Hangman's fracture means bilateral pedicle fractures of the axis accompanying displacement and angulations between the body of C2 and C3. The injury is often caused as a result of falling down or being involved in a vehicular accident. In 1985, based on the classification of Effendi et al,1 Levine and Edwards2 proposed a new classification of Hangman's fracture according to the mechanism, morphology and stability. The Hangman's fracture was classified as type I, II, IIA and III, with type II being the most common of the four types.
The characteristics in the case of Hangman's fracture that we reported were consistent with those of type II fracture. But the dislocation was much more severe, and the body of C2 was lying anterior onto C3 vertebra combined with the compression fracture of C3 vertebra. This type of fracture is extremely rare, and the cause of the injury and treatment required remains unclear. In this research, we try to analyze the mechanism of injury and discuss the reasonable treatment.
A 37-year-old male was admitted to our hospital six hours after a nighttime freeway accident. Before the injury, the patient was seating in the front seat of the car on the passenger side, and a driver and two passengers in the rear seats were also in the vehicle. The driver was the only one wearing a seat belt. The car was traveling at 120 kilometer per hour when it crashed into the rear of a cargo truck, which turned left suddenly. The forehead and right shoulder of the patient made direct impact with the windshield and upon impact the back of his head was struck by the person in the rear seat. After the injury, he felt pain in the neck and the right clavicular area; he experienced no chest pain or abdominal pain. When examined, there were skin injuries in the frontal region and face, tenderness and friction sound on the middle of right clavicular, and his neck motion was limited. No deformity or percussion pain on the thoracic or lumbar vertebrae and neurological examinations were negative. Radiological examination showed right clavicular fracture, bilateral pedicle fractures of C2, total dislocation of C2, the body of the C2 vertebra seen to be lying onto the body of the C3 vertebra and without C2-3 locked joint (Figures 1-3).
Five kilograms of traction was immediately applied with skull tongs in the neck midline position. During the traction, we kept monitoring the vital signs and the spinal function of the patient. In the next few days, we gradually increased the traction load by 1.5 kilograms each time and a bedside plain radiography was taken. When the traction load increased to 8 kilograms, plain radiography revealed partial reduction (Figure 4), and obvious displacement of bilateral pedicles of the axis still existed. The patient complained of aggravated neck pain, so we decreased the traction load to 5 kilograms.
A single-stage posterior surgery of reduction was performed twenty-four hours after traction. During the operation, bilateral pedicle fractures of C2, complete fluctuation of the spinous process and lamina of C2 were observed; bilateral joints of C2-3 remained intact. Multi-axial screws with a diameter of 3.5 mm (SUMMIT™ SI OCT System, Depuy, USA) and upward openings on top were inserted into the lateral mass of the C1 and C3. In order to avoid injuring the spinal cord, vertebral artery and venous sinus, the superior, inferior, internal and external margin of the C1 lateral mass should be exposed completely before the insertion of the C1 screws, Magerl technique for implant of C3 lateral mass screws. Reduction rods pre-curved to 30° were initially fixed to the screws of C1. The end of the rod should have a 30° angulations with the screws of C3 before locking the nuts. Skull tong traction was applied to assist the reduction. We reduced the C2 vertebra by gradual adjusting the locking nuts. Bone fusion was performed with autogenous iliac crest. Plain radiography and computed tomography taken after the operation revealed good position of the screws and complete reduction of C2 vertebra (Figure 5). The patient was discharged twelve days after the operation (The clavicular fracture was treated by external fixation). Four months after surgery, the patient was examined by X-ray and by CT scan. The results showed that there was no fixation failure, reduction was maintained and bony fusion gained (Figure 6).
Total anterior displacement of the vertebra of C2 without neurological deficit and C2-3 locked joint in Hangman's fracture of the axis was an extremely rare case. In 1981, Pepin and Hawkins3 studied 42 cases of Hangman's fracture, there were 27 patients defined as type II, of which only one of these cases had complete dislocation of C2, but no compression fracture of C3 vertebra. The study showed hyperextension is the main force. In 1997, Choi et al4 reported a complete anterior dislocation of the C2 body, bilateral neural arch fractures, and a unilateral locked facet in a 25-year-old man who sustained a neck injury in an industrial accident and symptoms indicated a mild central spinal cord syndrome, the mechanism was flexion and compression. The patient was treated by posterior decompression, reduction, and C2-3 fixation. The patient recovered and was without neurological dysfunction several days after surgery.
The cause of the fracture in our case was not similar to the patient in Pepin's and Choi's research. The forehead of the patient was impacted directly with the windshield when the freeway accident occurred, Primary hyperextension power was transmitted to C2 spinal process via occipital bone and posterior arch of C1, and caused bilateral pedicle fracture of C2. Second hyperflexion power was created by the collision of the back head resulted in the fracture of C3 and the injury of anterior, posterior longitudinal ligament and disc of C2-3. The complete injury of the three column of the spine caused the body of C2 marked anterior dislocation. Due to hyperextension power was primary, the patient had no C2-3 joint locked. Spinal cord injury was common in Hangman's fracture with total anterior displacement of the C2 vertebra. In our case, it was an extreme condition for the patient who manifested no neurological dysfunction. The enlargement of the spinal canal, no C2-3 locked joint and C2-3 disc herniated onto the body of C3 were the main reasons.
The Hangman's fracture with total anterior displacement of the C2 vertebra was a three-column lesion of the cervical spine; this increased the risk of a second spinal cord injury. Even though no paralysis happened after the injury, we should pay attention to the possibility of severe fracture and dislocation as well before diagnosis was completed. The external fixation was very important for patient. In the past, Pepin adopted conservative treatments such as traction and external fixation after partial reduction of the fracture, but there were some drawbacks, such as a long treatment period, unsatisfactory reduction and fixation, and the reduction would possibly regress. Tuite et al5 reported that over 50% of the patients experienced neck pain and an unstable cervical spine after the conservative treatment of unstable C2-3 fracture. The operative reduction for severe Hangman's fracture was advocated by Li et al.6 Choi4 suggested posterior approach with reconstruction of the short level of C2-3 in order to preserve the rotation movement. However, good reduction of the fracture should be the prerequisite conditions to this technique.
In our study, the vertebra of C2 was reduced partially after the heavy load of skull tong traction. Reconstruction of the short level of C2-3 could not be adopted. Wang et al7 reported that the good reduction of the atlanto-axial articulation can be achieved by initially inputting the screws into the integral lateral mass of the axis combined reduction plates. This technique is similar to what we used in our study by inputting the screws into the lateral mass of the C1 and C3 initially, then raised the atlanto-axial complex at the supporting point of C3 by the lever principle. This technique avoided the difficulty in inputting the screws into C2 vertebra. In practice, due to obvious anterior displacement and instability of the posterior arch of C1, surgical exposure, establishment of C1 lateral mass passage and screw insertion could increase the risk of spinal cord injury. We regarded that the exposure of circumscription of C1 lateral mass, implant of C1 screw under euthyphoria and remain light and soft manipulation are reasonable techniques for avoiding complications. During the course of the reduction, skull traction and bilateral screws should be used simultaneously to control the rotation and avoid the back out of the screw.
Bone fusion through anterior combined posterior or posterior alone were frequently used after the reduction of C2. According to Pepin's research, the anatomy of C2-3 was different from the lower cervical vertebra. If there was some contact between the C2 and C3 vertebra, even if the reduction was partial, anterior spontaneous union could occur, and in our case, the space of the pars interarticularis of axis and the C2 and C3 vertebra became smaller. So we selected the posterior-only autogenous iliac crest fusion. The hangman's fracture with total anterior displacement of the C2 vertebra could cause severe spinal instability and the solid fusion was necessary for such patients, therefore the fusion from C1 to C3 was used in this research and positive results were identified 4 months after operation. However, long segment fixation and fusion between C1 and C3 showed disadvantage of atlanto-axial rotational dysfunction. For this reason, the instrumentation should be removed after bony fusion occurred so as to restore atlantoaxial motion to some degree.
In summary, hangman's fracture with total anterior displacement of the C2 vertebra without neurological deficit and C2-3 locked joint we reported in present paper was an extremely rare case. Understanding the cause and events surrounding the injury is important for the treat ment of hangman's fracture with total anterior displacement of the C2 vertebra. For the case that can receive completely reduction by traction, Halo vest fixation is a type of method. But if reduction cannot occur, we suggest that the surgical treatment option should be considered. Since well biomechanics, cervical lateral mass screw from C1 to C3 is crucial to gain and maintain C2/3 reduction by a single-stage posterior approach. Further study and a prolonged follow-up period should be applied in the future.
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