Traumatic Posterior Atlantoaxial Dislocation with Intact Odontoid Treated by C2 Laminar Screw Fixation: A Case Report

Abstract

Background

Atlantoaxial dislocation (AAD) is a rare but potentially life-threatening condition characterized by an abnormal alignment between the atlas and axis. Traumatic AAD are commonly associated with severe ligamentous injury and may result in spinal cord compression or neurological deficits. Posterior atlantoaxial dislocation with an intact odontoid process and without associated fracture is extremely uncommon and has rarely been reported in literature.

Objective

To report a rare case of traumatic posterior atlantoaxial dislocation with an intact odontoid process and describe its management strategy, including emergency reduction and posterior C1–C2 fixation using a C2 laminar screw.

Methods

A 51-year-old man was admitted after a traffic accident with severe polytrauma including traumatic brain injury, multiple rib fractures, bilateral hemopneumothorax, splenic injury, and fractures of the left tibia and fibula. Cervical computed tomography revealed a posterior atlantoaxial dislocation without odontoid fracture. Emergency skull traction was performed under general anesthesia with a gradual increase in traction weight from 5 to 10 kg under fluoroscopic guidance. Posterior C1–C2 fixation was subsequently performed because of the redislocation observed on follow-up imaging. Because of a narrow left C2 pedicle and a high-riding vertebral artery, a C2 laminar screw was used as an alternative fixation technique.

Results

Intraoperative fluoroscopy and postoperative imaging confirmed a satisfactory reduction and stable fixation of the atlantoaxial complex. However, despite intensive treatment, the patient died 10 days postoperatively due to multiple organ failure secondary to severe polytrauma rather than complications related to the spinal procedure.

Conclusion

Emergency skull traction may achieve temporary reduction in traumatic atlantoaxial dislocation; however, surgical stabilization is often required in cases with significant instability. C2 laminar screw fixation is a safe and effective alternative when pedicle screw placement is limited by anatomical variations.

Introduction

Atlantoaxial dislocation (AAD) is a rare pathological condition characterized by abnormal alignment between the atlas (C1) and axis (C2). It may result from trauma, inflammatory diseases, congenital malformations, or infection.¹ Among the various types of AAD, anterior dislocation is the most common and may lead to severe neurological deficits due to compression of the spinal cord or medulla oblongata.² The stability of the atlantoaxial complex mainly depends on the integrity of the transverse and alar ligaments. Injury to these stabilizing structures can cause significant instability, and temporary reduction achieved by traction may be followed by redislocation due to persistent ligamentous insufficiency. In contrast, posterior atlantoaxial dislocation is extremely uncommon, with only a limited number of cases reported in the literature.³ Most traumatic C1–C2 dislocations are anterior. Here, we report a rare case of traumatic posterior C1–C2 dislocation that was treated surgically and discuss its clinical characteristics and management.

Case Report

A 51-year-old man was admitted to our hospital after a traffic accident. He was diagnosed with atlantoaxial dislocation, spinal cord injury, severe closed traumatic brain injury, skull fracture, multiple rib fractures, left tibial and fibular fractures, splenic injury, and bilateral hemopneumothorax.

On admission, his Glasgow Coma Scale (GCS) score was 13. Initial cranial computed tomography (CT) revealed subarachnoid hemorrhage and bilateral frontal lobe hemorrhage. Cervical CT demonstrated posterior atlantoaxial dislocation (Figure 1).

Figure 1.

Preoperative computed tomography (CT) images demonstrating traumatic posterior atlantoaxial dislocation. (A) Sagittal CT image showing posterior atlantoaxial dislocation with an intact odontoid process (yellow arrow). (B) Coronal CT image demonstrating the relationship between the atlas and axis, with the odontoid process indicated by the yellow arrow. (C) Axial CT image showing the odontoid process (yellow arrow) and the posterior displacement of the atlas relative to the axis.

Emergency reduction was attempted using skull traction under general anesthesia. The traction weight was gradually increased from 5 kg to 10 kg under continuous intraoperative fluoroscopic monitoring, which demonstrated a satisfactory reduction in atlantoaxial dislocation. After reduction, the cervical spine was immobilized using a cervical collar (Figure 2). The patient remained intubated and was transferred to the intensive care unit (ICU) for advanced life support.

Figure 2.

Intraoperative reduction of the posterior atlantoaxial dislocation using skull traction. (A) Pre-reduction lateral fluoroscopic image demonstrating posterior atlantoaxial dislocation (yellow arrow). (B) Post-reduction lateral fluoroscopic image showing satisfactory realignment of the atlantoaxial joint after skull traction (yellow arrow). (C and D) Intraoperative photographs illustrating the skull traction procedure performed under general anesthesia.

A follow-up CT scan performed on postoperative day 2 confirmed a satisfactory reduction, and conservative management was continued (Figure 3). However, repeat CT and magnetic resonance imaging (MRI) on postoperative day 4 demonstrated a redislocation of the atlantoaxial joint (Figure 4).

Figure 3.

Post-reduction computed tomography (CT) images confirming satisfactory reduction of the atlantoaxial joint. (A) Sagittal CT image demonstrating satisfactory reduction of the posterior atlantoaxial dislocation (yellow arrow). (B) Axial CT image confirming satisfactory realignment of the atlantoaxial joint (yellow arrow).

Figure 4.

Follow-up imaging demonstrating redislocation of the atlantoaxial joint and preoperative vascular and magnetic resonance imaging evaluation. (A) Sagittal CT image demonstrating recurrent posterior atlantoaxial dislocation (yellow arrow). (B) Coronal CT image confirming redislocation of the atlantoaxial joint (yellow arrow). (C) Axial CT image showing recurrent posterior displacement of the atlas relative to the axis (yellow arrow). (D) Computed tomography angiography (CTA) demonstrating a high-riding vertebral artery (yellow arrow). (E) Sagittal magnetic resonance imaging (MRI) showing the redislocated atlantoaxial joint (yellow arrow). (F) Axial MRI demonstrating the relationship between the spinal cord and the redislocated atlantoaxial complex (yellow arrow).

Considering the need for further systemic treatment and the risk of spinal cord injury caused by persistent instability, posterior C1–C2 screw fixation was planned.

On postoperative day 5, the patient underwent surgery under general anesthesia. Skull traction of 2 kg was applied, and after adjusting the traction angle, intraoperative fluoroscopy confirmed successful reduction of atlantoaxial dislocation. Posterior C1–C2 fixation was performed using a screw-rod construct to stabilize the atlantoaxial complex.

After surgery, the patient remained intubated and was transferred back to the intensive care unit (ICU) under continuous monitoring. Postoperative lateral cervical radiographs and CT scans confirmed satisfactory reduction and stable fixation of the atlantoaxial complex (Figure 5).

Figure 5.

Postoperative computed tomography (CT) images demonstrating satisfactory reduction and posterior C1–C2 fixation. (A) Sagittal CT image showing satisfactory reduction of the atlantoaxial joint (yellow arrow). (B) Sagittal CT image demonstrating the position of the C1 screw-rod construct (yellow arrow). (C) Sagittal CT image showing the C2 screw-rod construct, including the C2 laminar screw (yellow arrow). (D) Axial CT image demonstrating bilateral C1 pedicle screws (yellow arrow). (E) Axial CT image showing the right C2 pedicle screw (yellow arrow). (F) Axial CT image demonstrating the left C2 laminar screw (yellow arrow).

Despite intensive treatment, the patient developed multiple organ failure and died 10 days after the surgery.

Discussion

Atlantoaxial dislocation (AAD) is a rare but potentially life-threatening condition characterized by abnormal alignment between the atlas (C1) and axis (C2). Because of the close anatomical relationship between the atlantoaxial complex and the upper cervical spinal cord as well as the medulla oblongata, severe neurological deficits or even sudden death may occur if the condition is not promptly recognized and treated. AAD may result from trauma, inflammatory diseases, congenital anomalies, or infections. Among these etiologies, traumatic injury is an important cause of acute instability of the craniovertebral junction. Disruption of the transverse and alar ligaments is considered the primary mechanism leading to atlantoaxial instability and subsequent dislocation.⁴ Among the different patterns of AAD, anterior dislocation is the most commonly reported, whereas posterior dislocation is extremely rare and only sporadically described in the literature.⁵

Early reduction of the atlantoaxial joint is crucial in patients with acute traumatic AAD because persistent malalignment may result in ongoing spinal cord compression and secondary neurological deterioration. Skull traction is widely used as an initial management strategy to restore anatomical alignment of the atlantoaxial joint. By gradually increasing the traction weight under close monitoring, skull traction can effectively reduce dislocation and alleviate neural compression in many cases.⁶ In the present case, emergency skull traction was performed under general anesthesia immediately after the diagnosis. The traction weight was progressively increased from 5 to 10 kg, and satisfactory reduction of the atlantoaxial joint was achieved under continuous intraoperative fluoroscopic guidance. This result suggests that skull traction can be an effective emergency intervention for restoring the anatomical relationship of the atlantoaxial complex.

However, traction reduction alone may not provide sufficient stability in patients with severe ligamentous disruptions. Previous studies have demonstrated that when the transverse ligament is completely ruptured or the atlantoaxial joint becomes highly unstable, reduction achieved by traction may be temporary, and redislocation may occur after removal of traction or during conservative treatment.⁷ Previous reports of traumatic posterior atlantoaxial dislocation without odontoid fracture have also emphasized the importance of recognizing underlying ligamentous instability, as temporary reduction may not prevent recurrent displacement and surgical stabilization is frequently required. In our patient, although satisfactory reduction was confirmed by CT two days after traction, follow-up imaging on postoperative day four revealed a redislocation of the atlantoaxial joint. This finding strongly indicates a significant instability of the atlantoaxial complex. Therefore, surgical stabilization is necessary to restore long-term stability and prevent potential spinal cord injury.

Posterior C1–C2 fusion is currently regarded as a reliable surgical strategy for the treatment of atlantoaxial instability.⁸ Various fixation techniques have been described, including transarticular screw fixation (Magerl technique) and C1 lateral mass screw combined with C2 pedicle screw fixation (Harms technique).⁹ Among these methods, the Harms technique has gained widespread acceptance because of its strong biomechanical stability, reliable fusion rate, and ability to facilitate intraoperative reduction. Nevertheless, the placement of C2 pedicle screws may be challenging or unsafe in certain anatomical situations. In particular, the presence of a narrow C2 pedicle or high-riding vertebral artery significantly increases the risk of vertebral artery injury during screw insertion.¹⁰

Therefore, preoperative imaging is essential to determine the optimal fixation strategy. In the present case, preoperative CT demonstrated that the left C2 pedicle was relatively narrow and was accompanied by a high-riding vertebral artery, which significantly increased the risk associated with pedicle screw placement. To minimize the possibility of vascular injury, a C2 laminar screw was selected as an alternative fixation technique on the left side. The C2 laminar screw technique was first described by Wright as a safe and effective alternative for posterior fixation of the axis.¹¹ This technique involves the insertion of screws through the C2 lamina rather than the pedicle, thereby avoiding the vertebral artery and reducing the risk of vascular complications. Biomechanical studies have demonstrated that C2 laminar screws provide comparable stability to pedicle screws in resisting flexion, extension, and rotational forces.¹² Consequently, laminar screws have become an important alternative when pedicle screw placement is not feasible owing to anatomical constraints.

In our case, posterior fixation was achieved by using C1 screws combined with a left C2 laminar screw construct. Postoperative radiographs and CT confirmed satisfactory reduction and stable fixation of the atlantoaxial complex. These findings indicate that C2 laminar screw fixation can serve as a reliable alternative for patients with high-risk vertebral artery anatomy or narrow pedicles.

Despite successful surgical stabilization of the atlantoaxial joint, the patient ultimately died of multiple organ failure. Traumatic atlantoaxial dislocation is frequently associated with severe polytrauma, including traumatic brain injury, thoracic injury, and abdominal organ damage. These injuries may significantly influence patient prognosis and survival.¹³ In the present case, the patient sustained multiple severe injuries including traumatic brain injury, bilateral hemopneumothorax, splenic injury, and multiple fractures. Such extensive trauma places patients at a high risk for systemic inflammatory response syndrome and subsequent multiple organ dysfunction.

Previous studies have shown that multiple organ failure remains one of the leading causes of death in severely injured trauma patients, particularly those with significant head injuries and systemic inflammatory responses.¹⁴ Therefore, although surgical stabilization of the cervical spine may successfully address local spinal instability, the overall outcome of these patients often depends on the severity of associated systemic injuries and effectiveness of multidisciplinary critical care management. This study has several limitations. As a single case report, the findings cannot be generalized to all patients with traumatic posterior atlantoaxial dislocation. In addition, although satisfactory reduction and stable fixation were achieved, the patient’s severe polytrauma and subsequent multiple organ failure prevented long-term evaluation of neurological recovery and spinal functional outcomes.

In conclusion, this case report highlights several important clinical considerations. Emergency skull traction can be an effective initial treatment for traumatic atlantoaxial dislocation and may help restore the anatomical alignment. However, in cases with severe ligamentous disruption, the atlantoaxial complex may remain highly unstable, and redislocation can occur despite successful initial reduction. Therefore, careful monitoring with serial imaging and early surgical stabilization should be considered once instability is confirmed. Posterior C1–C2 fixation remains a reliable method for restoring atlantoaxial stability. When anatomical variations, such as a narrow pedicle or high-riding vertebral artery, are present, C2 laminar screws provide a safe and effective alternative fixation strategy. Finally, in patients with severe polytrauma, the overall prognosis may be determined not only by spinal injury, but also by the extent of associated systemic injuries.

Funding Statement

This project was financially supported by the Guangdong Basic and Applied Basic Research Foundation (Grant No. 2022A1515220139), the Talent Development Foundation of the First Dongguan Affiliated Hospital of Guangdong Medical University (Grant No. GCC2023009), and Medical-Enterprise Collaborative Funding Program (Grant No. ZWYX2023K004).

Ethics and Consent to Participate Declarations

All treatments described in this article were performed with the informed consent of the patient’s family. Ethical clearance was obtained from the Ethics Committee of the First DongGuan Affiliated Hospital of Guangdong Medical University to publish the case report, and written consent was obtained from the patient’s sole surviving next of kin sister for the use of the patient’s clinical data and pictures in the report, as the patient ultimately died of multiple organ failure. The presented case report was conducted in accordance with the Declaration of Helsinki. All data used were anonymized.

Disclosure

First author: XinQia Huang. The authors declare that they have no known competing financial interests or personal relationships that could have influenced the work reported in this study.