cervical vertebra disease with Traditional Chinese Traumotology Manipulation (TCTM). A series of computed tomography (CT) images of C4-7 segments were processed to establish the finite element model using softwares Mimics 17.0, Geromagic12.0, and Abaqus 6.13. A reference point (RP) was created on the endplate of C4 and coupled with all nodes of C4. All loads (±0.5, ±1, ±1.5 and ±2 Nm) were added to the RP for the six simulations (flexion, extension, lateral bending and axial rotation). Then, the range of motion of each segment was calculated and compared with experimental measurements of in vitro studies. On the other hand, 1 Nm moment was loaded on the model to observe the main stress regions of the model in different status. We successfully established a detail model of inferior cervical spinal segments C4-7 of a healthy volunteer with 591 459 elements and 121 446 nodes which contains the structure of the vertebra, intervertebral discs, ligaments and facet joints. The model showed an accordance result after the comparison with the in vitro studies in the six simulations. Moreover, the main stress region occurred on the model could reflect the main stress distribution of normal human cervical spine. The model is accurate and realistic which is consistent with the biomechanical properties of the cervical spine. The model can be used to explore the biomechanical mechanism of treating cervical vertebra disease with TCTM.