The Hangman’s fracture was initially described in 1965 and is the most frequent upper cervical fracture after the odontoid fracture. However, optimal treatment for the Hangman’s fracture is still unclear. The fractures are classified based on classification proposed by Effendi et al 7 and modified by Levine and Edwards.8 Type I has stable and minimal translation (< 2 mm) without C2-C3 angulation; Type II has C2-C3 angulation and translation (> 2 mm); Type IIA is unstable due to flexion-distraction injury and has more angulation without translation; and Type III is unstable and has severe C2-C3 angulation and translation.
In most cases of type I Hangman’s fractures, the conservative treatment is used the most.9,10 However, the halo or traction device immobilizing time and the possibility of pseudarthrosis, anterior dislocation, and kyphosis suggest that surgical treatment might be a good option. Surgical stabilization is recommended for Levine-Edwards type II, IIA and type III fractures with obvious dislocation.11–13 The treatment goals in Hangman’s fracture are to achieve anatomical reduction, maintain alignment, and maintain the patients’ ability to have an active life. Different surgical approaches, both anterior and posterior, have been described for treating Hangman’s fracture.14,15 An anterior approach, which has the advantage of a technically simple and relatively short fusion construct involving a C2-C3 discectomy with interbody fusion and plating.16,17 The anterior approach, however, cannot address the detached posterior arch of C2 and may have approach-related problems. The high risks of anterior approach were mainly embodied in injuries to vital structures, especially in the facial and hypoglossal nerves, branches of the external carotid artery, contents of the carotid sheath and the superior laryngeal nerve.18,19 The posterior approach was associated with a relatively simple exposure with no major vascular and visceral structures as well as a lower complication rate. However, both the anterior cervical discectomy and fusion (ACDF) and posterior C1-C2 or C2-C3 screw fixation will lose mobility of the fused segment. Direct repair of the pars fracture with a transpedicular screw across the fracture line has the advantage of preserving motion of the axis 16,20,21 and is recognized as a “physiologic operation”. Borne et al 21 reported a direct transpedicular screw fixation in 13 cases of Hangman’s fractures, and all the patients had excellent results. ElMiligui et al 20 also performed the operation in 15 patients and found it to be a simple and safe method. However, traditional transpedicular screw fixation for a Hangman’s fracture has several disadvantages. First, the reduction cannot be easily achieved with a traditional transpedicular screw because the direction of the screw hole is not usually perpendicular to the fracture line, which may cause loss of reduction during the compression. Second, it could not offer sufficient stability because the traditional transpedicular screw has only head thread. Third, this approach easily causes excessive compression, and the amplitude of compression relies on the surgeon’s experience.
This new transpedicular lag-screw is a double-thread screw based on a Herbert screw and can compress the fracture twice. The diameter of the head thread is less than the tail thread, and the corresponding pitch of the head thread is longer than the pitch of the tail thread. This design offers finite compression that could avoid the loss of reduction in fractures. Compared to the traditional transpedicular screw, this lag-screw is associated with significant benefits: (1) It is a biomechanically stronger repair method with a double-thread and can help to decrease stress shielding and increase osseous union; (2) It is a safer operation with the finite compression; and (3) It can shorten a hospital stay, and allow for early rehabilitation with better quality of life. In our study, the results showed the new transpedicular lag-screw fixation was effective for treating a Hangman’s fracture. There were no infections or hemorrhages, and the postoperative CT showed there were no instances of loose screws or ruptures. All patients obtained excellent osseous union and good stability by the end of their follow-up period.
Although the direct transpedicular lag-screw fixation for Hangman’s fracture is considered to be physiologic reconstruction and has been advocated for, it is not appropriate for all types of Hangman’s fractures. According to the Levine-Edwards classification, type I, type II and type IIA after reduction with skull traction can be performed with transpedicular lag-screw fixation. It is not advised to manage the fractures with direct C2 transpedicular lag-screw fixation if there was excessive disc and ligament damage. As such, MRI was performed to exclude spinal cord compression and evaluation the integrity of the C2-C3 intervertebral disc preoperatively. In addition, a type III Hangman’s fracture combined with bilateral facet dislocation, is not indicated for the method. For this instance, we advocate a posterior C2-C3 screw technique.
Direct transpedicular lag-screw fixation is technically difficult because of the large individual variation in the pedicle dimensions and the course of the vertebral artery. Therefore, the successful placement of cervical pedicle screws requires a 3-dimensional knowledge of the pedicle morphology to identify an ideal screw axis accurately and to avoid neuro-vascular injury.17,22 Accordingly, the rate of injury to vital structures varied between 11% and 66%,23,24 which motivated adequate preoperative examination. CT scanning with 3-dimensional reconstruction or a MRI evaluation of the spine is essential for detecting individual variations in the dimensions of the pedicle before surgery. Furthermore, all the surgeries were carried out under fluoroscopy, which allowed for accurate intraoperative control of instruments and implant placement, determination of appropriate screw length, anatomical fracture reduction and anchoring of the screw tip in the opposite cortex. Finally, this technique requires thorough knowledge of spinal anatomy and a great deal of experience in subaxial cervical surgery. Our clinical results suggest that the trajectory guide towards the C2 vertebral body should maintain more inclination inwards and upwards in the axial and sagittal planes. In our study, all the patients regained satisfactory functional outcomes with no limitation of motion and obtained excellent osseous union as well as good stability by their last follow-up.
Our study has several limitations. First of all, the number of cases in this study is small. Experience with a greater number of patients and long-term follow-up is still necessary to further evaluate this technique. Secondly, this study is an uncontrolled case series which only manifested the feasibility, safety and effectiveness of a new C2 transpedicular lag-screw fixation for treatment of an unstable Hangman’s fracture. Further controlled prospective studies comparing our lag-screw with ordinary screws and conservative treatment are needed.