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Year : 2015  |  Volume : 10  |  Issue : 4  |  Page : 282-285

The AOSpine thoracolumbar spine injury classification system: A reliability and agreement study

1 Department of Neurosurgery, Shahid Beheshti University of Medical Sciences, Tehran, Iran
2 Mental Health Research Group, Health Metrics Research Centre, Iranian Institute for Health Sciences Research, ACECR, Tehran, Iran

Date of Web Publication13-Aug-2015

Correspondence Address:
Parisa Azimi
Department of Neurosurgery, Imam Hossain Medical Center, University of Shahid Beheshti Medical Sciences, Shahid Madani Street, Tehran, PA 1617763141
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Source of Support: None, Conflict of Interest: None

DOI: 10.4103/1793-5482.162703

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Aim: Recently, AOSpine trauma knowledge forum proposed the AOSpine thoracolumbar injury classification (AOSTLIC) system and suggested that it was reliable. However, reliability data from additional institutions for the AOSTLIC system are not available. This study was to examine the reliability of the AOSTLIC system in patients with thoracolumbar (TL) fractures.
Materials and Methods: Between August 2009 and June 2012, 56 patients with 74 levels traumatic TL spinal injuries were recruited. Two classifiers, consisting of two spine surgeons, assessed clinical and imaging data. Initially, one surgeon reviewed the data in order to classify and calculate injury severity score according to the AOSTSIC system. This process was repeated on a 5-week interval by another surgeon. Then we analyzed data for intra-observer and inter-observer reliability using the kappa statistic (k). Finally, validity was assessed using the known-groups comparison.
Results: The mean age of patients was 59.5 ± 11.5 years. The k values for the AOSTSIC system for intra-observer and inter-observer reliability ranged from 0.83 to 0.89, indicating nearly perfect agreement agreements. Known-groups analysis showed satisfactory results. The AOSTSIC system discriminated well between sub-groups of patients who differed in Oswestry disability index.
Conclusion: The findings showed that the morphologic classification in AOSTSIC system appears to be reliable and reproducible classification.

Keywords: AOSTSIC system, reliability, spine injury classification, thoracolumbar fracture

How to cite this article:
Azimi P, Mohammadi HR, Azhari S, Alizadeh P, Montazeri A. The AOSpine thoracolumbar spine injury classification system: A reliability and agreement study. Asian J Neurosurg 2015;10:282-5

How to cite this URL:
Azimi P, Mohammadi HR, Azhari S, Alizadeh P, Montazeri A. The AOSpine thoracolumbar spine injury classification system: A reliability and agreement study. Asian J Neurosurg [serial online] 2015 [cited 2021 Nov 28];10:282-5. Available from:

  Introduction Top

Thoracolumbar (TL) fractures are usually related with major trauma and can cause spinal cord impairment that result in neural deficits. [1],[2] The correct management of TL fractures contains several steps including an accurate diagnosis by imaging, classification, and treatment. [1],[2] The goals of treatment are to achieve a painless, balanced, stable spine with optimum neurological function and maximum spine mobility. Classification of TL fractures is an on-going endeavor for the medical community in order to improve the decision-making process. Several classifications of TL fractures have been proposed over recent decades. Many investigators such as Nicoll, Holdsworth, Louis, and Denis, Magerl et al., and Vaccaro et al. have contributed to the evolution of fracture classification. [1],[2],[3],[4],[5],[6] However, proposed systems have used various injury characteristics, and none has achieved universal approval. [7]

Recently, to develop a widely accepted classification system including both fractures morphology and clinical factors relevant for surgical decision-making, the association for the study of internal fixation (AOSpine) proposed the AOSpine thoracolumbar injury classification (AOSTLIC) system and found that it is a reliable measure. A primary management decision in the treatment of TL injuries may decrease using this type of classification system. [7] However, reliability data from additional institutions for the AOSTLIC system are not available. This study aimed to examine the reliability of the AOSTLIC system in patients with TL fractures.

  Materials and Methods Top

Patients and data collection

In this retrospective study, we included 56 patients with 74 levels of TL spinal injuries who had treated between August 2010 and June 2012 at a teaching hospital, in Tehran, Iran. All cases were initially assessed in the emergency department or referred from an outside institution for treatment of their spinal injuries. Diagnosis of TL injury was established using clinical symptoms, description of the traumatic injury, neurological examinations, and imaging including combinations of X-ray, computed tomography and magnetic resonance images and was confirmed by experienced spine surgeons. Demographics variables were extracted from case records. Each case was classified according to AOSTLIC system. The methods that presented by Vaccaro et al. were considered for type A, type B, and type C injuries to confirm that the surgeons were evaluating the same injury. [7] There were no limitations on patient selection with regard to types of TL fracture, age or other characteristics. The exclusion criteria were prior lumbar spine surgery, spinal anomalies, and polyneuropathy. Patients underwent surgery or conservative treatment.

The AOSpine thoracolumbar spine injury classification system

An international team developed the AOSTLIC system that includes features of both the Magerl et al. and TLICS. In addition to the morphological description, this system considers the neurological status and patient-specific modifiers that are important for surgical decision-making. The morphologic classification is based on three main injury patterns: Type A (compression injuries of the vertebral body), type B (tension band disruption), and type C (displacement/translation injury) injuries. In an accompanying commentary, Vaccaro et al. indicate that this new classification scheme may be used to refine patient treatment plans and expand our understanding of TL injury. The AOSTLIC system and their relate subtypes are shown in [Table 1]. [7]
Table 1: AOSpine thoracolumbar spine injury classification system*

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Additional measure

The Iranian version of the Oswestry disability index (ODI): This is a measure of functionality and contains 10 items. The possible score on the ODI ranges from 0 to 50, with higher scores indicating worse conditions. The psychometric properties of the Iranian version of the questionnaire are well-documented. [8] This was used for known-groups comparison.

Statistical analysis

In order to assess the reliability of the classification system, all patients were randomly selected with all types of TL fracture. Two independent observers classified each case twice within a 5-week interval to measure intra- and inter-observer differences. The weighted kappa coefficient (k) was calculated for each spine surgeon based on his/her first and second observations for within and between comparisons. k varies between 0 and 1; the greater the k, the higher agreement rate. k value of 0-0.20 indicate slight agreement, 0.21-0.40 fair agreement, 0.41-0.60 moderate agreement, 0.61-0.80 substantial perfect agreement and ≥0.81 is regard as almost perfect agreement according to the interpretation by Landis and Koch. [9] k coefficients were calculated for injury type (A, B, or C), and their subtype (A0, A1, A2, A3, or A4 and B1, B2, B3).

Known groups comparison


We used known-groups comparison (discriminant validity). It was carried out to test how well the AOSTLIC system discriminates between sub-groups of patients who differed in functionality as measured by the ODI. It was hypothesized that patients with a higher score on the ODI would have a lower condition on the AOSTLIC. One-way analysis of variance was performed to test the hypothesis. [10]

The statistical software was SPSS for Windows (Version 17.0, IBM, SPSS Inc., Chicago, Illinois, USA).


The Ethics Committee of Shahid Beheshti University of Medical Sciences, Tehran, Iran approved the study.

  Results Top

The characteristics of patients and their scores on the AOSTLIC system based on two observers are shown in [Table 2].
Table 2: The characteristics of the study patients and their AOSTLIC system with 74 TL injuries (n=56)

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Kappa statistics was calculated for the AOSTLIC system and its domain and are shown in [Table 3]. The k values of the AOSTLIC system for the intra-observer and inter-observer ranged from 0.83 to 0.89, indicating almost perfect agreement.
Table 3: Inter- and Intra-observer AOSTSIC system (n=74 pairs of repeated evaluations)*

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Validity of the AOSTLIC system was examined using the known groups comparison. The AOSTLIC system discriminated well between sub-groups of patients who differed in functionality as measured by the ODI (P < 0.001). The results are shown in [Table 4].
Table 4: The pretreatment ODI by AOSpine thoracolumbar spine injury classification system among the study sample (known groups comparison)

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  Discussion Top

Decision-making is of prime importance for patients suffering from TL injuries. As such the AOSTLIC is a tool that could help clinicians to make a fair decision and in turn provide better outcomes for patients. In fact, the fundamental intent of the AOSTLIC system is to improve the management of TL injury through a reproducible and valid classification system that is easy to learn and that is readily applicable in clinical practice.

The findings from this study confirmed that the AOSTLIC system was generally reliable and valid with good inter- and intra-observer agreements for classifying patients with TL injuries. Although the AOSTLIC system showed promise, however since the study sample was small, thus the procedure will need to be repeated with larger, multicenter datasets to indicate its classification power convincingly.

Vaccaro et al. demonstrated well to excellent inter-observer and intra-observer reliability with the AOSTLIC system (reference). They reported that k (k, agreement index) values for the inter-observer agreement were 0.72 for type A injuries, 0.58 for type B injuries, and 0.7 for type C injuries. They also reported that k values for intra-observer had substantial to excellent reproducibility results for the AOSTLIC system with an average k value of 0.77 (ranging from 0.6 to 0.97), which is in line with our findings.

Various developed classification systems for spinal fractures or injuries have been used. However, no classification system has been able to satisfy the clear communication between clinicians and researchers. Recently, however, a unique cooperative effort among experts from the AOSpine created a uniform international classification system with the objective to develop a widely accepted, comprehensive yet simple classification system with proven intra- and inter- observer reliability that reflects the current understanding of the various forms of TL injuries. [7] Vaccaro et al. who led the effort, hope that the classification system will standardize definitions of different classes of TL injury and encourage uniform and reproducible reporting of cases among different medical centers. [7] For this aim, we encourage other researchers to validate the new AOSTLIC system in different countries and medical institutions.

The findings from the current study showed that patients who differed in the ODI were differed in the type of TL injury as expected. However, we only carried out a limited test to perform validity. In future, it might be necessary to perform other tests to establish stronger psychometric indexes for the AOSTLIC system.

There were some limitations in our study. First, since this was a retrospective study, there were some missing data. Second, the sample size was small and thus we were unable to perform those analyses that need bigger sample size (e.g., factor analysis).

  Conclusion Top

The findings showed that AOSTLIC system is a useful and reliable tool in terms of intra-observer and inter-observer agreements for classification and evaluation of the TL fractures. Thus, the AOSTLIC system may be used in the decision-making process.

  References Top

Nicoll EA. Fractures of the dorso-lumbar spine. J Bone Joint Surg Br 1949;31B: 376-94.  Back to cited text no. 1
Holdsworth F. Fractures, dislocations, and fracture-dislocations of the spine. J Bone Joint Surg Am 1970;52:1534-51.  Back to cited text no. 2
Louis R. Unstable fractures of the spine. III. Instability. A. Theories concerning instability. Rev Chir Orthop Reparatrice Appar Mot 1977;63:423-5.  Back to cited text no. 3
Denis F. The three column spine and its significance in the classification of acute thoracolumbar spinal injuries. Spine (Phila Pa 1976) 1983;8:817-31.  Back to cited text no. 4
Magerl F, Aebi M, Gertzbein SD, Harms J, Nazarian S. A comprehensive classification of thoracic and lumbar injuries. Eur Spine J 1994;3:184-201.  Back to cited text no. 5
Vaccaro AR, Lehman RA Jr, Hurlbert RJ, Anderson PA, Harris M, Hedlund R, et al. A new classification of thoracolumbar injuries: The importance of injury morphology, the integrity of the posterior ligamentous complex, and neurologic status. Spine (Phila Pa 1976) 2005;30:2325-33.  Back to cited text no. 6
Vaccaro AR, Oner C, Kepler CK, Dvorak M, Schnake K, Bellabarba C, et al. AOSpine thoracolumbar spine injury classification system: Fracture description, neurological status, and key modifiers. Spine (Phila Pa 1976) 2013;38:2028-37.  Back to cited text no. 7
Mousavi SJ, Parnianpour M, Mehdian H, Montazeri A, Mobini B. The Oswestry Disability Index, the Roland-Morris Disability Questionnaire, and the Quebec Back Pain Disability Scale: Translation and validation studies of the Iranian versions. Spine (Phila Pa 1976) 2006;31:454-9.  Back to cited text no. 8
Landis JR, Koch GG. The measurement of observer agreement for categorical data. Biometrics 1977;33:159-74.  Back to cited text no. 9
Nunnally JC, Bernstien IH. Psychometric Theory. 3 rd ed. New York: McGraw-Hill; 1994.  Back to cited text no. 10


  [Table 1], [Table 2], [Table 3], [Table 4]

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