Development of a New Therapy-Oriented Classification of Intervertebral Vacuum Phenomenon With Evaluation of Intra- and Interobserver Reliabilities

Abstract

Study Design: Diagnostic study, level of evidence III. Objectives: Low back pain is a common cause of disability among elderly patients. Percutaneous discoplasty has been developed as a tool to treat degenerative disease when conservative management is not successful. Indications for this procedure include low back pain and the presence of vacuum phenomenon. The objective of this study was to describe a new classification of vacuum phenomenon based on computed tomography scan in order to improve the indications for percutaneous discoplasty. Methods: We developed a classification of vacuum phenomenon based on computed tomography scan images. We describe 3 types of vacuum based on the relationship between vacuum and the superior/inferior endplates and 2 subtypes based on the presence of significant subchondral sclerosis. A validation study was conducted selecting 10 orthopedic residents with spine surgery training to analyze 25 vacuum scenarios. Inter- and intraobserver reliabilities were assessed through the Fleiss’s and Cohen’s kappa statistics, respectively. Results: The overall Fleiss’s κ value for interobserver reliability was 0.85 (95% CI 0.82-0.86) in the first reading and 0.93 (95% CI 0.92-0.95) in the second reading. Cohen’s κ for intraobserver reliability was 0.88 (95% CI 0.77-0.99). Conclusion: The new classification has shown almost perfect inter- and intraobserver reliabilities for grading the vacuum phenomenon and could be an important tool to improve the indications for percutaneous cement discoplasty.