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 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 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 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.
ObjectiveTo investigate the effectiveness of treatment of locked lower cervical fracture and dislocation with anterior cervical fusion and internal fixation combined with the release of the interlocking facet through the Luschka joint and anterior lamina space.MethodsTwelve patients with lower cervical interlocking fracture and dislocation were analyzed retrospectively between January 2013 and June 2015. There were 7 males and 5 females, aged 25-59 years with an average age of 38.4 years. The disease duration was 9.6 hours to 100 days with an average of 7.3 days. There were 8 cases of unilateral locking and 4 cases of bilateral locking; 4 cases of old injury and 8 cases of fresh injury. The injured segments were 2 cases of C3, 4, 5 cases of C4, 5, 3 cases of C5, 6, and 2 cases of C6, 7. According to Meyerding classification, there were 9 cases of grade Ⅰ and 3 cases of grade Ⅱ. According to the functional classification of American Spinal Injury Association (ASIA), there were 2 cases of grade C, 6 cases of grade D, and 4 cases of grade E. The interlocking facet was released through the Luschka joint and anterior lamina space, and the anterior cervical fusion and internal fixation were used to treat the fracture and dislocation of the lower cervical spine. The recovery of spinal cord function was judged by the functional classification of ASIA; visual analogue scale (VAS) score, neck disability index (NDI) score, modified Japanese Orthopaedic Association (m-JOA) score were used to evaluate the clinical efficacy; the Cobb angle of fusion segment were observed by X-ray film. The intervertebral bone graft fusion was evaluated at 6 months after operation.ResultsThe average operation time was 78.30 minutes, the average intraoperative blood loss was 167.30 mL, and the average postoperative drainage volume was 58.12 mL. No blood transfusion was given during or after operation. During the operation, there was no accidental injury of large blood vessels, esophagus, and trachea; no laryngo edema, dysphagia, hoarseness, and cerebrospinal fluid leakage occurred after operation; no spinal cord injury or nerve root injury aggravated; the incision healed by first intention, and no infection occurred. All 12 cases were followed up 15-20 months, with an average of 16.5 months. The symptoms and function of the nerve injury were significantly improved when compared with that before operation. Re-examination of the cervical spine X-ray film at 6 months after operation showed that the Cage or bone graft was not displaced or broken, the screw was not loosened or detached, and the intervertebral graft fusion rate was up to 100%. At last follow-up, the ASIA grade, Cobb angle of fusion segment, neck pain VAS score, m-JOA score, and NDI score were significantly improved when compared with preoperative one (P<0.05).ConclusionThe effectiveness of treatment of locked lower cervical fracture and dislocation with anterior cervical fusion and internal fixation combined with the release of the interlocking facet through the Luschka joint and anterior lamina space is clear, which not only can make the injured segment get satisfactory reduction, immediate stability and reconstruction, and full decompression, but also can effectively prevent the secondary injury of spinal cord.
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.
ObjectiveTo review the present situation of experimental study and clinical application of middle and lower cervical anterior transpedicular screw (CATPS) fixation. MethodsThe literature on the CATPS fixation was reviewed and summarized. ResultsThere is a safe area to implement the CATPS fixation and anterior decompression, and fusion can be done at the same time. It can provide a new idea for surgical treatment of complex cervical disease. Although it has so many advantages, its complex operating methods and optimal design of plate should be attended. Long-term effectiveness and specific indications still should be researched. ConclusionMiddle and lower cervical anterior transpedicular screw is an effective and safe fixation for cervical diseases. But the time for clinical use is short, the long-term effectiveness, surgical technique, and internal fixation devices are still need further study.