Clarification on the Measurement of Vertebral Body Loss in the Spinal Tuberculosis Instability Score

We read with great interest the article titled “A Validated Score for Evaluating Spinal Instability to Assess Surgical Candidacy in Active Spinal Tuberculosis—An Evidence Based Approach and Multinational Expert Consensus Study” by Rajasekaran et al describing a validated scoring system for evaluating spinal instability in active spinal tuberculosis, which provides an objective framework for assessing surgical candidacy and represents a valuable contribution to the management of this challenging condition. ¹ One of the principal variables in the scoring system is the vertebral body loss (VBL)-segmental ratio, calculated as previously described by the authors. ² The manuscript states that vertebral body height is divided into 10 equal fractions; the lost fractions are summed to obtain the total vertebral body loss (TVBL), and the TVBL is divided by the number of involved motion segments. ¹ While the accompanying schematic effectively illustrates the concept, we would appreciate further clarification regarding several practical aspects of the measurement protocol. Specifically, how should the reference vertebral body height be determined when extensive collapse has already occurred? Is VBL based solely on anterior vertebral body height or another standardised measurement? Which imaging modality is recommended for performing these measurements (plain radiographs, CT, or MRI)? Furthermore, how should irregular or asymmetric vertebral destruction, which is frequently encountered in spinal tuberculosis, be quantified? Finally, additional clarification on the definition of the denominator in the TVBL-segmental ratio would also be helpful, particularly in cases involving multiple adjacent vertebrae with varying degrees of destruction. These methodological details assume particular importance because a TVBL-segmental ratio of ≥0.5 contributes two points to the nine-point instability score and may influence the classification of a lesion as stable or unstable and, consequently, the recommendation for surgical stabilisation. We believe that further elaboration of these technical aspects would enhance the reproducibility of the scoring system across different institutions and facilitate its broader adoption in both clinical practice and future research. We thank the authors on this important work and look forward to their clarification.