First case of completely asymptomatic traumatic posterior atlantoaxial dislocation without odontoid fracture and literature review

Abstract

Traumatic posterior atlantoaxial dislocation (PAAD) without odontoid fracture is exceptionally rare. We report the first documented case entirely asymptomatic at presentation. A 78-year-old woman, evaluated after a motor vehicle collision, presented with no neck pain, neurological deficits, or loss of consciousness. Computed tomography scan revealed PAAD without odontoid fracture. Closed reduction was successfully performed, followed by posterior C1–C2 fixation with the Goel technique, extended to C3 due to C2–C3 instability. Postoperative imaging confirmed complete reduction, and the patient remained neurologically intact at 6-month follow-up. This case highlights the potential for silent presentation and the need for individualized management.

INTRODUCTION

Traumatic posterior atlantoaxial dislocation (PAAD) without an associated odontoid fracture is an exceptionally rare injury, first described by Haralson and Boyd in 1969.[1] Since then, only isolated cases have been described in the literature. Although a large proportion of patients with PAAD in the absence of odontoid fracture have been reported as neurologically intact,[1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16] all previously published cases exhibited at least neck pain or loss of consciousness. To our knowledge, no report has documented a patient with traumatic PAAD who was entirely asymptomatic, without neurological deficits, cervical pain, or alteration of consciousness at the time of presentation. This raises important questions regarding the anatomical or biomechanical factors that may protect certain individuals from neurological compromise despite significant atlantoaxial displacement. Proposed explanations include congenital or age-related variations in spinal canal diameter, craniovertebral morphology, and the buffering effect of cerebrospinal fluid (CSF) surrounding the spinal cord.[2,3,9,17] In this report, we describe the first documented case of completely asymptomatic traumatic PAAD without associated odontoid fracture, and we provide a review of previously published cases, discussing potential protective anatomical factors and implications for diagnosis and management.

CASE REPORT

A 78-year-old woman presented to our emergency department following a low-energy frontal motor vehicle collision. She was alert and hemodynamically stable at admission, reporting no neck pain, sensory disturbances, or motor weakness. Physical examination revealed no tenderness or deformity in the neck area, and neurological assessment was unremarkable. Her Glasgow Coma Scale was 15/15 at presentation. Given the dynamics of trauma, the patient underwent an urgent computed tomography (CT) scan. Unexpectedly, imaging revealed a PAAD [Figure 1].

Figure 1.

Posterior atlantoaxial dislocation without odontoid fracture – Three-dimensional reconstruction of the computed tomography scan; (a) Frontal view; (b) Sagittal view; (c) Axial view; (d) Mid-sagittal section

No fracture of the odontoid process, posterior arch, or lateral masses of C1 was detected. The facet joints appeared intact with preserved cortical margins. Measurements of the sagittal canal diameter and craniovertebral angles were performed on mid-sagittal and axial planes using PACS workstation tools. The foramen magnum diameter measured 37.5 mm at the CT mid-sagittal cut, while the C1 diameter measured 31.5 mm. The spinal canal diameter was 16.9 mm at C2 level. The posterior translation of C1 relative to C2 measured 16 mm on the axial plane [Figure 2].

Figure 2.

Computed tomography (CT) scan of the posterior atlantoaxial dislocation (PAAD); (a) Sagittal CT scan showing the PAAD; (b) Sagittal CT scan with measurement of the foramen magnum, C1 diameter and spinal canal diameter; (c) Axial view of the CT scan showing the entity of the dislocation and distance from the anterior facet of the odontoid process to the articular surface of the atlas

A closed manual reduction was performed under general anesthesia with fluoroscopic guidance. Gentle traction and extension maneuvers achieved successful correction of the posterior displacement. Subsequently, posterior C1–C2 stabilization using the Goel technique was performed. Due to mild C2–C3 instability, the screw fixation was extended to C3. Final intra-operative radiograph and postoperative CT scan confirmed complete reduction and stabilization of the dislocation, correct screw placement, and restoration of the normal relationship between the anterior arch of C1 and the odontoid process [Figure 3]. Postoperatively, the patient was hospitalized in the ICU without complications and was discharged on postoperative day 25, after complete rehabilitation of all trauma-related injuries, including rib fractures. At 6-month follow-up, the patient remained neurologically intact and demonstrated stable fixation of the atlantoaxial complex on imaging.

Figure 3.

Postoperative imaging after reduction and stabilization of the posterior atlantoaxial dislocation (PAAD); (a) Intra-operative fluoroscopy after screw fixation; (b) Sagittal computed tomography scan showing reduction of the PAAD; (c) Sagittal scan showing the C1–C3 screw fixation

This work was conducted as a single-patient case report in accordance with the CARE guidelines.[18] Written informed patient consent for participation and publication was obtained, and institutional review board approval was deemed unnecessary according to institutional policy for anonymized descriptive study.

DISCUSSION

We conducted a literature search of previously published studies using the keyword “posterior atlantoaxial dislocation” in PubMed, Scopus, and EMBASE. Our review identified 16 reported cases of PAAD without odontoid fracture in patients presenting without neurological deficits. However, none of the published cases described a completely asymptomatic patient. All reported patients exhibited neck pain and/or loss of consciousness at presentation [Table 1]. In contrast, our patient presented without neurological symptoms, neck pain, or loss of consciousness, suggesting that individual anatomical or physiological factors may contribute to preserved neurological function in selected cases.

Table 1.

Summary of cases from literature review presenting with posterior atlantoaxial dislocation without odontoid fracture and without neurological deficit

Study	Country	Sex	Age (years)	Trauma cause	Loss of consciousness	Neck pain	Closed reduction attempt (day)	Intervention	Follow-up (months)
Haralson and Boyd (1969)[1]	USA	Male	30	MVA	Yes	NA	Success (6)	Posterior wiring	18
Patzakis et al. (1974)[4]	USA	Male	37	MVA	Yes	NA	Success (1)	-	36
Jamshidi et al. (1983)[5]	USA	Male	22	MVA	Yes	Yes	Success (2)	Posterior wiring	NA
Wong et al. (1991)[6]	USA	Male	23	MVA	Yes	Yes	Success (1)	Posterior wiring	84
Fujimura et al. (1997)[7]	Japan	Male	54	MVA	No	Yes	Success (1)	-	NA
Neumann et al. (2003)[8]	Germany	Male	22	MVA	Yes	NA	Success (1)	-	24
Jiang et al. (2010)[9]	China	Male	48	MVA	Yes	Yes	Failed (2)	Anterior trans-articular screws	21
Zhen et al. (2011)[10]	China	Male	44	EQ	Yes	Yes	Failed (9)	Posterior wiring	NA
Jagannatha et al. (2013)[11]	India	Male	32	MVA	Yes	Yes	Success (1)	Posterior C1–C2 screws	12
Hu et al. (2015)[12]	China	Male	50	HOT	Yes	Yes	Failed (1)	Posterior C1–C2 screws	15
Yu et al. (2015)[13]	China	Male	43	FFH	Yes	No	Failed (24)	Anterior trans-articular screws and posterior C1–C2 screws	12
Ning et al. (2019)[14]	China	Male	52	MVA	No	Yes	Not attempted	Posterior C1–C2 screws	6
Peterson et al. (2020)[15]	USA	Male	39	MVA	Yes	NA	Success (1)	Occipito-cervical (C5) fusion	NA
Sumethvanich et al. (2021)[16]	Thailand	Female	40	MVA	Yes	Yes	Success (1)	Posterior C1–C2 screws	12
Ibrahim et al. (2024)[2]	Egypt	Male	21	MVA	Yes	Yes	Success (1)	Posterior C1–C2 screws	36
Yan et al. (2025)[3]	China	Male	43	MVA	Yes	Yes	Failed (1)	Posterior C1–C2 screws	NA
Our case (2025)	Italy	Female	78	MVA	No	No	Success (1)	Posterior C1–C3 screws	6

MVA - Motor vehicle accident; EQ - Earthquake; FFH - Fall from height; HOT - Heavy object trauma; NA - Not available

Possible mechanisms of asymptomatic presentation

Several mechanisms have been proposed to explain how significant C1–C2 displacement may occur without producing neurological injury. One commonly cited concept is Steel’s “rule of thirds,” which states that at the level of the atlas, approximately one-third of the spinal canal is occupied by the odontoid process, one-third by the spinal cord, and the remaining third by CSF.[2,9,17] In this model, a sufficiently generous posterior CSF space could act as a protective buffer during posterior translation of C1, reducing the likelihood of direct cord compression. An alternative explanation involves individual anatomical variations. Patients with a congenitally wide spinal canal or an enlarged craniovertebral junction may tolerate a greater degree of atlantoaxial displacement before neurological structures become compromised. A further consideration relates to the biomechanics of trauma. Low rotational force or favorable motion vectors may allow joint displacement without significant cord compression.

However, these hypotheses remain speculative and are difficult to be demonstrated in large cohorts due to the exceptional rarity of this type of injury.

Management considerations

Management of PAAD without odontoid fracture remains challenging due to the potential for catastrophic neurological injury and not standardized due to the rarity of the condition.[2,3] Closed reduction remains the first-line approach whenever feasible, but surgical stabilization is needed to prevent redislocation.[2,3,19,20] The Goel technique is widely recognized for its biomechanical strength and versatility.[19,20] In our patient, the stabilization was extended to C3 to address mild C2–C3 instability, reflecting the need to individualize fixation strategies based on individual clinical and anatomical features.[15,20] This extended approach is not commonly reported in the management of PAAD without odontoid fracture, but this case may reflect the need for individualized management for each case.

CONCLUSION

This is the first known case of traumatic PAAD without odontoid fracture, completely asymptomatic at presentation. Our case highlights that such severe injury may be present without any symptoms and underscores the importance of careful trauma evaluation. Individualized surgical planning may be required, depending on clinical findings and anatomical variations.

Declaration of patient consent

The authors certify that they have obtained all appropriate patient consent forms. In the form, the patient has given her consent for her images and other clinical information to be reported in the journal. The patient understands that name and initials will not be published and due efforts will be made to conceal identity, but anonymity cannot be guaranteed.

Conflicts of interest

There are no conflicts of interest.

Funding Statement

Nil.