The Subaxial Cervical Spine Injury Classification System: an external agreement validation study

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

The upper cervical spine accounts for the largest proportion of cervical range of motion afforded by a complex system of bony morphology and ligamentous stability. Its unique anatomy, however, also makes it particularly vulnerable during both low and high energy trauma. Trauma to this area, referred to as upper cervical spine trauma, can disrupt the stability of the upper cervical spine and result in a wide spectrum of injury. Numerous upper cervical injury classification systems have been proposed, each of which have distinct limitations and drawbacks that have prevented their universal adoption. In this article, we provide an overview of previous classifications, with an emphasis on the development of the new AO Spine Upper Cervical Classification System (AO Spine UCCS).

The Subaxial Cervical AO Spine Injury Score

STUDY DESIGN

Global cross-sectional survey.

OBJECTIVE

To develop an injury score for the AO Spine Subaxial Cervical Spine Injury Classification System.

METHODS

Respondents numerically graded each variable within the classification system for severity. Based on the results, and with input from the AO Spine Trauma Knowledge Forum, the Subaxial Cervical AO Spine Injury Score was developed.

RESULTS

An A0 injury was assigned an injury score of 0, A1 a score of 1, and A2 a score of 2. Given the significant increase in severity, A3 was given a score of 4. Based on equal severity assessment, A4 and B1 were both assigned a score of 5. B2 and B3 injuries were assigned a score of 6. Unstable C-type injuries were given a score of 7. Stable F1 injuries were assigned a score of 2, with a 2-point increase for F2 injuries. Likewise, F3 injuries received a score of 5, whereas more unstable F4 injuries a score of 7. Neurologic status severity rating scores increased stepwise, with scores of 0 for N0, 1 for N1, and 2 for N2. Consistent with the Thoracolumbar AO Spine Injury Score, N3 (incomplete) and N4 (complete) injuries were given a score of 4. Finally, case-specific modifiers M1 (PLC injury) received a score of 1, while M2 (critical disc herniation) and M3 (spine stiffening disease) received a score of 4.

CONCLUSIONS

The Subaxial Cervical AO Spine Injury Score is an easy-to-use metric that can help develop a surgical algorithm to supplement the AO Spine Subaxial Cervical Spine Injury Classification System.

Establishing the Injury Severity of Subaxial Cervical Spine Trauma: Validating the Hierarchical Nature of the AO Spine Subaxial Cervical Spine Injury Classification System

STUDY DESIGN

Global cross-sectional survey.

OBJECTIVE

The aim of this study was to validate the AO Spine Subaxial Cervical Spine Injury Classification by examining the perceived injury severity by surgeon across AO geographical regions and practice experience.

SUMMARY OF BACKGROUND DATA

Previous subaxial cervical spine injury classifications have been limited by subpar interobserver reliability and clinical applicability. In an attempt to create a universally validated scheme with prognostic value, AO Spine established a subaxial cervical spine injury classification involving four elements: injury morphology, facet injury involvement, neurologic status, and case-specific modifiers.

METHODS

A survey was sent to 272 AO Spine members across all geographic regions and with a variety of practice experience. Respondents graded the severity of each variable of the classification system on a scale from zero (low severity) to 100 (high severity). Primary outcome was to assess differences in perceived injury severity for each injury type over geographic regions and level of practice experience.

RESULTS

A total of 189 responses were received. Overall, the classification system exhibited a hierarchical progression in subtype injury severity scores. Only three subtypes showed a significant difference in injury severity score among geographic regions: F3 (floating lateral mass fracture, P = 0.04), N3 (incomplete spinal cord injury, P = 0.03), and M2 (critical disk herniation, P = 0.04). When stratified by surgeon experience, pairwise comparison showed only two morphological subtypes, B1 (bony posterior tension band injury, P = 0.02) and F2 (unstable facet fracture, P = 0.03), and one neurologic subtype (N3, P = 0.02) exhibited a significant difference in injury severity score.

CONCLUSION

The AO Spine Subaxial Cervical Spine Injury Classification System has shown to be reliable and suitable for proper patient management. The study shows this classification is substantially generalizable by geographic region and surgeon experience, and provides a consistent method of communication among physicians while covering the majority of subaxial cervical spine traumatic injuries.Level of Evidence: 4.

Accuracy and reliability of the AO Spine subaxial cervical spine classification system grading subaxial cervical facet injury morphology

PURPOSE

A classification system was recently developed by the international association AO Spine for assessing subaxial cervical spine fractures. Significant variability exists between users of the facet component, which consists of four morphological types (F1-F4). The primary aims of this study were to assess the diagnostic accuracy and reliability of this new system's facet injury morphological classifications.

METHODS

A survey consisting of 16 computed tomography (CT) scans of patients with cervical facet fractures was distributed to spine surgeon members of AO Spine Latin America. To provide a gold standard diagnosis for comparison, all 16 injuries had been classified previously by six co-authors and only were included after total consensus was achieved. Demographic and surgical practice characteristics of all respondents were analyzed, and diagnostic accuracy calculated. Inter- and intra-observer agreement rates were calculated across two survey rounds, conducted one month apart.

RESULTS

A total of 135 surgeons completed both surveys, among whom the mean age was 41.6 years (range 26-71), 130 (96.3%) were men, and 83 (61.5%) were orthopedic surgeons. The mean time in practice as a spine surgeon was 9.7 years (1-30). The overall diagnostic accuracy of all responses was 65.4%. Inter-observer and intra-observer agreement rates for F1/F2/F3/F4 were 55.4%/47.6%/64.0%/94.7% and 60.0%/49.1%/58.0%/93.0%, respectively.

CONCLUSION

This study evaluates the AO Spine Classification System specifically for facet injuries involving the subaxial cervical spine in a large sample of spine surgeons. There was significant variability in diagnostic accuracy for F1 through F3-type fractures, whereas almost universal agreement was achieved for F4-type injuries.

External Multicenter Study of Reliability and Reproducibility for Lower Cervical Spine Injuries Classification Systems-Part 2: An Analysis of the Subaxial Cervical Spine Injury Classification and Cervical Spine Injury Severity Score Scale

STUDY DESIGN

A multicenter observational survey.

OBJECTIVE

To quantify and compare inter- and intraobserver reliability of the subaxial cervical spine injury classification (SLIC) and the cervical spine injury severity score (CSISS) in a multicentric survey of neurosurgeons with different experience levels.

METHODS

Data concerning 64 consecutive patients who had undergone cervical spine surgery between 2013 and 2017 was evaluated, and we surveyed 37 neurosurgeons from 7 different clinics. All raters were divided into 3 groups depending on their level of experience. Two assessment procedures were performed.

RESULTS

For the SLIC, we observed excellent agreement regarding management among experienced surgeons, whereas agreement among less experienced neurosurgeons was moderate and almost twice as unlikely. The sensitivity of SLIC relating to treatment tactics reached as high as 92.2%. For the CSISS, agreement regarding management ranged from medium to substantial, depending on a neurosurgeon's experience. For less experienced neurosurgeons, the level of agreement concerning surgical management was the same as for the SLIC in not exceeding a moderate level. However, this scale had insufficient sensitivity (slightly exceeding 50%). The reproducibility of both scales was excellent among all raters regardless of their experience level.

CONCLUSIONS

Our study demonstrated better management reliability, sensitivity, and reproducibility for the SLIC, which provided moderate interrater agreement with moderate to excellent intraclass correlation coefficient indicators for all raters. The CSISS demonstrated high reproducibility; however, large variability in answers prevented raters from reaching a moderate level of agreement. Magnetic resonance imaging integration may increase sensitivity of CSISS in relation to fracture management.

Injury classification and level detection of the spinal cord based on the optimized recurrent neural network

Objectives

Spinal cord damage is one of the traumatic situations in persons that may cause the loss of sensation and proper functioning of the muscles either temporarily or permanently. Hence, steps to assure the recovery through the early functioning and precaution could safe-guard a proper interceptive. To ensure the recovery of spinal cord damage through optimized recurrent neural network.

Methods

The research on the spinal cord injury classification and level detection is done using the CT images, which is initially given to the segmentation that is done using the adaptive thresholding methodology. Once the segments are formed, the disc is localized using the sparse fuzzy C-means clustering approach. In the next step, the features are extracted from the localized disc and the features include the connectivity features, statistical features, image-level features, grid-level features, Histogram of Oriented Gradients (HOG), and Linear Gradient Pattern (LGP). Then, the injury detection is done based on the Crow search Rider Optimization algorithm-based Deep Convolutional Neural Network (CS-ROA-based DCNN). Once the result regarding the presence of the injury is obtained, the injury-level classification is done based on the proposed Deep Recurrent Neural Network (Deep RNN), and in case of the absence of injury, the process is terminated. Therefore, the injury detection classifier derives the level of the injury, such as normal, wedge, biconcavity, and crush.

Results

The experimentation is carried out using an Osteoporotic vertebral fractures database. The performance of the injury level detection based on the proposed model is evaluated based on accuracy, sensitivity, and specificity. The proposed model achieves the maximal accuracy of 0.895, maximal sensitivity of 0.871, and the maximal specificity of 0.933 with respect to K-Fold.

Conclusions

The experimental results show that the proposed model is better than the existing models in terms of accuracy, sensitivity, and specificity.

Subaxial Cervical Spine Injuries: WFNS Spine Committee Recommendations

To formulate specific guidelines for the recommendation of subaxial cervical spine injuries concerning classification, management, posttraumatic locked facets and vertebral artery injury. Computerized literature was searched on PubMed and google scholar database from 2009 to 2020. For classification, keywords "Sub Axial Cervical Spine Classification," resulting in 22 articles related to subaxial cervical spine injury classification system (SLICS) system and 11 articles related to AO (Arbeitsgemeinschaft für Osteosynthesefragen, German for "Association for the Study of Internal Fixation") Spine system. The literature search yielded 210 and 78 articles on "management of subaxial cervical spine injuries" and the role of "SLICS" and "AO Spine" respectively. Keywords "management of traumatic facet locks" were searched and closed reduction, traction, approaches and techniques were studied. "Vertebral artery injury and cervical fracture" exhibited 2,328 references from the last 15 years. The objective was to identify the appropriate diagnostic tests and optimal treatment. Up-to-date information was reviewed, and statements were produced to reach a consensus in 2 separate consensus meetings of World Federation of Neurosurgical Societies (WFNS) Spine Committee. The statements were voted and reached a positive or negative consensus using Delphi method. Based on the most relevant literature, panelists in Moscow consensus meeting conducted in May 2019 drafted the statements, and after a preliminary voting session, the consensus was identified on various statements. Another meeting was conducted at Peshawar in November 2019, where in addition to previous statements, few other statements were discussed and voted. Specific recommendations were then formulated guiding classification, management, locked facets and vertebral artery injuries. This review summarizes the WFNS Spine Committee recommendations on subaxial cervical spine injuries.

Comparison of the AOSpine subaxial cervical spine injury classification system and the Allen classification

The AOSpine group has launched a new subaxial cervical spine injury system (AOSCIS) based on morphology. The objective of this study was to use the AOSCIS and compare it to the widely used Allen classification (AC) based on mechanics for subaxial cervical spine injury. Twenty-two consecutive patients with subaxial cervical spine injury who received posterior cervical fixation in our hospital were included in this study. Medical records were evaluated retrospectively. The evaluated factors were as follows: preoperative ASIA impaired scale (AIS), AOSCIS, AC, and diffuse idiopathic skeletal hyperostosis (DISH). There was AIS A in nine patients, AIS C in four patients, AIS D in four patients, and AIS E in five patients. Two patients with AOSCIS B2 were classified as AC DF1. Two AOSCIS F3 patients were classified as AC CE1. Eighteen AOSCIS C patients were classified into multiple categories: five as AC DF2, three as DF3, one as CF4, one as CF5, four as DE2, three as CE3 + DE1, and one as CE3 + VC2. All of the AOSCIS A0 (F) or B patients were classified as AC stage 1, and all of the AOSCIS C patients were classified as AC stage 2 and higher (P < 0.05). All of six patients with DISH were classified as AOSCIS C and CE3, DE2, or DF3. AOSCIS and AC are correlated. Conducting an evaluation using both systems helps us to better comprehend subaxial cervical spine injuries.

Predictors of Failure of Nonoperative Management Following Subaxial Spine Trauma and Creation of Modified Subaxial Injury Classification System

BACKGROUND

Subaxial cervical spine injuries may be treated with either nonoperative stabilization or surgical fixation. The subaxial injury classification (SLIC) provides 1 method for suggesting the degree of necessity for surgery. In the current study, we examined if the SLIC score, or other preoperative metrics, can predict failure of nonoperative management.

METHODS

We performed a retrospective chart review to identify patients who presented with acute, nonpenetrating, subaxial cervical spine injury within our health system between 2007 and 2016. Patient demographics, medical comorbidities, injuries, and treatments were collected. Logistic regression analysis was used to determine potential predictors of failure of nonoperative management.

RESULTS

During the study period, 40 patients met the inclusion criteria. A small subset of patients failed nonoperative management (n = 5, 12.5%). The mean SLIC score was 3.9 ± 1.9; however, 14 (35%) patients had scores >4. Neither total SLIC score (P = 0.68) nor SLIC subscores (morphology [P = 0.96], discoligamentous complex [P = 0.83], neurologic status [P = 0.60]) predicted failure of nonoperative treatment. Time to evaluation/treatment did predict failure of nonoperative management. Evaluation within 8 hours of injury was a negative predictor of failure (odds ratio = 0.03, P = 0.001) and evaluation 24 hours or more after injury was a positive predictor of failure (odds ratio = 66.00, P < 0.001). We created a modified SLIC score on the basis of these findings, which significantly predicted failure of nonoperative management (P = 0.044).

CONCLUSIONS

Management of subaxial spine injuries is complex. In our cohort, SLIC scoring did not adequately predict odds of failure of nonoperative management. Time to evaluation, however, did. We created a modified SLIC score that significantly predicted failure of nonoperative management.

Reliability of Allen Ferguson classification versus subaxial injury classification and severity scale for subaxial cervical spine injuries: a psychometrics study

STUDY DESIGN

A psychometrics study.

OBJECTIVES

To determine intra and inter-observer reliability of Allen Ferguson system (AF) and sub-axial injury classification and severity scale (SLIC), two sub axial cervical spine injury (SACI) classification systems.

SETTING

Online multi-national study METHODS: Clinico-radiological data of 34 random patients with traumatic SACI were distributed as power point presentations to 13 spine surgeons of the Spine Trauma Study Group of ISCoS from seven different institutions. They were advised to classify patients using AF and SLIC systems. A reference guide of the two systems had been mailed to them earlier. After 6 weeks, the same cases were re-presented to them in a different order for classification using both systems. Intra and inter-observer reliability scores were calculated and analysed with Fleiss Kappa coefficient (k value) for both the systems and Intraclass correlation coefficient(ICC) for the SLIC.

RESULTS

Allen Ferguson system displayed a uniformly moderate inter and intra-observer reliability. SLIC showed slight to fair inter-observer reliability and fair to substantial intra-observer reliability. AF mechanistic types showed better inter-observer reliability than the SLIC morphological types. Within SLIC, the total SLIC had the least inter-observer agreement and the SLIC neurology had the highest intra-observer agreement.

CONCLUSION

This first external reliability study shows a better reliability for AF as compared to SLIC system. Among the SLIC variables, the DLC status and the total SLIC had least agreement. Low-reliability highlights the need for improving the existing classification systems or coming out with newer ones that consider limitations of the existing ones.

Variability in Treatment for Patients with Cervical Spine Fracture and Dislocation: An Analysis of 107,152 Patients

BACKGROUND

Cervical spine injuries are a common cause of morbidity and mortality; however, the optimal treatment of many of these injuries is debated, and previous studies have shown substantial variation in treatment. We sought to examined treatment variation in arthrodesis and halo/tong placement in cervical spine injury patients over a 12-year period.

METHODS

Data from the Healthcare Cost and Utilization Project National Inpatient Sample, from 2000 to 2011, were used for this study. Patients were identified with a cervical vertebral facture or dislocation based on the International Classification of Diseases, 9th Revision codes. Using χ² analysis, spinal arthrodesis rates and halo/tong placement rates were compared between hospitals based on teaching status for patients with and without spinal cord injury (SCI).

RESULTS

The records of 107,152 patients with cervical fractures were examined. From 2000 to 2011, the overall arthrodesis rates fell from 25.2% to 20.6% (P < 0.001), and halo/tong placement rates fell from 13.2% to 3.6% (P < 0.001). In patients with cervical fracture without SCI, arthrodesis rates fell from 17.6% to 13.9% (P < 0.001), in cervical fracture patients with SCI, arthrodesis rates rose from 50.0% to 58.9% (P < 0.001), and in cervical dislocation patients, arthrodesis rates rose from 47.6% to 57.5% (P < 0.001). During the 12-year period, teaching hospitals had higher arthrodesis rates compared with nonteaching hospitals for patients with cervical fractures with SCI (57.3% vs. 53.4%, P = 0.001) and higher halo/tong placement rates for patients with cervical dislocations (2.7% vs. 1.7%, P = 0.004). Individual hospital variation showed a 3.5-fold variation in arthrodesis rates in 2000 to 2002, which fell to 3.0-fold by 2009 to 2011.

CONCLUSIONS

Arthrodesis rates for cervical fracture patients significantly decreased, and arthrodesis rates for cervical dislocation and SCI patients increased from 2000 to 2011, with variability in treatment based on hospital teaching status. Rates of halo/tong placement rapidly decreased for cervical spine trauma at both teaching and nonteaching hospitals. Individual hospital treatment variation also decreased over the study period. Further clinical studies examining the optimal treatment for spine trauma may lead to continued decreases in treatment variability.

An Independent Inter- and Intraobserver Agreement Evaluation of the AOSpine Subaxial Cervical Spine Injury Classification System

STUDY DESIGN

An agreement study.

OBJECTIVE

The aim of this study was to perform an independent interobserver and intraobserver agreement assessment of the AOSpine subaxial cervical spine injury classification system.

SUMMARY OF BACKGROUND DATA

The AOSpine subaxial cervical spine injury classification system was recently described. It showed substantial inter- and intraobserver agreement in the study describing it; however, an independent evaluation has not been performed.

METHODS

Anteroposterior and lateral radiographs, computed tomography scans, and magnetic resonance imaging of 65 patients with acute traumatic subaxial cervical spine injuries were selected and classified using the morphologic grading of the subaxial cervical spine injury classification system by 6 evaluators (3 spine surgeons and 3 orthopedic surgery residents). After a 6-week interval, the 65 cases were presented to the same evaluators in a random sequence for repeat evaluation. The kappa coefficient (κ) was used to determine the inter- and intraobserver agreement.

RESULTS

The interobserver agreement was substantial when considering the fracture main types (A, B, C, or F), with κ = 0.61 (0.57-0.64), but moderate when considering the subtypes: κ = 0.57 (0.54-0.60). The intraobserver agreement was substantial considering the fracture types, with κ = 0.68 (0.62-0.74) and considering subtypes, κ = 0.62 (0.57-0.66). No significant differences were observed between spine surgeons and orthopedic residents in the overall inter- and intraobserver agreement, or in the inter- and intraobserver agreement of specific A, B, C, or F type of injuries.

CONCLUSION

This classification allows adequate agreement among different observers and by the same observer on separate occasions. Future prospective studies should determine whether this classification allows surgeons to decide the best treatment for patients with subaxial cervical spine injuries.

LEVEL OF EVIDENCE

3.

Subaxial cervical spine trauma

Subaxial cervical spine trauma is common and an often missed diagnosis. Accurate and efficient diagnosis and management is necessary to avoid devastating complications such as spinal cord injury. Several classification schemes have been devised to help categorize fractures of the subaxial spine and define treatment algorithms. The Subaxial Cervical Spine Injury Classification System (SLIC) is widely used and evaluates not only fracture morphology but also considers ligamentous injury and neurological status in surgical decision making. However, interobserver reliability is poor, which proves to be the defining pitfall of this tool. More modern classification systems have been developed, which aim to improve the interobserver reliability; however, further large-scale studies are needed for more definitive evaluation. Overall, treatment of subaxial cervical spine injuries should include a protocol with initial trauma evaluation, leading to expedient operative intervention if indicated. Surgical techniques include both anterior and posterior approaches to the cervical spine depending on fracture classification.

Classification and Management of Pediatric Subaxial Cervical Spine Injuries

Appropriate management of subaxial spine injury in children requires an appreciation for the differences in anatomy, biomechanics, injury patterns, and treatment options compared with adult patients. Increased flexibility, weak neck muscles, and cranial disproportion predispose younger children to upper cervical injuries and spinal cord injury without radiographic abnormality. A majority of subaxial cervical spine injuries can be treated nonoperatively. Surgical instrumentation options for children have significantly increased in recent years. Future studies of outcomes for children with subaxial cervical spine injury should focus on injury classification and standardized outcome measures to ensure continued improvement in quality of care for this patient population.

Limitation of previous Allen classification and subaxial cervical spine injury classification (SLIC) system in distractive-extension injury of cervical spine: proposal of modified classification system

PURPOSE

To verify the clinical applicability of a modified classification system in distractive-extension cervical spine injury that reflects the degrees of soft tissue damage and spinal cord injury while complementing previous Allen classification and subaxial cervical spine injury classification (SLIC) system.

METHODS

A total of 195 patients with cervical spine distraction-extension (DE) injury were retrospectively classified. We added stages IIIA (with concomitant spinal cord injury without bony abnormalities) and IIIB (with concomitant additional soft tissue swelling) to the existing stages I and II of the Allen classification. We also supplemented the SLIC system by refining and assigning scores to bony morphology and soft tissue damage. The previous and proposed classification systems were compared by analyzing their scoring performances in terms of clinical features and prognosis.

RESULTS

The Allen classification yielded 153 and 42 patients with stage 1 and 42 stage 2 injuries, respectively. Patients classified according to the proposed system were stratified as follows: stage I, 58; stage II, 27; stage IIIA, 33; and stage IIIB, 77. Regarding neurological symptoms and prognosis, stages IIIA and IIIB were poorer than stage I but significantly better than stage II (P < 0.05). On the SLIC system, 146 patients scored ≥5; and 37 and 12 patients scored 4 and ≤3 points, respectively, whereas the numbers of patients who scored ≥5, 4, and ≤3 points on the modified SLIC system were 170, 21, and 4, respectively.

CONCLUSIONS

The proposed classification and scoring system to complement the Allen classification and SLIC system with respect to the degrees of soft tissue damage and spinal cord injury is considered effective for diagnosing and determining therapeutic directions and prognosis in cases of cervical spine extension injury.

Subaxial injury classification scoring system treatment recommendations: external agreement study based on retrospective review of 185 patients

STUDY DESIGN

Retrospective case series.

OBJECTIVE

To test validity of subaxial injury classification (SLIC) treatment recommendations.

SUMMARY OF BACKGROUND DATA

Although SLIC has been tested for reliability, external studies that test the validity of its treatment recommendations are lacking.

METHODS

The SLIC score was determined by reviewing imaging studies and clinical records in a consecutive series of 185 patients with subaxial cervical spine trauma presenting to a level 1 spinal injury referral center. Details including attending surgeon responsible for treatment decision, treatment received, and surgical approach were collected.

RESULTS

Treatment received matched SLIC guidelines in 93.6% nonsurgically managed patients and 96.3% surgically managed patients. The mean SLIC score of the surgically treated group of patients was significantly higher than that of the nonsurgical group (7.14 vs. 2.22; P<0.001). Sixty-six patients had a SLIC score of 3 or less, and 94% of them were nonsurgically managed (P<0.001). One hundred two patients had a SLIC score of 5 or more, and 95% of them were surgically managed (P<0.001). Seventeen patients had a SLIC score of 4, and 65% were nonsurgically managed (P=0.032). Injury morphology scores were not predictive of surgical approach. Increasing SLIC scores correlated with increasing complexity of treatment (r=0.77; P<0.001). The distribution of patients with regard to severity of injuries and treatment delivered by the 7 spinal surgeons was comparable. The past practice of these 7 fellowship-trained spine surgeons was individually in agreement with SLIC treatment recommendations.

CONCLUSION

Our past practice reflects SLIC treatment recommendations for nonsurgical treatment of patients with SLIC scores of 3 or less and surgical treatment of patients with SLIC scores of 5 or more. The use of SLIC as an ordinal severity scale is validated as increasing SLIC scores correlated with increasing complexity of treatment. The injury morphology score did not predict a surgical approach. Significantly higher numbers of patients with a SLIC score of 4 were treated nonsurgically.

LEVEL OF EVIDENCE

3.