Update on Upper Cervical Injury Classifications: The New AO Upper Cervical Spine Classification System

Global Validation of the AO Spine Upper Cervical Injury Classification: Geographic Region Affects Reliability and Reproducibility

STUDY DESIGN

Global Survey.

OBJECTIVE

To determine the accuracy, interobserver reliability, and intraobserver reproducibility of the AO Spine Upper Cervical Injury Classification System based on surgeons' AO Spine region of practice (Africa, Asia, Central/South America, Europe, Middle East, and North America).

METHODS

A total of 275 AO Spine members assessed 25 upper cervical spine injuries and classified them according to the AO Spine Upper Cervical Injury Classification System. Reliability, reproducibility, and accuracy scores were obtained over two assessments administered at three-week intervals. Kappa coefficients (ƙ) determined the interobserver reliability and intraobserver reproducibility.

RESULTS

On both assessments, participants from Europe and North America had the highest classification accuracy, while participants from Africa and Central/South America had the lowest accuracy (P < .0001). Participants from Africa (assessment 1 (AS1):ƙ = .487; AS2:0.491), Central/South America (AS1:ƙ = .513; AS2:0.511), and the Middle East (AS1:0.591; AS2: .599) achieved moderate reliability, while participants from North America (AS1:ƙ = .673; AS2:0.648) and Europe (AS1:ƙ = .682; AS2:0.681) achieved substantial reliability. Asian participants obtained substantial reliability on AS1 (ƙ = .632), but moderate reliability on AS2 (ƙ = .566). Although there was a large effect size, the low number of participants in certain regions did not provide adequate certainty that AO regions affected the likelihood of participants having excellent reproducibility (P = .342).

CONCLUSIONS

The AO Spine Upper Cervical Injury Classification System can be applied with high accuracy, interobserver reliability, and intraobserver reproducibility. However, lower classification accuracy and reliability were found in regions of Africa and Central/South America, especially for severe atlas injuries (IIB and IIC) and atypical hangman's type fractures (IIIB injuries).

Rethinking cervical spine clearance in obtunded trauma patients: An updated systematic review and meta-analysis

BACKGROUND

Cervical spine injuries (CSI) are often challenging to diagnose in obtunded adult patients with blunt trauma and the optimal imaging modality remains uncertain. This study systematically synthesized the last decade of evidence to determine the type of imaging required to clear the c-spine in obtunded patients with blunt trauma.

METHODS

A systematic review with meta-analysis was conducted and reported using PRISMA 2020 guidelines. The protocol was registered on June 22, 2022 (PROSPERO CRD42022341386). MEDLINE (Ovid), EMBASE, and Cochrane Library were searched for studies published between January 1, 2012, and October 17, 2023. Studies comparing CT alone to CT combined with MRI for c-spine clearance were included. Two independent reviewers screened articles for eligibility in duplicate. Meta-analysis was conducted using a random-effect model. Risk of bias and quality assessment were performed using the ROBINS-I and QUADAS-2. The certainty of evidence was assessed using the GRADE methodology.

RESULTS

744 obtunded trauma patients from six included studies were included. Among the 584 that had a negative CT scan, the pooled missed rate of clinically significant CSI using CT scans alone was 6 % (95 % CI: 0.02 to 0.17), and the pooled missed rate of CSI requiring treatment was 7 % (95 % CI: 0.02 to 0.18). High heterogeneity was observed among included studies (I² > 84 %). The overall risk of bias was moderate, and the quality of evidence was low due to the retrospective nature of the included studies and high heterogeneity.

CONCLUSIONS

Limited evidence published in the last decade found that CT scans alone may not be sufficient for detecting clinically significant CSI and injuries requiring treatment in obtunded adult patients with blunt trauma.

IMPLICATIONS OF KEY FINDINGS

Clinicians should be aware of the limitations of CT scans and consider using MRI when appropriate. Future research should focus on prospective studies with standardized outcome measures and uniform reporting.

Transoral unilateral lag screw osteosynthesis for coronal split fracture of the lateral mass of the atlas - case report, operative technique and review of the literature

Introduction

Atlas ring fractures, which account for 1.3% of all spinal fractures, are predominantly managed conservatively. However, in certain cases, surgical treatment may be necessary depending on the type of fracture, degree of comminution, fracture location, and associated ligamentous injuries. Surgical stabilization frequently results in a posterior C1-2 or C0-2 fusion, which restricts movement, particularly craniocervical rotation. Coronal split fractures of the lateral mass need to be reduced and fixed due to dislocation, instability and secondary osteoarthritis. The preferred treatment approach involves internal fixation of the reduced fracture fragments, while avoiding restriction of the upper cervical spine's range of motion (ROM).

Research question

Is unilateral anterior transoral lag screw for treatment of unstable coronal split fracture of lateral mass of the atlas feasible and a safe treatment option?

Case Report Material and Methods

We report on a 55-year-old female suffering from polytrauma with multiple spinal and extremity injuries.

Results

A coronal split fracture of the lateral mass of the atlas was treated minimally invasive with a transoral lag screw technique to reduce and fix the fracture that has a tendency for fracture gap widening. Stable fixation and fracture union and thus restoration of function was achieved.

Discussion and conclusion

Transoral lag screw osteosynthesis for coronal split fracture of the lateral mass of the atlas is a potential treatment option in selected cases to preserve mobility in the upper cervical spine after spinal trauma.

Injury patterns of the spine following blunt trauma: A per-segment analysis of spinal structures and their detection rates in CT and MRI

Rationale and objectives

To provide a detailed analysis of injury patterns of the spine following blunt trauma and establish the role of supplementary MRI by evaluating discrepancies in the detection rates of damaged structures in CT and MRI.

Method

216 patients with blunt trauma to the spine who underwent CT followed by supplementary MRI were included in this study. Two board-certified radiologists blinded to clinical symptoms and injury mechanisms independently interpreted all acquired CT and MRI images. The interpretation was performed using a dedicated catalogue of typical findings associated with spinal trauma and assessed for spinal stability using the AO classification systems.

Results

Lesions to structures associated with spinal instability were present in 31.0% in the cervical spine, 12.3% in the thoracic spine, and 29.9% in the lumbar spine. In all spinal segments, MRI provided additional information regarding potentially unstable injuries. Novel information derived from supplementary MRI changed clinical management in 3.6% of patients with injury to the cervical spine. No change in clinical management resulted from novel information on the thoracolumbar spine. Patients with injuries to the vertebral body, intervertebral disc, or spinous process were significantly more likely to benefit from supplementary MRI.

Conclusion

In patients that sustained blunt spinal trauma, supplementary MRI of the cervical spine should routinely be performed to detect injuries that require surgical treatment, whereas CT is the superior imaging modality for the detection of unstable injuries in the thoracolumbar spine.

The Reliability of the AO Spine Upper Cervical Classification System in Children: Results of a Multi-Center Study

BACKGROUND

There is no uniform classification system for traumatic upper cervical spine injuries in children. This study assesses the reliability and reproducibility of the AO Upper Cervical Spine Classification System (UCCS), which was developed and validated in adults, to children.

METHODS

Twenty-six patients under 18 years old with operative and nonoperative upper cervical injuries, defined as from the occipital condyle to the C2-C3 joint, were identified from 2000 to 2018. Inclusion criteria included the availability of computed tomography and magnetic resonance imaging at the time of injury. Patients with significant comorbidities were excluded. Each case was reviewed by a single senior surgeon to determine eligibility. Educational videos, schematics describing the UCCS, and imaging from 26 cases were sent to 9 pediatric orthopaedic surgeons. The surgeons classified each case into 3 categories: A, B, and C. Inter-rater reliability was assessed for the initial reading across all 9 raters by Fleiss's kappa coefficient (kF) along with 95% confidence intervals. One month later, the surgeons repeated the classification, and intra-rater reliability was calculated. All images were de-identified and randomized for each read independently. Intra-rater reproducibility across both reads was assessed using Fleiss's kappa. Interpretations for reliability estimates were based on Landis and Koch (1977): 0 to 0.2, slight; 0.2 to 0.4, fair; 0.4 to 0.6, moderate; 0.6 to 0.8, substantial; and >0.8, almost perfect agreement.

RESULTS

Twenty-six cases were read by 9 raters twice. Sub-classification agreement was moderate to substantial with α κ estimates from 0.55 for the first read and 0.70 for the second read. Inter-rater agreement was moderate (kF 0.56 to 0.58) with respect to fracture location and fair (kF 0.24 to 0.3) with respect to primary classification (A, B, and C). Krippendorff's alpha for intra-rater reliability overall sub-classifications ranged from 0.41 to 0.88, with 0.75 overall raters.

CONCLUSION

Traumatic upper cervical injuries are rare in the pediatric population. A uniform classification system can be vital to guide diagnosis and treatment. This study is the first to evaluate the use of the UCCS in the pediatric population. While moderate to substantial agreement was found, limitations to applying the UCCS to the pediatric population exist, and thus the UCCS can be considered a starting point for developing a pediatric classification.

LEVEL OF EVIDENCE

Level III.

Cervical spine trauma

Cervical spine trauma encompasses a wide of injuries, ranging from stable, minor lesions to unstable, complex lesions that can lead to neurologic sequelae or vascular involvement. The Canadian C-Spine Rule and the NEXUS criteria aim to identify individuals with a low risk of cervical spine trauma who can safely forgo imaging tests. In high-risk patients, an imaging test is indicated. In adult patients the imaging test of choice is multidetector computed tomography. Complementary imaging tests such as CT angiography of the supra-aortic vessels and/or magnetic resonance imaging are occasionally necessary. It can be challenging for radiologists to diagnose and classify these lesions, because some of them can be subtle and difficult to detect. This paper aims to describe the most important imaging findings and the most widely used classification systems.

An independent inter- and intra-observer agreement assessment of the AOSpine upper cervical injury classification system

BACKGROUND CONTEXT

The complex anatomy of the upper cervical spine resulted in numerous separate classification systems of upper cervical spine trauma. The AOSpine upper cervical classification system (UCCS) was recently described; however, an independent agreement assessment has not been performed.

PURPOSE

To perform an independent evaluation of the AOSpine UCCS.

STUDY DESIGN

Agreement study.

PATIENT SAMPLE

Eighty four patients with upper cervical spine injuries.

OUTCOME MEASURES

Inter-observer agreement; intra-observer agreement.

METHODS

Complete imaging studies of 84 patients with upper cervical spine injuries, including all morphological types of injuries defined by the AOSpine UCCS were selected and classified by six evaluators (from three different countries). The 84 cases were presented to the same raters randomly after a 4-week interval for repeat evaluation. The Kappa coefficient (κ) was used to determine inter- and intra-observer agreement.

RESULTS

The interobserver agreement was almost perfect when considering the fracture site (I, II or III), with κ=0.82 (0.78-0.83), but the agreement according to the site and type level was moderate, κ=0.57 (0.55-0.65). The intra-observer agreement was almost perfect considering the injury, with κ=0.83 (0.78-0.86), while according to site and type was substantial, κ=0.69 (0.67-0.71).

CONCLUSIONS

We observed only a moderate inter-observer agreement using this classification. We believe our results can be explained because this classification attempted to organize many different injury types into a single scheme.

Radiologic utility of the Gehweiler and AO spine classification systems for C1 Trauma: A retrospective review from a Level I trauma center

Objective

The purpose of our study was to identify adult trauma patients with an acute C1 burst fracture, evaluate for concomitant transverse atlantal ligament (TAL) injury, and apply the modified Gehweiler and AO spine classification systems to determine the utility of these classification systems in accurately defining C1 trauma.

Materials and Methods

Adult trauma patients with an acute C1 fracture were identified retrospectively using Nuance mPower software. The C1 fracture was described based on whether the fracture involved the anterior arch, posterior arch, lateral mass, medial tubercle, and/or transverse process. If follow-up cervical magnetic resonance imaging (MRI) was performed, the presence and location of an associated TAL injury was recorded. The anatomic location of the C1 burst fracture and TAL injury, if present, were compared with the descriptive classification systems outlined by Gehweiler/Dickman (modified) and the AO Spine society. Any additional osseous trauma of the skull base and C1-C2 was also recorded along with relevant clinical history and management.

Results

Thirty-nine patients were identified with an acute C1 burst fracture on cervical computed tomography (CT) with seventy-seven percent of patients undergoing follow-up cervical MRI. Observed fracture patterns were divided into five distinct types based on CT findings and further subdivided based on the integrity of the transverse altantal ligament on MRI. TAL tears were observed exclusively in type 3 fractures (anterior and posterior arch fractures) and type 4 fractures (anterior arch, posterior arch, and lateral mass fractures). The modified Gehweiler classification system failed to accurately describe the anatomic location of the C1 fracture in forty-four percent of patients, whereas the AO spine was too broad and failed to accurately describe fracture location in our cohort.

Conclusions

The Gehweiler and AO spine classifications demonstrated significant shortcomings in the accurate description of patients with C1 trauma. Whereas the Gehweiler system did not accurately describe the anatomic location of the various C1 fractures, the AO spine system was too broad and failed to radiologically classify fracture location. Moreover, there was a high number of patients with AO spine type B injuries without atlantoaxial translation that nevertheless required C1-C2 fusion for atlantoaxial instability. We suggest the need for an updated classification system that takes into account both the CT (fracture location) and MRI (TAL integrity) appearance of C1 trauma. An updated classification strategy will offer a radiologic standardization of C1 trauma that will aid in future research studies and help optimize patient management.