ABC/2 versus computer-assisted volumetric analysis for epidural hematoma: measurement variability, and the influence of hematoma morphology; a retrospective, multicenter, cohort study.

OBJECTIVE

Accurate estimation of epidural hematoma (EDH) volume is critical for clinical decision-making, as current traumatic brain injury guidelines recommend surgical evacuation for EDH volumes exceeding 30 cm³. The manual ABC/2 method is widely used for rapid estimation, but its accuracy for EDH remains incompletely defined. This study evaluated the accuracy of ABC/2 compared with computer-assisted volumetric analysis (CAVA) in a large, multicenter cohort.

METHODS

A retrospective analysis was performed on adult patients with traumatic EDH treated at two tertiary neurosurgical centers between 2017 and 2025. Hematoma volumes were calculated using the ABC/2 method and compared with CAVA using brainlab® or 3D-Slicer software. Correlation and agreement were assessed using Pearson correlation, paired testing, and Bland-Altman analysis, while inter-rater and intra-software reliability were assessed using intraclass correlation coefficients (ICC).

RESULTS

A total of 191 patients were included (mean age 40.0 ± 15.9 years). Bland-Altman analysis showed systematic overestimation by ABC/2 (mean bias - 13.45 mL) with wide limits of agreement. Log-transformed analysis confirmed substantial proportional variability (geometric mean ratio 0.72, 95% LoA 0.15-3.44), despite a strong overall correlation (r = 0.897, p < 0.001). Overestimation was greater in classic than irregular hematomas (16 vs. 8 mL), and classification discordance occurred in 56 patients (29.3%), including 28 (14.7%) crossing the 30-mL threshold.

CONCLUSIONS

Although the ABC/2 method provides a rapid, practical estimate of EDH volume, it systematically overestimates hematoma size compared with CAVA and shows substantial shape- and patient-level variability. The two methods are not interchangeable, and volumes near commonly referenced operative thresholds should be interpreted cautiously. As CAVA tools become increasingly accessible, future studies should evaluate how CAVA-based measurements correlate with clinical presentation, treatment decisions, and patient outcomes, and determine how historical volume thresholds translate to modern volumetric techniques.