AOSpine subaxial cervical spine injury classification system
This project describes a morphology-based subaxial cervical spine injury classification system. Using the same approach as the AOSpine Thoracolumbar Classification System, the goal was to develop a comprehensive yet simple classification system with high intra- and interobserver reliability to be used for clinical and research purposes.
A subaxial cervical spine injury classification system was developed using a consensus process among clinical experts. All investigators were required to successfully grade 10 cases to demonstrate comprehension of the system before grading 30 additional cases on two occasions, 1 month apart. Kappa coefficients (κ) were calculated for intraobserver and interobserver reliability.
The classification system is based on three injury morphology types similar to the TL system: compression injuries (A), tension band injuries (B), and translational injuries (C), with additional descriptions for facet injuries, as well as patient-specific modifiers and neurologic status. Intraobserver and interobserver reliability was substantial for all injury subtypes (κ = 0.75 and 0.64, respectively).
The AOSpine subaxial cervical spine injury classification system demonstrated substantial reliability in this initial assessment, and could be a valuable tool for communication, patient care and for research purposes 1).
The AOSpine subaxial cervical spine injury classification system (using the four main injury types or at the sub-types level) allows a significantly better agreement than the Allen and Ferguson classification of subaxial cervical spine injury. The A&F scheme does not allow reliable communication between medical professionals 2).
see also Subaxial Injury Classification (SLIC).
Aarabi et al. analyzed the relevant clinical, imaging, management, and American Spinal Injury Association (ASIA) impairment scale (AIS) grade conversion of 92 AIS grades A-C patients with cervical spine injury. We correlated morphology class with age, injury severity score (ISS), follow-up ASIA motor score (AMS), intramedullary lesion length (IMLL), and AIS grade conversion at 6 months after injury.
The mean age of patients was 39.3 years, 83 were men, and 69 were injured during an automobile accident or after a fall. The AOSpine class was A4 in 8, B2 in 5, B2A4 in 16, B3 in 19, and C in 44 patients. The mean ISS was 29.7 and AMS was 17.1. AIS grade was A in 48, B in 25, and C in 19 patients. Mean IMLL on postoperative magnetic resonance imaging was 72 mm: A4 = 68.1; B2A4 = 86.5; B2 = 59.3; B3 = 46.8; and C = 79.9. At a mean follow-up of 6 months, the mean AMS was 39.6. Compared to patients with class B3 injuries, those with class C injuries were significantly younger (P < 0.0001), had longer IMLL (P < 0.002), and were less likely to have AIS grade conversion to a better grade (P < 0.02).
The AOSpine subaxial cervical spine injury classification system successfully predicted injury severity (longer IMLL) and chances of neurologic recovery (AIS grade conversion) across different class subtypes 3).
Silva et al., evaluated the new classification
Patients with subaxial cervical spine trauma (SCST) treated at the authors’ institution according to the Subaxial Cervical Spine Injury Classification system were included. Five different blinded researchers classified patients’ injuries according to the new AOSpine system using CT imaging at 2 different times (4-week interval between each assessment). Reliability was assessed using the kappa index (κ), while validity was inferred by comparing the classification obtained with the treatment performed.
Fifty-one patients were included: 31 underwent surgical treatment, and 20 were managed nonsurgically. Intraobserver agreement for subgroups ranged from 0.61 to 0.93, and interobserver agreement was 0.51 (first assessment) and 0.6 (second assessment). Intraobserver agreement for groups ranged from 0.66 to 0.95, and interobserver agreement was 0.52 (first assessment) and 0.63 (second assessment). The kappa index in all evaluations was 0.67 for Type A, 0.08 for Type B, and 0.68 for Type C injuries, and for the facet modifier it was 0.33 (F1), 0.4 (F2), 0.56 (F3), and 0.75 (F4). Complete agreement for all components was attained in 25 cases (49%) (19 Type A and 6 Type C), and for subgroups it was attained in 22 cases (43.1%) (16 Type A0 and 6 Type C). Type A0 injuries were treated conservatively or surgically according to their neurological status and ligamentous status. Type C injuries were treated surgically in almost all cases, except one.
While the general reliability of the newer AOSpine system for SCST was acceptable for group classification, significant limitations were identified for subgroups. Type B injuries were rarely diagnosed, and only mild (Type A0) and extreme severe (Type C) injuries had a high rate of interobserver agreement. Facet modifiers and intermediate injury patterns require better descriptions to improve their low agreement in cases of SCST 4).