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Use of Intraoperative Imaging to Preserve C1-C2 Mobility in Complex Atlas-Hangman Fractures
Correspondence Address: Source of Support: None, Conflict of Interest: None DOI: 10.4103/0028-3886.336335
Keywords: C1 fracture, Hangman's fracture, O-arm, pedicle screw
Hangman's fracture, also known as traumatic spondylolisthesis of the axis, is defined as a fracture involving the lamina, articular facets, pedicles or pars of the axis vertebra. Variable displacement of C2 on C3 is seen.[1] According to the classification by Levine and Edwards,[2] fractures with concomitant severe circumferential discoligamentous injuries (type II, type IIA, and type III) are thought to be unstable and require rigid immobilization. Combination fractures of the C1–C2 complex are relatively uncommon. In the presence of a hangman's fracture, the reported incidence of a C1 fracture ranges from 6 to 26%.[3],[4],[5],[6],[7],[8] The purpose of this study was to assess the outcome of combined C1 hangman's fracture as there are very few specific studies on this combination of fractures in recent literature. Various methods of fixation have been described in literature.[9] This study focuses on advancement from conventional to more anatomic and motion preserving procedures with acquisition of intra operative CT scan and advanced navigation system.
A retrospective analysis of patients with hangman's fracture who were managed at a tertiary level hospital from February 2009 to December 2016 was done. Patients who had a combined C1 and hangman's fracture, with a minimum of 6 months follow up were included in the study. Patient details were obtained from the medical records of the hospital and images were obtained from the picture archiving and communication system. CFR (cervical flexion rotation) test was administered independently by two authors (PKS, DA) and results were assessed. Patient consent was taken for the study, and no patient is identifiable from the images or description used for the study. Since this was a retrospective study, with no patient management or outcome parameters being modified as a result, ethical approval was not sought.
Patient details A total 60 patients with hangman's fracture were treated at our trauma center. Eleven patients (18.33%) had combined C1 and hangman's fracture. We included 10 patients in our study who fulfilled the inclusion criteria [Table 1]. There were 9 males and 1 female with age ranging from 23 to 81 years (mean age - 47.7 ± 17.5 years). Injuries resulted from fall in 6 patients, motor vehicle accident in other 3 patients and fall of object on neck in 1 patient. Six patients were neurologically intact, while one patient was ASIA B, 2 were ASIA C and 1 was ASIA D. Fracture combinations are detailed in [Table 1].
Management We operated on all the 9 patients with type 2 hangman's fractures and managed the single patient with hangman's type 1 fracture in a collar. Specific treatment was determined by the combination of fractures. Four patients were operated with the use of intraoperative fluoroscopy. Two patients underwent occipito-cervical fusion. One patient underwent C1-C2 transarticular screw fixation and one patient underwent C2-3 anterior cervical discectomy and plating with occipito-cervical fusion. We used O-arm (intraoperative CT scan with navigation) in 5 patients (after we got one in our hospital). Its use allowed us to do more anatomical and motion preserving procedures in these 5 patients. Of these, four patients underwent C2 pedicle screw and C3-C4 lateral mass screw with rod fixation and fusion. One patient underwent C2 pedicle screw and C3 lateral mass screw with rod fixation and fusion. Details of surgical procedure under intraoperative CT guidance All 5 patients (operated under intraoperative CT guidance) were operated in prone position on Allen's table (Allen Medical Systems, A Hill-Rom Company, Massachusetts, US). After induction of general anesthesia, cervical traction was applied in extension with weight of 3 to 4 kilograms. Iliac crest was prepared in all cases. O-Arm (intra operative CT scan with 3D navigation system, Medtronic, Inc, Minneapolis, Minnesota, US) was kept from starting and draped. Vertical mid line incision was given and C1 to C5 posterior elements were exposed. A dynamic reference array was put on C1 posterior arch and CT was performed of cervical spine with center at C2 level. The gantry rotates 360 degrees, scanning and transfer of images takes few seconds. We defined the fracture site by dissecting around the upper border of pedicle. After registration with the help of 3D navigation the entry point and trajectory of both C2 pedicle screws was identified. The K wire was advanced bit by bit while confirming the direction with repeated antero-posterior and lateral fluoroscopy. When the K wire tip reached the fracture site a CT scan was repeated to confirm the position and direction of the K wire. If it was found to be appropriate, then the K wire was advanced further after compressing C2 lamina anteriorly so that there was minimal or no space between fractured ends of pedicle on both sides. This was again confirmed with CT scan. Now bilateral C2 pedicles were tapped and screws inserted in both the C2 pedicles. This was followed by bilateral lateral mass screws in C3 and sometimes C4 depending upon severity of disco-ligementous injury, severity of listhesis and need to correct angulation. After screw insertion, bilateral rod fixation was done connecting the screw heads. The traction weight was then taken off. Autologous bone graft was put after decortication between C2 C3 and C2 C3 C4 depending on level of fixation . Wound was closed in layers. Post-operative outcome Intraoperative period was uneventful in all 9 patients who were managed operatively and there was no new neurological deficit in postoperative period in any of the patients. Postoperatively, all patients were immobilized in a hard collar for 3 months. Follow up ranged from 6 to 70 months with a mean of 28.7 months. Postoperative CT revealed fusion in all the cases. All 4 patients who had neurological deficits in preoperative period improved neurologically (one patient improved from ASIA B to C, one improved from ASIA C to D, one improved from ASIA C to E and one improved from ASIA D to E). Rotation, as assessed by the CFR test, was preserved in all 5 cases operated under O-Arm guidance and one patient with C1 Type 1 hangman's fracture who was managed conservatively. Sample cases Case 1 ([Table 1], patient no 6) A 50 year old gentleman sustained injury to neck due to fall of a heavy object on his neck. He was referred to our hospital few days after injury. He was ASIA B on neurological examination. His MRI revealed cord signal change at C2 with anterolisthesis and retro angulation of C2 body [Figure 1]. His CT scan revealed type 2 hangman's fracture with 3 point fracture of C1 ring, anteriorly on left side and bilateral posteriorly [Figure 2]. He was operated under intra operative CT guidance (O-arm). Bilateral K wires were inserted in C2 pedicles under image guidance and a CT scan was done to confirm trajectory [Figure 3], which was followed by tapping. After tapping, bilateral pedicle screws were placed. Lateral mass screws were inserted in C3 and C4. As retrolisthesis was not corrected by traction, slight distraction was done between C2 and C3 after putting rods on both sides. Patient improved to ASIA C and follow up CT revealed good healing of fractures of both C1 and C2 and bony fusion [Figure 4].
Case 2 ([Table 1], patient 7) An 81-year-old gentleman sustained injuries due to fall from height with chin striking on the edge of a table. CT cervical spine, at the time of presentation to our hospital, showed 2 point fracture of anterior C1 arch with hangman's fracture with minimal anterolisthesis [Figure 5]. Repeat CT after 1 week revealed increased anterolisthesis with more forward movement of fractured C1 anterior arch and body of C2 [Figure 6]. He was operated - bilateral C2 pedicle screws and C3-C4 lateral mass screws and rods were inserted. Post-operative CT at 3 months following surgery revealed ongoing healing of C1 anterior arch fracture and C2 fracture with good reduction of anterolisthesis [Figure 7]. CT at 1 year follow up showed good healing of C1 fracture [Figure 8]a and hangman's fracture [Figure 8]b with normal alignment of the spine and patient was doing well clinically.
Hangman's fracture was initially described by Schneider et al.[1] in 1965 and is the most frequent upper cervical fracture after the odontoid fracture. Classification of hangman's fracture was described by Effendi et al.[3] and was modified by Levine and Edwards.[2] Conservative treatment is usually indicated. Described union rates following conservative management are 60% in type 2, 45% in type 2A, and 35% in type 3.[10] In countries with hot and humid climate, halo immobilization and prolonged traction is very cumbersome and compliance is very poor.[11] Many a times hangman's fracture is associated with other injuries. In the presence of a hangman's fracture, the reported incidence of a C1 fracture ranges from 6 to 26%.[3],[4],[5],[6],[7],[8] Ryan and Henderson[8] reviewed 717 spine fractures and found combination Atlas More Details-axis fractures in 15% of odontoid fractures and in 9% of hangman's fractures. In our series, combined atlas and axis fractures were seen in 18.33% of the cases. Most reported combination injuries of the atlas and the posterior elements of the axis have been successfully managed with semi rigid or rigid external immobilization (with or without initial traction) as shown in [Table 2].[2],[4],[7],[12],[13],[14],[15],[16],[17],[18],[19],[20],[21] Lee et al.[13] and Coric et al.[18] described the successful treatment of nine patients with this combination fracture type with a cervical collar only. As with an isolated unstable hangman's fracture, surgical fixation may be an option. The report by Fielding et al.[4] included 15 patients with C1–hangman's combination fractures. These authors recommended that fractures with angulation between C2 and C3 of 11 degrees or more be treated surgically. These combination fractures with angulation of more than 11 degrees were associated with an 85% non-union rate with no operative management, in their experience. Unstable injuries, as defined by C2–C3 angulation of 11 degrees or more, may require surgical management.
Four patients were operated without intraoperative CT scan with navigation (O-arm). These patients underwent occipito cervical/C1-C2 transarticular fixation thus compromising the rotation at C1-2 joint in these patients. We used O-arm (intraoperative CT scan with navigation) in 5 patients (after we got one in our hospital) and its use allowed us safely to do more anatomical and more motion preserving procedure especially rotation at C1-2 joint. The screw placement is more precise under intra operative navigation as shown by Singh et al.[11] and Wei Tian et al.[22] In the CFR test the cervical spine was fully flexed, to isolate the neck movement to C1/2, which has the distinct ability to rotate in flexion. The normal rotation reported is 44 degrees. C1-C2 dysfunction has been assessed using this test with a good level of interobserver variability.[23],[24]
The goal in treating these complex fractures is to achieve early maximum stability and preserving maximum range of motion. These are often competing phenomena. Treatment is based on the type of hangman's fracture. Good healing can be achieved in elderly patients also and we should be aggressive in management of these patients with new intraoperative CT scan and navigation system. The aim should be maximum motion preservation and early stabilization. CT based intraoperative navigation system makes motion preserving procedures possible by avoiding C1 instrumentation and allows accurate C2 pedicle screw placement. Financial support and sponsorship Nil. Conflicts of interest There are no conflicts of interest.
[Figure 1], [Figure 2], [Figure 3], [Figure 4], [Figure 5], [Figure 6], [Figure 7], [Figure 8]
[Table 1], [Table 2]
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