Intratumoral Flow Void Diameter as a Predictor of High Intraoperative Blood Loss in Palliative Excisional Surgery for Metastatic Spinal Tumors

<b>Background/Objectives:</b> Massive intraoperative blood loss (IBL) is one of the major complications in metastatic spinal tumor surgery (MSTS), and understanding the predictors of this risk is essential. This study aimed to determine the impact of the intratumoral flow void (IFV) observed on standard magnetic resonance imaging (MRI) and its association with IBL in palliative surgery for metastatic spinal tumors. <b>Methods:</b> This retrospective analysis included 88 palliative excisional surgeries performed at a single hospital between 2010 and 2024. Factors such as age, sex, body mass index, tumor location, histological tumor type, spinal instability neoplastic score, revised Tokuhashi score, preoperative radiation, presence of IFV, and IFV diameter were assessed in addition to surgical details such as the number of resected and instrumented vertebrae and surgical duration. <b>Results:</b> Of the 88 patients, 71 (80.7%) exhibited IFV, with a mean IFV diameter of 1.8 ± 1.3 mm. The univariate analysis identified a significant association between IBL and several factors, including the presence of IFV, IFV diameter, hypervascular tumor type, number of instrumented vertebrae, and surgical duration. The multivariate analysis indicated that IFV diameter had the highest standardized coefficient among the examined variables, suggesting its strong potential as a predictor of IBL. <b>Conclusions:</b> This is the first study to identify the IFV diameter as a critical and independent predictor of IBL in MSTS. IFV diameter, which can be easily assessed using standard MRI, should be considered in surgical planning to effectively manage bleeding.