This is the 2019 APSS-Asian Spine Journal Best Paper Award.
Prospective observational study.
To assess the safety, efficacy, and benefits of computed tomography (CT)-guided C1 fracture fixation.
The surgical management of unstable C1 injuries by occipitocervical and atlantoaxial (AA) fusion compromises motion and function. Monosegmental C1 osteosynthesis negates these drawbacks and provides excellent functional outcomes.
The patients were positioned in a prone position, and cranial traction was applied using Mayfield tongs to restore the C0–C2 height and obtain a reduction in the displaced fracture fragments. An intraoperative, CT-based navigation system was used to enable the optimal placement of C1 screws. A transverse rod was then placed connecting the two screws, and controlled compression was applied across the fixation. The patients were prospectively evaluated in terms of their clinical, functional, and radiological outcomes, with a minimal follow-up of 2 years.
A total of 10 screws were placed in five patients, with a mean follow-up of 40.8 months. The mean duration of surgery was 77±13.96 minutes, and the average blood loss was 84.4±8.04 mL. The mean combined lateral mass dislocation at presentation was 14.6±1.34 mm and following surgery, it was 5.2±1.64 mm, with a correction of 9.4±2.3 mm (
Successful C1 reduction and fixation allows a motion-preserving option in unstable atlas fractures. CT navigation permits accurate and adequate monosegmental fixation with excellent clinical and radiological outcomes, and all patients in this study returned to their preoperative functional status.
The reported incidence of atlas fractures ranges from 2% to 13% of all cervical spine injuries and constitutes around 1%–2% of all spine injuries [
Isolated C1 osteosynthesis is an effective alternative strategy, whereby a monosegmental fixation provides stability as well as mobility in UAF [
This study was performed after obtaining approval from the Institutional Review Board of the Ganga Medical Center and Hospitals Pvt. Ltd. (IRB approval no., 2014-13), and informed consent was obtained from all participants. All ethics pertaining to the Helsinki declaration were followed.
A prospective observational and interventional study was performed that examined five cases of isolated UAF. Only patients with an intact neurological status and a normal Glasgow Coma Scale score of 15 were included in the study; patients with other skeletal and systemic injuries (such as to the head, chest, or abdomen) were excluded. The surgeries were performed by a single surgeon in a single institution.
The surgical workflow (
After minimal standard midline posterior surgical exposure, a meticulous dissection was performed to expose the posterior arch of C1 so as to avoid bleeding from the venous plexus. Using a blunt periosteal elevator, the inferior surface of C1 was exposed up to the junction of the lateral mass and arch. A minimally invasive reference array was attached to the cranial portion of the C2 spinous process. Using a mobile intraoperative AIRO CT scanner (Brainlab AG) and infrared tracking camera with image guidance system (BrainLab CurveTM, Brainlab AG), the optimal entry points were determined by the placement of the navigation probe, and with a high-speed 2-mm Midas Rex Legend (Medtronic, Fort Worth, TX, USA) motorized burr, the entry points were marked and created on both sides. Motorized drill bits were then used to create trajectories along the planned direction. Handheld devices were avoided to prevent wobbling and motionrelated artifacts.
The clinical, functional, and radiological findings were evaluated periodically. Patients were allowed to engage in normal activities after ruling out instability at 3 months by the absence of AA displacement in flexion-extension dynamic lateral cervical radiographs. At 1 year, a CT was taken to assess healing, as shown in
A total of 10 screws were placed in five patients, and the demographic characteristics are listed in
Most authors have arrived at a common consensus: to treat stable atlas fractures conservatively [
The monosegmental fixation of atlas fractures was first performed by Ruf et al. [
In this study, we performed a navigated primary osteosynthesis of these C1 injuries, which were unstable. The stability of the upper cervical spine primarily depends on ligamentous support [
Although the magnetic resonance imaging (MRI) is regarded as the gold standard modality of choice for documenting TAL disruption, the absence of neurological dysfunction or upper motor neuron signs in our series did not warrant an MRI, while a diagnosis of UAF was made based on substantial evidence such as excess lateral mass overhang, an increase in AA distance, and TAL avulsion injuries. Considering the severe displacement in these UAF, a primary internal osteosynthesis was performed, and we subsequently discuss our results and successful management.
One of the primary determinants of a successful outcome in this surgery was to restore C0–C2 height, and this was achieved by a controlled distraction using a Mayfield clamp. The traction also stabilized the longitudinal ligaments, and helped in the reduction of lateral mass over C2. A controlled compression of C1 will further help in fracture reduction, which requires the placement of C1 lateral mass screws. Although navigated surgery in degenerative cervical spine surgeries is a well-documented entity with proven outcomes [
Furthermore, to prevent dangling, entry points in the lateral mass were first created using a high-speed 2-mm Midas Rex Legend motorized burr, and the tract was further deepened with the burr after checking the accuracy of the entry point. The use of a small burr at a high revolution generates more friction, and enables the creation of a path inside the bony cortex, without wobbling the lateral mass. Handheld instruments have to be avoided. The creation of drill trajectories can be performed in two ways. A completely navigated power drill can be used to create the screw trajectory, but as per the author’s experience, there is always a movement in C1 while placing lateral mass screws, especially when the integrity of the arch is lost, as for these UAF. Using a modified technique, we first drilled the screw trajectory in the required path for a depth of 5 mm only. The accuracy of the navigation was confirmed, the screw trajectory made so far was checked, and the further trajectory then created; and this process was repeated. Minor adjustments in screw trajectories were made as and when required during this continual checking process. The same process had to be repeated on another side before the placement of final screws because inserting the screws on one side before creating a trajectory will cause excess movement in C1, leading to navigation inaccuracy on the contralateral side. After placing the C1 screws, care must be taken to apply controlled compression over the C1 screws because excessive force will result in the opening of fractured anterior ends.
Aside from accuracy, the navigation allows us to perform this surgery more efficiently in terms of blood loss (84.4±8 mL) and operating time (77±14 minutes), compared to 650 mL of blood loss and 110 minutes of operating time in the standard OC and AA fusion [
Hu et al. [
A recent systematic review of the literature in non-navigated C1 solitary fixations evaluated seven clinical studies, and found that three reported screw misplacements [
To the best of our knowledge, this is the first-ever case series on the primary AIRO CT navigated limited osteosynthesis of UAF. The navigation allowed us to place the lateral mass screws in the best possible biomechanically sound trajectory, which then permitted fracture reduction and maintenance through controlled compression across the fixation. The follow-up CT showed adequate healing, and a significant decrease in CLMD. There were no complications or evidence of AA instability. The goals of our surgical intervention were to restore alignment and reasonable anatomy to allow for the physiological healing of the TAL and C1 fracture, with the objective of attaining stability and retaining mobility to achieve excellent clinical, radiological, and functional outcomes.
This technique of fixation can be successfully performed in unstable burst fractures; however, it should be used with caution in patients with comminuted lateral mass fractures because the stability of this fixation primary depends on an adequate hold over the lateral mass [
AO and AA junction stability depends mainly on ligamentous structures, which work as a tension band only when C0–C2 height is maintained. Further stability is provided by the congruent articular integrity, which is bound to fail mechanically when the axial compressive load is applied, as it occurs in UAF. There is growing evidence to support a limited internal fixation for atlas through both anterior and posterior approaches in such injuries, which helps in restoring the alignment, potentiating the healing of such injuries, and preventing instability, while retaining movement of the OC and AA joints. The margin for error in such intricate fixations is very minimal, and the efficacy of construct primarily depends on two screws, which gives the surgeon only one chance to drill appropriate screw trajectories. The malposition of screws in the fracture interspace, foramen, and joint space has been reported and requires revision surgery. A navigated C1 lateral mass screw fixation can negate such complications and permit accurate and adequate fixation in such challenging situations.
No potential conflict of interest relevant to this article was reported.
The project was funded by Ganga Orthopaedic Research & Education Foundation, Coimbatore, India (Grant no., GOREF-01-2015).
(A) The operating room setup, showing the initial position of the patient supine on a stretcher during the intubation and placement of the Mayfield clamps; (B) the turning-over of the patient to a prone position on a radioluscent table, with a C-arm to mark the skin levels before surgical incision; and (C) after exposure of the surgical field, the patient is seen undergoing intraoperative CT scan. CT, computed tomography.
(A) An inadequate open-mouth anteroposterior view; (B) lateral cervical radiographs demonstrating a disruption to the spino-laminar line posteriorly, and an increase in anterior atlanto-dens interval (arrows); (C) a traction radiograph demonstrating reduction (arrows); (D) an axial CT showing disruption to the anterior and posterior arch, along with a fracture in the lateral mass and avulsion of the transverse atlantal ligament, suggesting instability (arrow); (E) a coronal CT shows the disruption of the atlantoaxial and atlanto-occipital joints with a combined lateral mass dislocation of 12 mm, further suggesting instability (arrows); and (F) the sagittal image shows cranial settling, due to a reduction in the C0–C2 height (arrow). CT, computed tomography.
(A–D) An intraoperative CT image with Brainlab navigation, showing the chosen entry point and trajectory for the right lateral mass screw. The arrow mark points toward the attachment of minimally invasive reference array to the cranial portion of the C2 spinous process; (E, F) screw measurements taken through the right and left lateral mass trajectories, measured to 26 mm bilaterally; (G, H) the intraoperative control CT demonstrates the adequate positioning of the lateral mass screws; (I) the immediate postoperative anteroposterior open-mouth view shows a reduction in the lateral mass displacement; and (J) the lateral view demonstrates the reduction in the anterior atlantoaxial distance, and maintenance of the overall cervical alignment, with the implant in a good position. CT, computed tomography.
(A, B) The dynamic flexion and extension radiograph shows no signs of instability at 6 months; (C) the coronal CT shows good articular congruity of the atlantooccipital and atlantoaxial joints, while the combined lateral mass dislocation was only 3 mm, and shows bridging at the avulsion site (arrows); (D) the axial CT with optimal placement of the C1 lateral mass screws, the complete healing of the posterior arch fracture, and the osseous bridging anteriorly indicate the complete healing of the fracture (arrows); and (E) the sagittal CT shows no evidence of cranial settling (arrow). CT, computed tomography.
(A, B) the clinical picture of the patient shows the arc of movement (flexion=40° and extension=50°), (C, D) the axial rotation of 80° to the right and 78° on the left; and (E, F) the right and left lateral bending of 40° and 35°. The patient provided written informed consent for publication of clinical details and images.
Demographic and surgical variables
No. | Age (yr) | Occupation | Mechanism of injury | Follow-up period (mo) | Duration of surgery (min) | Blood loss (mL) | Screw length (mm) |
Screw insertion in length (sec) |
||
---|---|---|---|---|---|---|---|---|---|---|
Right | Left | Right | Left | |||||||
1 | 35 | Bus driver | Road traffic accident | 59 | 96 | 84 | 28 | 28 | 482 | 434 |
2 | 45 | Cook | Road traffic accident | 48 | 84 | 88 | 24 | 24 | 456 | 420 |
3 | 55 | Farmer | Fall from height | 37 | 78 | 94 | 28 | 28 | 475 | 414 |
4 | 25 | Cab driver | Road traffic accident | 35 | 65 | 84 | 26 | 26 | 522 | 428 |
5 | 38 | Bus driver | Road traffic accident | 25 | 62 | 72 | 28 | 28 | 476 | 412 |
Radiological and clinical outcomes following surgical intervention
No. | Radiological outcomes (mm) |
Clinical range of movements following surgery (°) |
Neck Disability Index |
|||||||||||
---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
Combined lateral mass overhang |
Atlanto-axial distance at final follow-up | Rotation |
Flexion | Extension | Lateral bending |
Preoperative | 6 mo | 12 mo | 24 mo | |||||
Before surgery | After surgery | Correction achieved | Right | Left | Right | Left | ||||||||
1 | 16 | 6 | 10 | 2 | 80 | 78 | 40 | 50 | 40 | 35 | 76 | 18 | 10 | 2 |
2 | 13 | 4 | 9 | 1.7 | 76 | 69 | 32 | 44 | 24 | 18 | 72 | 22 | 12 | 2 |
3 | 14 | 7 | 7 | 1.8 | 58 | 64 | 40 | 30 | 15 | 15 | 80 | 24 | 14 | 4 |
4 | 14 | 6 | 8 | 2.1 | 74 | 71 | 30 | 45 | 25 | 16 | 84 | 12 | 8 | 0 |
5 | 16 | 3 | 13 | 1.5 | 80 | 76 | 35 | 50 | 38 | 40 | 78 | 14 | 6 | 0 |
0.001 | - | - | <0.001 |