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Study Design: We evaluated the trajectory and the entry points of anterior transpedicular screws (ATPS) in the cervicothoracic junction (CTJ)., Objective: This study aimed at investigating the feasibility of ATPS fixation in the CTJ. Application of an ATPS in the lower cervical spine has been reported; however, there were no reports exploring the feasibility of anterior transpedicular screw fixation in the CTJ., Methods: CT scans were performed in 50 cases and multiplanar reformation was used to measure the related parameters on pedicle axis view at C6-T2. Transverse pedicle angle, outer pedicle width, pedicle axis length, distance transverse intersection point (DtIP), sagittal pedicle angle, anterior vertebral body height, outer pedicle height, and distance sagittal intersection point (DsIP) were measured. The prozone of CTJ was divided into three different regions, which were named as the "manubrium region", the region "above" and "below" the manubrium. The distribution of the trajectory of sagittal pedicle axes was recorded in the three regions and the related data were statistically analyzed., Results: There was no statistical difference in gender (P > 0.05). The transverse pedicle angle decreased from C6 (46.77° ± 2.72°) to T2 (20.62° ± 5.04°). DtIP increased from C6 to T2. DsIP was an average of 7.17 mm. The sagittal pedicle axis lines of the C6 and C7 were located in the region above the manubrium. T1 was mainly in the manubrium region followed by the region above the manubrium. T2 was mainly located in the manubrium region followed by the region below the manubrium., Conclusion: Implantation of ATPS at C6, C7, and some T1 is feasible through the low anterior cervical approach, while it is almost impossible to approach T2 that way.

Objective: To evaluate the biomechanical effects of the anterior cervical transpedicular-screw system (ACTPS), compared to the anterior cervical screw plate system (ACLP), in the subaxial cervical spine after 2-level corpectomy., Methods: A verified intact finite element subaxial cervical (C3-C7) model was established and analyzed by Mimics 10.0, Rapidform XOR3, Hypermesh 10.0, CATIA5V19, ANSYS 14.0 softwares based on the CT data (C1-T1) was collected from a 28 years old male volunteer. The axial force of 75 N and moment couple of 1N·m was loaded on the upper surface of C3, which made the model movement in flexion extension, lateral bending, rotating direction, respectively. Then, recorded the range of motion, and compared the results with the in vitro biomechanical experimental data to verify the effectiveness of the model. The ACTPS model and the ACLP model were analyzed using the finite element method. The range of motion at the operation segments (C4-C7), the range of motion at the adjacent segment (C3-C4) and stress distribution under flexion, extension, lateral bending, and axial rotation were calculated, and compared the range of motion with intact model., Results: There were 85,832 elements and 23,612 nodes in the intact model of subaxial cervical spine (C3-C7) in this experiment,and the range of motion of intact model validated with the reported cadaveric experimental data. In ACTPS group the stress was been well-distributed, but the stress concentrated on the interface between screw and the titanium plate in ACLP group. There were obvious differences of the maximum stress value between the two groups. The range of motion of fixed segments in ACTPS group was smaller than ACLP group, however adjacent segment range of motion showed no significant difference. Compared with the intact group, the range of motion in flexion extension, lateral flexion, rotation direction was decreased respectively about 25°, 20° and 8°, the range of motion at adjacent segment (C3-C4) was correspondingly compensated about 0.3°, 3° and 0.1°., Conclusions: ACTPS is better than ACLP in terms of biomechanical properties. It offers rigid stability, and may be more suitable for reconstruction stability of 2-level and more than 2 levels corpectomy in the subaxial cervical spine. Meanwhile, the risk of fracture of ACTPS system is lower than that of the ACLP system.

Study Design: Prospective comparative study., Objective: To compare 3 techniques for transarticular screw placement in the lower cervical spine., Summary of Background Data: The transarticular screw is found to have satisfactory biomechanical stability. According to current studies, there are several techniques for the placement of transarticular screws in the lower cervical spine. Although several techniques are available for transarticular screw implantation in the lower cervical spine, only a few studies in the literature have been carried out to compare these techniques., Methods: The techniques of transarticular screw placement used by Takayasu (group A), Dalcanto (group B), and Klekamp (group C) were applied in 24 cervical specimens. The facet fractures, the encroachment of the cervical anterior branches of nerve roots and vertebral arteries and the failure of the screws to go through the facets were observed and analyzed., Results: One hundred ninety-two transarticular screws were implanted on both sides in 24 cervical cadavers, 64 for each group. There were 25 splits of inferior facets in group B, 2 splits in group C, and none in group A. Thirty-six screws encroached the vertebral arteries in group A, none in groups B and C. Forty anterior branches of lower cervical nerve roots were involved in group A, 5 in group B, and 3 in group C. Although all screws went through facets in the study except for 5 in group A, there were no significant differences between each group (χ(AB)2 = 3.33, P > 0.05; χ(AC)2 = 3.33, P > 0.05)., Conclusion: There is a high risk of injury to the anterior branch of the cervical nerve roots and vertebral artery if the screws were too long, and the Takayasu technique was used. However, the rate of facet splitting is high if the Dalcanto technique was applied. Klekamp's technique is recommended.

Study Design: Cross-sectional study., Objective: To compare 2 techniques of transarticular screw placement in the subaxial cervical spine., Summary of Background Data: Transarticular screws have been used as an alternative method to achieve posterior cervical spine stability. According to current studies there are several techniques for the placement of transarticular screws in the subaxial cervical spine; however, there is no study that has compared these techniques., Methods: The techniques of transarticular screw placement by Takayasu (group A) and Dalcanto (group B) were used in 8 cervical specimens. The position, number of facet fractures, involvement of the vertebral artery, encroachment of the anterior branches of cervical nerve roots, and instances that failed to go through the facets were observed and analyzed., Results: Sixty-four screws were implanted, 32 for group A and the same for group B. Although no facet fractures were seen in group A, there were 10 in group B (χ=9.6, P<0.01). Eight screws involved the vertebral artery in group A and 0 in group B (χ=22.3, P<0.001). Eleven anterior branches of lower cervical nerve roots were encroached in group A and 2 in group B (χ=22.0, P<0.001). No screws failed to go through the facets in group B whereas 2 screws failed in group A, resulting in no significant difference (χ=0.52, P>0.05)., Conclusions: There was a high risk of injury to the vertebral artery and anterior branches of the cervical nerve roots if the screws were too long and Takayasu technique was used. However, more facets were fractured if Dalcanto technique was applied.

Study Design: A retrospective study. OBJECTIVE.: To introduce the method of C2-C3 posterior short-segment fixation and fusion in unstable Hangman's fracture and to evaluate the clinical effects., Summary of Background Data: Hangman's fracture can be managed by closed reduction and immobilization. However, surgery is usually preferable in highly unstable cases and in rigid arthrodesis failure. The outcome of surgical treatment for unstable Hangman's fracture has not been thoroughly investigated., Methods: Thirty-five patients with unstable Hangman's fracture were treated using C2-C3 posterior short-segment fixation and fusion. Twenty-six cases used C2-C3 short-segment pedicle screw fixation. Nine cases used both C2 pedicle screw and C3 lateral mass screw short-segment fixation and fusion. C-arm fluoroscopy was used for the whole procedure. RESULTS.: All patients were observed for an average of 44 months, ranging from 12 to 78 months. There was no screw loosening or breakage, nor was there any spinal cord or vertebral artery injury intraoperatively. A total of 140 screws were placed, with 70 screws inserted into the C2 pedicle, 52 into the C3 pedicle, and 18 into the C3 lateral mass. Computed tomography scans indicated 9 screws were placed too close to the vertebral artery canal in C2, and 12 screws were too close to the canal in the C3 pedicle, all without clinical consequences. C3 lateral mass screws were placed successfully. Neurologic status improved from C and D to E in all 8 cases. Static and dynamic films demonstrated that fusion was achieved in all cases 6 months after surgery. No graft or plate-related complications were observed in any patients during the entire follow-up period., Conclusion: C2-C3 posterior short-segment fixation and fusion is an effective method for the management of unstable Hangman's fracture, proving its value as a technique for achieving solid bony fusion combined with a low rate of complications.

This study assessed the ideal district of lateral radiograph in evaluation of transarticular screw placement in the lower cervical spine. To assess the ideal zone of lateral radiographs in determining the safe or hazardous locations of the screw tips during transarticular screw implantation in the lower cervical spine. Transarticular screw in the lower cervical spine had been used as an alternative technique to achieve posterior cervical spine stability. Injury to the spinal nerves caused by transarticular screws which are too long must be identified quickly to minimize the neurologic complication. No previous radiological study regarding evaluation of the transarticular screw placement using lateral radiographs has been reported. Twelve cervical spines were removed from embalmed cadavers. Four transarticular screw placements with Dalcanto's technique under direct visualization, including placement of the screw tip staying the ventral cortex, 2, 4 and 6 mm over-penetration of the ventral cortex, were performed on each specimen. Following each placement, a lateral radiograph was taken. Each vertebral body was divided vertically into four equal zones, and another equal zone posterior to the posterior border of the vertebral body was defined as Zone pre-1. The numbers of screw tips seen in each zone were quantified for each placement. Partitions of chi (2) method was used to evaluate the ideal zone on lateral radiograph for transarticular screw insertion. At C34 and C45, no significant difference was found between Zone pre-1 and Zone 1 (chi(2) = 0.18, P > 0.50), while there was significant difference between Zones 1 and 2 (chi(2) = 73.6, P < 0.005), as well as Zones 2 and 3 (chi(2) = 13.2, P < 0.005). At C56 and C67, No significant difference was found between Zones 2 and 3 (chi(2) = 0.25, P > 0.50), while there was significant difference between Zone pre-1 and Zone 1 (chi(2) = 66.2, P < 0.005), as well as Zones 1 and 2 (chi(2) = 10.5, P < 0.005). Ideal screw tip positions on lateral radiograph for transarticular screw by Dalcanto's technique should be in Zone 1 at C34 and C45, in Zone pre-1 at C56 and C67. If the screw tip was in Zones 3 and 4, the safe rate will be decreased significantly and it might be too deep and be dangerous.