Validation of the Hierarchical Nature of the AO Spine Sacral Classification and the Development of the Sacral AO Spine Injury Score.

STUDY DESIGN: Global cross-sectional survey. OBJECTIVE: The objective of this study was to validate the hierarchical nature of the AO Spine Sacral Classification System and develop an injury scoring system. SUMMARY OF BACKGROUND DATA: Although substantial interobserver and intraobserver reliability of the AO Spine Sacral Classification System has been established, the hierarchical nature of the classification has yet to be validated. METHODS: Respondents numerically graded each variable within the classification system for severity. Based on the results, a Sacral AO Spine Injury Score (AOSIS) was developed. RESULTS: A total of 142 responses were received. The classification exhibited a hierarchical Injury Severity Score (ISS) progression (A1: 8 to C3: 95) with few exceptions. Subtypes B1 and B2 fractures showed no significant difference in ISS (B1 43.9 vs. B2 43.4, P =0.362). In addition, the transitions A3→B1 and B3→C0 represent significant decreases in ISS (A3 66.3 vs. B1 43.9, P <0.001; B3 64.2 vs. C0 46.4, P <0.001). Accordingly, A1 injury was assigned a score of 0. A2 and A3 received scores of 1 and 3 points, respectively. Posterior pelvic injuries B1 and B2 both received a score of 2. B3 received a score of 3 points. C0, C1, C2, and C3 received scores of 2, 3, 5, and 6 points, respectively. The scores assigned to neurological modifiers N0, N1, N2, N3, and NX were 0, 1, 2, 4, and 3, respectively. Case-specific modifiers M1, M2, M3, and M4 received scores of 0, 0, 1, and 2 points, respectively. CONCLUSIONS: The results of this study validate the hierarchical nature of the AO Spine Sacral Classification System. The Sacral AOSIS sets the foundation for further studies to develop a universally accepted treatment algorithm for the treatment of complex sacral injuries. LEVEL OF EVIDENCE: Level IV-Diagnostic.

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).

Validation of the AO Spine Sacral Classification System: Reliability Among Surgeons Worldwide.

OBJECTIVES: To (1) demonstrate that the AO Spine Sacral Classification System can be reliably applied by general orthopaedic surgeons and subspecialists universally around the world and (2) delineate those injury subtypes that are most difficult to classify reliably to refine the classification before evaluating clinical outcomes. DESIGN: Agreement study. SETTING: All-level trauma centers, worldwide. PARTICIPANTS: One hundred seventy-two members of the AO Trauma and AO Spine community. INTERVENTION: The AO Sacral Classification System was applied by each surgeon to 26 cases in 2 independent assessments performed 3 weeks apart. MAIN OUTCOME MEASUREMENTS: Interobserver reliability and intraobserver reproducibility. RESULTS: A total of 8097 case assessments were performed. The kappa coefficient for interobserver agreement for all cases was 0.72/0.75 (assessment 1/assessment 2), representing substantial reliability. When comparing classification grading (A/B/C) regardless of subtype, the kappa coefficient was 0.84/0.85, corresponding to excellent reliability. The kappa coefficients for interobserver reliability were 0.95/0.93 for type A fractures, 0.78/0.79 for type B fractures, and 0.80/0.83 for type C fractures. The overall kappa statistic for intraobserver reliability was 0.82 (range 0.18-1.00), representing excellent reproducibility. When only evaluating morphology type (A/B/C), the average kappa value was 0.87 (range 0.18-1.00), representing excellent reproducibility. CONCLUSION: The AO Spine Sacral Classification System is universally reliable among general orthopaedic surgeons and subspecialists worldwide, with substantial interobserver and excellent intraobserver reliability.

The Influence of Surgeon Experience and Subspeciality on the Reliability of the AO Spine Sacral Classification System.

STUDY DESIGN: Cross-sectional survey. OBJECTIVE: To determine the influence of surgeons' level of experience and subspeciality training on the reliability, reproducibility, and accuracy of sacral fracture classification using the Arbeitsgemeinschaft für Osteosynthesefragen Spine Sacral Classification System. SUMMARY OF BACKGROUND DATA: A surgeons' level of experience or subspecialty may have a significant effect on the reliability and accuracy of sacral classification given various levels of comfort with imaging assessment required for accurate diagnosis and classification. METHODS: High-resolution computerized tomography (CT) images from 26 cases were assessed on two separate occasions by 172 investigators representing a diverse array of surgical subspecialities (general orthopedics, neurosurgery, orthopedic spine, orthopedic trauma) and experience (<5, 5-10, 11-20, >20 yrs). Reliability and reproducibility were calculated with Cohen kappa coefficient (k) and gold standard classification agreement was determined for each fracture morphology and subtype and stratified by experience and subspeciality. RESULTS: Respondents achieved an overall k = 0.87 for morphology and k = 0.77 for subtype classification, representing excellent and substantial intraobserver reproducibility, respectively. Respondents from all four practice experience groups demonstrated excellent interobserver reliability when classifying overall morphology (k = 0.842/0.850, Assessment 1/Assessment 2) and substantial interobserver reliability in overall subtype (k = 0.719/0.751) in both assessments. General orthopedists, neurosurgeons, and orthopedic spine surgeons exhibited excellent interobserver reliability in overall morphology classification and substantial interobserver reliability in overall subtype classification. Surgeons in each experience category and subspecialty correctly classified fracture morphology in over 90% of cases and fracture subtype in over 80% of cases according to the gold standard. Correct overall classification of fracture morphology (Assessment 1: P = 0.024, Assessment 2: P = 0.006) and subtype (P2 < 0.001) differed significantly by years of experience but not by subspecialty. CONCLUSION: Overall, the Arbeitsgemeinschaft für Osteosynthesefragen spine sacral classification system appears to be universally applicable among surgeons of various subspecialties and levels of experience with acceptable reliability, reproducibility, and accuracy.Level of Evidence: 4.

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.

Does Riluzole Influence Bone Formation?: An In Vitro Study of Human Mesenchymal Stromal Cells and Osteoblast.

STUDY DESIGN: A post-test design biological experiment. OBJECTIVE: The aim of this study was to evaluate the osteogenic effects of riluzole on human mesenchymal stromal cells and osteoblasts. SUMMARY OF BACKGROUND DATA: Riluzole may benefit patients with spinal cord injury (SCI) from a neurologic perspective, but little is known about riluzole's effect on bone formation, fracture healing, or osteogenesis. METHODS: Human mesenchymal stromal cells (hMSCs) and human osteoblasts (hOB) were obtained and isolated from healthy donors and cultured. The cells were treated with riluzole of different concentrations (50, 150, 450 ng/mL) for 1, 2, 3, and 4 weeks. Cytotoxicity was evaluated as was the induction of osteogenic differentiation of hMSCs. Differentiation was evaluated by measuring alkaline phosphatase (ALP) activity and with Alizarin red staining. Osteogenic gene expression of type I collagen (Col1), ALP, osteocalcin (Ocn), Runx2, Sox9, Runx2/Sox9 ratio were measured by qRT-PCR. RESULTS: No cytotoxicity or increased proliferation was observed in bone marrow derived hMSCs and primary hOBs cultured with riluzole over 7 days. ALP activity was slightly increased in hMSCs after treatment for 2 weeks with riluzole 150 ng/mL and slightly upregulated by 150% (150 ng/mL) and 90% (450 ng/mL) in hMSCs at 3 weeks. In hOBs, ALP activity almost doubled after 2 weeks of culture with riluzole 150 ng/mL (P < 0.05). More pronounced 2.6-fold upregulation was noticed after 3 weeks of culture with riluzole at both 150 ng/mL (P = 0.05) and 450 ng/mL (P = 0.05). No significant influence of riluzole on the mRNA expression of osteocalcin (OCN) was observed. CONCLUSION: The effect of riluzole on bone formation is mixed; low-dose riluzole has no effect on the viability or function of either hMSCs or hOBs. The activity of ALP in both cell types is upregulated by high-dose riluzole, which may indicate that high-dose riluzole can increase osteogenic metabolism and subsequently accelerate bone healing process. However, at high concentrations, riluzole leads to a decrease in osteogenic gene expression, including Runx2 and type 1 collagen. LEVEL OF EVIDENCE: N/A.

The Influence of Spine Surgeons' Experience on the Classification and Intraobserver Reliability of the Novel AOSpine Thoracolumbar Spine Injury Classification System-An International Study.

STUDY DESIGN: International validation study. OBJECTIVE: To investigate the influence of the spine surgeons' level of experience on the intraobserver reliability of the novel AOSpine Thoracolumbar Spine Injury Classification system, and the appropriate classification according to this system. SUMMARY OF BACKGROUND DATA: Wide variability has been demonstrated for intraobserver reliability of the AOSpine classification system. The spine surgeons' level of experience may play a crucial role in the appropriate classification of thoracolumbar fractures, and the degree of reproducibility of the same observer on separate occasions. However, this has not been previously investigated. METHODS: After a training on the classification system, high quality CT images together with clinical data from 25 patients with thoracolumbar fractures were independently assessed by 100 spine surgeons from across the world on 2 different occasions, 1 month apart from each other. The spine surgeons were allocated to a subgroup, according to their years of experience. Intraobserver reliability was calculated for each individual surgeon and for each subgroup, using the Kappa statistics (κ). Descriptive statistics was used to describe any differences between the subgroups. Analysis of any misclassifications was performed by calculating sensitivity and specificity estimates. RESULTS: Almost all surgeons demonstrated at least moderate intraobserver reliability. All surgeon subgroups demonstrated substantial reliability (κ = 0.67-0.69) for fracture subtype grading, and almost all subgroups demonstrated excellent reliability (κ = 0.79-0.83) for fracture morphology type regardless of subtype identified. In general, the fractures were most frequently misclassified by the most experienced surgeons. No major differences were observed among the subgroups when comparing the sensitivity and specificity rates. CONCLUSION: This international study demonstrated that the spine surgeons' level of experience does not substantially influence the classification and intraobserver reliability of the recently described AOSpine Thoracolumbar Spine Injury Classification System. LEVEL OF EVIDENCE: 4.